September 2018
The Lancet
published the result of the study
Prospective Urban Rural Epidemiology
(PURE). A large cohort study – of 136,384 individuals aged 35-70 years, enrolled in 21 countries on five continents and followed for more than nine years – that marks an important point in favor of the consumption of milk. (1)
The Lancet
, a study of 136,000 individuals
Using validated attendance questionnaires, country-specific, the researchers recorded the habitual intake–by each study participant–of milk and dairy products, including yogurt and cheese, which were further divided into whole and skimmed dairy products. Consumption frequencies were then correlated with death from major cardiovascular events (cardiovascular causes, nonfatal myocardial infarction, stroke, or heart failure).
The results indicate
that: a) whole milk intake (> 2 servings per day
vs
none) is associated with a lower risk of death from cardiovascular and other diseases; b) intake of milk and yogurt (> 1 servings per day
vs
none) is associated with lower risk; (c) cheese and butter intake are not significantly associated with clinical outcomes.
The authors conclude
that higher consumption of dairy products is found to be associated with lower risks of mortality from cardiovascular disease, particularly
stroke,
and suggest that dairy consumption should not be discouraged and perhaps should even be encouraged, especially in low- and middle-income countries.
Building on the results of this scientific work, it is incumbent on us to take stock of the age-old question that follows.
Is milk good or bad for you?
Basic premise.
, some people cannot take milk because of intolerances or food allergies. Beware, there is often much confusion between milk protein allergy and intolerance. It is essential to point out in this regard:
– Intolerance
means the inability to degrade lactose (milk sugar)
, as lactase, the enzyme essential for its breakdown, is not expressed in the intestine;
– for allergy means milk protein allergy, related to the production of antibodies to these proteins and linked to even very severe symptoms such as anaphylactic shock. Milk is definitely bad for these people.
Milk detractors
The China Study is undoubtedly the most famous text, internationally, where it is claimed that milk, and in particular the caseins present in it, may even be carcinogenic. (2)
The China Study
is a book published in 2005 by biochemist and nutritionist T. Colin Campbell, one of the leaders of the
China Project
. A very large epidemiological study – the result of collaboration between
Cornell University,
Chinese Academy of Preventive Medicine, Chinese Academy of Medical Sciences, and
Oxford University –
aimed at investigating the possible correlation between certain foods and the development of cardiovascular disease and cancer.
An experiment
in-vivo
on laboratory guinea pigs
is placed at the basis of Campbell’s assertions. Guinea pigs were given a diet consisting of 20 percent casein to one group of mice and 5 percent to another group. The guinea pigs had been given aflatoxin to induce tumor growth. In the second group of mice, the tumors that developed were significantly smaller than those in the mice in the first group. Based on this finding, Campbell concluded that casein might be “the most potent carcinogen ever discovered.”
The weaknesses
of Campbell’s theorem are obvious:
(a) the mouse experiment was based on the administration of casein and not milk of which this protein is only one of the components. Neglecting the identification in whey, by various scientific studies, of certain proteins that have anti-cancer properties instead;
(b) the study has serious methodological flaws. Because it relates a huge number of variables (367 with more than 8,000 different correlations) and this allows, with appropriate uses of statistics and in the absence of control studies, to prove almost any preconceived theory;
(c) the study did not generate published articles in scientific journals that were signed by all of its investigators and evaluated through the international method of
peer-review.
The scientific community
considers
The China Study
unreliable, for the reasons given and other critical aspects of it. So much so that the Italian Association for Cancer Research (AIRC) has published a document where it states that there are no scientific studies in favor of a diet totally devoid of proteins of animal origin, particularly dairy products. (3)
Scientific studies in favor of milk and dairy products
The study published in
Lancet
confirms what multiple studies have already indicated over the years. Milk is defined as a ‘nutrient,’ meaning a food with a high nutrient density-such as protein, vitamins and minerals-with the added advantage of having a low energy density. Numerous articles demonstrate the valuable role of calcium and the favorable relationship between dietary milk intake and bone health in various age groups from infancy to old age. (4,5,6)
The Guidelines for Healthy Nutrition in Italy suggest consumption of 2-3 servings of milk or yogurt per day. In line with the suggestions of the
Harvard University
, which indicates as optimal the consumption of a
serving size
Of milk per day (equal to 240 ml). (7) And it is useful to note how the reference portion used in the U.S. is different from that reported in the Italian Guidelines, which is about half (125 ml). (8)
Various research groups are investigating possible relationships between milk consumption and cancers, prostate cancer in particular. A fairly recent work, carried out with a model in-vivo, shows that the consumption of milk (skim or whole) does not promote the progression of existing prostate cancers and instead shows mild protective effects against the prostate by decreasing the expression of some tumor markers. (9)
A very recent study
, where researchers fed rodents a diet rich in complex carbohydrates but low in protein – using casein (yes, that’s it!) from cheese and milk as the protein source – shows that such a diet improves cardiometabolic health in mice and especially promotes health and biology of the hippocampus (area of the brain responsible for learning and memory) to a far greater extent than the low-calorie diet. (10)
Paola Palestini
Biochemistry Professor, University Milano-Bicocca
ADA master’s coordinator, Dietetic and Applied Nutrition
Bibliography
1. Dehghan M., Mente A., Rangarajan S., Sheridan P., Mohan V., et al., on behalf of the Prospective Urban Rural Epidemiology (PURE) study investigators. Association of dairy intake with cardiovascular disease and mortality in 21 countries from five continents (PURE): a prospective cohort study. Lancet 2018; 392: 2288-97.http://dx.doi.org/10.1016/S0140-6736(18)31812-9.
2.
The China Study
https://www.amazon.com/China-Study-Comprehensive-Nutrition-Implications/dp/1932100660.
3. AIRC. Is it true that, based on the China Study, there is scientific evidence to support a vegan diet to reduce the risk of cancer? Update July 7, 2015, http://www.airc.it/cancro/disinformazione/the-china-study/.
4. Rizzoli R1. Dairy products, yogurts, and bone health. Am J Clin Nutr. 2014 May;99(5 Suppl):1256S-62S.
5. Moschonis G The effects of a 30-month dietary intervention on bone mineral density: the Postmenopausal Health Study. Br J Nutr. 2010 Jul;104(1):100-7.
6. Cadogan J Milk intake and bone mineral acquisition in adolescent girls: randomized, controlled intervention trial. BMJ. 1997 Nov 15;315(7118):1255-60.
7. Harvard School of Public Health, The Nutrition Source. Calcium and Milk: What’s Best for Your Bones and Health? https://www.hsph.harvard.edu/nutritionsource/calcium-full-story/.
8. http://www.salute.gov.it/portale/documentazione/p6_2_2_1.jsp?id=652.
9. Bernichtein S., Pigat N., Capiod T., Boutillon F., Verkarre V., et al, High Milk Consumption Does Not Affect Prostate Tumor Progression in Two Mouse Models of Benign and Neoplastic Lesions. PLOS ONE 2015 doi:10.1371/journal.pone.0125423.
10. Wahl D., Solon-Biet SM., Wang Q-P., Cogger VC.,Simpson SJ. and Le Couteur DG. Comparing the Effects of Low-Protein and High-Carbohydrate Diets and Caloric Restriction on Brain Aging in Mice 2018, Cell Reports 25, 2234-2243 DOI: doi.org/10.1016/j.celrep.2018.10.070.
Associate Professor of Biochemistry at the Department of Medicine and Surgery, since 2000 at the University of Milan-Bicocca, since 2014 he has coordinated the master in Applied Nutrition and Dietetics (ADA) and is the holder of Biochemistry in numerous degree courses and specialization schools. She is a member of the scientific council of the POLARIS center (Dust in the Environment and Health Risk) of the University of Milan-Bicocca, for the study of environmental nano- and micro-particles and their impact on human health. She is the author of 75 papers - published in peer-rewiev international journals - on the impact of environmental factors (food and air pollution) on health. She co-author of the book 'Mamma mia diet' (ed. Hatherleigh, 2018), aimed at promoting the Mediterranean diet in the world.
