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LETTERS TO THE EDITOR |
Department of Pediatrics
Nihon University School of Medicine
30-1, Oyaguchi-kamimachi
Itabashi-ku
Tokyo 173-8610
Japan
E-mail: tomo{at}med.email.ne.jp
Dear Sir:
Black et al (1) studied prepubertal children who had a long history of avoiding consumption of cow milk and found that such children tend to have short stature and high adiposity. Blanaru et al (2) confirmed that dietary arachidonic acid alters bone mass in piglets fed cow milk–based formula. We are very interested in their results because in a previous prospective study, we examined the effect of cow milk consumption on longitudinal height gain in children (3).
The subjects were 122 children (60 boys and 62 girls) aged 9.5 ± 0.2 y (
± SD). Standing height and weight were measured, and relative weight was obtained according to the standard weight for sex, age, and height. Three years later, we recruited the subjects for the second part of the study, which included anthropometric measurements and the questionnaire about cow milk consumption. The question was "How much cow milk do you usually drink a day?" The possible answers were "<250 mL," "250–500 mL," "500–1000 mL," and ">1000 mL." We investigated the relation between cow milk consumption and longitudinal changes in height, weight, and relative weight.
Ninety-two children (47 boys and 45 girls; 75.4% of the original sample) volunteered to participate in the second series of examinations. There were no significant differences in mean height, weight, or relative weight between the participants and the nonparticipants at the first examination. The participants were divided into 2 subgroups according to cow milk consumption: high consumption (>500 mL/d; 16.5%) and low consumption (<500 mL/d; 83.5%). The 3-y changes in height, weight, and relative weight in the high- and low-consumption groups were 18.8 ± 0.5 and 21.3 ± 1.1 cm, 13.3 ± 0.5 and 13.3 ± 0.8 kg, and –2.6 ± 0.8% and –5.6 ± 2.9%, respectively. The difference between the 2 groups was statistically significant for height (P = 0.042, Mann-Whitney U test) but not for weight or relative weight.
Several previous studies showed an effect of milk on height gain in pubertal children. In 1984 Takahashi (4) reported an acceleration of growth in Japan from the 1950s and suggested the importance of milk consumption. And this increase in height was prominent during puberty. In a cross-sectional study, Jirapinyo et al (5) reported that milk intake and parents' height contributed to adolescent height in females. Bonjour et al (6) found that prepubertal girls who consumed a diet including calcium-enriched foods grew in height in a randomized, double-blind, placebo-controlled study. In our longitudinal study, the mean height gain in the high-consumption group was higher than that in the low-consumption group, and the difference in height gain between the 2 groups was 2.5 cm/3 y.
Calcium itself has an important role in bone health, and many studies have shown the contribution of cow milk or dairy products to bone mass and bone mineral content. However, cow milk may have other components that promote bone health. Insulin-like growth factor I, which is present in much higher concentrations in cow milk than in human milk, is important for bone mineral accrual on periosteal surfaces. It is relatively stable to both heat and acidic conditions; therefore, it survives the conditions of commercial milk processing (7). Milk whey protein, especially milk basic protein, was reported to promote bone formation and to suppress bone resorption, and daily supplementation with milk basic protein significantly increases bone mineral density independently of dietary intake of minerals and vitamins (8). In addition, Blanaru et al (2) showed that whole-body bone mineral content was elevated in piglets fed arachidonic acid and that liver arachidonic acid was positively related to plasma insulin-like growth factor I and calcitriol. Furthermore, transforming growth factor ß2 was also well preserved in human milk after holder pasteurization at 56.5 °C (9). Transforming growth factor ß2 inhibits the differentiation of human adipocyte precursor cells and reduces the activity of the lipogenic enzyme glycero-3-phosphate dehydrogenase (10). This may explain why Black et al (1) found a high proportion of obese children among the milk-avoiding children in their study. In our longitudinal study, the change in relative weight in the high-consumption group was lower than that in the low-consumption group. Cow milk may also have some effect on adipose tissue.
In summary, in our prospective study, we observed a height gain in the children who consumed a high amount of cow milk. Milk is regarded as the best nutritional support for neonatal growth and development. In pubertal children, cow milk may also be an important nutrient for growth and for achieving optimal bone mass to prevent osteoporosis in later life. Finally, height gain in children may depend not only on the calcium in cow milk but also on some of its bioactive components.
REFERENCES
This article has been cited by other articles:
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  C. S. Berkey, H. R. H. Rockett, W. C. Willett, and G. A. Colditz Milk, Dairy Fat, Dietary Calcium, and Weight Gain: A Longitudinal Study of Adolescents Arch Pediatr Adolesc Med, June 1, 2005; 159(6): 543 - 550. [Abstract] [Full Text] [PDF]
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