New evidence for vitamin D supplementation
Vitamin D is big news just now, and two studies published only this week suggest potential benefits for supplementing. The first study looked at the association of vitamin D status with muscle strength and the other looked at lung infections.
Muscle strength and vitamin link
We already know that vitamin D helps the absorption of calcium into our bodies, and calcium is important for bone and teeth health. But British researchers at the University of Birmingham have found that low levels of inactive vitamin D in our blood and higher levels of active vitamin D may also be linked to higher levels of lean muscle mass – at least in women! More studies are required to see if the same would be true in men, although current evidence suggests that there was no link.
What this means is, women with greater levels of muscle compared to fat had better vitamin D status, suggesting that people who have good muscle strength are better equipped to convert inactive vitamin D to active. It is not completely understood why this is the case or what the exact biological differences are between men and women. Women therefore should be encouraged to engage in strength training to get the most out of their vitamin D supplementation.
Coughs, colds and vitamin D
The other study looking at vitamin D was a large US meta analysis, a type of study that pools together the results of many studies to see what the combined effect would be on a given test. In this case, they looked at the effect of supplementing vitamin D and protection against coughs and colds on over 11,000 people. What they found was, even supplementing vitamin D on a weekly rather than daily basis, appeared to have a protective effect in people who showed to have a deficiency in vitamin D.
The only way to determine whether you are vitamin D deficient or not is to have a blood test. However, it is estimated that 20% of the UK population (higher in the aged population) are probably deficient, particularly during the winter months when we see so little sunlight. This might also be because, despite living on an island, most of us don’t eat much fish – one of the richest sources of vitamin D in our diet.
Therefore, supplementing on vitamin D during the winter months of October through to March could be beneficial for many of us, particularly those of us who are have recurrent respiratory infections like coughs and colds, who do not eat much fish and who are light-skinned. If you are on any form of medication or have a medical condition that causes excess calcium in the blood (hypercalcaemia), discuss with your GP before supplementing.
For more information on vitamin D and health, visit the NHS site.
Cold? By Alan Foster
Hassan-Smith et al. (2017) 25-hydroxyvitamin D3 exert distinct effects on human skeletal muscle function and gene expression. PLoS One.
Massachusetts General Hospital News Release (2017) Study confirms vitamin D protection against cold and flu. http://www.massgeneral.org/about/pressrelease.aspx?id=2060
Scientific Advisory Committee on Nutrition (2016) Vitamin D and Health. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/537616/SACN_Vitamin_D_and_Health_report.pdf
Seb is a writer and blogger of food and nutrition. He holds a bachelors and a masters degree in nutrition science, and has studied sports and exercise nutrition at postgraduate level. He specialises in plant-based nutrition and believes passionately that we can all live with a little less meat.