table of contents
If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
The principle that it’s possible to get too much of a good thing even extends to cancer-fighting, heart-protective vitamin D. You can take too much of just about any vitamin or supplement, and it is possible to suffer vitamin D toxicity.
How much is enough vitamin D? The National Institutes of Health (NIH) Office of Dietary Supplements recommends a daily intake of vitamin D of 600 IU (15 mcg) for adults up to age 69 and 800 IU for adults 70 and older. The tolerable daily upper intake for vitamin D in adults is 4,000 IU (100 mcg).
Signs of too much vitamin D
Symptoms of vitamin D toxicity (a.k.a. hypervitaminosis D) can include a loss of appetite, weight loss, excessive urination, and heart arrhythmia.
High doses of vitamin D can raise blood levels of calcium (hypercalcemia), which can damage the heart, kidneys, and blood vessels. One example of the kidney damage hypervitaminosis D can cause is the formation of kidney stones.
Vitamin D toxicity is not very common. It results from taking too many vitamin D supplements. It’s not possible to overdose on vitamin D from the sun (the body self-regulates how much it takes in) and it’s very unlikely to do so via food.
The NIH points out that symptoms of vitamin D toxicity are unlikely if you take less than 10,000 IU (250 mcg) daily, but that doesn’t mean you want to go that high. Some studies have shown that it’s possible to have too high a blood level of vitamin D, which is associated with a higher risk of death from any cause, cancer in areas like the pancreas, and a higher risk of heart disease (NIH, n.d.).
What is vitamin D?
A bit of an impostor, for one. Vitamin D is technically a prohormone––not a vitamin––which means that it’s a substance that causes the body to create a hormone (which is simply something that spurs cells or body processes into action).
In the case of vitamin D, about 90% of what exists in the human body is produced in response to sun exposure on the skin, hence its nickname “the sunshine vitamin.” The remaining 10% comes from a variety of food sources, like fatty fish, milk, and egg yolks.
From there, the liver and kidneys turn vitamin D into various substances that can be used for key bodily processes, like immune system support, bone health, and cancer protection (Mendes, 2018).
Much of the world’s population is deficient in vitamin D––up to 1 billion people worldwide, and 40% of Americans. Some researchers call it a “silent epidemic.” But that doesn’t mean you should go balls-out in adding vitamin D to your daily routine (Parva, 2018).
Benefits of vitamin D
Let’s take a look at what vitamin D does in the body and its health benefits.
Vitamin D’s primary role is to help the body maintain the right levels of calcium and phosphorus. It affects how calcium is absorbed from food and how the body builds and reabsorbs bone (which the body is constantly doing; it’s a process called bone remodeling).
Studies suggest vitamin D could help prevent fractures and osteoporosis (bone loss) (Bischoff-Ferrari, 2005).
A lack of vitamin D has been associated with an increased risk of infection and a higher chance of autoimmune diseases. It seems to bolster the body’s innate immune system, helping it destroy bacteria and other invading microbes (Aranow, 2011).
Protection from certain cancers
Some studies have found that vitamin D might have a protective effect against a number of cancers, particularly colorectal and breast. A low vitamin D level is associated with a higher risk of those cancers (Meeker, 2016).
That could be because vitamin D regulates the genes that control cell differentiation, division, and death. This helps control cell growth, bolsters the immune system, and reduces inflammation––all processes that can affect the development of cancer.
Regular doses of vitamin D early in life have been found to reduce the risk of type 1 diabetes, and taking vitamin D later in life seems to reduce the risk of type 2. Vitamin D seems to help the body process insulin and control blood sugar (Schwalfenberg, 2008).
- Aranow C. (2011). Vitamin D and the immune system. Journal of investigative medicine : the official publication of the American Federation for Clinical Research, 59(6), 881–886. https://doi.org/10.2310/JIM.0b013e31821b8755. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3166406/
- Bischoff-Ferrari, H. A., Willett, W. C., Wong, J. B., Giovannucci, E., Dietrich, T., & Dawson-Hughes, B. (2005). Fracture Prevention With Vitamin D Supplementation. Jama, 293(18), 2257. doi:10.1001/jama.293.18.2257. https://pubmed.ncbi.nlm.nih.gov/15886381/
- Meeker, S., Seamons, A., Maggio-Price, L., & Paik, J. (2016). Protective links between vitamin D, inflammatory bowel disease and colon cancer. World journal of gastroenterology, 22(3), 933–948. https://doi.org/10.3748/wjg.v22.i3.933. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4716046/
- Mendes, M. M., Hart, K. H., Botelho, P. B., & Lanham-New, S. A. (2018). Vitamin D status in the tropics: Is sunlight exposure the main determinant? Nutrition Bulletin, 43(4), 428-434. doi:10.1111/nbu.12349. https://onlinelibrary.wiley.com/doi/full/10.1111/nbu.12349
- National Institutes of Health, Office of Dietary Supplements – Vitamin D. (n.d.). Retrieved June 05, 2020, from https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
- Parva, N. R., Tadepalli, S., Singh, P., Qian, A., Joshi, R., Kandala, H., Nookala, V. K., & Cheriyath, P. (2018). Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011-2012). Cureus, 10(6), e2741. https://doi.org/10.7759/cureus.2741. https://pubmed.ncbi.nlm.nih.gov/30087817/
- Schwalfenberg G. (2008). Vitamin D and diabetes: improvement of glycemic control with vitamin D3 repletion. Canadian family physician Medecin de famille canadien, 54(6), 864–866. https://pubmed.ncbi.nlm.nih.gov/18556494/
- Vacek, J. L., Vanga, S. R., Good, M., Lai, S. M., Lakkireddy, D., & Howard, P. A. (2012). Vitamin D Deficiency and Supplementation and Relation to Cardiovascular Health. The American Journal of Cardiology, 109(3), 359-363. doi:10.1016/j.amjcard.2011.09.020. https://pubmed.ncbi.nlm.nih.gov/22071212/
Dr. Mike is a licensed physician and the Director, Medical Content & Education at Ro.