On the benefits of milk, unfair verdicts

The study conducted by Dr. Feskanich that we chose to cite in our press review (see here) does nothing more than confirm how difficult it is to express definitive opinions on questions concerning the effect of specific foods or food groups on health in general or on specific diseases.

By way of commentary we report the review study conducted by Caroli and colleagues, entitled Invited review: Dairy intake and bone health: a viewpoint from the state of the art, published in J Dairy Sci. (2011 Nov;94(11):5249-62. doi: 10.3168/jds.2011-4578).

"Although studies supporting the beneficial effect of milk or calcium on bone health are predominant in the scientific literature, some authors express doubts or disagreement on this subject. Discordant data, especially on fracture risk, provide weak evidence of an unfavorable effect of consuming milk and dairy products. Much more often, discordant studies signify the absence of any effect of milk and dairy products on bone health. In this regard, some conclusions can be drawn. Milk and dairy products are an excellent source of calcium and other nutrients with important effects on bone health. The bioactive components of milk and dairy products may play an essential role in bone metabolism, as demonstrated by in vitro and in vivo studies on the acidic proteins of colostrum and the basic proteins of milk".

As further evidence of the discordance of the data cited by Caroli and colleagues, two very recent scientific works from different parts of the world reaffirm the positive effect of milk and dairy products on bone health.
In Nutrition Research and Practice (Nutr Res Pract. 2013;7(5):409-417) a review was published based on the analysis of data from a 2008-2009 surveillance program on the effects of consuming calcium, milk and dairy products and vitamin D on the risk of osteoporosis in Korean adults.
The risk of osteoporosis decreases significantly in relation to calcium intake, even after adjusting the data for sex, age, BMI, vitamin D, menstrual status and physical exercise. In fact, compared with those who consumed no milk and dairy products at all, the risk was 0.96 among those who consumed less than 1 serving of milk or dairy products per day and 0.71 among those who consumed more than one serving per day. The authors reaffirm the need to maintain a substantial consumption of milk and dairy products for the preservation of bone health and the prevention of osteoporosis in adults.
On the other side of the globe, therefore with a completely different genetic background, in the journal Nutrients (2013, 5, 2684-2707; doi:10.3390/nu5072684) a study appeared reporting the Polish experience on milk and dairy products, calcium and the possibility of preventing osteoporosis in women. The study showed that bone mineral density depends largely on the combined effect of dietary and non-dietary factors. These factors include age, the presence of the menstrual cycle and the consumption of abundant quantities of milk and dairy products in adulthood, as well as their daily consumption during childhood and adolescence. The non-modifiable factors nonetheless had a stronger effect than the dietary factors. The discussion emphasizes the importance of consuming milk and dairy products during childhood and adolescence, which has a significant impact on bone health even if intake during adulthood is not important.
This behavior is important in the development of prevention programs for at least two reasons: first, because it is during this period that peak bone mass is reached and —secondly— because it is during this period that eating habits are acquired.

Just as “one swallow does not make a summer,” a single scientific article is not enough to establish a scientific truth with certainty, least of all in the field of nutrition, and above all when it comes to epidemiological studies, which are therefore about association and not intervention, and thus not about cause and effect. Caution would therefore be in order before firing off a headline that already looks like a verdict… for now, an unjust one.

The Scientific Committee of Nutricity