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Consuming dairy: healthy or not?

Many debates on using animals for food are ground in ethics or environmental topics. The question whether we should consume animal products, however, can also be asked from a scientific point of view. In this post we will explore the aspect of health:

  • Should we consume milk and other dairy products, based on the effects this has on personal-health?

Even though this sounds like a straightforward question, it may not be so simple to answer.

But I think it’s worth trying. Health, of course is a central part in happiness and well-being. And I personally believe that I need to investigate questions like these in order to be able to perceive myself as an honest and responsible human being.

The alternative of not looking into topics like these, implies to be wilfully ignorant. In other words: I owe it to myself.

Now, before diving into the topic, I encourage you to NOT just take my words for granted. After reading this post, keep absorbing information and reflecting. Ask questions. Investigate this topic from other perspectives. Stay curious. Stay sceptical.

Semantics (i.e. the meaning of relevant terms).

Milk

When I write milk in this article (unspecified), what I mean is: “milk from a cow or other domestic animal (e.g. goat)”. I make this clear because there are also plant-based milks, such as soy-milk, oat-milk, rice-milk and almond milk, which are produced without animal products and are therefore vegan-products.

Dairy

To use the definition by Meriam-Webster, dairy is “food (such as ice cream, cheese, or yogurt) made primarily of or from milk”.1 Some advice for those who think eggs are dairy: try to turn milk into eggs to prove your statement.

Claims and biases

There are many different opinions and studies that make health related-claims about dairy consumption, and it gets more difficult when you realise that a part of the studies are funded by companies that participate in the dairy industry. In other words, these companies have an interest in study results that favour dairy. The statistics with food/beverage industry-funded research show this clearly: research with industry funding is approximately 4-8 times more likely to be favorable to the financial interests of the sponsors than research without industry funding.2 This is an important potential bias that we should be aware of when formulating a conclusion.

And a potential personal bias should be recognised as well. I like milk, I like ice cream, I like yoghurt … I’ve eaten dairy all my life. When health-related disadvantages outweigh the advantages, I might have to conclude that I should stop or limit consuming dairy. That situation would have big implications for my daily life. So after recognising this, I should focus on limiting the impact of my personal habits and emotions on the results and conclusions.

With some important semantics and biases covered, let’s now take a look at some data on dairy consumption. Afterwards we will have look at studies that have investigated health-related effects of dairy consumption and draw some conclusions based on them.

Global dairy consumption

The United Nations Food and Agricultural Organization (FAO) has shown data on dairy consumption (and production). The average global milk consumption is 90kg/person/year, with highest averages (>200kg/person/year) in Northern America, Australia and Europe.3,4 This number includes the milk equivalents of dairy products, but excludes butter!

Image: Average milk consumption per capita (globally, 1970-2013).

Milk consumption per capita globally

And to get a better understanding of these numbers, let’s do a calculation for daily average consumption. Milk is about 1,03kg per liter.5 Therefore, 200kg of milk per year translated into liters of milk per day: (200/365)/1,03= 0,53 liter of milk per day.

So inhabitants of the abovementioned regions consume on average more than half a liter of milk every single day.

Exploring advantages

Let’s now have a look at what health-related claims are made, and what studies focused on these questions tell us.

Nutrients

Milk contains 18 of 22 essential nutrients, including calcium, phosphorus, and vitamin D, which are of especial importance for the skeleton.6 And also the instinctive thought that milk may be beneficial is not that strange when you realise the reason why cows and other mammals produce it. Namely, milk is produced to feed a new-born child and provide them with nutrients for development. We are drinking the milk from cows who were pregnant, have given birth, and are now triggered biologically to produce milk for their calves. While there are ethical questions that can arise from this, this background information is also important for understanding the rational of thinking about milk as a nutrient-rich drink.

Bones (?)

It has often been stated that milk consumption is beneficial for bones, that it is recommended to prevent fractures (and osteoporosis).7–9 This message has been widespread by the dairy industry and from adult to child. But when we look, most studies of fracture risk provide little or no evidence that milk or other dairy products benefit bone.10 A systematic review and meta-analysis (2019) looked at “Consumption of milk and dairy products and risk of osteoporosis and hip fracture”. They concluded that a greater intake of milk and dairy products was not associated with a lower risk of osteoporosis and hip fracture.11 Long-term studies show similar results. One study followed 75.000 women for 12 years and another study followed over 60 thousand women for 11 years. Both showed no protective effect of increased milk consumption on fracture risk.12,13 And 2 other meta- analyses of studies of milk or dairy consumption and fracture risk also showed no reduction in fracture risk with higher intakes of milk, dairy, or total dietary calcium.14,15 So we should be very sceptical about the claims put forward by the industry. One study even suggested milk consumption may be associated with a higher rate of death.6 (To be fair, this study did not make dietary recommendations based on this).

But the topic of bones and fracture risk is not all, there are other potential benefits we can investigate.

Cancer

Consuming dairy is said to decrease the risk of colorectal cancer. And when we look at multiple studies for verification, this claim seems to hold more water.

A meta-analysis found that milk and total dairy products decreased the risk of colorectal cancer, while cheese did not.16 The World Cancer Research Fund & American Institute for Cancer Research (WCRF/AICR) also concluded that milk probably decreases the risk of colorectal cancer.17,18 But it’s important to note here that the inverse association between dairy foods and colorectal cancer may largely be attributable to the protective effect of calcium on colorectal cancer. It has been shown that total calcium intake is associated with a statistically significant lower risk of colon cancer, independent on the source of intake.19 To summarize, there is strong evidence that consumption of dairy products, and consumption of calcium in general, both help to protect against colorectal cancer.18,20

Furthermore, there is some limited evidence that high milk intake may also decrease the risk of getting bladder cancer.17,21  

Exploring disadvantages

Now, let’s also have a look at some potential disadvantages of consuming milk or dairy.

Cancer

First of all, dairy and diets high in calcium may increase the risk of prostate cancer.17,18

A review of literature (2019) also concluded that according to the analysis of the available information, it is possible to establish a relationship between the consumption of dairy products and both initiation and progression of prostate cancer.22 Therefore, they also explicitly advised men to reduce or minimize consumption of dairy products.22 Based on the evidence for potential harm the WCRF/AICR also has not made a recommendation for consuming dairy products.18

Next, some have suggested that consuming dairy products may increase the risk of getting endometrium cancer. In a meta-analysis ‘All-dairy products’ consumption was shown to increase the risk of endometrial cancer.23

And when we look at cancer in total, we can also see benefits when dairy intake is reduced! A meta-analysis, for example, reports a significant protective effect of a vegan diet in respect to the total cancer incidence: vegan diet conferred a significant reduced risk of 15%.24

And others have reported that consuming dairy also increases the risk of ovarian cancer, autoimmune conditions (such as multiple sclerosis and type 1 diabetes), acne and some childhood ailments (such as cow milk allergy).10,25

The breadth of research in this area is far less than seen in other nutritional subcategories, such as that for meat.17 However, as we can see, there are many studies that show consuming dairy can cause us harm.

Do we need milk to stay healthy? Do the advantages outweigh the disadvantages?

When we look at the total global population, many people don’t have the biological ability to process dairy because of lactose intolerance/malabsorption. About 68% (!) of the global population has this, and when they would consume lactose (a sugar found in dairy products), this could lead to diarrhoea, nausea, flatulence, abdominal pain and other symptoms.26 So a global recommendation of consuming dairy is already out of the question!

The best of both worlds

From what we have seen, there are some advantages of calcium intake (i.e. lower risk of colorectal cancer), irrespective of source. While, on the other hand, we have disadvantages of dairy consumption (i.e. prostate cancer, but potentially also other types of cancer and conditions).

Based on this, when looking at health alone, consuming dairy is not recommended.

I think we should ideally aim for having the best of both worlds by not consuming dairy/milk, and paying more attention to levels of calcium intake from non-dairy sources.

So, what about calcium supplements? Are they a suitable replacement for the calcium levels? While they have been studied and have shown some beneficial results, calcium supplements can increase the risk of cardiovascular events.27 Thus, preferably dietary calcium should be obtained through sources like green leafy vegetables, legumes etc.

Conclusion

To summarize, milk and dairy products are currently consumed by a minority of the global population, are not necessary in the diet and can even be harmful to our personal health. In my opinion, it would therefore be ideal to consume a healthy dairy-free diet with enough nutrient-dense (including calcium-rich) foods.

I think we should try to meet our nutrient requirements without the health risks associated with dairy products.

  • Note 1: It is recommended to take vitamin B12 supplements when becoming dairy-free! Also, read about other advice and tips when trying to change your diet! You may need to compensate your milk/dairy consumption with other foods in order to remain getting enough nutrients.
  • Note 2: I fully understand that being able to wilfully decide what to eat and drink is a big privilege. Yet, specifically to those with the practical possibility of making a change, I want to say: let’s not get stuck in our routines while being ignorant about the effects our actions have on us personally, as well as on the environment and other beings around us. Also, why not question and investigate this topic for yourself in more detail? Wonder, explore and reflect! 

Thanks for reading.

References:

  1. Dairy | Definition of Dairy by Merriam-Webster [Internet]. Available from: https://www.merriam-webster.com/dictionary/dairy
  2. Industry funding: Pros and cons | Michigan Today [Internet]. Available from: https://michigantoday.umich.edu/2016/01/18/industry-funding-pros-cons/
  3. Meat and Dairy Production – Our World in Data [Internet]. Available from: https://ourworldindata.org/meat-production#milk-production-across-the-world
  4. FAOSTAT [Internet]. Available from: http://www.fao.org/faostat/en/#data/FBS
  5. Density of Milk – The Physics Factbook [Internet]. Available from: https://hypertextbook.com/facts/2002/AliciaNoelleJones.shtml
  6. Michaëlsson K, Wolk A, Langenskiöld S, Basu S, Lemming EW, Melhus H, et al. Milk intake and risk of mortality and fractures in women and men: Cohort studies. BMJ. 2014 Oct 27;349.
  7. 10 tips on how to eat more calcium – Better Health Channel [Internet]. Available from: https://www.betterhealth.vic.gov.au/health/ten-tips/10-tips-on-how-to-eat-more-calcium
  8. Them bones, them bones, need calcium (TV Advert) – YouTube [Internet]. Available from: https://www.youtube.com/watch?v=Ygf0gRQsUb4
  9. 3 Ways to Build Strong Bones (for Parents) – Nemours KidsHealth [Internet]. Available from: https://kidshealth.org/en/parents/strong-bones.html
  10. Lanou AJ. Should dairy be recommended as part of a healthy vegetarian diet? Counterpoint. Am J Clin Nutr [Internet]. 2009 May 1;89(5):1638S-1642S. Available from: https://academic.oup.com/ajcn/article/89/5/1638S/4596954
  11. Malmir H, Larijani B, Esmaillzadeh A. Consumption of milk and dairy products and risk of osteoporosis and hip fracture: a systematic review and Meta-analysis. Crit Rev Food Sci Nutr [Internet]. 2019;0(0):1–16. Available from: https://doi.org/10.1080/10408398.2019.1590800
  12. Michaëlsson K, Melhus H, Bellocco R, Wolk A. Dietary calcium and vitamin D intake in relation to osteoporotic fracture risk. Bone. 2003;32(6):694–703.
  13. Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Milk, dietary calcium, and bone fractures in women: A 12-year prospective study. Am J Public Health. 1997;87(6):992–7.
  14. Kanis JA, Johansson H, Oden A, De Laet C, Johnell O, Eisman JA, et al. A meta-analysis of milk intake and fracture risk: Low utility for case finding. Osteoporos Int. 2005;16(7):799–804.
  15. Bischoff-Ferrari HA, Dawson-Hughes B, Baron JA, Kanis JA, Orav EJ, Staehelin HB, et al. Milk intake and risk of hip fracture in men and women: A meta-analysis of prospective cohort studies. J Bone Miner Res. 2011;26(4):833–9.
  16. Aune D, Lau R, Chan DSM, Vieira R, Greenwood DC, Kampman E, et al. Dairy products and colorectal cancer risk: A systematic review and meta-analysis of cohort studies. Ann Oncol [Internet]. 2012;23(1):37–45. Available from: http://dx.doi.org/10.1093/annonc/mdr269
  17. Abid Z, Cross AJ, Sinha R. Meat, dairy, and cancer. Am J Clin Nutr [Internet]. 2014 Jul 1;100(suppl_1):386S-393S. Available from: https://academic.oup.com/ajcn/article/100/suppl_1/386S/4576503
  18. World Cancer Research Fund/American Institute for Cancer Research. Diet, Nutrition, Physical Activity and Cancer: a Global Perspective [Internet]. Continuous Update Project Expert Report 2018. 2018. 1–53 p. Available from: http://gco.iarc.fr/today%0Adietandcancerreport.org
  19. Zhang X, Keum N, Wu K, Smith-Warner SA, Ogino S, Chan AT, et al. Calcium intake and colorectal cancer risk: Results from the nurses’ health study and health professionals follow-up study. Int J Cancer. 2016 Nov 15;139(10):2232–42.
  20. Aicr, WCRF. Summary of conclusions – Full evidence matrix. 2018; Available from: https://www.wcrf.org/sites/default/files/Matrix-for-all-cancers-A3.pdf
  21. Mao QQ, Dai Y, Lin YW, Qin J, Xie LP, Zheng XY. Milk consumption and bladder cancer risk: A meta-analysis of published epidemiological studies. Nutr Cancer. 2011;63(8):1263–71.
  22. Vasconcelos A, Santos T, Ravasco P, Neves PM. Dairy products: Is there an impact on promotion of prostate cancer? A review of the literature. Vol. 6, Frontiers in Nutrition. Frontiers Media S.A.; 2019. p. 62.
  23. Jeyaraman MM, Abou-Setta AM, Grant L, Farshidfar F, Copstein L, Lys J, et al. Dairy product consumption and development of cancer: An overview of reviews. Vol. 9, BMJ Open. BMJ Publishing Group; 2019. p. e023625.
  24. Dinu M, Abbate R, Gensini GF, Casini A, Sofi F. Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies. Crit Rev Food Sci Nutr. 2017;57(17):3640–9.
  25. Dai R, Hua W, Chen W, Xiong L, Li L. The effect of milk consumption on acne: a meta-analysis of observational studies. J Eur Acad Dermatology Venereol. 2018;32(12):2244–53.
  26. Storhaug CL, Fosse SK, Fadnes LT. Country, regional, and global estimates for lactose malabsorption in adults: a systematic review and meta-analysis. Lancet Gastroenterol Hepatol. 2017 Oct 1;2(10):738–46.
  27. Veettil SK, Ching SM, Lim KG, Saokaew S, Phisalprapa P, Chaiyakunapruk N. Effects of calcium on the incidence of recurrent colorectal adenomas. Vol. 96, Medicine (United States). Lippincott Williams and Wilkins; 2017.

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