Does dairy really have an effect on cancer?

– Dr.Preeyati Chopra,

Medical Intern,

Government Medical College & Rajindra Hospital, Patiala.

As children, we’ve been told to drink milk at least twice daily even thrice.

So when I question the fact that consuming milk might affect the risk of cancer, it feels like a fundamental thing in my life shifted.

Before getting into all the nitty gritty details, let’s get some facts straight, what exactly comes under dairy products?

• Liquid milk is the most consumed, processed, and marketed dairy product.
• Fermented milk is obtained from the fermentation of milk using suitable microorganisms to reach a desired level of acidity. These include yogurt, dahi, etc.
• Cheeses are produced through the coagulation of milk protein (casein), which is separated from the milk’s whey. Cheese’s diverse characteristics derive from differences in the compositions and types of milk, processes applied and microorganisms used.
• Butter and ghee (every grandmother’s go-to!) are fatty milk products. Butter is produced by churning milk or cream and ghee is obtained by removing the water from butter.
• Condensed milk is obtained from the partial removal of water from whole or skimmed milk. Processing includes heat-treating and concentration.
• Dry milk or milk powder is obtained from the dehydration of milk and is usually in the form of powder or granules.
• Cream is the part of milk that is comparatively rich in milk fat.
• Whey products: Whey is the liquid part of the milk that remains after the separation of curd in cheese making.
• Casein is the principal protein in milk and is used as an ingredient in several products, including cheese, bakery products, paints, and glues. It is extracted from skimmed milk by precipitation with rennet or by harmless lactic acid-producing bacteria (1).

Now that we have our dairy products in order, let’s move on to the reason why milk and its products form a large chunk of our childhood.

Dairy products with their wide range of nutrients and vitamins not only help in building and maintaining our bone health and dental health in childhood, but they have also been associated with weight management, decreased cardiovascular risk, maintaining your blood pressure in a healthy range as well as keeping your gut microflora happy (2). Thus, establishing their beneficial nature for all age groups.

Cancer is a group of diseases that starts with the uncontrolled growth of a single cell which ultimately takes over your body. Over the years, hundreds and thousands of studies on the causal factors of cancer have been released to ascertain what exactly leads to cancer. Risk factors have been categorized into internal and external. Internal factors answer questions like: Do our genes put us at greater risk? If my uncle died of cancer, can I? So on and so forth. External factors on the other hand include our dietary habits, exposure to smoking and alcohol, and various chemicals in our day-to-do life (3).

Sometimes, even if we have some of the internal risk factors we don’t develop cancer because our external factors keep us safe but sometimes, our external take the driving seat and can play a major role in the development of cancer. (It’s all very complex, I know, but bear with me!)

So, should we totally eliminate drinking milk or eating dahi if we saw an article that says milk *might* be associated with cancer? ABSOLUTELY NO.

For one maybe thing (which technically involves a lot of other factors), reducing or stopping the consumption of milk is not justified. Dairy products have innumerable benefits to our health and growth via their mineral and nutrient-rich profile along with the healthy micro-organisms it helps maintain in our body.

In an 11-year prospective study in Chinese adults by Kakkoura MG et al, they concluded that people who consumed dairy products regularly were at greater risk of developing liver and breast cancer, and regular consumption was also associated with an increased risk of lymphoma (not statistically significant). There was no association between intake and colorectal cancer, prostate cancer, or any other type of cancer investigated in the study* (5).

In comparison to a report by World Cancer Research Fund/American Institute for Cancer Research, studies done on the western population, a higher risk of prostate cancer was seen and a lower risk of colorectal cancer was seen. (6)

The above example again indicates that a lot of factors are involved for a disease process to occur that not only depend on our diet but also our internal makeup.

Evidence published thus far has shown a minimal association of milk as a causal factor for cancer but on the other hand, the addition of such products to our diet is strongly associated with health benefits. For example, Fermented dairy products are a rich source of probiotics**. From reduction in pathological alterations to enhancing our immune system, probiotics offer a wide range of benefits. These have been used safely in foods and dairy products for over a hundred years. Recently, there has been increasing interest in their use to prevent, mitigate or treat specific diseases (7).

In summarizing, if I was asked should I include milk in my daily diet?

It would be a strong yes from my side.

*The full list of site-specific cancer types investigated by the study is as follows: bladder, cervical, colorectal, endometrial, female breast, kidney, laryngeal, leukemia, liver, lung, lymphoma, oesophageal, oral cavity, ovarian, pancreatic, prostate, and stomach.

** Probiotics are foods or supplements that contain live microorganisms intended to maintain or improve the “good” bacteria (normal microflora) in the body.  Prebiotics on the other hand is food (typically high-fiber foods) that act as food for human microflora. Prebiotics are used to improve the balance of these microorganisms.

 References

1. Dairy production and products: Types and characteristics. Fao.org. https://www.fao.org/dairy-production-products/products/types-and-characteristics/en/. Published 2022. Accessed August 17, 2022.
2. Health Benefits Of Dairy Products | Main Dairy Benefits. Dairy.com.au. https://www.dairy.com.au/health/dairy-health-benefits. Published 2022. Accessed August 17, 2022.
3. Lampe J. Dairy Products and Cancer. J Am Coll Nutr. 2011;30(sup5):464S-470S. doi:10.1080/07315724.2011.10719991
4. Timon C, O’Connor A, Bhargava N, Gibney E, Feeney E. Dairy Consumption and Metabolic Health. 2020. doi:10.20944/preprints202008.0609.v1
5. Kakkoura, M.G., Du, H., Guo, Y. et al. Dairy consumption and risks of total and site-specific cancers in Chinese adults: an 11-year prospective study of 0.5 million people. BMC Med 20, 134 (2022). https://doi.org/10.1186/s12916-022-02330-3
6. World Cancer Research Fund/American Institute for Cancer Research. Meat, Fish and Dairy Products and the Risk of Cancer. Continuous Update Project Expert Report 2018.
7. Doron S, Snydman D. Risk and Safety of Probiotics. Clinical Infectious Diseases. 2015;60(suppl_2):S129-S134. doi:10.1093/cid/civ085