By Mark Messina, PhD, MS
Research suggests that the type of milk consumed may modestly impact childhood growth, although this effect most likely will be impacted by overall diet.1 However, there is no evidence to suggest that cow’s milk has advantages over other protein-rich milks like fortified soymilk despite the results of new research.
The research in question is a Canadian cross-sectional epidemiologic study that looked at height among children aged 24 to 72 months (mean age 38 ± 14 months). The researchers found that children who drank non-cow’s milk (including plant milks and goat’s milk) had slightly smaller heights on average. Of the 5,034 children in the study, 397 consumed both cow’s milk and non-cow’s milk, 156 consumed no milk of any type, 246 (less than 5% of the study population) consumed only non-cow’s milk. The majority of children in the study, 4,235 drank cow’s milk exclusively.
For each daily cup of non-cow’s milk consumed, children were 0.16 inch shorter. The height difference for three-year-olds who consumed three cups of non-cow’s milk per day was estimated to be ~0.6 inches compared to children who drank three cups of cow’s milk, although this finding was not statistically significant. The authors of this study suggested that the difference in height could be due to the higher protein content of cow’s milk and because cow’s milk increases insulin-like growth factor I (IGF-1) levels. IGF-1 is a hormone produced by the liver that stimulates growth.
These findings need to be viewed with caution for a number of reasons. First, cross-sectional studies provide only a snapshot of characteristics of a population at any point in time. For this reason, they carry much less weight than prospective studies. In addition, this study provided no information on other dietary factors that may contribute to height. It is likely that children consuming non-cow’s milk have considerably different diets overall compared to those who drink cow’s milk. The study also did not differentiate among types of non-cow’s milk.
Since the authors suggested that the protein content of milks may have contributed to the differences in height, it would be important to look specifically at children consuming high-protein milks like soymilk versus other plant milks that are often lower in protein. The protein content of soymilk is similar to that of cow’s milk and both soy protein and milk protein are high quality proteins.2 Other plant milks such as rice and nut milks are very low in protein and the quality of the protein is poor.2,3 This point is particularly important because the protein requirements of those consuming plant-based diets may be increased.4,5
Furthermore, the other explanation offered by the authors for the differences in height between users of cow’s and non-cow’s milk, that the former increases IGF-1 levels, isn’t applicable to soymilk. Clinical studies in adults show that soymilk leads to similar circulating levels of IGF-1 as dairy protein.6
Interestingly, one study found that among a group of female omnivores, vegetarians, and vegans, although soy protein was not correlated with IGF-I concentrations in the population as a whole, it was significantly associated with serum IGF-I concentration among vegan women.7 In addition, among vegan women who consumed the most soymilk IGF-1 levels were 28% higher than among those who did not drink soymilk.7
Overall, findings suggest that type of milk consumed may impact childhood growth to a modest degree, although this effect most likely will be impacted by overall diet. However, there is no evidence to suggest that cow’s milk has advantages over other protein-rich milks like soymilk.
Many studies have looked at the effects of vegetarian diets on growth and development. According to a recent comprehensive review of the research, the majority of these studies indicate that “body weight, body height, and other anthropometric measures of infants, children, and adolescents on vegan or vegetarian diets were in the range of or slightly below the references, or similar to omnivorous control groups.” In its position statement on vegetarian diets, the Academy of Nutrition and Dietetics (AND) states: “Well-planned vegan, lacto-vegetarian, and lacto-ovo-vegetarian diets are appropriate, and they satisfy the nutrient needs and promote normal growth at all stages of the life cycle, including pregnancy and lactation, infancy, childhood, adolescence, older adulthood, and for athletes.” 8,9
- Morency ME, Birken CS, Lebovic G, et al. Association between noncow milk beverage consumption andchildhood height. Am J Clin Nutr. 2017.
- Hughes GJ, Ryan DJ, Mukherjea R, Schasteen CS. Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: Criteria for evaluation. J Agric Food Chem. 2011;59:12707-12.
- Singhal S, Baker RD, Baker SS. A comparison of the nutritional value of cow’s milk and nondairy beverages. J Pediatr Gastroenterol Nutr. 2017;64:799-805.
- Mangels R, Messina V, Messina M. The Dietitian’s Guide to Vegetarian Diets. 3rd ed. Sudbury, MA: Jones and Bartlett; 2011.
- Mangels AR, Messina V. Considerations in planning vegan diets: infants. J Am Diet Assoc. 2001;101:670-7.
- Messina M, Gleason C. Evaluation of the potential antidepressant effects of soybean isoflavones. Menopause. 2016;23:1348-60.
- Allen NE, Appleby PN, Davey GK, Kaaks R, Rinaldi S, Key TJ. The associations of diet with serum insulin-like growth factor I and its main binding proteins in 292 women meat-eaters, vegetarians, and vegans. Cancer Epidemiol Biomarkers Prev. 2002;11:1441-8.
- Schurmann S, Kersting M, Alexy U. Vegetarian diets in children: a systematic review. Eur J Nutr. 2017.
- Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. Journal of the Academy of Nutrition and Dietetics. 2016;116:1970-80.