Nutrient Spotlight: Vitamin D
Vitamin D is an essential nutrient that, unfortunately, a lot of us are deficient in. Whether it’s due to lack of intake of vitamin D-rich foods, decreased exposure to UVB rays, age, skin tone, or other environmental factors, vitamin D insufficiency is prevalent.
So what’s the deal with vitamin D? Is deficiency in this nutrient a bad thing (it is) and why? Here we cover the basics of Vitamin D, the sunshine vitamin.
VITAMIN D, THE SUNSHINE VITAMIN
Vitamin D is sometimes referred to as the sunshine vitamin. This is because our bodies can actually make it themselves, from sunlight–and how this happens is truly fascinating. Our skin contains cholesterol compounds, which, when exposed to UVB rays from sunlight, are converted to a precursor to active vitamin D, known as previtamin D3. This previtamin undergoes another process to become a more active form of vitamin D [i]. See, cholesterol isn’t all bad!
Our bodies can accomplish this process pretty easily, but several factors do make it more difficult. As we age, the amount of cholesterol in our skin decreases, meaning we can still make vitamin D but not nearly as much. Melanin content of the skin, as well as sunscreen use, can also decrease our natural ability to create vitamin D, as both absorb the UVB rays and decrease the number of rays that can actually reach the cholesterol compounds [i].
Vitamin D is a fat-soluble vitamin, and any excess vitamin D that is made during the spring and summer months when UVB rays are stronger is stored in body fat for use during the winter months when our bodies cannot make as much vitamin D from UVB rays. Carrying excess body fat can lead to increased storage of vitamin D and potential insufficiency compared to normal-weight individuals.
Where can we find vitamin D in our food supply? Unfortunately, there aren’t many foods that contain enough vitamin D to maintain sufficient levels. Several foods are now fortified, but sunlight continues to be our main source of vitamin D, (accounting for 90% of our vitamin D requirement!), which is why many people need to supplement with vitamin D in order to keep vitamin D levels up.
Your best bet for vitamin D-containing foods are fatty fish like salmon, mackerel, and sardines, UV-exposed mushrooms, egg yolks (specifically from pasture-raised chickens that have more exposure to sunlight), and fortified milk and nut milk.
VITAMIN D BENEFITS
Bone health – Vitamin D and calcium are the two key nutrients necessary for bone health. Vitamin D aids in calcium absorption, ensuring that bones are strong and preventing osteoporosis and osteomalacia. Age-related bone loss typically begins to occur in your 40s, but adequate vitamin D status can help to prevent bone demineralization that occurs due to calcium release from bones. Vitamin D alone and with calcium improved bone mineral density, and vitamin D supplementation has been shown to significantly reduce fracture occurrence [ii].
Immune Health – Vitamin D is an essential nutrient for gene regulation. Especially important for the immune system, vitamin D is responsible for the up-regulation of proteins called defensins, which are antimicrobial proteins. Vitamin D is integral to the health of the innate immune system, enhancing the ability of our own innate cells to kill and fight off infection [iii].
In addition to the innate immune system, we also have an adaptive response, which gets kicked into high gear after infection and helps us to fight off future infections. Vitamin D plays the same regulation role here, helping to increase the production of certain cells to guarantee future immunity against bacteria [iii].
Mental Health – The relationship between vitamin D and mood, depression, and anxiety is an interesting area of study. Though there can be many causes for mental health disturbances, the association between vitamin d deficiency and mental health disorders is a strong one. Groups that are at increased risk for vitamin D deficiency are also at greatest risk for depression, and in some studies, high dose vitamin D supplementation has been shown to improve depression risk scores [iv]. More randomized control studies need to be done to make concrete conclusions, but past research has been promising. Need a mental health boost? Try a 15-minute walk in peak sun and a few servings of vitamin D rich foods. It certainly can’t hurt.
THE BOTTOM LINE
It only takes about 10-15 minutes of sun exposure to reach peak levels of vitamin D production in the skin. After that, vitamin D production quickly halts, and skin cancer risk increases, so consider that time to put on your sunscreen! Aim to get dietary vitamin D from fatty fish, mushrooms, egg yolks, and fortified milk when you’re able, and keep track of your vitamin D status with your doctor to know if you need to supplement.
References:
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- [i] Michael F Holick. “Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease.” The American Journal of Clinical Nutrition, Vol 80, 6, (2004). 1678S–1688S, https://doi.org/10.1093/ajcn/80.6.1678S
- [ii] Laird, Eamon et al. “Vitamin D and bone health: potential mechanisms.” Nutrients vol. 2,7 (2010): 693-724. doi:10.3390/nu2070693
- [iii] Aranow, Cynthia. “Vitamin D and the immune system.” Journal of investigative medicine: the official publication of the American Federation for Clinical Research vol. 59,6 (2011): 881-6. doi:10.2310/JIM.0b013e31821b8755
- [iv] Penckofer, Sue et al. “Vitamin D and depression: where is all the sunshine?.” Issues in mental health nursing vol. 31,6 (2010): 385-93. doi:10.3109/01612840903437657