To learn all about vitamin D, check out the answers to the 9 most frequently asked questions.
1. What is vitamin D?
Vitamin D is a fat-soluble vitamin that functions to maintain normal blood levels of calcium and phosphorus. Vitamin D enhances the absorption of calcium, thus helping to build and maintain strong bones. Without adequate vitamin D, bones become thin, brittle, or soft. The weakening of bones increases the risk of fractures and bone diseases such as rickets (in children), osteomalacia, and osteoporosis.
2. Ergocalciferol vs. cholecalciferol?
The two types of vitamin D are ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3).
Ergocalciferol (vitamin D2) is the plant form of vitamin D and typically comes from yeast. Prescription vitamin D products contain vitamin D2.
Cholecalciferol (vitamin D3) is the type of vitamin D our bodies produce after exposure to sunlight. It is also the type of vitamin D that is in fatty fish like salmon and herring. Most supplements source their vitamin D3 from lanolin.
Our bodies metabolize vitamin D3 more effectively than vitamin D2. Vitamin D3 supplementation is less likely to result in toxicity. In fact, studies have shown that daily vitamin D3 is two to three times more efficient than weekly or monthly high-dose vitamin D2. For these and other reasons, vitamin D3 is the superior supplemental form of vitamin D.
3. Can you get vitamin D from the sun?
Vitamin D is sometimes called the “sunshine vitamin.” And for good reason. With enough sun exposure, our bodies will make all the vitamin D we need.
However, if you not exposed to enough sunlight, you may not get enough vitamin D. The same is true if you have a hard time metabolizing vitamin D or have reduced liver or kidney function. The amount of vitamin D produced in the body from sun exposure can vary greatly depending on one’s age, location or latitude, time of day, smog, and use of sunscreen.
As we get older, our skin does not produce vitamin D as well as it did when we were younger. For example, a 70-year-old makes approximately 25% of the vitamin D that a 20-year-old person makes.
Location is also very important in determining the amount of vitamin D produced from exposure to the sun. In most of the U.S., you cannot make vitamin D from sunlight for four months of the year. If you live in the Northern U.S. or Canada, it may be difficult in as many as seven months.
Moreover, using sunscreen reduces the amount of vitamin D produced through sun exposure. A sunscreen with an SPF of 8 or greater will block 90% of the rays that you need to produce vitamin D.
4. Can you get vitamin D from food?
So if vitamin D is hard to get from the sun, can you can get it food? Unfortunately, it is difficult to acquire optimal levels of vitamin D from your diet alone because vitamin D occurs naturally in very few foods.
Fatty fish (such as salmon) and certain oils naturally contain some vitamin D. Breakfast cereals and milk are often fortified with vitamin D. The process of fortification adds vitamin D to food or beverages that may not contain it naturally. Drinking a quart of fortified milk each day provides you with about 400 IU of vitamin D. This low amount is much lower than the amount needed to ensure ideal blood levels of vitamin D.
5. How do I know if I’m vitamin D deficient?
Approximately 20-80% of all Americans have blood levels of vitamin D low enough to classify them as vitamin D deficient. To find out if you are deficient, your healthcare provider can perform a simple blood test to determine your level. Blood levels of vitamin D are measured as 25(OH)D.
The Institute of Medicine proposed that a vitamin D level of 20-50 ng/mL is sufficient for most people. However, many vitamin D experts recommend maintaining a level of at least 30 ng/mL, with 30-80 ng/mL considered vitamin D sufficiency, 20-30 ng/mL considered insufficiency, and below 20 ng/mL considered vitamin D deficiency. Common lab tests list 100 ng/mL as the upper limit, above which risk of vitamin D toxicity increases.
6. How much vitamin D do I need?
There is not complete agreement on the optimal daily dose of vitamin D. The current Recommended Dietary Allowance (RDA) is 600-800 IU per day, depending on age, and the upper limit for daily intake is 4,000 IU. Vitamin D experts, however, consider the RDA to be conservative. These experts typically recommend higher doses for most adults, particularly those who have low vitamin D levels.
According to the Endocrine Society, adults with vitamin D deficiency (below 20 ng/mL) should take 6,000 IU of vitamin D each day to achieve a normal blood level (above 30 ng/mL). Once you achieve optimal blood levels, you can reduce to a maintenance dose of 1,500-2,000 IU of vitamin D each day.
The Endocrine Society also recommends that if you are an obese adult, have a malabsorption syndrome, or take medications that affect vitamin D metabolism, you should take 6,000-10,000 IU of vitamin D each day until you achieve a normal blood level of 30 ng/mL. After reaching 30 ng/mL, you can reduce your dose to a maintenance dose of 3,000-6,000 IU of vitamin D each day.
As you can see, the answer to this question depends on your age, current vitamin D level, and health status. Please consult your healthcare provider to help determine what dose of vitamin D might be appropriate for you.
7. Why is vitamin D important for bones?
Vitamin D is an essential component in the regulation of calcium balance. It helps the body absorb calcium from our diet, thus promoting the development and maintenance of strong bones. Without adequate vitamin D, bones become thin, brittle, or soft. The weakening of bones increases the risk of fractures and bone diseases such as osteomalacia and osteoporosis.
Osteoporosis, which affects approximately 10 million Americans, is characterized by fragile, weak bones, and is associated with calcium and vitamin D deficiency. If you do not consume enough calcium, your body pulls it is from your bones. This can result in osteoporosis and fractured bones. Vitamin D deficiency alone can lead to osteomalacia in adults, which results in muscle and bone weakness and bone pain.
Bone health is of concern for individuals with autoimmune conditions. Risk factors include inflammatory disease activity, vitamin D deficiency, immobility, and use of corticosteroids and other medications. Corticosteroids such as prednisone may affect the metabolism of vitamin D, although the evidence is not completely clear. Since these medications can increase the risk for osteoporosis and fractures, calcium and vitamin D supplements are recommended.
8. Aside from bone health, what else can vitamin D help with?
Research over the last decade has revealed that vitamin D is not only important for bone health but also plays a role in regulating the immune system and may potentially decrease the risk of a variety of health conditions. Studies have shown that vitamin D decreases inflammation by suppressing the activity of immune cells that are part of the autoimmune reaction in these conditions.
Rheumatoid Arthritis (RA)
Vitamin D deficiency is common among individuals with rheumatoid arthritis (RA). In a study of over 29,000 women, those consuming adequate amounts of vitamin D from diet and/or supplements had a lower risk of RA.
Studies have shown that individuals with lupus have significantly lower blood levels of vitamin D than healthy adults, and vitamin D deficiency is common. Disease activity and symptoms such as fatigue may be higher in patients with lower vitamin D levels. Therefore, vitamin D levels may correlate with lupus symptom severity. In one study, increasing vitamin D levels was shown to have a beneficial effect on fatigue.
Emerging research suggests that women with normal vitamin D levels have higher in vitro fertilization (IVF) success rates when compared with those with low levels. In fact, one study found a 6 percent increase in clinical pregnancy rate with each ng/ml increase in vitamin D level.
Polycystic Ovarian Syndrome (PCOS)
According to an article by Amy Medling of PCOS Diva, 75% of women with PCOS may be deficient in vitamin D. For women with PCOS low vitamin D blood levels are associated with insulin resistance, metabolic issues, and menstrual irregularities.
Low blood levels of vitamin D have been associated with various cancers (breast, colorectal, prostate and others), heart disease, macular degeneration, depression, autoimmune diseases, and type 2 diabetes. Vitamin D is also important for neuromuscular function, and studies have shown that supplementing with vitamin D helps decrease the risk of falls in the elderly.
9. What are the side effects of too much vitamin D?
The good news is that vitamin D overdoses are relatively rare. Most people can safely take vitamin D supplements without any issues. That being said, vitamin D is fat soluble. Therefore, it is difficult for your body to get rid of it if you take too much, resulting in toxicity.
If you take too much vitamin D, higher blood levels of vitamin D (measured as 25(OH)D) can cause high levels of calcium in your blood (hypercalcemia). You are at risk for developing hypercalcemia if you take more than 10,000 IU of vitamin D every day for 3 months or more. Toxicity is more likely to develop if you take 40,000 IU of vitamin D every day for 3 months or more. You are also at higher risk of toxicity if you take more than 300,000 IU in a 24-hour period.
Increased exposure to sunlight does not cause vitamin D toxicity. The body is very efficient at limiting the amount of vitamin D produced by the body. Therefore, you do not have to worry about vitamin D toxicity from too much exposure to sunlight.
In conclusion, vitamin D may benefit many conditions and can be an important part of your health regimen. While it is often called the “sunshine vitamin,” many people will have a hard time getting the amount of vitamin D they need from the sun alone.
We hope this article helped you learn all about vitamin D. You can ask your doctor to perform a simple blood test to determine your vitamin D levels.
If necessary, you can begin taking a vitamin D supplement. It is very important to take vitamin D that has been independently tested and certified. Third-party verification ensures that you do not take more vitamin D than what is disclosed on the label.
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