Intense physical training in winter increases chances for upper respiratory tract infections (URTI). In this study, doctors gave 25 male taekwondo athletes a placebo or 5,000 IU of vitamin D per day during the four-week winter training session.
Vitamin D levels rose 255 percent in the vitamin D group and remained unchanged for placebo. Also compared to placebo, among those who came down with upper respiratory tract infections, the vitamin D group reported 40 percent less severe symptoms including sneezing, runny nose, and coughing. Athletes also answered questionnaires about quality of life, which scored 27.8 percent higher for the vitamin D group compared to placebo.
(Reference: International Journal of Environmental Research and Public Health; 2018, Vol. 15, No. 9)
Product Recommendations by Arnie Gitomer
Vitamin D 5,000 IU is available from many suppliers.