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2007-8-30 13:55:09 |
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Lower levels of vitamin D in the blood may be a precursor to high blood pressure, according to a new study appearing in the July 2007 issue of American Journal of Hypertension. Dr. Robert Scragg and colleagues from the University of Auckland, University of Michigan, Hunter New England Area Health Service ( Australia) found that those who had low levels of vitamin D in their blood had slightly higher blood pressure compared to those who had higher levels of vitamin D. Vitamin D generally refers to two entities cholecalciferol (D3) and ergocalciferol (D2). D3 is produced in the body following exposure to UVB radiation in the range of 290 to 320 nm, while D2 is obtained from dietary sources including oily fish, egg yolk and liver. Deficiency of vitamin D has been linked to many conditions including metabolic syndrome. The researchers intended to examine if there is any association between serum 25-hydroxyvitamin D (25OHD) , the non-active 'storage' form of both D3 and D2, and blood pressure in certain ethnic groups in an effect to explain why black people in the US and UK have increased blood pressure compared to whites. For the study, they analyzed data from the Third US National Health and Nutrition Examination Survey (NHANES III), which involved 12,644 people aged 20 and above with their 25- hydroxyvitamin D status and blood pressure measured. None of subjects were on medications indicated for treatment of hypertension. Non-Hispanic whites had the highest blood levels of vitamin D and second in line were Mexican Americans, the study showed. Non-Hispanic blacks had the lowest blood levels of vitamin D. It is commonly believed that black people have low levels of vitamin D is probably due to the fact that they cannot absorb ultraviolet rays well from sunlight because of their skin pigments. In the study, the researchers found systolic blood pressure in people with high levels of vitamin D was at least 3.0 mm of Hg lower than those with low vitamin D levels. Similarly, diastolic blood pressure was 1.6 mm of Hg lower in those with high levels of vitamin D than those with low levels. The results were obtained after age, sex, ethnicity, and physical activity were considered. The inverse association between vitamin D and blood pressure was weakened after body mass index was considered, but was still significant for systolic blood pressure. The association was more significant in people aged 50 or older than younger people. Early in 2004, the same team of researchers analyzed data from the same study and found that low vitamin D was linked with increased risk of diabetes among non-Hispanic whites and Mexican Americans, but not in non-Hispanic blacks. The risk was 75 percent lower in non-Hispanic whites in the highest quartile of vitamin D than those in the lowest quartile and was 83 percent lower in Mexican Americans in the highest quartile of the vitamin compared to those in the lowest. The results were reported in Diabetes Care 27:2813-2818, 2004. The current study is a statistic analysis, which could not reveal any causal relationship between vitamin D and blood pressure, meaning that taking vitamin D supplements or eating foods rich in the vitamin or high exposure to sun rays may or may not improve the blood pressure. In addition to sunlight, there are only a limited number of foods that contain natural vitamin D. Oily fish such as salmon, sardines and mackerel and cod liver oil contain decent mounts of vitamin D. Vitamin D is also commonly fortified in milk, cereal and orange juice. . ### . Copyright 2007 foodconsumer.org All rights reserved. Foodconsumer.org publishes daily news and reports on food and diet, some of which are not available from the mainstream news media. This article can be used by individuals and organizations for not-for-profit purposes without prior express permission from foodconsumer.org on condition that this article including the author and this copyright note should be used in entirety without alteration. |
