Vitamin D has been linked to some possible health advantages. This vitamin appears to be singled out as having the most pay-off for risk involved in my opinion. Many other vitamins appear more dangerous supplements. Particularly at higher doses! e.g. http://annals.org/aim/article/718049/meta-analysis-high-dosage-vitamin-e-supplementation-may-increase-all

Vitamin D may help reduce the elderly:

Some highly-cited work shows correlations between Vitamin D intake and bone health or reduced falls in elderly people. However, it appears there is more research needed to reach strong conclusions.

One study (https://www.algaecal.com/PDF/calcium-only-reduces-bone-density-loss.pdf) suggests that calcium or calcium and vitamin D does improve elderly bone density. Could it also help younger people – possibly.

Dose (as usual) appears important, with many studies suggesting higher doses are better 700- 1000 IU a day is quoted by http://www.bmj.com/content/339/bmj.b3692.full

Remember though – a higher dose does not always equal a better outcome; it can sometimes become dangerous and a doctor’s advice is required.

Vitamin D may help with fighting obesity:

Maybe not – it looks like the correlation is due to extra body fat reducing the amount of vitamin D stored in your body. The vitamin D does not seem to reduce obesity, but obesity reduces vitamin D.

However, some research suggests it is possible vitamin d may help (though the causal links are very weak): https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4658869/

This suggests maintaining a good level of vitamin D is recommended to fight obesity.

The study suggests they did not look enough at physical activity or sunlight exposure as other effects that could affect both vitamin D and obesity. These are some big limitations when determining what is causing the fat loss. Is it outdoor exercise that has caused vitamin D increases and weight loss?

Dose is important, and usually a healthy diet  and lifestyle is a safer way to get the right dose. Doctors’ advice is needed if you are deficient ! Don’t self-medicate!

So what approach makes sense from these study results?

Keeping a good level of Vitamin D makes sense- the body needs it for many functions. However, supplements may not help with the above and medical advice is needed.

Exercise in sunlight is probably the right way to get Vitamin D and lose weight in most cases. Sunlight is more convincing regarding how humans are designed to achieve healthy Vitamin D levels.

Some people may require supplements if deficient, but a number of people should rely on the natural sources and get outside. Absolutely get advice from a doctor if you feel you are deficient – clearly, Vitamin D is important.