| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
LETTER TO THE EDITOR |
11 Willard Road
Weston, MA
E-mail: pestep{at}post.harvard.edu
Dear Sir:
In their recent article in the Journal, Drewnowski and Bellisle (1) correctly pointed out several issues of importance in the study of the contribution of liquid sugar energy to rising rates of obesity; however, they overlooked some possibly even more important issues. They pointed out that the sugar contents of soft drinks, fruit juice drinks, some milks, and meal replacement (MR) shakes are comparable, and they cited studies showing MR shakes to be effective for weight loss. They implied that these facts should be considered as evidence that the physiologic effects of sugary beverages are not to blame for obesity; however, milks and typical MR shakes differ in numerous important ways from beverages providing 100% of energy in the form of sugar.
According to the Food and Agriculture Organization of the United Nations, average countrywide protein intakes range from 
11% to 14% of total dietary energy in countries with serious obesity problems (2), and all of the weight-loss studies cited by Drewnowski and Bellisle and by their primary references provide MR shakes with protein amounts that equal or exceed the upper end of these levels, ranging from 13% (3) to 67% (4, 5) of energy. These facts are relevant, because several studies have shown that protein not only induces but also prolongs satiety more than do either carbohydrates or fats, and these effects may be mediated through circulating concentrations of peptide YY (PYY) (6). Furthermore, these MR shakes provide protein, fat, and fiber in a form that is somewhat viscous and inseparable from the sugar. Fruit juice drinks and soft drinks are consumed with meals, but they are also consumed between meals, and all calories come in the form of sugar. In other words, MR shakes are necessarily accompanied by average-to-very-high concentrations of protein, whereas fruit juices and soft drinks—the primary culprits with respect to the rising rates of obesity—are not. MR shakes also contain fiber, and, although the role of fiber in weight loss is complex, existing bulk in distal portions of the gut tends to increase plasma concentrations of PYY after the ingestion of a liquid meal, as reported by van Hoek et al (7) (that study was, however, statistically underpowered).
Most of the successful weight-loss studies cited by Drewnowski and Bellisle involve milk (8) or milk-based MR shakes, and these beverages differ from fruit juice and soft drinks in another significant respect: lactose content. In fact, these MR shakes, especially those high in sugar, provide large amounts of lactose. Drewnowski and Bellisle stated the lactose content of MR shakes provided in the study of Yip et al (9)—17% of total energy and 34% of sugar energy from lactose—and they noted that the glucose and insulin responses did not differ between subjects consuming an MR shake and those consuming a solid breakfast that was assumed to be isocalorically equivalent (9). However, if the ethnic composition of the Los Angeles–based cohort of Yip et al was similar to the local ethnic composition, then possibly more than half of the participants were not digesting or absorbing significant amounts of lactose, which amount to 11 g of the sugar energy per replaced meal, or about one-third of the sugar energy (10, 11). Furthermore, not only was sugar energy greatly reduced for lactose nondigesters, but protein energy was very high for all participants; lactose digesters derived 30% of calories from protein in these MR shakes, and this proportion rose to 39% for nondigesters, or triple the typical protein intake.
The study of Yip et al was 1 of 5 studies performed in the United States used in the meta-analysis cited by Drewnowski and Bellisle, and the sixth study was based in Ulm, a city in southwestern Germany (12). Milk-based Slim-Fast MR shakes (Unilever, Englewood, NJ) were used in the Ulm study and in most US studies; approximately one-third of the sugar calories of those shakes are lactose. It is estimated that lactase nonpersistence occurs in about one-quarter to one-third of the overall population in the United States nationwide (with higher rates in large cities that have disproportionate populations of Asians, blacks, Hispanics, or all 3 groups) and in about one-quarter of the population of southwestern Germany (11, 13). Furthermore, lactase production appears to be trimodal, with heterozygotes (who are a large majority of the lactose digesters in the United States and Germany) producing an intermediate amount of lactase and possibly absorbing a lower percentage of energy from lactose than do homozygotes (14). And what happens to undigested lactose? It is fermented in the gut essentially as dietary fiber, sometimes causing gas and discomfort, but also possibly improving control of blood glucose, insulin, and body weight, much as do other fermentable fibers (15, 16).
In conclusion, despite their similar sugar contents, many fruit juice drinks and soft drinks are different in many respects from protein- and fiber-rich milk-based MR shakes, and these general types of differences have been shown in many studies to influence the physiologic variables focused on by Drewnowski and Bellisle.
ACKNOWLEDGMENTS
The author has a financial interest in Smooth Energy Nutritionals (St Louis, MO), a provider of meal replacement nutritional products.
REFERENCES
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
