Low vitamin D levels may raise heart attack risk
suggests a new study from Harvard School of Public Health.
A doubling of blood levels of vitamin D was associated with a halving of the risk of a heart attack (myocardial infarction), according to results published in the new issue of Archives of Internal Medicine. "Vitamin D deficiency has been related to an increasing number of conditions and to total mortality," wrote lead author Edward Giovannucci, M.D., Sc.D. "These results further support an important role for vitamin D in MI risk." "If this association is causal, which remains to be established, the amount of vitamin D required for optimal benefit may be much higher than would be provided by current recommendations (200-600 IU/d), especially in those with minimal sun exposure. "Thus, the present findings add further support that the current dietary requirements of vitamin D need to be increased to have an effect on circulating 25(OH)D levels substantially large enough for potential health benefits," he added. Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body. Study details Giovannucci and colleagues reviewed the medical records and blood samples of 454 men aged between 40 and 75 with a history of non-fatal heart attack or fatal heart disease. Data from these 'cases' were compared with data from 900 healthy 'control' men with no history of heart disease. Self-administered questionnaires provided information on diet and lifestyle factors. The Harvard researchers calculated that men with vitamin D deficiency, or 25(OH)D levels of 15 ng/mL or lower had were 142 per cent more likely to suffer from a heart attack than men with sufficient levels of the vitamin (25(OH)D levels of at least 30ng/mL). When the researchers adjusted these results to account for factors that may skew the results, such as omega-3 intake, family history of heart attack, high blood pressure or diabetes, BMI, alcohol consumption, physical activity, and cholesterol levels, a significant and important relationship was still observed. Men with vitamin D deficiency were 109 per cent more at risk of heart attack, compared to men with sufficient levels of the vitamin. "Even men with intermediate 25(OH)D levels were at elevated risk relative to those with sufficient 25(OH)D levels," wrote Giovannucci "In individuals in sun-rich environments, where clothing or cultural practices do not appreciably limit vitamin D production, 25(OH)D levels of 54 to 90 ng/mL are attained, but from the present study we cannot evaluate whether levels greater than 35 ng/mL would be associated with an even greater MI risk reduction," he added. Commenting on the potential mechanisms, the researchers note several possibilities including beneficial effects on improving the health of smooth muscle in the vascular system, reducing inflammation, reducing vascular calcification, and improving blood pressure. Calls becoming deafening? Calls to increase the current recommendations of 200 IU per day for children and adults up to 50 years of age for vitamin D up to 800 - 1000 IU vitamin D3, have become more frequent in both scientific and public circles. "To increase 25(OH)D levels from 12 to 35.5 ng/mL would require approximately 3000 IU of vitamin D daily," wrote Giovannucci and co-workers. "Although such intakes may seem high by current standards, increasing evidence demonstrates no toxic effects at intakes below 10 000 IU/d." Reports in prestigious journals such as the New England Journal of Medicine and the American Journal of Clinical Nutrition have called for raises to the recommendations. Only last week, researchers from the American University of Beirut-Medical Center, Lebanon stated that current vitamin D recommendations for children should be raised from 200 IU to 2,000 IU to boost bone health and produce long-term health benefits. Because of the low dietary amounts, and lack of sunshine in northern climates, some estimates claim that as much as 60 per cent of northern populations may be vitamin D deficient. In adults, vitamin D deficiency may precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases. Source: Archives of Internal Medicine Volume 168, Number 11, Pages 1174-1180 "25-Hydroxyvitamin D and Risk of Myocardial Infarction in Men - A Prospective Study" Authors: E. Giovannucci, Y. Liu, B.W. Hollis, E.B. Rimm
