Recommendations for daily vitamin D intake may be too low to prevent deficiencies in some women.

The study found that during the winter, many women in Canada had insufficient blood levels of vitamin D despite consuming more than 200 international units (IU) daily, the recommended intake for adults younger than 50 years of age, in milk or dietary supplements.

Vitamin D, which helps the body to absorb calcium, is added to milk and is also made by the body when skin is exposed to sunlight.

But a lack of sunlight in northern countries such as Canada means that dietary intake becomes even more crucial to prevent rickets in children and osteoporosis in adults.

Nutritional laws have been grossly wrong about adult needs for vitamin D.

A previous study showed that adults need at least 1,000 IU to ensure adequate blood levels of vitamin D.

The researchers measured blood levels of vitamin D in nearly 800 women aged 18 to 35 over the course of a year, and surveyed them about their food and multivitamin intake.

During the winter, low blood concentrations of vitamin D were not related to low vitamin D intake. For instance, 21% of women who consumed no vitamin D were found to have insufficient blood levels of the vitamin, compared with 26% of women who reported some vitamin D intake and 20% of women who said they consumed more than 200 units of vitamin D daily.

During the summer, however, women who took multivitamins had higher blood concentrations of vitamin D. The researchers explain that women who were physically active and engaged in outdoor activities where they were exposed to sunlight were also more likely to take multivitamins.

A woman's race did not affect her vitamin D levels in wintertime but during the summer, fewer white women had insufficient blood levels of the vitamin.

People with darker skin are at greater risk of vitamin D deficiency because they need more sunlight to trigger the reaction in the skin that makes vitamin D.

However, all women could benefit from more vitamin D in the diet regardless of their skin tone or country of residence.

European Journal of Clinical Nutrition December 2001;55:1091-1097

Dr. Mercola's Comments:

This is not the first time I have mentioned that the requirement of vitamin D should be raised to 1,000 units as I posted an article about that last year. Women who limit their exposure to sunshine will have lower vitamin D levels and an increased risk of breast cancer, in addition to an increased risk of osteoporosis. Most of you reading this newsletter live in places in the US where you are not receiving enough sun exposure on your skin to generate vitamin D. This can be partially compensated for by taking natural vitamin D. The best source I know of is Carlson's lemon-flavored cod liver oil. This is not the oil your grandmother gave you and caused you to grimace. This actually tastes like lemon melted butter and provides not only vitamin D but also vitamin A and the essential fatty acids DHA and EPA. You will need to take a bit more than two teaspoons to receive the 1,000 units. However, it is possible that when you are using the real vitamin D in cod liver oil you may actually need far less than the 1,000 units recommended. My suspicion is that most of the research that was reviewed to provide the higher dose recommendation was based on synthetic and natural vitamin D. However, during the winter it would certainly seem prudent to increase your dose to two teaspoons a day for adults. Breast feeding moms should also be aware that vitamin D may be the only supplement that their babies will require. Again, this is related to the fact that vitamin D is not really a vitamin but something that we normally get from exposure to sunshine, not food. Cod liver oil is one of the few food sources that will provide it. Not only will it provide vitamin D for infants, but the balanced DHA has been repeatedly shown to enhance brain and neurological development. Related Articles: Vitamin D Is Not A Vitamin But A Steroid Hormone Precursor RDA for Vitamin D Too Low Vitamin D May Prevent Skin Cancer