A study of two large populations of Swedish men and women suggests that a sizable intake of milk was associated with higher risk of death and with a higher risk of fractures in women (but not in men). The associations appeared to be stronger in women than men. The study, published in the British Medical Journal, tracked 106,000 Swedish men and women for up to 23 years. The researchers added that we should be cautious in interpreting the results because of the nature of the study, which cannot prove causality.
The researchers suspect that the lactose found in milk is the source of the problem because other fermented dairy products, such as yogurt, sour cream, buttermilk and cheese, did not produce the same result. A byproduct of the digestion of the lactose is called D-galactose. This byproduct can increase oxidative stress, which has been linked to aging, cardiovascular disease and cancer in animals. As people age, their natural ability to balance oxidative stress is reduced, compounding the imbalance. In a subset of participants in both studies they found that milk intake was positively associated with 8‑iso‑PGF2α (an oxidative stress marker in the urine) in both sexes, and with serum interleukin 6 (a marker of systemic inflammation) in men.
What can you do
Because there are inherent challenges in attributing cause and effect based on an observational study, we should be cautious in the interpretation of the results. Additionally, the biggest effects were seen in individuals who drank more than 3 glasses of milk daily, with little-or-no effect on most endpoints in those who drank only 1-2 glasses of milk daily. On the other hand, the analysis appears sound and the mechanism plausible.
The study findings apply only to older adults — age 45+. For children, milk is still a great source of calcium during bone building years.
Adults need between 1,000 and 1,200 mg of calcium a day:
- If you currently consume 3+cups of milk per day, consider moderating your milk intake
- Consider lactose-free options, including other milk sources, such as soy and almond milk, that do not contain lactose or D-galactose
- Choose cheese and yogurt as a healthier high-calcium food
How can you be sure
Use the calcium rule of 300 to assess your daily intake.
Posted: 12/7/2016; Revised: 12/1/19.
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