Revisiting dairy, calcium and vitamin D

By David Dunaief, M.D.

The prevalence of osteoporosis in the U.S. is increasing as the population ages, especially among women. Why is this important? Osteoporosis may lead to increased risk of fracture due to a decrease in bone strength (1). Hip fractures are most concerning, because they increase mortality risk dramatically. In addition, more than 50 percent of hip fracture survivors lose the ability to live independently (2).

That is what we know. But what about what we think we know?

The importance of drinking milk for strong bones has been drilled into us since we were toddlers. Milk has calcium and is fortified with vitamin D, so milk could only be helpful, right? Not necessarily.

The data is mixed, but studies indicate that milk may not be as beneficial as we have been led to believe. Even worse, it may be harmful. The operative word here is “may.”

We need Vitamin D and calcium for strong bones, but do supplements help prevent osteoporosis and subsequent fractures? Again, the data are mixed, but supplements may not be the answer for those who are not deficient.

Let’s look more closely at what the research tells us.

Milk and dairy

The results of a large, observational study involving men and women in Sweden showed that milk may actually be harmful (3). When comparing those who consumed three or more cups of milk daily to those who consumed less than one, there was a 93 percent increased risk of mortality in women between the ages of 39 and 74. There was also an indication of increased mortality based on dosage.

For every one glass of milk consumed there was a 15 percent increased risk of death in these women. There was a much smaller, but significant, three percent per glass increased risk of death in men. For both men and women, biomarkers that indicate higher levels of oxidative stress and inflammation were found in the urine.

This 20-year study was eye-opening. We cannot make any decisive conclusions, only associations, since it is not a randomized controlled trial. But it does get you thinking. The researchers surmise that milk has high levels of D-galactose, a simple sugar that may increase inflammation and ultimately contribute to this potentially negative effect.

Ironically, the USDA recommends that, from 9 years of age through adulthood, we consume about three cups of dairy per day (4). Prior studies show milk may not be beneficial for preventing osteoporotic fractures. Specifically, in a meta-analysis that used data from the Nurses’ Health Study for women and the Health Professionals Follow-up Study for men, neither men nor women saw any benefit from milk consumption in preventing hip fractures (5).

In a 2020 meta-analysis of an array of past studies, researchers concluded that increased consumption of milk and other dairy products did not lower osteoporosis and hip fracture risks (6).

Reconsidering calcium

Unfortunately, it is not only milk that may not be beneficial. In a meta-analysis involving a group of observational studies, there was no statistically significant improvement in hip fracture risk in those men or women ingesting at least 300 mg of calcium from supplements and/or food on a daily basis (7).

The researchers did not differentiate the types of foods containing calcium. In a group of randomized controlled trials analyzed in the same study, those taking 800 to 1,600 mg of calcium supplements per day also saw no increased benefit in reducing nonvertebral fractures. In fact, in four clinical trials the researchers actually saw an increase in hip fractures among those who took calcium supplements. A weakness of the large multivaried meta-analyses is that vitamin D baseline levels, exercise and phosphate levels were not taken into account.

What about vitamin D?

Finally, though the data is not always consistent for vitamin D, when it comes to fracture prevention, it appears it may be valuable. In a meta-analysis involving 11 randomized controlled trials, vitamin D supplementation resulted in a reduction in fractures (8). When patients were given a median dose of 800 IUs (ranging from 792 to 2,000 IUs) of vitamin D daily, there was a significant 14 percent reduction in nonvertebral fractures and an even greater 30 percent reduction in hip fractures in those 65 years and over. However, vitamin D in lower levels showed no significant ability to reduce fracture risk.

Where does that leave us?

Just because something in medicine is a paradigm does not mean it’s correct. Milk and dairy may be an example of this. No definitive statement can be made about calcium, although even in randomized controlled trials with supplements, there seemed to be no significant benefit. However, the patients in these trials were not necessarily deficient in calcium or vitamin D.

In order to get benefit from vitamin D supplementation to prevent fracture, older patients may need at least 800 IUs per day, which is the Institute of Medicine’s recommended amount for a population relatively similar to the one in the study.

Remember that studies, though imperfect, are better than tradition alone. Prevention and treatment therefore should be individualized, and deficiency in vitamin D or calcium should usually be treated, of course. Please, talk to your doctor before adding or changing any supplements.

References: 

(1) JAMA. 2001;285:785-795. (2) EndocrinePractice. 2020 May;26(supp 1):1-46. (3) BMJ 2014;349:g6015. (4) health.gov. (5) JAMA Pediatr. 2014;168(1):54-60. (6) Crit Rev Food Sci Nutr. 2020;60(10):1722-1737. (7) Am J Clin Nutr. 2007 Dec;86(6):1780-1790. (8) N Engl J Med. 2012 Aug. 2;367(5):481.

Dr. David Dunaief is a speaker, author and local lifestyle medicine physician focusing on the integration of medicine, nutrition, fitness and stress management. For further information, visit www.medicalcompassmd.com.