Best food groups: Fatty fish, meat, eggs, dairy
Also consider: Fortified milk and other fortified foods, beef liver, shrimp, egg yolks, mushrooms
The best ever source: The sun
What is vitamin D and why is it so important? Vitamin D is really not a vitamin; rather, it is a hormone made by the body in response to the exposure of skin to sunlight. Whether it comes from sunlight or the food you eat, it must be converted into an active form that the body can use, called calcitriol. We need vitamin D for the maintenance of strong bones and teeth and the prevention of rickets, a disease characterized by soft, thin, and brittle bones. The vitamin helps the body absorb calcium from food and it is required to coax the immune system into action. Without adequate amounts of vitamin D in the body, a part of the immune system called T cells remains dormant and unresponsive to invading viruses and bacteria. Inadequate vitamin D intake may also be linked to a such conditions as heart disease, diabetes, multiple sclerosis (MS), high blood pressure, certain types of cancer, and depression.
How much is enough?
The DV for vitamin D is 400 IU, based on a 2,000-calorie diet.
Many experts contend the recently revised DRI is still far too low and only addresses bone health and not other medical conditions. In multiple sclerosis, higher levels of vitamin D were associated with lower risk of developing the disease. High levels are also associated with lower relapse rates.
The UL established for vitamin D is 4,000 IU; however, levels far above that have been known to be well tolerated for short periods of time. Signs of vitamin D toxicity include loss of appetite; weight loss; frequent urination; abnormal heart rhythm; and hypocalcaemia (high calcium), which can harden the circulatory system and organs in the body.
Everyone agrees that overexposure to the sun is not a good thing, but oddly enough, it is not one of the causes of vitamin D toxicity. The heat given off the skin limits the amount of vitamin D your body will absorb.
Supplements: You'll find vitamin D supplements in a variety of multivitamins and bone-building formulations. Individual vitamin D supplements come in two different forms, D2 (ergocalciferol, a vegetarian source) and D3 (cholecalciferol, from animal sources), and can be found in liquid, capsule, tablet, and chewable forms. About ten minutes in the midday summer sun, clad in a bathing suit but minus the sunscreen, is thought to produce about 10,000 IU of vitamin D for fair-skinned people. The elderly and darker-skinned individuals don't produce as much vitamin D from UV ray exposure.
1. Rainbow Trout
For a rainbow of information on the healthy properties of trout, see page 292. A review of thirteen studies revealed that eating a serving of fatty fish, such as trout, only once a week could reduce your risk of dying from heart disease by 15 percent. If you added in another 5-ounce serving, total risk was reduced the risk by 22 percent!
You no longer have to don your waders, grab your fly-fishing gear, and head out west to enjoy a delicious dinner of rainbow trout. There are over eight hundred trout-rearing farms in the United States.
2. Sockeye Salmon, Pink, and Chinook
In addition to being a great source of vitamin D, Chinook salmon is an excellent source of niacin and protein, and a good source of omega-3 fatty acids and selenium. Pink and sockeye salmon are runners-up to this runner-up, in terms of vitamin E content. A study that looked at the blood of women who ate two servings of salmon/week found that they had superior antioxidant protection status compared to those women who ate fewer. Higher vitamin A and selenium levels were observed in the two-servings /week group.
Chinook (or king) salmon is not only the largest of the salmon family, with mature adults commonly exceeding 40 pounds and some reportedly as large as 120 pounds, but is also the state fish of Alaska.
3. Swordfish
No doubt about it . . . swordfish is quite nutritious. However, because of its large size and predatory nature, methyl mercury accumulation is a concern with swordfish consumption and the FDA and the EPA have advised pregnant women and children not to eat it.
4. Tuna, Light
The term light tuna actually refers to a combination of species of tuna that are lighter in appearance such as skipjack, yellowfin, tongol, and bigeye. Light tuna varieties are lower in mercury than albacore and are an excellent source of niacin, phosphorus, and vitamins B6, B12, and D; and a good source of iron. The cornerstone of a healthy Mediterranean diet is fatty fish, such as tuna. A review of several studies showed that the risk of having a stroke was fairly significant for those who ate fatty fish once a week. However, those who ate fatty fish five or more times each week had a 31 percent reduced risk of stroke. Elderly subjects who consumed tuna fish had less strokes and more normal MRI scans of the brain.
5. Halibut
Halibut are an excellent source of magnesium, niacin, phosphorus, protein, selenium, and vitamin D, and a good source of omega 3-fats and vitamin B12. In a study of rats that were fed selenium from a variety of dietary sources, halibut proved most efficient in restoring depleted stores out of any food tested.
6. Sardines
Vitamin D plays a very important role in pregnancy, especially in the development of fetal bone health. However, in a study that looked at consumption trends in pregnant women, fewer than 25 percent of those women consumed vitamin D–rich fatty fish, such as sardines.
7. Rockfish
Besides providing vitamin D, a 3-ounce portion of rockfish is also an excellent source of choline and selenium, and a good source of potassium. A study conducted in the United Kingdom found that vitamin D status was best in meat and fish eaters, compared to vegan and vegetarians.
Did you know?
Nutritionally, white button and brown portobello mushrooms compare well to the more expensive shiitake mushroom, though shiitakes are higher in vitamin E and polyunsaturated fatty acids. Much like human skin, mushrooms exposed to ultraviolet light can generate large amounts of vitamin D2. Dole, of pineapple and banana fame, has ramped up this process by drying and grinding portobello mushrooms before exposing them to UV rays. This greatly increases their surface area and their vitamin D production. One teaspoon of the dried mushroom powder provides 600 IU of vitamin D, enough to meet the needs of a vegan.
Source: USDA National Nutrient Database for Standard Reference, Release 24