Vitamin D deficiency is associated with increased risk of illness. In one study, 27% of athletes with vitamin D levels above 48 ng/mL experienced one or more upper-respiratory tract infections over a 4-month period, compared to 67% of those with levels below 12 ng/mL. Athletes with vitamin D below 12 ng/mL also experienced more total symptomatic days compared to athletes with vitamin D levels above 12 ng/ml.
Your blood vitamin D is likely much lower in the winter due to a lack of sunlight (you can make some vitamin D if your bare skin is exposed to the sun; if you have darker skin you have natural sunscreen so you won’t make much though exposure to sunlight). Studies in nonathletes tell the same story.
Where is the sweet spot for the lowest possible risk of infection? We don’t know. But, based on the research (which I won’t cover in detail here but you can read about it in the book referenced below 😁) it is likely > 30 ng/ml.
Vitamin D has profound effects on the immune system. So where can you get vitamin D?
– Swordfish (566 IU in 3 oz.)
– Salmon (447 IU in 3 oz.)
– Tuna (154 IU in 3 oz.)
– Vitamin D fortified orange juice (137 IU in 8 oz. but, check the label)
– 🥛Milk (115 – 124 IU in 8 oz.)
– Yogurt, some brands only
– Beef liver (42 IU in 3 oz.)
– 1 🍳 Egg (41 IU)
* Mushrooms exposed to UV light when growing also have vitamin D (look for this on the package).
The RDA for vitamin D for adults is 600 IU per day up to age 70 and 800 IU if you are above 70. How much do you need per day to put your vitamin D in a healthy range? It depends on the person, many need a maintenance dose of 1,500 – 2000 IU/day according to the American Society for Endocrinology. Another research article suggests the average person may need 2909 IU per day (some need more, some less).
SN: Vitamin D deficiency is also independently associated with mortality in critically ill patients.
Spano MA, Kruskall L, Thomas T. Nutrition for Sport, Exercise and Health. Human Kinetics Publishers 2017.