Vitamin D: It’s not a vitamin at all
March 23, 2021
Get to know the elusive “sunshine vitamin,” that’s actually a hormone and not a vitamin at all. Dive into the risks associated with deficiency and how you can make sure you’re getting enough in your daily diet.
Despite what its name might have you believe, vitamin D is not a vitamin at all—it’s a hormone. The misleadingly-named hormone has a vital function in your body: Helping to absorb calcium from your gut. Calcium is a critical mineral for forming a strong, healthy skeleton.
Vitamin D3 vs. vitamin D2
There are two main forms of vitamin D: vitamin D3 (cholecalciferol) and vitamin D2 (Vitamin D2 (ergocalciferol). The two types of vitamin D differ based on their sources. Vitamin D3 comes from animals, whereas D2 predominantly comes from plants like mushrooms.
Sun exposure. Your body produces vitamin D—or the “sunshine vitamin”—when your skin is exposed to sunlight. When the body is exposed to the ultraviolet B (UVB) from the sun, your cells use the energy to convert the 7-dehydrocholesterol found in your skin into vitamin D. The form of vitamin D produced in your skin in response is called vitamin D3.
Vitamin D-rich foods. In addition to production in response to sunlight, your body absorbs around 10 percent of its vitamin D through food. Certain foods, like fatty fish and seafood, are naturally high in vitamin D. Animal-sourced foods that are naturally vitamin D-rich contain vitamin D3.
Fortified foods. Because only a few foods naturally contain high levels of vitamin D, many staples—like milk, orange juice, and cereals—are fortified with this hormone. Since plant-based vitamin D2 is cheaper to produce, it is the most common form included in fortified foods.
Supplements. You can find vitamin D supplements in the form of capsules, liquids, gummies, and drops that contain either vitamin D3 and vitamin D2. Vitamin D2 supplements are typically extracted from plants like mushrooms, and vitamin D3 supplements are usually extracted from sheep wool.
Should you take vitamin D2 or D3 supplements?
Regardless of how vitamin D is acquired, it is stored in your body’s fat cells. Through a process called hydroxylation, the liver and kidneys turn vitamin D into calcitriol, its hormonally active form. It’s calcitriol that’s responsible for helping your body absorb calcium from the stomach.
Since their function is virtually the same, vitamin D3 and D2 are usually simply referred to as vitamin D. However, some studies have suggested that vitamin D3, the form naturally found in your body, may be more effective at increasing and preserving overall vitamin D levels than D2. If you choose to supplement your vitamin D intake, look for brands with vitamin D3 like Pure Encapsulations or NOW.
Vitamin D deficiency
Once called “an ignored epidemic,” vitamin D deficiency is a problem for over a billion people around the world. In the U.S. alone, it is estimated that more than 40.6 percent of adults do not get sufficient vitamin D. The problem is particularly prevalent among Hispanic (69.2 percent) and Black (76 percent) adults. Although this phenomenon is not fully understood, experts believe that darker skin contains more of the melanin that inhibits the skin’s ability to synthesize vitamin D.
Vitamin D is needed to absorb, build, and maintain strong, healthy bones. It’s also vital to cell growth and blood sugar regulation and assists in the functioning of muscles, nerves, and the immune system.
Without sufficient vitamin D, you are left vulnerable to a number of serious conditions. The health effects associated with vitamin D deficiency include:
Osteoporosis, a disease characterized by brittle bones
Heart disease and high blood pressure
Diabetes
Multiple sclerosis
Cancer, including colon, prostate, and breast cancer
Cognitive impairment in older adults
Severe asthma in children
Rickets, or the softening and weakening of bones in children
Osteomalacia, or the softening and weakening of bones in adults
Who is at risk of vitamin D deficiency?
The following groups may be at higher risk of vitamin D deficiency:
People who have limited sun exposure. People with limited sun exposure may be unable to get sufficient vitamin D from sunlight. Homebound individuals and people who live in countries far from the equator may be particularly at risk.
People with darker skin. Some research has suggested that adults with darker skin may be at a higher risk for vitamin D deficiency. Darker skin contains more melanin, which protects the skin from sun damage but also inhibits the skin’s ability to synthesize vitamin D. However, the health consequences of lower levels of vitamin D due to dark skin are not yet fully understood.
People who are obese. Individuals with a high body fat percentage tend to have higher amounts of subcutaneous fat, which inhibits the release of vitamin D into the blood. Other conditions—including end-stage liver disease and fat malabsorption syndromes like cystic fibrosis —can also hinder the skin’s production of vitamin D.
Newborn babies. Breastfeeding infants may need vitamin D supplements if their mother is vitamin D deficient. Recognizing the importance of vitamin D intake, many milk formulas tend to be fortified with vitamin D.
Older adults. As people age, their skin becomes less efficient at synthesizing vitamin D. Production of this hormone falls around 50% as a result of an age-related decline in renal function. Aging also causes a decrease in calcium absorption that is followed by a decline in calcitriol. Vitamin D also needs to be activated in the kidneys before it can be used by the body—a function that also decreases with aging. In addition to inhibited vitamin D synthesis, older adults are more likely to spend more time indoors and experience inadequate sun exposure. Health experts recommend that aging adults receive at least 30 minutes of sun exposure twice a week to generate adequate levels of vitamin D from sunshine.
How much vitamin D should you be getting?
According to the National Institutes of Health, most children and adults should get at least 600 international units (IU) or 15 micrograms (mcg) of vitamin D per day. Adults over 71+ need 800 IU (20 mcg) per day, while infants need 400 IU (10 mcg).
How much of this can you get from natural sun exposure? It may vary greatly depending on the time of the year, location relative to the equator, and your skin color. But to give you a ballpark idea, someone in Miami with fair to beige skin color would need around six minutes of sun exposure on their face, neck, hands, and arms in the summer to synthesize 1,000 IU (25 mcg) of vitamin D, and 15 minutes in the winter. Someone in Miami with dark brown to black skin would need 15 and 29 minutes, respectively.
If you are unable to go outside or belong to a group at risk of vitamin D deficiency, health experts recommend taking a daily supplement containing 600 IU (15 mcg) of vitamin D.
Sources of vitamin D
As we’ve demonstrated, sunlight is the best source of vitamin D. However, sun exposure alone may not be enough to get your body all the vitamin D it needs—particularly if you fall into one of the at-risk groups listed above. But even if you do get plenty of outside time, you may have a hard time getting sufficient vitamin D from sunlight during October through March. To naturally increase vitamin D intake, add these foods and supplements to your diet:
Salmon
Like its fellow fatty fishes—including tuna, mackerel, and sardines—salmon is an excellent source of vitamin D. However, not all salmon is created equal, whether the salmon is wild or farmed can have a major impact on its vitamin D content. While a 3.5-ounce serving of farmed Atlantic salmon has 526 IU of vitamin D, a wild-caught salmon can have 988 IU per 3.5-ounce serving.
Eggs
One large egg typically has 41 IU of vitamin D. Farm-raised chickens are free to roam outside in the sunshine and lay eggs that contain three to four times higher levels of vitamin D. Similarly, chickens that are raised on vitamin D-enriched feed may lay eggs with up to 6,000 IU (150 mcg) of vitamin D per egg.
Mushrooms
Mushrooms are the only plants containing natural vitamin D (if you recall, that’s vitamin D3 since it comes from a plant). Virtually all varieties—including maitake, morel, chanterelle, oyster, and shiitake—produce natural levels of vitamin D when exposed to sunlight (not unlike humans). And, like humans, mushrooms produce higher levels of vitamin D when exposed to prolonged UV light.
Unfortunately, most commercially cultivated mushrooms are grown in the dark and, therefore, lack vitamin D. The benefit of raising mushrooms in the dark is to preserve the moisture that mushroom spores need to reproduce. However, mushrooms do not need a dark environment to grow. Some commercial growers produce vitamin D-enhanced mushrooms by exposing them briefly to UV lights. UV-treated portobello mushrooms can pack between 130 and 450 IU (3.25 to 3.5 mcg) of vitamin D per 3.5-ounce serving. Similarly, button mushrooms that are exposed to midday sun for as little as 15 minutes can generate more than 400 IU (10 mcg) of vitamin D.
On the other hand, wild mushrooms, which are naturally exposed to sunlight, can pack astounding levels of vitamin D. Certain types of wild mushrooms can come with up to 2,300 IU (57.5 mcg) per 3.5-ounce serving. But careful! Many wild mushrooms are similar in appearance, making it all too easy to mistake an edible variety with a poison variety. It’s best to purchase wild mushrooms from a reputed vendor or learn about mushroom hunting and identification from an expert.
Fortified milk
The cow milk sold in the U.S. is typically fortified with vitamin D. One cup of fortified milk contains 115 to 130 IU (2.875 mcg to 3.25 mcg). In addition, plant-based milk is often fortified with vitamin D. A cup of soymilk can have 107 to 117 IU (2.68 to 2.93 mcg) of vitamin D, while a cup of almond milk can pack 150 IU (3.75 mcg).
Cod liver oil
A centuries-old supplement, cod liver oil has long been used to prevent rickets, a now not-so-common disease caused by vitamin D deficiency. As its name suggests, cod liver oil comes from the liver of Atlantic cod. One teaspoon of cod liver oil contains a whopping 1,360 IU (34 mcg) of vitamin D, along with plenty of vitamin A and omega-3 fatty acids to boot.
Capsules, liquids, chewables, and drops
Vitamin D supplements come in the form of capsules, liquids, chewables, and drops. Supplements typically pack anywhere from 1,000 IU (25 mcg) to 10,000 IU (250 mcg) per serving.
The benefits of vitamin D
In addition to its critical role in growing and maintaining healthy bones, vitamin D comes with an array of other health benefits. Here are just six of the many benefits of vitamin D:
Vitamin D can strengthen your muscles.
In addition to its well-known bone-building and fortifying powers, vitamin D can help strengthen muscles. Research has found that vitamin D plays a role in developing and optimizing muscle strength and performance. On the other hand, low levels of vitamin D are associated with a higher risk of falling and weakness in older adults.
Vitamin D can help you maintain healthy body composition.
Mounting evidence suggests that higher levels of vitamin D may be helpful in maintaining healthy body composition. Research has linked higher body fat levels with low levels of vitamin D. Other studies have suggested that getting adequate vitamin D may help with weight loss and decreasing body fat.
Vitamin D can fight depression.
Researchers have found a significant link between depression and vitamin D deficiency. Studies have also indicated that vitamin D deficiency may be more common in individuals experiencing anxiety.
Vitamin D can boost the immune system.
Vitamin D has clear benefits for the immune system and plays an important role in fighting off viral infections and other illnesses. Research has found that healthy levels of vitamin D may help protect against respiratory illnesses—like COVID-19. Other studies have found that patients with sufficient levels of vitamin D had a lower risk of mortality and complications due to COVID-19.
Vitamin D can help prevent cancer.
A growing body of research suggests that vitamin D supplementation may improve cancer outcomes. Activated vitamin D, or calcitriol, is believed to help regulate cell growth and may be a powerful inhibitor of cancer cell formation. And because vitamin D can help regulate weight and decrease body fat, it may be effective in reducing the visceral fat linked to colon cancer, breast cancer, and prostate cancer.
Vitamin D can help keep your teeth healthy.
Because it helps our body absorb calcium, vitamin D is key in promoting oral health and preventing tooth decay. Research has also found that vitamin D can help fight cavities and stave off gum diseases like gingivitis and periodontitis.
How to find out if you’re getting enough vitamin D
Because you can’t determine whether you’re getting sufficient levels of vitamin D on your own, your most accurate, efficient option is to test your health blood panels. In addition to revealing your body’s baseline values for vital general health markers like cholesterol, blood testing can provide useful data on performance biomarkers like vitamin D. By measuring the levels of the 25-hydroxyvitamin D (25(OH)D)—the major circulating form of vitamin D—in your blood, blood panel tests can detect deficiencies in your blood. Order an at-home health blood panel test today.
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