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. 

This work is published in the second best journal in its category, according to the international research journal rating standards. Therefore, articles published here go through a tough peer-review process.  

In recent years there has been much scientific discussion about which of the two nutrients, calcium or vitamin D, is more important for bones in adulthood. While the role of calcium is out of question during childhood and adolescence, in adults, its ability to prevent bone fractures is more questionable. Vitamin D is the most effective alternative in this area. In fact, it has even been proposed that the daily recommended intake of vitamin D should be increased. However, so far, research has so far yielded mixed results.  

This paper adds to this controversy by showing that vitamin D supplementation does not protect bones from fracture. In fact, it does not do so in vitamin D-deficient participants either, which is a somewhat unexpected result. The negative results extend even to participants taking calcium supplements, a combination that has shown a positive effect in other studies.  

While it is true that fracture risk is only one of the indicators of bone health, the same authors have previously published that vitamin D supplementation does not improve bone density and structure, nor the risk of falling.  

It should be noted that this work has been carried out in healthy people. Therefore, as the authors themselves indicate, this result cannot be extrapolated to people with bone problems such as osteoporosis or osteomalacia.  

Therefore, it can be said that this study leaves the widespread interest in vitamin D in relation to bone health in healthy adults unfounded. However, it is important to mention that other dietary factors affecting bone, such as protein or phosphorus, are not taken into account here, nor is physical exercise. Perhaps this is the key to interpreting the negative results found in this and previous studies. 

It should be remembered that vitamin D is not only important for bone, but is also involved in other cellular processes, such as muscle function, immune system function, tooth maintenance and cell division. In addition, vitamin D deficiencies have been associated with increased risk of upper respiratory tract infections, autoimmune diseases or allergies, cardiovascular problems and even increased mortality. Lower levels of vitamin D have also been linked to obesity, type 2 diabetes and metabolic syndrome.