Vitamin D, also known as the sunshine vitamin, can be produced in the body with mild sun exposure or consumed in food or supplements. Adequate vitamin D intake is important for the regulation of calcium and phosphorus absorption, maintenance of healthy bones and teeth, and is suggested to supply a protective effect against multiple diseases and conditions such as cancer, type 1 diabetes and multiple sclerosis.
In spite of the name, vitamin D is not actually considered a vitamin. Because the body can produce its own vitamin D, it is not necessarily an essential part of the diet and is considered a pro-hormone.
It is estimated that sensible sun exposure on bare skin for 5-10 minutes 2-3 times per week allows the body the ability to produce sufficient vitamin D. Despite this, recent studies have suggested that up to 50% of adults and children worldwide are vitamin D deficient.
This MNT Knowledge Center feature is part of a collection of articles on the health benefits of popular vitamins and minerals. It provides an in-depth look at recommended intake of vitamin D, its possible health benefits, foods high in vitamin D and any potential health risks of consuming vitamin D.
Recommended intake
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.
- 0-50 years:5 micrograms or 200 IU per day
- 51-70 years: 10 micrograms of 400 IU per day
- 71+: 600 IU per day.
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 UVB rays required to produce vitamin D.
A sunscreen with 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.
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.
Possible health benefits of consuming vitamin D
Healthy bones
Vitamin D plays a substantial role in the regulation of calcium and maintenance of phosphorus levels in the blood, two factors that are extremely important for maintaining healthy bones. Vitamin D deficiency in children can cause rickets, a disease characterized by a severely bow-legged appearance triggered by impaired mineralization and softening of the bones.
In adults, vitamin D deficiency manifests as osteomalacia or osteoporosis. Osteomalacia results in poor bone density, muscular weakness and often causes small pseudo fractures of the spine, femur and humerus. Osteoporosis is the most common bone disease among post-menopausal women and older men.
Reduced risk of flu
Children given 1,200 IU of vitamin D per day for 4 months during the winter reduced their risk of influenza A infection by over 40%.2
Reduced risk of diabetes
Several observational studies have shown an inverse relationship between blood concentrations of vitamin D in the body and risk of type 2 diabetes. In type 2 diabetics, insufficient vitamin D levels may have an adverse effect on insulin secretion and glucose tolerance.3 In one particular study, infants who received 2,000 IU/day of vitamin D had an 88% lower risk of developing type 1 diabetes by the age of 32.
Healthy infants
Children with normal blood pressure who were given 2,000 IU/day had significantly lower arterial wall stiffness after 16 weeks compared with children who were given only 400 IU/day.
Healthy pregnancy
Pregnant women who are deficient in vitamin D seem to be at greater risk of developing preeclampsia and needing a cesarean section. Poor vitamin D status is also associated with gestational diabetes mellitus and bacterial vaginosis in pregnant women. It is also important to note that vitamin D levels that were too high during pregnancy were associated with an increase in food allergy of the child during the first two years of life.
Cancer prevention
Vitamin D is extremely important for regulating cell growth and for cell-to-cell communication. Some studies have suggested that calcitriol (the hormonally active form of vitamin D) can reduce cancer progression by slowing the growth and development of new blood vessels in cancerous tissue, increasing cancer cell death and by reducing cell proliferation and metastases. Vitamin D has an influence on more than 200 human genes, which can be impaired when D status is suboptimal.3
Vitamin D deficiency has also been associated with an increased risk of cardiovascular disease, hypertension, multiple sclerosis, autism, Alzheimer's disease, rheumatoid arthritis, asthma severity and swine flu, however more reliable studies are needed before these associations can be proven.
Foods sources of vitamin D
Sunlight is the most common and efficient source of vitamin D. The richest food sources of vitamin D are fish oil and fatty fish.
- 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.
Recent developments on vitamin D food sources from MNT news
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.
Written by Megan Ware, RDN, LD, registered dietitian and nutritionist
Vitamin D Deficiency There are some effects of Vitamin D deficiency. Dizziness, Hair loss, Pain in the joints, gloom. Especially dizz...
Vitamin D and Skin of Hair Loss About 100 hairs fall out every day, and this is normal. Hair loss is referred to only fail if significa...