|
|
||||||||
Special Article |
1 From the Department of Nutrition, University of California, Davis (SSE, JSS, and PJH); the US Department of Agriculture Western Human Nutrition Research Center, Davis, CA (NLK); and the Monell Chemical Senses Institute and the University of Pennsylvania, Philadelphia (KT).
2 Supported by the NIH (DK-50129), the University of California Davis Clinical Nutrition Research Unit (DK-35747), the American Diabetes Association, and the US Department of Agriculture. 3 Address reprint requests to PJ Havel, Department of Nutrition, University of California, Davis, One Shields Avenue, Davis, CA 95616. E-mail: pjhavel{at}ucdavis.edu.
| ABSTRACT |
|---|
|
|
|---|
Key Words: Fructose leptin weight gain insulin resistance triacylglycerol hypertension obesity review
| INTRODUCTION |
|---|
|
|
|---|
20 y are considered overweight [ie, a body mass index (BMI; in kg/m2)
25], and nearly one-fourth are clinically obese (BMI
30) (3, 4). Although extreme obesity has received the most attention in the clinical setting, most obesity in the population can be described as moderate to marked. However, even moderate obesity can contribute to chronic metabolic abnormalities characteristic of the insulin resistance syndrome, such as dyslipidemia, hypertension, insulin resistance, and glucose intolerance (1), particularly when it is associated with intraabdominal fat deposition (ie, central obesity) (5). Although it is likely that no single factor is responsible for the increased prevalence of moderate obesity, environmental elementsinteracting with predisposing genetic factorsclearly must be involved (1). Identification of the acquired causes contributing to an increase in the prevalence of obesity is necessary to develop public health policy and dietary and physical activity recommendations that are both comprehensive and effective in reversing the current trend. The purpose of this review is to explore whether the increased consumption of dietary fructose might be one of the environmental factors contributing to the development of obesity and the accompanying abnormalities of the insulin resistance syndrome. The insulin resistance syndrome is a cluster of related variables that appears to be of major importance in the pathogenesis of coronary artery disease. The syndrome originally included resistance to insulin-stimulated glucose uptake, glucose intolerance, hyperinsulinemia, hypertension, dyslipidemia characterized by high triacylglycerol concentrations, and low concentrations of HDLs (6). More recently, the list of abnormalities has been expanded to include central obesity (7); small, dense LDLs (8); increased uric acid concentrations (9); higher circulating concentrations of plasminogen activator inhibitor 1 (10); and decreased circulating concentrations of adiponectin (11). In addition, a link between local adipose steroid metabolism and the insulin resistance syndrome has been suggested by reports that the activity of 11ß-hydroxysteroid dehydrogenase (EC 1.1.1.146) is increased in the adipose tissue of obese humans (12). Increased expression of this enzyme, specifically in adipose tissue, was shown recently to induce visceral obesity, insulin-resistant diabetes, and hyperlipidemia in a transgenic mouse model (13).
The terms syndrome X, metabolic syndrome, and insulin resistance syndrome have been used in the literature to describe the observed clustering of metabolic abnormalities. It has been hypothesized that insulin resistance, which may affect 25% of middle-aged adults in this country (14), is the common etiologic factor in the syndrome (6). The macronutrient content of the diet has been linked to the insulin resistance syndrome. For example, high-fat, particularly high saturated fat, diets induce weight gain, insulin resistance, and hyperlipidemia in humans and animals (1518). In addition to the known effects of dietary fat, dietary fructose has been shown to produce weight gain and induce insulin resistance, hyperlipidemia, and hypertension in experimental animals. It is therefore possible that increased consumption of fructose could contribute to weight gain and its accompanying metabolic disturbances in humans.
| FRUCTOSE CONSUMPTION |
|---|
|
|
|---|
35% of the total amount of sweeteners by dry weight in the food supply (21). Although HFCS can contain up to 90% fructose (22), most of the HFCS used in beverages contains
55% fructose. In a 1993 article, the authors estimated the mean individual consumption of fructose in adolescents and adults to be 40 g/d, the range being 2954 g/d (21). Thirteen of the 40 g of dietary fructose is estimated to come from naturally occurring sources of fructose, and 27 g is estimated to come from added sources of fructose. Young males (1518 y of age) reported the highest fructose intakes with a 90th percentile intake of fructose from all sources of nearly 100 g/d. However, these intakes were based on the 19771978 US Department of Agriculture Nationwide Food Consumption Survey and are likely to seriously underestimate current consumption, because the consumption of HFCS-sweetened beverages has increased markedly during the intervening time. In addition, at the time that the article by Park and Yetley (21) was written, the use of crystalline fructose had just been expanded to the general food supply. To our knowledge, aside from the food disappearance data discussed below, there are no more recent data available on the amount of fructose currently consumed in the United States.
Food disappearance data serve as indicators of trends in consumption over time (19). As depicted in Figure 1
, although the per capita use of sucrose decreased moderately from 46.4 kg (102 lb) in 1970 to 30.5 kg (67 lb) in 1997, the per capita use of HFCS increased from a negligible 0.23 kg (0.5 lb) in 1970 to 28.4 kg (62.4 lb) in 1997 (19). The use of glucose syrup also increased, whereas the contribution of other sweetenerssupplied as honey, molasses, and maple syrupremained constant at
1% (Figure 1
). The use of glucose and fructose calculated from sweetener disappearance increased in parallel during this time period (Figure 2
). Calculated on a daily basis, the per capita use of added fructose, obtained by combining the disappearance data for the fructose contained in sucrose and in HFCS, increased by 26%, from 64 g/d in 1970 to 81 g/d in 1997. This represents an average daily energy intake from added fructose of
1356 kJ (324 kcal). In addition, a 19% increase in fruit and vegetable consumption was observed between 1982 and 1997 (19). This could lead to a small (2.5 g/d) increase in naturally occurring fructose in the diet, raising the estimated amount of naturally occurring fructose in the diet to
1516 g/d for an average total fructose use of 97 g/d (1624 kJ, or 388 kcal) in 1997. Just two 355-mL (12-oz) soft drinks can supply up to 50 g/fructose (
840 kJ, or 200 kcal) or > 10% of the energy requirements for an average-weight woman, without considering any other dietary sources of fructose. Thus, fructose consumption makes up a significant proportion of energy intake in the American diet, and an increased fructose consumption has coincided with an increase in the prevalence of obesity over the past 2 decades. It therefore is prudent to ask whether current fructose intakes could contribute to weight gain and its metabolic sequelae.
|
|
| FRUCTOSE METABOLISM |
|---|
|
|
|---|
|
In contrast with low doses of fructose, when much larger amounts of fructose are consumed (eg, in sucrose- and HFCS-sweetened beverages), fructose continues to enter the glycolytic pathway distal to phosphofructokinase (Figure 3
), and hepatic triacylglycerol production is facilitated. Fructose can provide carbon atoms for both the glycerol and the acyl portions of acylglycerol molecules (23). Thus, unlike glucose metabolism, in which the uptake of glucose is negatively regulated at the level of phosphofructokinase, high concentrations of fructose can serve as a relatively unregulated source of acetyl-CoA. Indeed, studies in human subjects have shown that fructose ingestion results in markedly increased rates of de novo lipogenesis (29, 30), whereas de novo lipogenesis does not increase in response to eucaloric glucose ingestion (31). Thus, fructose is more lipogenic than is glucose, an effect that might be exacerbated in subjects with existing hyperlipidemia (32) or insulin resistance or type 2 diabetes (33). In addition, as discussed below, fructose does not stimulate the production of 2 key hormones, insulin and leptin, which are involved in the long-term regulation of energy homeostasis. Therefore, the decrease in insulin responses to meals and leptin production associated with chronic consumption of diets high in fructose may have deleterious long-term effects on the regulation of energy intake and body adiposity.
| FRUCTOSE, ENERGY INTAKE, AND WEIGHT GAIN |
|---|
|
|
|---|
Fructose, unlike glucose, does not stimulate insulin secretion from pancreatic ß cells (40, 41). The lack of stimulation by fructose is likely due to the low concentrations of the fructose transporter GLUT5 in ß cells (42). Insulin is involved in the regulation of body adiposity via its actions in the central nervous system (CNS) to inhibit food intake and increase energy expenditure (see reviews in references 43 and 44). Briefly, insulin receptors are localized in CNS areas involved in the control of food intake and energy homeostasis. Insulin administration into the CNS inhibits food intake in animals, including nonhuman primates. Insulin does not enter the brain, but is transported into the CNS via a saturable receptor-mediated process. Using compartmental modeling, Kaiyala et al (45) showed that the obesity induced by a high-fat diet was associated with a 60% reduction of the transport of insulin into the CNS in dogs. This impairment of central insulin transport was inversely related to an increase in body weight in response to high-fat feeding. Specifically, knocking out the insulin receptor in neurons results in hyperphagia and obesity in mice (46). Thus, reduced insulin delivery into the CNS or disruption of the insulin-signaling pathways in the CNS may result in weight gain and the development of obesity.
As discussed above, there is considerable evidence in support of the hypothesis that insulin signaling in the CNS lowers food intake and that insulin functions as a negative feedback signal of recent energy intake and body adiposity. However, because of the known anabolic effects of insulin to simulate lipid synthesis and promote fat storage, there is a widespread belief that insulin induces weight gain and obesity. This misconception has led to the promotion of numerous diets suggesting that weight loss can be achieved by avoiding foods that stimulate insulin secretion. However, the proponents of such diets do not distinguish between normal insulin responses to meals in which circulating insulin concentrations increase and quickly return to fasting concentrations and the chronic hyperinsulinemia secondary to ß cell adaptation to insulin resistance. Note that reduced glucose-stimulated insulin secretion has been shown to be prognostic of greater future weight gain; therefore, increased insulin secretion in response to meals is unlikely to contribute to weight gain and obesity (47).
A major breakthrough in obesity research came with the cloning of the defective gene (ob) responsible for hyperphagia and obesity in an obese diabetic mouse strain (48). The gene is expressed in adipose tissue (49) and its protein product, leptin, functions as a circulating signal from body fat stores to the CNS, where it acts to limit adiposity by inhibiting food intake and increasing energy expenditure (50, 51). The effects of insulin and leptin on food intake appear to share a common signaling pathway via activation of phosphatidylinositol-3-kinase (EC 2.7.1.137) (52). The increase in energy expenditure in rodents may be mediated by activation of the sympathetic nervous system (53). Leptin administration decreases food intake and activates the sympathetic nervous system in rhesus monkeys (54, 55), indicating that leptin has similar biological effects in primates. In addition, human subjects have been identified with hyperphagia and marked obesity, resulting from a failure to produce leptin (56) or from defects in the leptin receptor (57), and leptin administration decreases the hyperphagia and body adiposity resulting from leptin deficiency (58). Relative leptin deficiency, associated with heterozygous leptin gene mutations, was also shown recently to have a significant biological effect, resulting in increased body adiposity in humans (59). Decreases in circulating leptin concentrations correlate with increased sensations of hunger during prolonged energy restriction in women (60), and leptin administration can reduce appetite in humans (61). Together, the available evidence strongly suggests an important role for leptin in the regulation of energy balance in humans (11, 62).
Plasma leptin concentrations are strongly correlated with adiposity in rodents (63, 64), nonhuman primates (65), and humans (64, 66). In humans, plasma leptin decreases after fasting (67) or energy restriction (68) to a much greater degree than would be expected from modest changes in body adiposity. However, meal ingestion does not increase plasma leptin concentrations in short-term (24 h) studies (67), indicating that leptin functions as a medium- to long-term regulator of energy balance rather than as a short-term satiety factor such as cholecystokinin (see review in reference 69). There is a diurnal pattern of plasma leptin concentrations in humans, with peak concentrations occurring 68 h after the evening meal (70). The nocturnal increase in leptin is entrained by meal timing (71) and does not occur if the subjects are fasted (72). Insulin stimulates leptin gene expression and secretion and appears to have a major role in the physiologic regulation of leptin production and in determining the magnitude of its diurnal fluctuation (11). Insulin infusions producing physiologic increments in plasma insulin have been found to increase circulating leptin concentrations in humans after several hours (73).
Studies in isolated adipocytes have provided evidence that increases in glucose transport and metabolism are key steps in insulin-stimulated leptin expression and secretion in vitro (74). A blockade of glucose transport or inhibition of glycolysis inhibits insulin-induced leptin secretion and ob gene expression, and the activation of the leptin promoter (75) in proportion to the inhibition in adipocyte glucose utilization. Furthermore, results from these and other experiments (76) indicate that anaerobic glucose metabolism does not stimulate leptin secretion, suggesting that glucose oxidation is involved in the effects of insulin on increases in leptin production. Glucose metabolism has also been suggested to mediate the effects of insulin and glucose infusion to increase leptin production in humans (77). Thus, increases in insulin-stimulated glucose metabolism after meals would be expected to influence the diurnal pattern of circulating leptin concentrations (71, 78, 79).
If, as suggested by the in vitro studies, leptin secretion is dependent on insulin-mediated adipocyte glucose transport and metabolism, then meals high in carbohydrate, which induce larger postprandial insulin and glucose excursions, should increase circulating leptin more than would low-carbohydrate meals. When the ratio of dietary carbohydrate to fat was altered, consumption of 3 meals with a high proportion of glucose carbohydrate enhanced insulin secretion, produced larger glucose excursions, and increased plasma leptin concentrations over 24 h relative to high-fat, low-carbohydrate meals (80). In another study, when women were placed on a weight-maintaining regimen, such that energy intake was adjusted to offset weight loss or weight gain, the subjects needed to be fed significantly more energy (500 ± 125 kJ/d, or 120 ± 30 kcal/d) when the fat content of the diet was lowered from 35% to 15% of energy and was replaced with complex carbohydrate (66). Poppitt et al (81) compared the effects over 6 mo of a low-fat, complex-carbohydrate diet; a low-fat, simple-carbohydrate diet; and a control diet in overweight volunteers with
3 risk factors for metabolic syndrome. Weight loss was greatest in the low-fat, complex-carbohydrate group. These data suggest that low-fat, high-carbohydrate feeding may have altered the regulated level of adiposity, an effect that could be mediated in part by a long-term increase in leptin production. Conversely, decreased leptin secretion could contribute to the reported effect of high-fat diets, ie, weight gain and obesity (8284).
As previously discussed, fructose, unlike glucose, does not stimulate insulin secretion (41). Although high-carbohydrate meals stimulate leptin production in humans relative to high-fat meals (80), if the carbohydrate provided in this study had been fructose rather than glucose, the results would probably have been different because of the dissimilar effects of the 2 sugars on insulin secretion. To compare the effects of glucose and fructose on leptin production, plasma leptin concentrations were measured in rhesus monkeys after intravenous infusion with saline, glucose, or fructose. Glucose infusion markedly increased plasma glucose and insulin concentrations and progressively increased plasma leptin 48 h into the infusions. In contrast, an intravenous infusion of the same amount of fructose only modestly increased plasma glucose and did not stimulate insulin secretion or increase circulating leptin concentrations over an 8-h period (65). To test whether ingested fructose would produce results similar to those of fructose infusion, 12 women were studied during the randomized consumption of 3 meals accompanied by fructose-containing beverages on 1 d and of 3 meals accompanied by glucose-containing beverages on a separate day. The sweetened beverages supplied 30% of the total energy provided during the test days. As predicted, the consumption of fructose-containing beverages with the meals resulted in smaller postprandial glucose and insulin excursions than did the consumption of glucose-containing beverages. In addition, the consumption of 3 high-fructose meals resulted in lower circulating leptin concentrations over 24 h than did the consumption of 3 high-glucose meals (85). Furthermore, during consumption of meals accompanied by glucose beverages, circulating concentrations of the orexigenic gastric hormone ghrelin (see review in reference 86) clearly decreased 13 h after each meal, whereas ghrelin was much less suppressed after meals with fructose-containing beverages (85). Because insulin and leptin, and possibly ghrelin, function as key signals to the CNS in the long-term regulation of energy balance (see review in reference 69), the observed decreases in circulating insulin and leptin and increases in ghrelin could lead to increased energy intake and thereby contribute to weight gain, obesity, and its metabolic consequences during long-term consumption of diets high in energy derived from fructose.
| FRUCTOSE CONSUMPTION AND INSULIN RESISTANCE |
|---|
|
|
|---|
The classic relation between insulin resistance, increased fasting plasma insulin concentrations, and glucose intolerance has been hypothesized to be mediated by changes in ambient nonesterified fatty acid concentrations (see review in reference 96). Elevated nonesterified fatty acid concentrations are one of the metabolic consequences of a chronic positive energy balance and increased body adiposity (97). If, as discussed above, fructose consumption leads to increased body weight as a result of decreased insulin secretion and reduced leptin production, an increase in circulating nonesterified fatty acids might follow. The exposure to increased concentrations of nonesterified fatty acids may reduce insulin sensitivity by increasing the intramyocellular lipid content (98). Increased portal delivery of nonesterified fatty acids, particularly from visceral adipose tissue, could also lead to impaired carbohydrate metabolism, because elevated portal nonesterified fatty acid concentrations increase hepatic glucose production (99, 100). In addition, over time, increased nonesterified fatty acid concentrations may have a deleterious effect on ß cell function (101).
An increased supply of nonesterified fatty acids in the liver also leads to an increase in the production of VLDL triacylglycerol (102). Fructose consumption has been shown to induce hypertriacylglycerolemia (as discussed below). Because insulin resistance and reduced insulin binding have been reported in hypertriacylglycerolemic persons (103), this may be one mechanism by which fructose diets promote insulin resistance. Administration of benfluorex, a hypolipidemic agent, reversed the insulin resistance induced by fructose feeding in rats. The improvement was associated with the normalization of triacylglycerol concentrations (104). However, 3 mo of gemfibrozil administration to 24 persons with endogenous hypertriacylglycerolemia resulted in marked decreases in both plasma triacylglycerol and nonesterified fatty acid concentrations but did not enhance insulin-mediated glucose disposal and did not lower plasma insulin concentrations (105). Therefore, the role of triacylglycerol in the development of insulin resistance remains controversial. On the other hand, postprandial hypertriacylglycerolemia after fructose ingestion is exacerbated in subjects with higher fasting insulin concentrations (33), suggesting an interaction between insulin resistance and the lipogenic effects of fructose (see below).
Another potential mechanism leading to insulin resistance could involve decreased production of the adipocyte protein, adiponectin, because reduced circulating concentrations of this hormone are associated with insulin resistance independently of body adiposity (11, 106). We are currently investigating the effects of dietary fructose compared with those of glucose on circulating adiponectin concentrations. Whatever the underlying mechanism, it is clear that fructose feeding induces insulin resistance and glucose intolerance in rodents. Given the increase in fructose consumption in the American diet, it is important to examine whether fructose has similar effects on insulin action and glucose tolerance in humans, particularly those persons who are likely to be susceptible to insulin resistance and impaired glucose metabolism.
| FRUCTOSE CONSUMPTION AND LIPIDS |
|---|
|
|
|---|
Fructose is the component of sucrose that is considered to be responsible for some of the adverse effects of this disaccharide on blood triacylglycerol (113). After extensive work on the metabolic effects of sucrose at the Beltsville Human Nutrition Research Center, the investigators focused on fructose specifically. Hallfrisch et al (114) fed 12 hyperinsulinemic men and 12 male control subjects diets containing 0%, 7.5%, and 15% of energy from fructose for 5 wk each in a crossover study. Total plasma cholesterol and LDL-cholesterol concentrations were higher when the men consumed 7.5% or 15% of energy as fructose than as starch. Plasma triacylglycerol concentrations in the hyperinsulinemic subjects increased as the amount of fructose increased. In 1989 Reiser et al (115) reported results from another 5-wk crossover study in which 10 hyperinsulinemic and 11 nonhyperinsulinemic men consumed diets containing 20% of energy as fructose or as high-amylose cornstarch. Triacylglycerol and cholesterol concentrations increased in both groups of subjects when they consumed fructose, but not cornstarch. Thus, consumption of fructose compared with the same amount of high-amylose cornstarch, produced undesirable changes in cardiovascular risk factors in both hyperinsulinemic and nonhyperinsulinemic men.
Not all studies that have evaluated the effects of fructose have reported increased lipids. In the Turku sugar studies (116), the effect of chronic consumption of sucrose, xylitol, and fructose was studied for 2 y in 127 healthy subjects. Substituting fructose or xylitol for sucrose did not influence plasma cholesterol or triacylglycerol concentrations. Effects on body weight were not reported. It is important to note, however, that an effect of fructose alone may have been obscured by comparing its effects with those of sucrose, which is composed of 50% fructose. In a review article on the effects of dietary fructose on lipid metabolism, Hollenbeck (117) concluded that there is strong evidence that fructose consumed at
20% of total energy results in an increase in total and LDL-cholesterol concentrations but added that the effect of dietary fructose on triacylglycerol concentrations is less clear. Because most studies reported fasting plasma triacylglycerol concentrations, differences in postprandial triacylglycerol excursions in response to dietary changes may have been missed in some of the reported studies.
In a recent study in which 17% of energy was consumed as either crystalline fructose or glucose for 6 wk, both fasting and postprandial triacylglycerol concentrations were measured (118). The fructose diet produced significantly higher fasting, postprandial, and daylong plasma triacylglycerol values in older men, although this effect of fructose was not seen in younger (< 40 y of age) men or in the older (
40 y of age) women included in the study. The fructose diet had no significant effects on fasting plasma cholesterol, HDL cholesterol, or LDL cholesterol in either men or women. In healthy persons, increases in triacylglycerol concentrations can decrease over time as a result of metabolic adaptation, but there does appear to be a subset of individuals who are particularly sensitive to dietary fructose, including those with hyperinsulinemia (28). We recently compared the effects of fructose- and glucose-sweetened beverages (providing 30% of total energy) consumed with 3 meals over 24 h in 12 young, normal-weight women without hypertriacylglycerolemia (119). Plasma triacylglycerol concentrations increased more rapidly and peaked at higher concentrations after consumption of fructose-containing than after glucose-containing beverages. Plasma triacylglycerol concentrations remained elevated after fructose but declined to or below fasting concentrations several hours after glucose consumption. In addition, fasting triacylglycerol concentrations the morning after fructose consumption were increased above baseline concentrations and were elevated compared with fasting triacylglycerol concentrations after glucose consumption. Evidence exists that this effect of fructose (ie, an increase in postprandial triacylglycerol concentrations) may be exacerbated in subjects with hypertriacylglycerolemia (32) or insulin resistance (33).
In a comprehensive review of carbohydrate-induced hypertriacylglycerolemia, Parks and Hellerstein (120) reviewed potential biological mechanisms for the phenomenon in humans. The authors concluded that elevated triacylglycerol concentrations observed with increased consumption of dietary carbohydrates result from elevated triacylglycerol synthesis and, in some persons, from reduced triacylglycerol clearance. The increased synthesis of triacylglycerol results primarily from both increases in the VLDL particle secretion rate by the liver and in VLDL particle size. Reductions in triacylglycerol clearance may be due in part to reductions in lipoprotein lipase (EC 3.1.1.34) activity (119). Using a fructose-fed Syrian golden hamster animal model, Taghibiglou et al (121) investigated mechanisms potentially responsible for the overproduction of VLDL in the insulin-resistant state. They found evidence for enhanced lipoprotein assembly, reduced intracellular apolipoprotein B degradation, and increased expression of microsomal triacylglycerol transfer protein. Together, these findings help to explain the increased assembly and secretion of apolipoprotein-Bcontaining lipoprotein particles in a fructose-fed, insulin-resistant animal model (121).
In summary, there is an abundance of data in rodents that show that fructose feeding causes chronic hyperlipidemia. Several short-term studies in humans have implicated fructose consumption as a factor promoting unfavorable lipid profiles. Many persons consume sucrose and fructose at amounts in the range of 30% of energy intake (113). This appears to be particularly true for children (122) and adolescents (123). In the adolescent population in the United States, total milk consumption decreased by 36% from 1965 to 1996. During the same time period, soft drink consumption increased 287% in boys and 224% in girls (124). The long-term effects of increased consumption of fructose on fasting and postprandial HDL and LDL cholesterol as well as on circulating triacylglycerol concentrations need further investigation. A better understanding of whether the initial responses to increased fructose consumption persist, worsen, or improve with time should result. In addition, the potential role of fructose in the hypertriacyglycerolemia often observed during the consumption of high-carbohydrate, low-fat diets needs to be clarified.
| FRUCTOSE AND HYPERTENSION |
|---|
|
|
|---|
Compared with individuals with normal blood pressure, persons with high blood pressure are relatively glucose intolerant (6). Additionally, lowering blood pressure in hypertensive individuals does not necessarily reduce the degree of glucose intolerance and hyperinsulinemia. Two potential explanations for how insulin resistance and hyperinsulinemia could lead to an increase in blood pressure are as follows: 1) increases in sympathetic neural outflow and plasma catecholamine concentrations associated with increased plasma insulin concentrations, and 2) insulin action at the level of the proximal tubule to increase fluid reabsorption (6). Because hypertension is a well-known comorbidity associated with obesity, insulin resistance, hyperinsulinemia, and hyperlipidemia, it is important to determine the effects of fructose consumption on blood pressure in human subjects.
| CONCLUSIONS |
|---|
|
|
|---|
|
|
|
|
A considerable amount of research needs to be done to more completely appreciate the effect of fructose in the American diet. In the meantime, a prudent approach concerning recommendations for dietary fructose would consider the following 2 points. First, added fructose (in the forms of sucrose and HFCS) does not appear to be the optimal choice as a source of carbohydrate in the diet. Small amounts of added fructose are probably benign and may even have some favorable metabolic effects. However, on the basis of the available data regarding the endocrine and metabolic effects of consuming large quantities of fructose and the potential to exacerbate components of the insulin resistance syndrome, it is preferable to primarily consume dietary carbohydrates in the form of glucose (free glucose and starch). This may be particularly important in subjects with existing hyperlipidemia or insulin resistance who could be more susceptible to the adverse metabolic effects of fructose. Second, the concerns raised about the addition of fructose to the diet as sucrose or HFCS should not be extended to naturally occurring fructose from fruit and vegetables. The consumption of fruit and vegetables should continue to be encouraged because of the resulting increased intake of fiber, micronutrients, and antioxidants. In addition, the intake of naturally occurring fructose is low,
15 g/d, and is unlikely to contribute significantly to the untoward metabolic consequences associated with the consumption of large amounts of fructose. Certainly, it would be desirable to have more precise data regarding the current amounts and patterns of fructose consumption. Unfortunately, to our knowledge, no accurate data on fructose consumption more recent than 19771978 are available. Although fructose disappearance data show a clear-cut pattern toward increased consumption of fructose, more definitive measurements of intake in different populations require large-scale surveys. In addition, it is important to gain a better understanding of the effects and mechanisms of fructose consumption on metabolic indexes such as insulin sensitivity and lipid metabolism, including triacylglycerol production.
| ACKNOWLEDGMENTS |
|---|
| REFERENCES |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
R. K. Johnson, L. J. Appel, M. Brands, B. V. Howard, M. Lefevre, R. H. Lustig, F. Sacks, L. M. Steffen, J. Wylie-Rosett, and on behalf of the American Heart Association Nutrit Dietary Sugars Intake and Cardiovascular Health: A Scientific Statement From the American Heart Association Circulation, September 15, 2009; 120(11): 1011 - 1020. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. M. Siegel, W. Rich, E. C. Joseph, J. Linhardt, J. Knight, J. Khoury, and S. R. Daniels A 6-Month, Office-Based, Low-Carbohydrate Diet Intervention in Obese Teens Clinical Pediatrics, September 1, 2009; 48(7): 745 - 749. [Abstract] [PDF] |
||||
![]() |
K.-A. Le, M. Ith, R. Kreis, D. Faeh, M. Bortolotti, C. Tran, C. Boesch, and L. Tappy Fructose overconsumption causes dyslipidemia and ectopic lipid deposition in healthy subjects with and without a family history of type 2 diabetes Am. J. Clinical Nutrition, June 1, 2009; 89(6): 1760 - 1765. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. H. Moran Fructose and Satiety J. Nutr., June 1, 2009; 139(6): 1253S - 1256S. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. P. Bantle Dietary Fructose and Metabolic Syndrome and Diabetes J. Nutr., June 1, 2009; 139(6): 1263S - 1268S. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. J. Angelopoulos, J. Lowndes, L. Zukley, K. J. Melanson, V. Nguyen, A. Huffman, and J. M. Rippe The Effect of High-Fructose Corn Syrup Consumption on Triglycerides and Uric Acid J. Nutr., June 1, 2009; 139(6): 1242S - 1245S. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. L. Stanhope and P. J. Havel Fructose Consumption: Considerations for Future Research on Its Effects on Adipose Distribution, Lipid Metabolism, and Insulin Sensitivity in Humans J. Nutr., June 1, 2009; 139(6): 1236S - 1241S. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. Cirillo, Y. Y. Sautin, J. Kanellis, D.-H. Kang, L. Gesualdo, T. Nakagawa, and R. J. Johnson Systemic inflammation, metabolic syndrome and progressive renal disease Nephrol. Dial. Transplant., May 1, 2009; 24(5): 1384 - 1387. [Full Text] [PDF] |
||||
![]() |
L. Chen, L. J Appel, C. Loria, P.-H. Lin, C. M Champagne, P. J Elmer, J. D Ard, D. Mitchell, B. C Batch, L. P Svetkey, et al. Reduction in consumption of sugar-sweetened beverages is associated with weight loss: the PREMIER trial Am. J. Clinical Nutrition, May 1, 2009; 89(5): 1299 - 1306. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. Cirillo, M. S. Gersch, W. Mu, P. M. Scherer, K. M. Kim, L. Gesualdo, G. N. Henderson, R. J. Johnson, and Y. Y. Sautin Ketohexokinase-Dependent Metabolism of Fructose Induces Proinflammatory Mediators in Proximal Tubular Cells J. Am. Soc. Nephrol., March 1, 2009; 20(3): 545 - 553. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Barone, S. L. Fussell, A. K. Singh, F. Lucas, J. Xu, C. Kim, X. Wu, Y. Yu, H. Amlal, U. Seidler, et al. Slc2a5 (Glut5) Is Essential for the Absorption of Fructose in the Intestine and Generation of Fructose-induced Hypertension J. Biol. Chem., February 20, 2009; 284(8): 5056 - 5066. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. L Stanhope and P. J Havel Endocrine and metabolic effects of consuming beverages sweetened with fructose, glucose, sucrose, or high-fructose corn syrup Am. J. Clinical Nutrition, December 1, 2008; 88(6): 1733S - 1737S. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. J Melanson, T. J Angelopoulos, V. Nguyen, L. Zukley, J. Lowndes, and J. M Rippe High-fructose corn syrup, energy intake, and appetite regulation Am. J. Clinical Nutrition, December 1, 2008; 88(6): 1738S - 1744S. [Abstract] [Full Text] [PDF] |
||||
![]() |
N. Stefan, K. Kantartzis, and H.-U. Haring Causes and Metabolic Consequences of Fatty Liver Endocr. Rev., December 1, 2008; 29(7): 939 - 960. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Bogdanov, T. Jurendic, R. Sieber, and P. Gallmann Honey for Nutrition and Health: A Review J. Am. Coll. Nutr., December 1, 2008; 27(6): 677 - 689. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. H Halsted Perspectives on obesity and sweeteners, folic acid fortification and vitamin D requirements Fam. Pract., December 1, 2008; 25(suppl_1): i44 - i49. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. H. Cha, M. Wolfgang, Y. Tokutake, S. Chohnan, and M. D. Lane Differential effects of central fructose and glucose on hypothalamic malonyl-CoA and food intake PNAS, November 4, 2008; 105(44): 16871 - 16875. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. Livesey and R. Taylor Fructose consumption and consequences for glycation, plasma triacylglycerol, and body weight: meta-analyses and meta-regression models of intervention studies Am. J. Clinical Nutrition, November 1, 2008; 88(5): 1419 - 1437. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. H. Tetri, M. Basaranoglu, E. M. Brunt, L. M. Yerian, and B. A. Neuschwander-Tetri Severe NAFLD with hepatic necroinflammatory changes in mice fed trans fats and a high-fructose corn syrup equivalent Am J Physiol Gastrointest Liver Physiol, November 1, 2008; 295(5): G987 - G995. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. L. Rosenzweig, E. Ferrannini, S. M. Grundy, S. M. Haffner, R. J. Heine, E. S. Horton, and R. Kawamori Primary Prevention of Cardiovascular Disease and Type 2 Diabetes in Patients at Metabolic Risk: An Endocrine Society Clinical Practice Guideline J. Clin. Endocrinol. Metab., October 1, 2008; 93(10): 3671 - 3689. [Abstract] [Full Text] [PDF] |
||||
![]() |
O. Glushakova, T. Kosugi, C. Roncal, W. Mu, M. Heinig, P. Cirillo, L. G. Sanchez-Lozada, R. J. Johnson, and T. Nakagawa Fructose Induces the Inflammatory Molecule ICAM-1 in Endothelial Cells J. Am. Soc. Nephrol., September 1, 2008; 19(9): 1712 - 1720. [Abstract] [Full Text] [PDF] |
||||
![]() |
V. Douard and R. P. Ferraris Regulation of the fructose transporter GLUT5 in health and disease Am J Physiol Endocrinol Metab, August 1, 2008; 295(2): E227 - E237. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. R. Palmer, D. A. Boggs, S. Krishnan, F. B. Hu, M. Singer, and L. Rosenberg Sugar-Sweetened Beverages and Incidence of Type 2 Diabetes Mellitus in African American Women Arch Intern Med, July 28, 2008; 168(14): 1487 - 1492. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. A. Bazzano, T. Y. Li, K. J. Joshipura, and F. B. Hu Intake of Fruit, Vegetables, and Fruit Juices and Risk of Diabetes in Women Diabetes Care, July 1, 2008; 31(7): 1311 - 1317. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. G. Sanchez-Lozada, E. Tapia, P. Bautista-Garcia, V. Soto, C. Avila-Casado, I. P. Vega-Campos, T. Nakagawa, L. Zhao, M. Franco, and R. J. Johnson Effects of febuxostat on metabolic and renal alterations in rats with fructose-induced metabolic syndrome Am J Physiol Renal Physiol, April 1, 2008; 294(4): F710 - F718. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. H Song Review: Early-onset type 2 diabetes mellitus: a condition with elevated cardiovascular risk? The British Journal of Diabetes & Vascular Disease, March 1, 2008; 8(2): 61 - 65. [Abstract] [PDF] |
||||
![]() |
S. A Harrison and C. P. Day Benefits of lifestyle modification in NAFLD Gut, December 1, 2007; 56(12): 1760 - 1769. [Full Text] [PDF] |
||||
![]() |
T. Akhavan and G H. Anderson Effects of glucose-to-fructose ratios in solutions on subjective satiety, food intake, and satiety hormones in young men Am. J. Clinical Nutrition, November 1, 2007; 86(5): 1354 - 1363. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. Yasuda, R. Maiorano, R. M. Welch, D. D. Miller, and X. G. Lei Cecum Is the Major Degradation Site of Ingested Inulin in Young Pigs J. Nutr., November 1, 2007; 137(11): 2399 - 2404. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. J Johnson, M. S Segal, Y. Sautin, T. Nakagawa, D. I Feig, D.-H. Kang, M. S Gersch, S. Benner, and L. G Sanchez-Lozada Potential role of sugar (fructose) in the epidemic of hypertension, obesity and the metabolic syndrome, diabetes, kidney disease, and cardiovascular disease Am. J. Clinical Nutrition, October 1, 2007; 86(4): 899 - 906. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Mosdol, D. R Witte, G. Frost, M. G Marmot, and E. J Brunner Dietary glycemic index and glycemic load are associated with high-density-lipoprotein cholesterol at baseline but not with increased risk of diabetes in the Whitehall II study Am. J. Clinical Nutrition, October 1, 2007; 86(4): 988 - 994. [Abstract] [Full Text] [PDF] |
||||
![]() |
I. Aeberli, M. B Zimmermann, L. Molinari, R. Lehmann, D. l'Allemand, G. A Spinas, and K. Berneis Fructose intake is a predictor of LDL particle size in overweight schoolchildren Am. J. Clinical Nutrition, October 1, 2007; 86(4): 1174 - 1178. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Tiwari, V. K.M. Halagappa, S. Riazi, X. Hu, and C. A. Ecelbarger Reduced Expression of Insulin Receptors in the Kidneys of Insulin-Resistant Rats J. Am. Soc. Nephrol., October 1, 2007; 18(10): 2661 - 2671. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. S. Gersch, W. Mu, P. Cirillo, S. Reungjui, L. Zhang, C. Roncal, Y. Y. Sautin, R. J. Johnson, and T. Nakagawa Fructose, but not dextrose, accelerates the progression of chronic kidney disease Am J Physiol Renal Physiol, October 1, 2007; 293(4): F1256 - F1261. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Yoshida, N. M. McKeown, G. Rogers, J. B. Meigs, E. Saltzman, R. D'Agostino, and P. F. Jacques Surrogate Markers of Insulin Resistance Are Associated with Consumption of Sugar-Sweetened Drinks and Fruit Juice in Middle and Older-Aged Adults J. Nutr., September 1, 2007; 137(9): 2121 - 2127. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Dhingra, L. Sullivan, P. F. Jacques, T. J. Wang, C. S. Fox, J. B. Meigs, R. B. D'Agostino, J. M. Gaziano, and R. S. Vasan Soft Drink Consumption and Risk of Developing Cardiometabolic Risk Factors and the Metabolic Syndrome in Middle-Aged Adults in the Community Circulation, July 31, 2007; 116(5): 480 - 488. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. Monsivais, M. M Perrigue, and A. Drewnowski Sugars and satiety: does the type of sweetener make a difference? Am. J. Clinical Nutrition, July 1, 2007; 86(1): 116 - 123. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. F-F Chong, B. A Fielding, and K. N Frayn Mechanisms for the acute effect of fructose on postprandial lipemia Am. J. Clinical Nutrition, June 1, 2007; 85(6): 1511 - 1520. [Abstract] [Full Text] [PDF] |
||||
![]() |
W. Huang, N. Dedousis, and R. M. O'Doherty Hepatic steatosis and plasma dyslipidemia induced by a high-sucrose diet are corrected by an acute leptin infusion J Appl Physiol, June 1, 2007; 102(6): 2260 - 2265. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Montonen, R. Jarvinen, P. Knekt, M. Heliovaara, and A. Reunanen Consumption of Sweetened Beverages and Intakes of Fructose and Glucose Predict Type 2 Diabetes Occurrence J. Nutr., June 1, 2007; 137(6): 1447 - 1454. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. G. Sanchez-Lozada, E. Tapia, A. Jimenez, P. Bautista, M. Cristobal, T. Nepomuceno, V. Soto, C. Avila-Casado, T. Nakagawa, R. J. Johnson, et al. Fructose-induced metabolic syndrome is associated with glomerular hypertension and renal microvascular damage in rats Am J Physiol Renal Physiol, January 1, 2007; 292(1): F423 - F429. [Abstract] [Full Text] [PDF] |
||||
![]() |
K.-A. Le, D. Faeh, R. Stettler, M. Ith, R. Kreis, P. Vermathen, C. Boesch, E. Ravussin, and L. Tappy A 4-wk high-fructose diet alters lipid metabolism without affecting insulin sensitivity or ectopic lipids in healthy humans Am. J. Clinical Nutrition, December 1, 2006; 84(6): 1374 - 1379. [Abstract] [Full Text] [PDF] |
||||
![]() |
V. S Malik, M. B Schulze, and F. B Hu Intake of sugar-sweetened beverages and weight gain: a systematic review. Am. J. Clinical Nutrition, August 1, 2006; 84(2): 274 - 288. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. McAuley and J. Mann Thematic review series: Patient-Oriented Research. Nutritional determinants of insulin resistance J. Lipid Res., August 1, 2006; 47(8): 1668 - 1676. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. R Jacobs Jr Fast food and sedentary lifestyle: a combination that leads to obesity Am. J. Clinical Nutrition, February 1, 2006; 83(2): 189 - 190. [Full Text] [PDF] |
||||
![]() |
M. Bes-Rastrollo, A. Sanchez-Villegas, E. Gomez-Gracia, J A. Martinez, R. M Pajares, and M. A Martinez-Gonzalez Predictors of weight gain in a Mediterranean cohort: the Seguimiento Universidad de Navarra Study 1 Am. J. Clinical Nutrition, February 1, 2006; 83(2): 362 - 370. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Welsh and W. Dietz Sugar-Sweetened Beverage Consumption Is Associated With Weight Gain and Incidence of Type 2 Diabetes Clin. Diabetes, October 1, 2005; 23(4): 150 - 152. [Full Text] [PDF] |
||||
![]() |
Y. Wei, D. Wang, and M. J. Pagliassotti Fructose Selectively Modulates c-jun N-Terminal Kinase Activity and Insulin Signaling in Rat Primary Hepatocytes J. Nutr., July 1, 2005; 135(7): 1642 - 1646. [Abstract] [Full Text] [PDF] |
||||
![]() |
X.-L. Cui, A. M. Schlesier, E. L. Fisher, C. Cerqueira, and R. P. Ferraris Fructose-induced increases in neonatal rat intestinal fructose transport involve the PI3-kinase/Akt signaling pathway Am J Physiol Gastrointest Liver Physiol, June 1, 2005; 288(6): G1310 - G1320. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. Cordain, S B. Eaton, A. Sebastian, N. Mann, S. Lindeberg, B. A Watkins, J. H O'Keefe, and J. Brand-Miller Origins and evolution of the Western diet: health implications for the 21st century Am. J. Clinical Nutrition, February 1, 2005; 81(2): 341 - 354. [Abstract] [Full Text] [PDF] |
||||
![]() |
N. J Krilanovich Fructose misuse, the obesity epidemic, the special problems of the child, and a call to action Am. J. Clinical Nutrition, November 1, 2004; 80(5): 1446 - 1447. [Full Text] [PDF] |
||||
![]() |
Y. Wei and M. J. Pagliassotti Hepatospecific effects of fructose on c-jun NH2-terminal kinase: implications for hepatic insulin resistance Am J Physiol Endocrinol Metab, November 1, 2004; 287(5): E926 - E933. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Wu, E. Giovannucci, T. Pischon, S. E Hankinson, J. Ma, N. Rifai, and E. B Rimm Fructose, glycemic load, and quantity and quality of carbohydrate in relation to plasma C-peptide concentrations in US women Am. J. Clinical Nutrition, October 1, 2004; 80(4): 1043 - 1049. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. H. Schlenker, Y. Shi, J. Wipf, D. S. Martin, and C. K. Kost Jr. Fructose feeding and intermittent hypoxia affect ventilatory responsiveness to hypoxia and hypercapnia in rats J Appl Physiol, October 1, 2004; 97(4): 1387 - 1394. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. N. Gross, S. R. Farmer, and P. F. Pilch Glut4 Storage Vesicles without Glut4: Transcriptional Regulation of Insulin-Dependent Vesicular Traffic Mol. Cell. Biol., August 15, 2004; 24(16): 7151 - 7162. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Miyazaki, A. Dobrzyn, W. C. Man, K. Chu, H. Sampath, H.-J. Kim, and J. M. Ntambi Stearoyl-CoA Desaturase 1 Gene Expression Is Necessary for Fructose-mediated Induction of Lipogenic Gene Expression by Sterol Regulatory Element-binding Protein-1c-dependent and -independent Mechanisms J. Biol. Chem., June 11, 2004; 279(24): 25164 - 25171. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. de Graaf, W. A. Blom, P. A. Smeets, A. Stafleu, and H. F. Hendriks Biomarkers of satiation and satiety Am. J. Clinical Nutrition, June 1, 2004; 79(6): 946 - 961. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. L. Teff, S. S. Elliott, M. Tschop, T. J. Kieffer, D. Rader, M. Heiman, R. R. Townsend, N. L. Keim, D. D'Alessio, and P. J. Havel Dietary Fructose Reduces Circulating Insulin and Leptin, Attenuates Postprandial Suppression of Ghrelin, and Increases Triglycerides in Women J. Clin. Endocrinol. Metab., June 1, 2004; 89(6): 2963 - 2972. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. S Gross, L. Li, E. S Ford, and S. Liu Increased consumption of refined carbohydrates and the epidemic of type 2 diabetes in the United States: an ecologic assessment Am. J. Clinical Nutrition, May 1, 2004; 79(5): 774 - 779. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. A Bray, S. J. Nielsen, and B. M Popkin Consumption of high-fructose corn syrup in beverages may play a role in the epidemic of obesity Am. J. Clinical Nutrition, April 1, 2004; 79(4): 537 - 543. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. Wei, M. E. Bizeau, and M. J. Pagliassotti An Acute Increase in Fructose Concentration Increases Hepatic Glucose-6-Phosphatase mRNA via Mechanisms That Are Independent of Glycogen Synthase Kinase-3 in Rats J. Nutr., March 1, 2004; 134(3): 545 - 551. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. J. Havel Update on Adipocyte Hormones: Regulation of Energy Balance and Carbohydrate/Lipid Metabolism Diabetes, February 1, 2004; 53(90001): S143 - 151. [Abstract] [Full Text] |
||||
![]() |
T. J Vasankari Metabolic effects of dietary fructose Am. J. Clinical Nutrition, October 1, 2003; 78(4): 804 - 805. [Full Text] [PDF] |
||||
![]() |
P. J Havel, S. S Elliott, J. S Stern, N. L Keim, and K. Teff Reply to TJ Vasankari Am. J. Clinical Nutrition, October 1, 2003; 78(4): 805 - 806. [Full Text] [PDF] |
||||
![]() |
Y. Shimizu, M. Yamazaki, K. Nakanishi, M. Sakurai, A. Sanada, T. Takewaki, and K. Tonosaki Enhanced Responses of the Chorda Tympani Nerve to Sugars in the Ventromedial Hypothalamic Obese Rat J Neurophysiol, July 1, 2003; 90(1): 128 - 133. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. A. Bray Low-Carbohydrate Diets and Realities of Weight Loss JAMA, April 9, 2003; 289(14): 1853 - 1855. [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | SEARCH RESULT |