Guest post by Dr Laura Villa
Did you know that vitamin D deficiency is prevalent? It is estimated that about 1 billion people worldwide have low levels.
Vitamin D is a fat-soluble vitamin, meaning it is absorbed along with fats in the diet and stored in the body’s fatty tissue and the liver. It plays a vital role in the balance of calcium and phosphorus and bone metabolism. Vitamin D has other roles in the body, including reducing inflammation, improving immune function, and helping with blood sugar metabolism. Unlike other vitamins, vitamin D functions like a hormone as well, and every single cell in your body has a receptor for it.
The major sources of vitamin D are exposure of the skin to UVB radiation from the sun and dietary intake.
- Twenty minutes of sunshine daily with other 40% of skin exposed is required to prevent deficiency.
- The best dietary sources are fatty fish (mackerel, sardines, and salmon) and fortified foods like milk. Because it is fat-soluble, it does not dissolve in water and is best absorbed when paired with high-fat foods — avocados, nuts, seeds, eggs, etc.
Vitamin D deficiency can result from several causes:
- Decreased dietary absorption. Vitamin D requires no digestion and is absorbed in the small intestine, so conditions that affect that area, like celiac disease and inflammatory bowel disease, would decrease absorption.
- Decreased sun exposure and using sunscreen. About 80% of vitamin D is absorbed through the skin, while the rest comes from diet.
- You have dark skin. The pigment melanin reduces the skin’s ability to make vitamin D in response to sunlight exposure.
- Your kidneys cannot convert vitamin D to its active form. As people age, their kidneys are less able to convert vitamin D to its active form, thus increasing their deficiency risk.
- Age. The skin’s ability to make vitamin D lessens with age.
- Medications. Levels can be lowered by certain medications like laxatives, steroids, cholesterol-lowering drugs, etc.
Signs that you might be deficient:
- Getting sick often
- Feeling fatigued
- Bone pain or back pain
- Hair loss
- Muscle pain
The dosing of vitamin D depends on the severity of the deficiency. However, a good maintenance dose is between 1000 to 2000 international units. Because vitamin D is fat-soluble, toxicity is possible, although rarely noted. So please consult your doctor before beginning supplementation.
- Sizar O, Khare S, Goyal A, et al. Vitamin D Deficiency. [Updated 2020 Jul 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-.
- Chen TC, Chimeh F, Lu Z, et al. Factors that influence the cutaneous synthesis and dietary sources of vitamin D. Arch Biochem Biophys. 2007;460(2):213-217. doi:10.1016/j.abb.2006.12.017
- Maurya VK, Aggarwal M. Factors influencing the absorption of vitamin D in GIT: an overview. J Food Sci Technol. 2017;54(12):3753-3765. doi:10.1007/s13197-017-2840-0
- García JD PhD. Vitamin D. Salem Press Encyclopedia of Health. 2019. Accessed February 9, 2021.