Vitamin D and Colds: What Studies Show

A German nutrition review found that low vitamin D levels are statistically linked to a higher risk of respiratory infections, but it does not guarantee protection against colds. Experts do not recommend high-dose supplements for everyone. The German Nutrition Society analyzed 73 studies and suggests supplementation may help prevent infections only in cases of deficiency. However, a 2021 Australian study of over 21,000 older adults found no significant difference in infection rates between those taking vitamin D and a placebo. Doctors can determine vitamin D status via a blood test, with deficiency defined as below 25-30 nmol/l. For those needing supplements, the recommended daily dose is 20 micrograms, or 800 international units.