Yoga Health Portal

Vitamins

Vitamin D

Vitamin D is both a vitamin and a hormone. It's a vitamin because your body cannot absorb calcium without it; it's a hormone because your body manufactures it in response to your skin's exposure to sunlight.
There are two major forms of vitamin D, and both have the word calciferol in their names. In Latin, calciferol means "calcium carrier." Vitamin D 3 (cholecalciferol) is made by the body and is found in some foods. Vitamin D 2 (ergocalciferol) is the form most often added to milk and other foods, and the form you're most likely to use as a supplement.

Strong evidence tells us that the combination of vitamin D and calcium supplements can be quite helpful for preventing and treating osteoporosis. Other potential uses of vitamin D have little supporting evidence.

Dosages of vitamin D

Dosages of vitamin D are often expressed in terms of international units (IU) rather than milligrams. The official US and Canadian recommendations for daily intake of vitamin D are as follows:

•    Infants 0-12 months: 200 IU (5 mcg)
•    Males and females
o    1-50 years: 200 IU (5 mcg)
o    51–70 years: 400 IU (10 mcg)
o    71 years and older: 600 IU (15 mcg)
•    Pregnant women: 200 IU (5 mcg)
•    Nursing women: 200 IU (5 mcg)

However, growing evidence suggests that these recommendations may be too low. In a study of military personnel in submarines, use of 400 IU of vitamin D daily was inadequate to maintain bone health, while six days of sun exposure proved capable of supplying enough vitamin D for 49 sunless days. In addition, a study of veiled Islamic women living in Denmark found that 600 IU of vitamin D daily was insufficient to raise vitamin D levels in the blood to normal levels. The authors of this study recommend that sun-deprived individuals should receive 1,000 IU of vitamin D daily.

There is very little vitamin D found naturally in the foods we eat (the best sources are coldwater fish). In many countries, vitamin D is added to milk and other foods like breakfast cereals and margarine, contributing to our daily intake.

As indicated by the study of submarine personnel noted above, by far the best source of vitamin D is sunlight. However, current recommendations, which stress sun avoidance and the use of sunblock, may have the unintended effect of increasing the prevalence of vitamin D deficiency. Severe vitamin D deficiency was common in England in the 1800s due to coal smoke obscuring the sun. During that time, cod liver oil, which is high in vitamin D, became popular as a supplement for children to help prevent rickets. (Rickets is a disease caused by vitamin D deficiency in which developing bones soften and curve because they aren't receiving enough calcium.)
Without question, if you are concerned about osteoporosis, you should take calcium and vitamin D. The combination appears to help prevent bone loss.  This is true even if you are taking other treatments for osteoporosis; after all, you can't build bone without calcium, and you can't properly absorb and utilize calcium without adequate intake of vitamin D. Interestingly, vitamin D may also help prevent the falls that lead to osteoporotic fractures.

Other uses of vitamin D are less well documented.
Some evidence suggests that getting adequate vitamin D may help prevent cancer of the breast, colon, pancreas, prostate, and skin, but the research on this question has yielded mixed results. One study suggests that combined use of calcium plus vitamin D, but not either supplement separately, can help reduce risk of colon cancer. However, an extremely large study involving over 36,000 post-menopausal women found that supplementing the diet with 1,000 mg of calcium plus 400 IU of vitamin D daily did not lower the risk of breast cancer over a period of 7 years. Based on the results of this placebo-controlled study, there does not appear to be a connection between vitamin D and breast cancer risk.
Weak evidence hints that adequate vitamin D intake might reduce the risk of hypertension and diabetes.
One preliminary study suggests that supplementation with vitamin D and calcium may be helpful for women with polycystic ovary syndrome.

A meta-analysis (formal statistical review) of published studies found some evidence that use of vitamin D at recommended levels may reduce overall mortality. This article suggested, but did not attempt to establish, just how vitamin D might accomplish this.
Vitamin D is sometimes mentioned as a treatment for psoriasis. However, this recommendation is based on Danish studies using calcipotriol, a variation of vitamin D 3 that is used externally (applied to the skin). Calcipotriol does not affect your body's absorption of calcium, so it is a very different substance from the vitamin D you can purchase at a store.

It has been suggested that since vitamin D levels in the body drop in the wintertime, vitamin D supplements might be helpful for seasonal affective disorder ("winter blues"). A small double-blind, placebo-controlled trial conducted during winter on 44 people found that vitamin D supplements produced improvements in various measures of mood. However, a double-blind, placebo-controlled study of 2,217 women over 70 failed to find benefit.  It has been hypothesized that light therapy (used successfully for SAD) works by raising vitamin D levels, but there is some evidence that this is not the case. 

Vitamin D supplements also do not appear to help enhance growth in healthy children.
When taken at recommended dosages, vitamin D appears to be safe. However, when used at considerable excess, vitamin D can build up in the body and cause toxic symptoms. At an intake level of about 40,000 IU daily (about 100 times the recommended daily intake) vitamin D can cause dangerous elevations in blood calcium levels. Doses five times higher than this were consumed by a few individuals due to a manufacturing error; the resulting toxicity was severe and may have caused death in one individual.

However, short of these vastly excessive dosages, it is not clear at what level vitamin D becomes toxic. The official safe upper limits for vitamin D daily intake are as follows:

•    Infants 0-12 months: 1,000 IU (25 mcg)
•    Males and females 1 year and older: 2,000 IU (50 mcg)
•    Pregnant and nursing women: 2,000 IU (50 mcg)

Note, however, that some authorities believe these upper limits have been set a bit too low. Their arguments closely parallel those discussed in the Requirements/Sources section regarding nutritional needs.
There is no disagreement that people with sarcoidosis or hyperparathyroidism should never take vitamin D without first consulting a physician.
Taking vitamin D and calcium supplements might interfere with some of the effects of drugs in the calcium-channel blocker family. It is very important that you consult your physician before trying this combination.
The combination of calcium, vitamin D, and thiazide diuretics could potentially lead to excessive calcium levels in the body. If you are taking thiazide diuretics, you should consult with a physician about the right doses of vitamin D and calcium for you.

Natural vegetarian sources of vitamin D include:
Mushrooms are the only vegan source of vitamin D; (after UV light or sunlight exposure).

Vitamin A

Vitamin A is a fat-soluble vitamin.
Vegetarians, young children, and alcoholics may need extra Vitamin A. You might also need more if you have certain conditions, such as liver diseases, cystic fibrosis, and Crohn’s disease. Check with your health care provider to see if you need to take vitamin A supplements.

Function

Vitamin A helps form and maintain healthy teeth, skeletal and soft tissue, mucous membranes, and skin. Vitamin A promotes good vision, especially in low light. It may also be needed for reproduction and breast-feeding. It is also known as retinol because it produces the pigments in the retina of the eye. Retinol is an active form of vitamin A. It is found in animal liver, whole milk, and some fortified foods.
Vitamin A is an antioxidant because of Beta-carotene. Carotenoids are dark colored dyes found in plant foods that can turn into a form of vitamin A. One such carotenoid is beta-carotene. Beta-carotene is an antioxidant.
Antioxidants are substances that may protect your cells against the effects of free radicals. Free radicals are molecules produced when your body breaks down food, or by environmental exposures like tobacco smoke and radiation. Free radicals are believed to contribute to certain chronic diseases and play a role in the degenerative processes seen in aging.
Sources of beta-carotene are carrots, pumpkin, sweet potatoes, winter squashes, cantaloupe, pink grapefruit, apricots, broccoli, spinach, and most dark green, leafy vegetables. The more intense the color of a fruit or vegetable, the higher the beta-carotene content. These vegetable sources of beta-carotene are free of fat and cholesterol.

Food Sources

Vitamin A can come from plant or animal sources. Plant sources include colorful fruits and vegetables. Vitamin A is also added to foods like cereals.
Animal sources include eggs, meat, milk, cheese, cream, liver, kidney, cod, and halibut fish oil. However, all of these sources are high in saturated fat and cholesterol (except for skim milk that has been fortified with Vitamin A).

Natural sources of vitamin A include:
milk                 28 mcg (3%)

Side Effects

If you don't get enough vitamin A, you are more susceptible to infectious diseases and vision problems.
If you get too much vitamin A, you can become sick. Large doses of vitamin A can also cause birth defects. Acute vitamin A poisoning usually occurs when an adult takes several hundred thousand IU. Symptoms of chronic vitamin A poisoning may occur in adults who regularly take more than 25,000 IU a day. Babies and children are more sensitive and can become sick after taking smaller doses of vitamin A or vitamin A-containing products such as retinol (found in skin creams).
Increased amounts of beta-carotene can turn the color of skin to yellow or orange. The skin color returns to normal once the increased intake of beta-carotene is reduced.

Recommendations

The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a lot of grains, vegetables, milk, fruits, a bit less of meat and beans, and  smaller part of oils. The Food and Nutrition Board at the Institute of Medicine recommends the following:
Infants
•    0 - 6 months: 400 micrograms per day (mcg/day)
•    7 - 12 months: 500 mcg/day
Children
•    1 - 3 years: 300 mcg/day
•    4 - 8 years: 400 mcg/day
•    9 - 13 years: 600 mcg/day
Adolescents and Adults
•    Males age 14 and older: 900 mcg/day
•    Females age 14 and older: 700 mcg/day
Specific recommendations depend on age, gender, and other factors (such as pregnancy). Women who are pregnant or producing breast milk (lactating) need higher amounts. Ask your doctor what dose is best for you.