Some more research concerning Vitamin D
I have two Updates concerning this topic, one on 5/23/2003 and the other on 5/29/2003 which you might also want to read, and which are similar in their findings to what I'm presenting with the following research. But, this is an important topic, so it won't hurt to reemphasize it. Also, you can look at these Updates to get the various measurements used in evaluating serum levels of vitamin D, different methods are used by different labs.
Minimum requirement of vitamin D to reduce the risk of osteoporosis and fracture and to increase calcium absorption from the gut. This study by Dr. Heaney, one of the world's authorities on calcium and vitamin D metabolism, is in Am J Clin Nutr. 2004 Dec;80(6):1706S-9S, Heaney RP, PMID: 15585791. It is a review of several studies which shows that serum vitamin D concentrations of less than 80 nmol/L are associated with reduced calcium absorption, osteoporosis, and increased fracture risk. He suggests that, particularly for older persons, daily oral intake of 1300 IU/day of vitamin D is required to reach the lower end of this optimal range. He also notes that there is need for standardization of the tests used to measure serum vitamin D concentrations. Patients need to know exactly what measurement is done and that the test results are reliable. Editor's comments: We all probably need an annual blood test to find out our serum vitamin D concentration and then adjust our intake accordingly to reach at least the minimal level. Remember that supplements might not be needed for persons who get a lot of sunshine in their daily routine.
Variations in production of vitamin D in blacks vs. whites. See Am J Clin Nutr 2004 Dec;80(6):1763S-6S., Dawson-Hughes B. PMID: 15585802. This article notes that several variables affect the production of vitamin D from skin exposure to sunlight, including skin pigmentation. Blacks produce less vitamin D3 than whites in response to usual levels of sun exposure and thus have lower serum vitamin D concentrations in summer and winter. In US blacks with low 25(OH)D concentrations there is a higher concentration of PTH (parathyroid hormone), which is associated with lower bone mineral density. Vitamin D supplements decrease PTH and markers of bone turnover in blacks suggesting that such supplementation would be beneficial to blacks as well as whites. A 1000 IU/d supplement of vitamin D is suggest by Dr. Dawson-Hughes as needed to maintain proper levels of vitamin D and reduce potential risks associated with low serum concentrations.
Sunlight and vitamin D for bone health and for prevention of other diseases. See: Am J Clin Nutr. 2004 Dec;80(6):1678S-88S, Holick MF. PMID: 15585788. First this is a nice summary of the metabolism of vitamin D to help you keep track of its various forms, names and numbers. The author feels that vitamin D deficiency is an unrecognized epidemic in the U.S. We are familiar with the association of vitamin D and osteoporosis, but this article notes that it relates to other diseases and conditions such as cancer, cardiovascular disease, multiple sclerosis, rheumatoid arthritis and type I diabetes mellitus. Although it is important not to get too much sun exposure to avoid increased risk of cancers such as melanoma, about 10-15 minutes of exposure of the arms and legs or the hands, arms and face two or three times per week should prevent vitamin D deficiency while minimizing the risk of skin cancer. If testing shows vitamin D levels are still less than 80 nmol/L then supplements will be needed, too.
Is there a need to increase magnesium intake?
There is a constant barrage of information about the need to increase calcium intake in order to avoid or treat osteoporosis, but other minerals are seldomly mentioned as being needed. One of those important minerals is magnesium (Mg), and other trace minerals that are needed include copper and zinc. A recent article mentions that we might be overlooking the importance of also increasing intakes of these other minerals as we add calcium to the diet either in food or supplements. See: Clin Calcium. 2004 Dec;14(12):1902-5, Yamada S, Inaba M. PMID: 15577181. Additionally there is a recent paper directed to women, particularly those affected by the negative findings of the World Health Initiative concerning hormone replacement therapy. See: J Am Coll Nutr. 2004 Oct;23(5):482S96S, Seelig MS and others. PMID: 15466949. Although the paper is mainly for women, the information concerning low magnesium intakes is important for both men and women. Magnesium is essential in bone metabolism, and it is also important in blood clotting, with a deficiency increasing the risk of blood clotting, strokes, etc. The authors note that in 1901 the dietary Ca/Mg ratio in the U.S. was 2/1 whereas today it is greater than 6/1. This change is due to an increase in the intake of calcium from all the effort to prevent or treat osteoporosis and to a declining intake of magnesium. Editor's comment. From these articles it is apparent that there is a need to increase Mg intake in order to reduce the current Ca/Mg ratio to try to get it closer to 3/1 or less. Mg supplements are available in 250, 400 mg and other strengths, so you might want to talk to your care provider about adding this to your regimen, especially if you are taking calcium supplements. You can also balance your magnesium intake with foods. Those foods rich in magnesium (mg per 100 gm [about 3.5 ounces] of edible portion) include: cocoa, 420; cashew nuts, 267; almonds, 252; Brazil nuts, 225; soy flour, 223; lima beans, 181, whole barley, 171, peanuts, 167, whole wheat, 165; pecans, 152, oatmeal, 145; hazelnuts, 140, walnuts, 134, corn, 121; and brown rice 119. Therefore nuts, cereals and legumes are the highest sources of magnesium. Note that milk is not a particularly good source of magnesium, so don't think you are balancing your Ca/Mg ratio by drinking milk.