Is Dairy Scary?

Is Dairy Scary?

Milk and milk products are popularly enjoyed as a good source of calcium and vitamin D.

In contrast, critics of dairy products (for medical reasons, rather than ethical, which is another matter entirely and beyond the scope of this article) point to risks of cancer, heart disease, and—counterintuitively—osteoporosis. We’ll focus more on the former, but touch on the latter two before closing.

Dairy & Cancer

Evidence is highly conflicting. There are so many studies with so many different results. This is partially explicable by noting that not only is cancer a many-headed beast that comes in more than a hundred different forms and all or any of them may be affected one way or another by a given dietary element, but also… Not all milk is created equal, either!

Joanna Lampe, of the Public Health Sciences division, Fred Hutchinson Cancer Research Center in Seattle, writes:

❝Dairy products are a complex group of foods and composition varies by region, which makes evaluation of their association with disease risk difficult. For most cancers, associations between cancer risk and intake of milk and dairy products have been examined only in a small number of cohort studies, and data are inconsistent or lacking❞

In her systematic review of studies, she noted, for example, that:

• Milk and dairy products contain micronutrients and several bioactive constituents that may influence cancer risk and progression
• There’s probable association between milk intake and lower risk of colorectal cancer
• There’s a probable association between diets high in calcium and increased risk of prostate cancer
• Some studies show an inverse association between intake of cultured dairy products and bladder cancer (i.e., if you eat yogurt you’re less likely to get bladder cancer)

Since that systemic review was undertaken, more research has been conducted, and the results are… Not conclusive, but converging towards a conclusion:

• Dairy products can increase or decrease cancer risk
• The increase in cancer risk seems strongest when milk is consumed in quantities that result in too much calcium. When it comes to calcium, you can absolutely have too much of a good thing—just ask your arteries!
• The decrease in cancer seems to be mostly, if not exclusively, from fermented dairy products. This usually means yogurts. The benefit here is not from the milk itself, but rather from the gut-friendly bacteria.

You may be wondering: “Hardened arteries, gut microbiome health? I thought we were talking about cancer?” and yes we are. No part of your health is an island unrelated to other parts of your health. One thing can lead to another. Sometimes we know how and why, sometimes we don’t, but it’s best to not ignore the data.

The bottom line on dairy products and cancer is:

• Consuming dairy products in general is probably fine
• Yogurt, specifically, is probably beneficial

Dairy and Heart Disease

The reason for the concern is clear enough: it’s largely assumed to be a matter of saturated fat intake.

The best combination of “large” and “recent” that we found was a three-cohort longitudinal study in 2019, which pretty much confirms what was found in smaller or less recent studies:

• There is some evidence to suggest that consumption of dairy can increase all-cause mortality in general, and death from (cancer and) cardiovascular disease in particular
• The evidence is not, however, overwhelming. It is marginal.

Dairy and Osteoporosis

Does dairy cause osteoporosis? Research here tends to fall into one of two categories when it comes to conclusions, so we’ll give an example of each:

1. “Results are conflicting, saying yes/no/maybe, and basically we just don’t know”
2. “Results are conflicting, but look: cross-sectional and case-control studies say yes; cohort studies say maybe or no; we prefer the cohort studies”

See them for yourself:

1. Osteoporosis: Is milk a kindness or a curse?
2. Consumption of milk and dairy products and risk of osteoporosis and hip fracture

Conclusion: really, the jury is very much still out on this one

Summary:

• Moderate consumption of dairy products is almost certainly fine
• More specifically: it probably has some (small) pros and some (small) cons
• Yogurt is almost certainly healthier than other dairy products, and is almost universally considered a healthy food (assuming not being full of added sugar etc, of course)
• If you’re going to have non-dairy alternatives to milk, choose wisely!

That’s all we have time for today, but perhaps in a future edition we’ll do a run-down of the pros and cons of various dairy alternatives!