Marta Beltrá García-Calvo
Researcher at the Department of Applied Biology.
This scientific article supports what has been said before: several studies, with a high level of evidence, show that vitamin D supplementation does not reduce the risk of either total fracture or hip fracture, so there is no current scientific justification for the use of vitamin D supplementation to reduce fractures.
In the article the authors want to test whether taking vitamin D supplements would result in a lower risk of fractures compared to not taking them (placebo). The data come from a larger vitamin D and omega-3 study (VITAL) published in November 2018, a two-by-two factorial, randomised, controlled trial of either vitamin D3 (2000 IU per day) or omega-3 fatty acid supplementation of (1 g per day) or both, but on the prevention of cancer and cardiovascular disease in 25. 871 men (age, ≥50 years) and women (age, ≥55 years) from all 50 US states and followed up with different questionnaires for 5.3 years.
Participants were randomised to one of four groups: vitamin D plus n-3 fatty acids, vitamin D plus placebo, n-3 fatty acids plus placebo or double placebo. The mean (± SD) age of participants was 67.1±7.1 years, 50.6% (13,085 of 25,871) were female and 20.2% (5,106 of 25,304) were black. The mean body mass index was 28.1±5.7 (indicating overweight). Only 4.8% of participants (1240 of 25,690) were taking osteoporosis medications at baseline, however, 10.3% (2578 of 25,023) had a history of fragility fractures. Adherence to supplements was 87.3% at two years and 85.4% at five years.
In this article they only present the effects of vitamin D3 supplementation compared to placebo, because there was no interaction between vitamin D and omega-3 fatty acids in the analysis of fracture outcomes.
As a conclusion: vitamin D3 supplementation did not result in a significantly lower risk of fractures than placebo among generally healthy middle-aged and older adults. The hazard ratios (how risk varies over time) are always close to 1 for all fracture types studied, so there are no significant differences.