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Recommended intake of vitamin D
Vitamin D intake can be measured in two ways: in micrograms (mcg) and International Units (IU). One microgram of vitamin D is equal to 40 IU of vitamin D. The recommended intakes of vitamin D throughout life were updated by the US Institutes of Medicine (IOM) in 2010 and are currently set at:
- Infants 0-12 months - 400 IU (10 mcg)
- Children 1-18 years - 600 IU (15 mcg)
- Adults to age 70 - 600 IU (15 mcg)
- Adults over 70 - 800 IU (20 mcg)
- Pregnant or lactating women - 600 IU (15 mcg).
Although the body has the ability to make vitamin D, there are many reasons deficiency occurs. Darker skin pigments and sunscreen use can significantly decrease the body's ability to absorb the ultraviolet radiation B (UVB) rays required to produce vitamin D.
The sunshine vitamin - vitamin D - can be produced in the body with sun exposure or consumed in food or supplements.
A sunscreen with sun protection factor (SPF) 30 can reduce the body's ability to synthesize the vitamin by 95%. The skin also has to be directly exposed to the sunlight, not covered by clothing, in order to start vitamin D production. Even the angle at which sunrays hit the earth can affect absorption.
People who live in northern latitudes or areas of high pollution, work at night and stay home during the day or are homebound should aim to consume extra vitamin D from food sources whenever possible. Infants who are exclusively breastfed are also at high risk of vitamin D deficiency, especially if they are dark-skinned or have minimal sun exposure. The American Academy of Pediatrics recommends that all breastfed infants receive 400 IU/day of an oral vitamin D supplement.
Vitamin D supplements are available, but it is best to obtain any vitamin or mineral through natural sources first. It is not the individual vitamin or mineral alone that make certain foods an important part of our diet, but the synergy of that foods nutrients working together and allowing for greater absorption. For example, vitamin D is fat soluble, meaning that its absorption requires dietary fat. In addition, magnesium is needed to convert vitamin D into its active form.
It has been proven time and again that isolating certain nutrients in supplement form will not provide the same health benefits as consuming the nutrient from a whole food. First focus on obtaining your daily vitamin D requirement from sunlight and foods then use supplements as a backup.
Researchers from Boston University School of Medicine found that higher vitamin D levels in healthy individuals have a significant impact on the genes that are involved in several biologic pathways associated with illnesses, including cancer, autoimmune disease, cardiovascular disease and infectious diseases.
Researchers at the University of Minnesota found that Vitamin D levels in the body at the start of a low-calorie diet predict weight loss success,suggesting a possible role for vitamin D in weight loss.
Many cases of leukemia across the globe may be caused by vitamin D deficiency as a result of low sunlight exposure. This is the conclusion of a new study published in PLOS One.
Vitamin D food sources
The richest sources of vitamin D are fish oil and fatty fish - with 1 tablespoon of cod liver oil containing 1,360IU.
Sunlight is the most common and efficient source of vitamin D. The richest food sources of vitamin D are fish oil and fatty fish. Here is a list of foods with good levels of vitamin D:
- Cod liver oil, 1 tablespoon: 1,360 IU
- Herring, fresh, raw, 4 ounces: 1,056 IU
- Swordfish, cooked, 4 ounces: 941 IU
- Raw maitake mushrooms, 1 cup: 786 IU
- Salmon, sockeye, cooked, 4 ounces: 596 IU
- Sardines, canned, 4 ounces: 336 IU
- Fortified skim milk, 1 cup: 120 IU
- Tuna, canned in water, drained, 3 ounces: 68 IU
- Egg, chicken, whole large: 44 IU.
Fortifying bread with vitamin D - an episode in the American Chemical Society's (ACS) award-winning "Global Challenges/Chemistry Solutions" podcast series stated that vitamin D-fortified bread could join milk "as a mainstay for providing an essential nutrient that is difficult to get naturally in foods."
Potential health risks of consuming vitamin D
The Upper Level (UL) limit recommended for vitamin D is 4000 IU per day. However, the National Institutes of Health (NIH) has suggested that vitamin D toxicity is unlikely at daily intakes below 10,000 IU/day.
Excessive consumption of vitamin D can lead to the over calcification of bone and the hardening of blood vessels, kidney, lungs and heart. The most common symptoms of hypervitaminosis D are headache and nausea but can also include loss of appetite, dry mouth, a metallic taste, vomiting, constipation, and diarrhea.
It is the total diet or overall eating pattern that is most important in disease prevention and achieving good health. It is better to eat a diet with a variety than to concentrate on one individual nutrient as the key to good health.
Higher monthly doses of vitamin D do not appear to improve the function of lower extremities, but they may increase the risk of falls in senior patients, according to research published online by JAMA Internal Medicine.