Vitamin D3: benefits, sources, deficiency and risks (2023)

Vitamin D comes in two different forms; ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3), each slightly different in chemical structure. "Vitamin D3 is obtained from animal sources, while vitamin D2 is mainly derived from mushroom sources," explains Dr. John White, head of the department of physiology at McGill University in Montreal and a molecular biologist who has conducted extensive research on vitamin D.

Although both forms are well absorbed in the gut, vitamin D3 may be a better choice for supplementation. According to a small study, vitamin D3 may be more effective at raising blood levels of vitamin D than vitamin D2^[2]Shieh A i in.Effect of high doses of vitamin D2 versus D3 on total and free 25-hydroxyvitamin D and markers of calcium balance. J Clin Endocrinol Metab. 2016;101(8):3070-8.. On the other hand, Dr. White notes that vitamin D2 may be a better choice if you follow a vegan diet becausevitamin D3 supplementsthey are often of animal origin.

Maintaining adequate levels of vitamin D can have several potential benefits:

Improves bone health

"Vitamin D3 is essential for the absorption and use of calcium and phosphorus, which are essential for maintaining strong and healthy bones," says Sam Schleiger, functional medicine nutritionist and founder of Simply Nourished, a nutrition practice in Elkhorn, Wisconsin.

Vitamin D is also needed to support bone growth and bone remodeling, the body's process that removes old bone tissue from the skeleton and creates new bone tissue. “Severe vitamin D deficiency leads to rickets [softening and weakening of the bones] in children andosteomalaciaor soft bones in adults because there is not enough calcium in the bones,” notes Dr. White.

Promotes immune functions

Vitamin D is essential forimmune healthand disease prevention. Some studies even suggest that vitamin D deficiency may exacerbate or increase the incidence of certain autoimmune diseases, such asRheumatoid arthritis^[3]Ao T i in.Effects of vitamin D on the immune system and inflammatory diseases. biomolecule. 2021;11(11):1624.. "There is also evidence that maintaining adequate levels of vitamin D reduces the long-term risk of certain types of cancer," adds Dr. White for it.

According to one review, vitamin D supplementation may be associated with a reduced risk of certain infections, including influenza and COVID-19^[4]Grant WB i in.Evidence that vitamin D supplementation may reduce the risk of infection and death from influenza and COVID-19. Nutrients. 2020;12(4):988.. What's more, another study shows that low levels of vitamin D may even be associated with a higher risk of multiple sclerosis^[5]Sintzel MB i in.Vitamin D and multiple sclerosis: a comprehensive review. Neurol Ther. 2018;7(1):59-85..

May help with weight management

Some research suggests that obesity may be related to low vitamin D levels. It is also believed that vitamin D may affect body weight by regulating the growth of fat cells and altering the expression of certain genes and the levels of hunger-influencing hormones such as leptin^[6]Karampela I i in.Vitamin D and obesity: current evidence and controversy. Curr Obes 2021;10(2):162-180..

While more research is needed, a very small study found that combining vitamin D supplements with a weight loss diet resulted in greater weight and fat loss than using a weight loss diet alone^[7]Lotfi-Dizaji L, et al.Effect of vitamin D supplementation along with a weight loss diet on meta-inflammation and fat mass in vitamin D-deficient obese subjects: a double-blind, placebo-controlled, randomized clinical trial. Clin Endocrinol (Oxf). 2019;90(1):94-101..

It regulates the mood

"Vitamin D3 is involved in the production and regulation of neurotransmitters such as serotonin, which is important for mood regulation," says Schleiger. "Adequate levels of vitamin D3 can help improve mood and overall mental well-being."

Interestingly, a review of 25 studies found that vitamin D supplementation may reduce negative emotions, especially in people with major depressive disorder or vitamin D deficiency.^[8]Cheng Y-C i in.The effect of vitamin D supplementation on negative emotions: a systematic review and meta-analysis. Depressive anxiety. Jun 2020;37(6):549-564.. In addition, other studies show that low vitamin D levels may be associated with elevated vitamin D levelsdepression symptomsand fear^[9]Akpinar S i in.Is Vitamin D Important for Anxiety or Depression? What's the truth?. Representative of Curr Nutr 2022;11(4):675-681..

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Vitamin D3 is found naturally in several food sources, including fatty fish and cod liver oil. Other animal products such as egg yolks, cheese and beef liver also contain a small amount of vitamin D3 per serving.

Here are some food sources of vitamin D3 and the percentage of the Daily Value (DV) they provide, according to the National Institutes of Health^[10]Vitamin D. National Institutes of Health. Accessed May 17, 2023.:

Can you get vitamin D3 from the sun?

While vitamin D3 is available in supplements and various dietary sources, you can also meet your needs through regular sun exposure. This is because the skin produces vitamin D when exposed to ultraviolet rays from the sun.

However, you don't need to sunbathe to meet your vitamin D needs (and sun protection is still important to reduce your risk of skin cancer). As long as the outside temperature is above 45 degrees Fahrenheit, about 20 minutes of sun exposure on the face and hands is generally enough to produce enough vitamin D in the skin to maintain adequate vitamin D levels, notes Dr. Whiten.

Keep in mind that certain factors can affect the amount of sunlight you need to meet your vitamin D needs, including skin pigmentation and age. Your location, time of year, and time of day can also affect the amount of vitamin D your skin produces.

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It's best to talk to your doctor before starting supplementation, especially if you're taking other medications or have underlying medical conditions. According to Schleiger, vitamin D supplements may interact with certain medications, including corticosteroids and medications for seizures or high cholesterol. It also adds that high-dose supplements may not be appropriate for people with certain medical conditions, such as hyperparathyroidism, sarcoidosis or kidney disease.

While it is possible to get too much vitamin D3, it is rare. "Supplementation can cause vitamin D toxicity, but you have to try very, very, very hard," says Dr. White. "For example, there are clinical trials where patients receive 100,000 to as much as 600,000 IU (International Units) in boluses without side effects."

However, taking very high doses of vitamin D over a long period of time can cause vitamin D toxicity, which can lead to elevated blood calcium levels, explains Schleiger. "[It] can cause symptoms such as nausea, vomiting, constipation, weakness, excessive thirst, frequent urination, and in severe cases, kidney stones or organ damage," she says.

The upper limit of supplementation is 4,000 international units per day, according to Dr. White. And while he notes that this amount is most likely conservative, 4,000 IU is still more than most people should take.

"Following recommended dosing guidelines and regularly monitoring your vitamin D levels with blood tests can help ensure safe and effective supplementation," says Schleiger.