Vitamin D is both a nutrient we eat and a hormone our bodies make. It is a fat-soluble vitamin that has long been known to help the body absorb and retain calcium and phosphorus; both are critical for building bone. Also, laboratory studies show that vitamin D can reduce cancer cell growth, help control infections and reduce inflammation. Many of the body’s organs and tissues have receptors for vitamin D, which suggest important roles beyond bone health, and scientists are actively investigating other possible functions.
Few foods naturally contain vitamin D, though some foods are fortified with the vitamin. For most people, the best way to get enough vitamin D is taking a supplement because it is hard to eat enough through food. Vitamin D supplements are available in two forms: vitamin D2 (“ergocalciferol” or pre-vitamin D) and vitamin D3 (“cholecalciferol”). Both are also naturally occurring forms that are produced in the presence of the sun’s ultraviolet-B (UVB) rays, hence its nickname, “the sunshine vitamin,” but D2 is produced in plants and fungi and D3 in animals, including humans.
Vitamin D production in the skin is the primary natural source of vitamin D, but many people have insufficient levels because they live in places where sunlight is limited in winter, or because they have limited sun exposure due to being inside much of the time. Also, people with darker skin tend to have lower blood levels of vitamin D because the pigment (melanin) acts like a shade, reducing production of vitamin D (and also reducing damaging effects of sunlight on skin, including skin cancer).
What is the recommended amounts of vitamin D?
The Recommended Dietary Allowance for vitamin D provides the daily amount needed to maintain healthy bones and normal calcium metabolism in healthy people. It assumes minimal sun exposure.
RDA: The Recommended Dietary Allowance for adults 19 years and older is 600 IU daily for men and women, and for adults >70 years it is 800 IU daily.
UL: The Tolerable Upper Intake Level is the maximum daily intake unlikely to cause harmful effects on health. The UL for vitamin D for adults and children ages 9+ is 4,000 IU.
Many people may not be meeting the minimum requirement for the vitamin. NHANES data found that the median intake of vitamin D from food and supplements in women ages 51 to 71 years was 308 IU daily, but only 140 IU from food alone (including fortified products).
Worldwide, an estimated 1 billion people have inadequate levels of vitamin D in their blood, and deficiencies can be found in all ethnicities and age groups. In industrialized countries, doctors are seeing the resurgence of rickets, the bone-weakening disease that had been largely eradicated through vitamin D fortification. There is scientific debate about how much vitamin D people need each day and what the optimal serum levels should be to prevent disease. The Institute of Medicine (IOM) released in November 2010 recommendations increasing the daily vitamin D intake for children and adults in the U.S. and Canada, to 600 IU per day.
The report also increased the upper limit from 2,000 to 4,000 IU per day. Although some groups such as The Endocrine Society recommend 1,500 to 2,000 IU daily to reach adequate serum levels of vitamin D, the IOM felt there was not enough evidence to establish a cause and effect link with vitamin D and health benefits other than for bone health. Since that time, new evidence has supported other benefits of consuming an adequate amount of vitamin D, although there is still not consensus on the amount considered to be adequate.
How To Take Vitamin D Correctly
Generally, it is quite common to hear people asking if vitamin D should be taken with food or not. According to Healthline, Vitamin D is a fat-soluble vitamin, meaning that it does not dissolve in water and is absorbed best in your bloodstream when paired with high-fat foods. For this reason, it’s recommended to take vitamin D supplements with a meal to enhance absorption.
Supplementation with 800 to 1000 IU/d of vitamin D or 50,000 IU monthly is safe for most people and can ensure levels of vitamin D within the optimal range. This intake is within the currently recommended safe upper tolerable limit for vitamin D of 2000 IU/d for those aged 1 year and older.
Vitamin D Content of Selected Foods
|Cod liver oil, 1 tablespoon||34.0||1,360||170|
|Trout (rainbow), farmed, cooked, 3 ounces||16.2||645||81|
|Salmon (sockeye), cooked, 3 ounces||14.2||570||71|
|Mushrooms, white, raw, sliced, exposed to UV light, ½ cup||9.2||366||46|
|Milk, 2% milkfat, vitamin D fortified, 1 cup||2.9||120||15|
|Soy, almond, and oat milks, vitamin D fortified, various brands, 1 cup||2.5-3.6||100-144||13-18|
|Ready-to-eat cereal, fortified with 10% of the DV for vitamin D, 1 serving||2.0||80||10|
|Sardines (Atlantic), canned in oil, drained, 2 sardines||1.2||46||6|
|Egg, 1 large, scrambled**||1.1||44||6|
|Liver, beef, braised, 3 ounces||1.0||42||5|
|Tuna fish (light), canned in water, drained, 3 ounces||1.0||40||5|
|Cheese, cheddar, 1.5 ounce||0.4||17||2|
|Mushrooms, portabella, raw, diced, ½ cup||0.1||4||1|
|Chicken breast, roasted, 3 ounces||0.1||4||1|
|Beef, ground, 90% lean, broiled, 3 ounces||0||1.7||0|
|Broccoli, raw, chopped, ½ cup||0||0||0|
|Carrots, raw, chopped, ½ cup||0||0||0|
|Almonds, dry roasted, 1 ounce||0||0||0|
|Rice, brown, long-grain, cooked, 1 cup||0||0||0|
|Whole wheat bread, 1 slice||0||0||0|
|Lentils, boiled, ½ cup||0||0||0|
|Sunflower seeds, roasted, ½ cup||0||0||0|
|Edamame, shelled, cooked, ½ cup||0||0||0|
* DV = Daily Value. The FDA developed DVs to help consumers compare the nutrient contents of foods and dietary supplements within the context of a total diet. The DV for vitamin D is 20 mcg (800 IU) for adults and children aged 4 years and older. The labels must list vitamin D content in mcg per serving and have the option of also listing the amount in IUs in parentheses. Foods providing 20% or more of the DV are considered to be high sources of a nutrient, but foods providing lower percentages of the DV also contribute to a healthful diet.
** Vitamin D is in the yolk.
The U.S. Department of Agriculture’s (USDA’s) FoodData Central lists the nutrient content of many foods and provides a comprehensive list of foods containing vitamin D arranged by nutrient content and by food name. However, FoodData Central does not include the amounts of 25(OH)D in foods.