By Pam Harrison
WebMD Health News
March 08, 2017
Consumption of dairy products helps preserve bone-mineral density (BMD) in older adults, but only in the presence of vitamin D supplementation, a new cross-sectional analysis of the Framingham Osteoporosis Study (FOS) indicates.
Reporting in the Journal of Nutrition, Shivani Sahni, PhD, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, and colleagues note that an estimated 10 million Americans over the age of 50 have osteoporosis.
Osteoporosis prevention includes regular physical exercise and adequate intakes of calcium and vitamin D — dairy foods are good sources of these nutrients, but > 80% of the US population does not meet the recommended dairy intake of three servings/day, they add.
While previous research has suggested a positive link between milk intake and BMD, most has concentrated on younger individuals and did not consider other dairy foods with different nutritional profiles or total vitamin D intake. And randomized controlled trials to date have focused almost exclusively on calcium and vitamin D supplement use and not on dairy intake.
"Our hypothesis was that higher intake of all dairy foods, except cream, would be associated with higher BMD and lower BMD loss in this older population of men and women, but that vitamin D supplement users would realize greater benefits than nonusers," they explain.
Dairy Food Intake Alone Didn't Affect BMD
For this analysis, the sample from FOS included 628 men and women who had a valid food frequency questionnaire (FFQ) in 1988–1989 and at least one bone-density site measured at baseline and at a mean of 3.9 years later.
The mean age of the cohort was 75 years, and slightly over one-quarter of the cohort, at 27%, took vitamin D supplements.
Total milk intake was similar between those who took vitamin D supplements, at 6.3 servings per week, and non–vitamin D supplement users, at 5.8 servings per week. However, total calcium intake was higher among vitamin D users, at 966 mg per day, compared with 745 mg per day for non–vitamin D users.
And as would be expected, vitamin D intake was higher, at 591 IU per day in vitamin D supplement users, compared with nonusers, at 184 IU per day.
Dairy food intake was not associated with BMD overall or with 4-year percentage change in BMD.
Among vitamin D supplement users, higher milk, fluid dairy (milk and yogurt), and milk, yogurt, and cheese intakes were associated with higher lumbar spine BMD (P = .011 to 0.009), while there were no associations among non–vitamin D supplement users.
And among vitamin D supplement users, but not among nonusers, higher milk, yogurt, cheese intake was protective against trochanter BMD loss (P = .009).
Trochanter BMD was 0.23% greater for each additional serving of milk, yogurt, and cheese per week.
"The main findings from the current study showed that specific dairy foods appeared to be protective against trochanteric bone loss, but only among those with higher vitamin D intakes through supplements," Dr Sahni and colleagues note.
"These findings suggest that individuals who use vitamin D supplements may reap bone-protective benefits with higher dairy intakes," they conclude.
Don't Test, and Don't Overprescribe Vitamin D to Elderly
Meanwhile, experts at the recent American Academy of Dermatology meeting have warned that physicians can easily overprescribe toxic levels of vitamin D, sometimes 4000 to 10,000 IU a day, to the elderly, which can lead to adverse effects such as exacerbation of arthritis.
This is primarily driven by testing for vitamin D, which is likely unnecessary and in the elderly in particular can produce misleading results, Susan Roper, MD, a dermatologist with Countryside Dermatology and Laser Center in Clearwater, Florida, told attendees.
If there's any question a person isn't getting enough vitamin D from incidental sun exposure and diet, the answer is just to take one supplement a day; tests are unnecessary, added Barbara A Gilchrest, MD, a dermatologist with Massachusetts General Hospital in Boston.
The research was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health, the National Heart Lung and Blood Institute's Framingham Heart Study, an unrestricted institutional grant from the General Mills Bell Institute of Health and Nutrition, NIH's National Institute of Aging, and Friends of Hebrew SeniorLife. Dr Sahni has received institutional grants from General Mills Bell Institute of Health and Nutrition, PAI/Amgen, and Dairy Management. Disclosures for the coauthors are listed in the paper.