Vitamin D helps the body absorb and hold on to the nutrients calcium and phosphorus, which are critical for building bone. Though sun exposure and diet largely determine vitamin D levels, your DNA also plays a small role. AncestryDNA^® + Traits can tell you if people with DNA like yours tend to have typical vitamin D levels.

Vitamin D Deficiency Symptoms and Causes

Because your body relies mostly on sunlight exposure to make vitamin D, you may be at higher risk of having low vitamin D if you spend little time outside, cover your skin completely with clothing when outdoors, or live in northern latitudes where UV light is weaker and winter days are shorter.

Skin pigmentation is another factor: Melanin acts as a natural sunscreen, and some studies have indicated that people with darker skin tones may have a higher risk of vitamin D deficiency.

Also, certain digestive problems cause lower vitamin D levels because you don't retain enough vitamin D from food.

For many people, the symptoms of low levels of vitamin D can be subtle, but they can include bone pain and muscle weakness. A more severe vitamin D deficiency can cause soft, weak bones, as vitamin D helps you absorb calcium, an essential nutrient for your bones.

What Science Says About Vitamin D Levels for Women and Men

On average, people need more vitamin D once they are over the age of 70. The recommended dietary allowance (RDA) for both men and women is 15 mcg (600 IU) for people aged 1 to 70, and 20 mcg (800 IU) if you're over 70.

Certain groups, such as older adults and postmenopausal women, may have a higher chance of running low on vitamin D and could benefit from more vitamin D-rich foods in their diets. For some people, healthcare providers could recommend supplements as part of a vitamin D deficiency treatment. But taking more than 1,000 IUs daily is not a good idea—unless your doctor prescribes it. This is because too much vitamin D can be toxic. Vitamin D increases calcium absorption in your digestive tract and, in excessive levels, can lead to hypercalcemia—which can lead to an array of symptoms including nausea and vomiting, loss of appetite, dehydration, muscle weakness and pain, excessive thirst, and kidney stones.

Vitamin D and Genetics

Some researchers have noticed low vitamin D can run in families, indicating a possible genetic connection.

AncestryDNA looks at a gene called GC. This gene codes for a protein that binds to vitamin D, so it can be activated and then carried to the tissues in your body that need it.

Certain DNA differences in the GC gene are more common in people whose ancestors come from regions where people have darker skin; other DNA differences are more common in people with very fair ancestors.

Overall the role of genetics in determining your vitamin D levels is small, and the GC gene is just one of the genetic factors that can affect them.

Interesting Facts About Vitamin D5

Vitamin D is sometimes referred to as the “sunshine vitamin” because your body makes most of your vitamin D when your skin is exposed to sunlight.

But you can also dial up your vitamin D intake through what you choose to eat and drink. Good sources of vitamin D include fatty fish like salmon or sardines, as well as egg yolks, fortified milk, orange juice, and cereal.

Interestingly, mushrooms absorb vitamin D when they're exposed to sunlight. So they can be a good choice for more of that sunshine vitamin too, especially if you put them in the sun before eating them.

References

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Elkum N, Alkayal F, Noronha F, et al. Vitamin D Insufficiency in Arabs and South Asians Positively Associates with Polymorphisms in GC and CYP2R1 Genes. PLoS ONE. 2014;9(11). doi:10.1371/journal.pone.0113102.

GC Vitamin D Binding Protein [Homo Sapiens (human)]. National Center for Biotechnology Information. March 28, 2019. https://www.ncbi.nlm.nih.gov/gene/2638

Manousaki D, Dudding T, Haworth S, et al. Low-Frequency Synonymous Coding Variation in CYP2R1 Has Large Effects on Vitamin D Levels and Risk of Multiple Sclerosis. The American Journal of Human Genetics. 2017;101(2):227–238. doi:10.1016/j.ajhg.2017.06.014.

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Mushrooms and Vitamin D. Berkeley Wellness. December 5, 2016. http://www.berkeleywellness.com/healthy-eating/nutrition/article/mushrooms-and-vitamin-d

Sapkota BR, Hopkins R, Bjonnes A, et al. Genome-wide association study of 25(OH) Vitamin D concentrations in Punjabi Sikhs: Results of the Asian Indian diabetic heart study. The Journal of Steroid Biochemistry and Molecular Biology.2016;158:149–156. doi:10.1016/j.jsbmb.2015.12.014.

Vitamin D. Linus Pauling Institute at Oregon State University. February 15, 2018. http://lpi.oregonstate.edu/mic/vitamins/vitamin-D

Vitamin D. NIH Office of Dietary Supplements. Accessed April 6, 2018. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional

Wang TJ, Zhang F, Richards JB, et al. Common genetic determinants of vitamin D insufficiency: a genome-wide association study. The Lancet.2010;376(9736):180–188. doi:10.1016/s0140-6736(10)60588-0.

Zhang Y, Yang S, Liu Y, Ren L. Relationship between polymorphisms in vitamin D metabolism-related genes and the risk of rickets in Han Chinese children. BMC Medical Genetics. 2013;14(1). doi:10.1186/1471-2350-14-101.