Dairy? Is it so bad for your health?

Dairy products are a convenient source of calcium and vitamin D, but are there any health risks associated with eating and drinking them?

Saturated fat 

There has been concern that diary products, especially full fat ones, contain saturated fat and therefore could increase your risk of cardiovascular disease.

A recent study of dairy consumption in 25,000 people investigated the risk of cardiovascular disease, but found that moderate consumption was not associated with adverse risk. 

Hormones in milk

What about the hormones in milk? Some hormones are given to cows to increase milk production. There is inconclusive evidence that these are harmful for humans1, but to avoid any risk, it would be better to choose organic products instead.  

Cancer and dairy products

Does consumption of dairy products increase your risk of cancer? There has been growing concern that a signalling molecule called Insulin Like Growth Factor 1 (IGF1), which is naturally present in dairy products is associated with an increased risk of cancer. There is already evidence that consumption of animal products increases the risk of cancers such as colon and breast2, but there is mixed evidence as to whether this is due to dairy products or meat consumption, and more research is needed to answer this question. 

There is also mixed evidence that diary consumption and in particular milk, may increase the risk of prostate cancer in men. Recently a study has performed a meta-analysis (aggregate) looking at 172 independent studies and found that the hormone IGF1 (Insulin Like Growth Factor 1) naturally present in dairy products, could be the mechanism behind this association3. While consumption of dairy, in particular milk and cheese has been associated with an increased risk of liver cancer4

Fermented milk, Kefir, has been shown to have limited anti-cancer properties in the laboratory5, but how this evidence translates from exposing cultured tumour cells to Kefir, to ingestion and digestion of kefir in real life is not yet known. 

In summary

Dairy can be a convenient source of protein, calcium and vitamin D, but protein and calcium are also found in many other food including vegetables, tofu, seafood, and some beans. There is an increasing body of evidence that eating dairy products is associated with a small increase in risk of cancer. If you choose to cut down or out dairy there are now a large number of readily available diary-free alternatives. 

References

1.      Malekinejad, H. & Rezabakhsh, A. Hormones in Dairy Foods and Their Impact on Public Health – A Narrative Review Article. Iran. J. Public Health44, 742–758 (2015).

2.     Grasgruber, P., Hrazdira, E., Sebera, M. & Kalina, T. Cancer Incidence in Europe: An Ecological Analysis of Nutritional and Other Environmental Factors. Front Oncol8, 151 (2018).

3.     Harrison, S. et al.Does milk intake promote prostate cancer initiation or progression via effects on insulin-like growth factors (IGFs)? A systematic review and meta-analysis. Cancer Causes Control28, 497–528 (2017).

4.     Duarte-Salles, T. et al.Dairy products and risk of hepatocellular carcinoma: the European Prospective Investigation into Cancer and Nutrition. Int. J. Cancer135, 1662–1672 (2014).

5.     Sharifi, M. et al.Kefir: a powerful probiotics with anticancer properties. Med Oncol34, 183 (2017).

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