New analyzes from the large prospective study called VITAL cast further doubt on the value of routine vitamin D and omega-3 fatty acid supplements for generally healthy people.
Daily administration of 2,000 IU of vitamin D, in many cases in addition to the supplements the study participants were taking themselves, had no effect on fracture risk for about 5 years, said Meryl LeBoff, MD, of Brigham and Women’s Hospital, Boston, at the American Society for Bone and Mineral Research (ASBMR) Annual Meeting held online and in San Diego.
With an almost equal number of participants receiving vitamin D compared to placebo, the number of incident fractures of all types was also almost equal, at 769 versus 782, for a risk ratio of 0.98 (95% CI 0 , 89-1.08), said LeBoff. The numbers were also very similar between the groups for non-vertebral fractures and hip fractures.
And two other sub-studies of VITAL, both presented as “electronic posters” to ASBMR by Sharon Chou, MD, also of Brigham and Women’s, found no benefit of omega-3 supplements over participants’ physical abilities or bone health biomarkers.
It is just the example of a rigor randomized trial contradicting anecdotal and observational reports that supplements have important preventive effects.
VITAL, you may remember, randomized some 25,000 generally healthy people, of which about 20% were black, in a 4 Ã 4 design to double the placebo, 2,000 IU / day of vitamin D3, 1000 mg / day of omega-3 capsules, or both supplements. The median follow-up was just over 5 years. Cancer and cardiovascular events were the predefined primary outcomes (for which there was no advantage), but the design included additional substudies to examine other suspected effects of these supplements.
Of particular interest is the new analysis of fracture rates in VITAL because, of all the claimed benefits for vitamin D, bone health is the strongest evidence. The current government recommendation of 400 IU per day is based on studies indicating that vitamin D is needed to maintain bone integrity.
But whether supplementation at 2,000 IU per day in addition to normal sources – food intake and sun exposure – provides additional protection was less clear.
VITAL recruited a relatively unselected group of men (aged 50 and over) and women (aged 55 and over) to receive daily vitamin D and / or omega-3 supplements as part of the placebo-controlled, double-blind, double-sham study. The relatively young age of the participants (mean 67) was a point of interest for at least one member of LeBoff’s audience, who questioned whether the results were relevant to older people, for whom the risk of fracture is highest.
“We can’t generalize to people in their 80s,” LeBoff admitted.
And vitamin D advocates may well be critical of other aspects of the trial, such as dosing (7,000 IU / day or more is often recommended) and target levels of vitamin D in the blood.
But the results were also reinforced by the rigorous judgment of the fractures. LeBoff pointed out that the supplements were very effective in increasing blood levels of the active vitamin D metabolite, 25- (OH) D, with most participants receiving the active product reaching levels of at least 40 ng / mL. (Levels of 30 ng / mL have traditionally been considered adequate for bone health.)
In addition, fracture rates were similar among groups of participants defined by baseline levels (
In the poster presentations, Chou and his colleagues explained that bone benefits have also been claimed for omega-3 fatty acids, with animal studies indicating “increased calcium absorption, decreased urinary calcium excretion, and reduced urinary calcium excretion. reduction of inflammation and bone resorption “.
They sought to examine the issue in a VITAL subgroup, made up of participants from the New England area who were brought in for imaging tests and physical exams. No signs of the alleged benefits were seen. Measurements of overall bone mineral density and at key locations, bone strength, cortical thickness, and polar stress resistance index were all similar in participants receiving the active supplements compared to placebo.
The same goes for physical abilities, as measured by tests of grip strength, walking speed, sitting, balance, and other objective assessments of performance.
VITAL was funded by the NIH.