When we think of vitamin D, sunshine or the popular orange “Sunny D” drink may come to mind, but vitamin D plays many important roles in the body and helps regulate weight, mood, heart health, bone health, diabetes, cancer risk, autoimmune disorders, and neuromuscular disorders. Due to limited sun exposure at northern latitudes in the winter months and low availability of vitamin D in foods, many people living in the northwest are at risk for vitamin D deficiency. Overweight/obese individuals are also at greater risk for vitamin D deficiency.

With exposure to UVB rays, vitamin D is made in the skin and converted to its active form in the body by the kidneys and liver. The Institute of Medicine classifies vitamin D levels of 20-50 ng/mL sufficient for bone health and calcium absorption; however, the U.S. Endocrine Society recommends levels of 30-100 ng/mL to sufficiently reduce the burden of chronic diseases. Anyone with vitamin D levels less than 20 ng/mL would be considered deficient.

Vitamin D plays a major role in helping your cells communicate and divide properly, thus impacting cancer prevention. Studies have found a link between adequate vitamin D levels and lower risk of colon, prostate, and breast cancers. Vitamin D also boosts hormones that play a role in mood regulation and appetite, and impacts bone health by increasing calcium absorption. Furthermore, vitamin D can help suppress the autoimmune response in multiple sclerosis, arthritis, fibromyalgia, and lupus by helping the body’s immune system to function better. Autoimmune disorders are more common in people living at temperate and northern latitudes, thus suggesting a link between inadequate sunlight and the progression of autoimmune disorders. In terms of diabetes, both type 1 and type 2 diabetes are associated with lower blood levels of vitamin D at diagnosis.

Signs and symptoms of vitamin D deficiency include fatigue, difficulty concentrating, depression, and muscle weakness/pain. Rickets is the classical manifestation of severe vitamin D deficiency.

The recommended dietary allowance for vitamin D is 600-800 International Units (IUs) per day for adults. This range is aimed at the amount healthy adults would need to take to maintain bone health. However, higher amounts (1,000-2,000 IUs/day) are recommended for those living in temperate latitudes to achieve adequate blood levels of vitamin D, according to the U.S. Endocrine Society. This amount can be hard to get with diet alone, especially if sun exposure is limited. To put that into perspective, one cup of fortified milk or orange juice contains 90-100 IUs, three ounces of canned salmon contains 465 IUs, and one egg yolk has a mere 37 IUs. Vitamin D toxicity is extremely rare, and most people can safely take 1,000-2,000 IUs of a maintenance dose daily. Those who are deficient likely need more until levels are within a normal range. The best way to determine how much vitamin D to take is to get your blood levels checked by a doctor, who will dose according to the results.

•••

Natalie Colla, RDN, LDN, is a graduate of the University of Idaho Dietetics Program and dietitian at Kootenai Clinic Diabetes & Endocrinology.