Recently I have had a few clients tell me that when the had their blood tested at the doctor, the findings indicated that they were low in vitamin D. Here is some helpful information about the vitamin...
Vitamin D is naturally produced by the human body when exposed to direct sunlight. Season, geographic latitude, time of day, cloud cover, smog, and sunscreen affect UV ray exposure and vitamin D synthesis in the skin, and it is important for individuals with limited sun exposure to include good sources of vitamin D in their diet. Extra vitamin D is also recommended for older adults and people with dark skin. Individuals having a high risk of deficiency should consume 25 μg (1000 IU) of vitamin D daily to maintain adequate blood concentrations of 25-hydroxyvitamin D.
As civilization and the Industrial Revolution enabled humans to work indoors and wear more clothes when outdoors, these cultural changes reduced natural production of vitamin D and caused deficiency diseases. In many countries, such foods as milk, yogurt, margarine, oil spreads, breakfast cereal, pastries, and bread are fortified with vitamin D2 and/or vitamin D3, to minimize the risk of vitamin D deficiency. In the United States and Canada, for example, fortified milk typically provides 100 IU per cup, or a quarter of the estimated adequate intake for adults over age 50. A 1992 study, however, found that the actual vitamin D content of milk varies widely. Supplementation of 100 IU (2.5 microgram) vitamin D3 raises blood calcidiol levels by 2.5 nmol/litre (1 ng/ml).
Natural sources of vitamin D include:
- Fish liver oils, such as cod liver oil, 1 Tbs. (15 ml) provides 1,360 IU (one IU equals 25 ng)
- Fatty fish species, such as:
- Herring, 85 g (3 ounces (oz)) provides 1383 IU
- Catfish, 85 g (3 oz) provides 425 IU
- Salmon, cooked, 100 g (3.5 oz]) provides 360 IU
- Mackerel, cooked, 100 g (3.5 oz]), 345 IU
- Sardines, canned in oil, drained, 50 g (1.75 oz), 250 IU
- Tuna, canned in oil, 85 g (3 oz), 200 IU
- Eel, cooked, 100 g (3.5 oz), 200 IU
- A whole egg, provides 20 IU
- Beef liver, cooked, 100 g (3.5 oz), provides 15 IU
- UV-irradiated mushrooms (Vitamin D2)
In the United States (U.S.), the 100% Daily Value used for product labels is 800 IU/day (as of new 2009 data) and typical diets provide about 100 IU/day. Although milk is usually fortified, the average daily consumption by most Americans is insufficient in obtaining levels of vitamin D recommended by various medical authorities. While adequate intake has been defined as 200 IU/day for ages infant to 50, 400/day for 51-70, and 600/day over 70, the American Academy of Pediatrics argues that these recommendations are insufficient and recommends a minimum of 400 IU, even for infants. The NIH has set the safe upper limit at 2000 IU, but acknowledges newer data supporting a UL as high as 10,000 IU/day. Some experts have recommended greatly increasing vitamin D intake.  The Institute Of Medicine is revisiting vitamin D and calcium recommendations with a report expected to be released before the end of summer 2010.
Vitamin D malnutrition may also be linked to an increased susceptibility to several chronic diseases, such as high blood pressure, tuberculosis, cancer, periodontal disease, multiple sclerosis, chronic pain, seasonal affective disorder , peripheral artery disease, cognitive impairment which includes memory loss and foggy brain, and several autoimmune diseases including type 1 diabetes (see role in immunomodulation). There is an association between low vitamin D levels and Parkinson's disease, but whether Parkinson's causes low vitamin D levels, or whether low vitamin D levels play a role in the pathogenesis of Parkinson's disease has not been established. A resurgence of interest in vitamin D deficiency has led to continued studies on the topic and a focus on educating the consumer on the prevalence and degree of deficiency among the general public.
I would recommend clients to supplement with extra vitamin d unless they are in the sunlight quite often. I would recommend around 1000-2000 iu a day taken in smaller doses at several intervals! The TopForm Be a Man multivitamin and the TopForm Pretty on the Inside Women multivitamin each contain around 400 iu