|Vitamins for Chronic Disease Prevention in Adults - Clinical Applications|
|Wednesday, 19 June 2002 00:00|
"In the absence of specific predisposing conditions, a usual North American diet is sufficient to prevent overt vitamin deficiency diseases such as scurvy, pellagra, and beriberi. However, insufficient vitamin intake is apparently the cause of chronic diseases. Recent evidence has shown that suboptimal levels of vitamins, even well above those causing deficiency syndromes, are risk factors for chronic diseases such as cardiovascular disease, cancer, and osteoporosis. A large portion of the general population is apparently at increase risk for this reason."
"Suboptimal Amounts of Vitamins - Suboptimal levels of a vitamin can be defined as those associated with abnormalities of metabolism that can be corrected by supplementation with that vitamin. For example, many people in the general population have serum homocysteine levels from 1.62 to 2.03 mg/L (12-15 µmol/L), which fall to baseline levels of 1.08 to 1.35 mg/L (8-10 µmol/L) after a few weeks of supplementation with folate, along with vitamins B12 and B6. Similarly, in many elderly people, methylmalonic acid levels fall with vitamin B12 supplementation, and elevated levels of parathyroid hormone fall with vitamin D supplementation. Measurements of vitamin levels in blood, serum, or red blood cells, at least with current reference points for abnormality, are not a reliable guide to this form of deficiency; in one study, supplementation substantially reduced serum homocysteine levels in elderly patients with normal serum folate concentrations."
"For some vitamins, the concept of suboptimal levels is also supported by randomized trial evidence that supplementation reduces the rate of clinical events. The research evidence is conclusive that folate during the first trimester of pregnancy reduces the risk of neural tube defects in women at increased risk. Similarly, with vitamin D supplementation, along with calcium, reduces the risk of fractures in elderly women with osteoporosis."
"The high prevalence of suboptimal vitamin levels implies that the usual US diet provides and insufficient amount of these vitamins. Fruits and vegetables are the main dietary sources of many vitamins, and health experts have long recommended at least 5 daily servings. A recent survey showed that only 20% to 30% of the population actually met this goal. Although vitamin D is added to milk, many people (especially the elderly) do not consume enough dairy products to get a sufficient amount of vitamin D. Folate supplementation of cereal products is sufficient to raise folate intake only by about 100µg, so many people do not meet the goal of 400 µg/d. Food preparation may decrease the activity for some vitamins; for example, keeping foods hot longer than 2 hours results in a more than 10% loss of vitamin C, folate, and vitamin B6. Vitamins are also lost during chilling, storage, and reheating, including more than 30% of vitamin C and folate. Alcohol consumption increases folate requirements, and aging is associated with decreased absorption of some vitamins such as B12."
"We recommend that all adults take one multivitamin daily. This practice is justified mainly by the known and suspected benefits of supplemental folate and vitamins B12, B6, and D in preventing cardiovascular disease, cancer, and osteoporosis and because multivitamins at that dose are safe and inexpensive. It is reasonable to consider a dose of 2 ordinary multivitamins daily in the elderly, specifically because of the high prevalence of suboptimal vitamin B12 and D intake. However, it might be safer to supplement 1 multivitamin with additional vitamins B12 and D, taken separately, given the possibility that increased vitamin A intake might increase the risk of hip fracture and that the iron in most multivitamins may increase the risk of hemochromatosis in some people. The increased folate requirement in people with high alcohol intake can be met with 1 multivitamin daily or folic acid supplementation alone. For women attempting to conceive, a multivitamin plus folate at 400 µg/d is appropriate, given evidence of additional benefit with higher folate levels. We recommend multivitamins, rather than individual vitamins, because multivitamins are simpler to take and cheaper than the individual vitamins taken separately and because a large proportion of the population needs supplements of more than one vitamin."
"Physician often do not ask about vitamin use. Patients may not volunteer information about their vitamin use, fearing that the physician would disapprove of unconventional use of vitamins. Therefore, physicians should specifically ask about vitamin use with 2 goals in mind. First, they should be sure that patients know about the vitamin supplements they clearly should be taking, such as folate during childbearing years. Second, physicians should be sure the patient is not taking vitamins in harmful doses, such as very large doses of vitamin D or even moderate doses of vitamin A during the first trimester of pregnancy. Within these broad limits, we believe that physicians should be interested and not directive, even when it seems the patient has unfounded beliefs or apparently unhelpful practices. In this way, physicians can avoid incurring a substantial chance of losing access to important information about patients' vitamin use."
Fletcher, Robert H., MD, MSc; and Fairfield, Kathleen M., MD, DrPH, "Vitamins for Chronic Disease Prevention in Adults - Clinical Applications", JAMA, June 19, 2002, Vol. 287, Num. 0, pp. 3127-3129