Nutritional support of successful reproduction: An update

While a multitude of factors influence the reproduc­ tive process, only some of these factors are under a woman's control. Diet and nutrition are "controlla­ ble" variables and attention to them may improve fer­ tility and reduce risk of adverse pregnancy course and outcome. Data available on diet, nutrition, and repro­ duction are largely based on research with animals. Even so, a number of epidemiologic reports and results from controlled laboratory and clinical investi­ gations with pregnant women have provided the basis for reasonable guidelines regarding pre gravid and prenatal diet and supplements. Since new develop­ ments are regularly reported, professionals need to keep' informed. The purpose of this review is to pro­ vide a brief update focused on selected issues in the area of nutrition and reproduction. The significance of maternal nutrition in the repro­ ductive process is now well recognized, and unlike some genetic and environmental variables, women have control over their nutritional status. Not only does maternal diet during pregnancy influence fetal development, diet before pregnancy can affect fertility and determine the adequacy of nutritional support for the embryo. Educators should direct their messages about nutritional support of the fetus to potential par­ ents well before conception. The obvious goal for a woman who wants to conceive should be to conceive when her nutritional status and other controllable en­ vironmental factors provide for optimal fetal develop­ ment. Early nutritional experience. A woman's childhood nutritional experience may affect her own growth such that inadequate nutrient intake may limit linear growth and compromise development of the pelvic girdle. Numerous examples of such compromised growth have been reported over the years in women from impoverished societies. We may speculate, how­ ever, that in this era of growing concern about body fatness and increasing incidence of anorexia nervosa and bulimia, permanent effects on today's young women may result from dietary abuses during child­ hood (1) . Nutrition and fertility. Reproduction is possible only when the process of ovulation and menstruation is normal. Suboptimal nutrition and/or unusual die­ tary patterns may lead to delayed onset of menarche, irregular cycling, or frank amenorrhea. These abnor­ malities occur in women with anorexia nervosa; they are also seen in women pursuing less rigorous weight­ reduction regimens (2). Observations of the hormonal patterns of women on weight-reduction regimens show that reduction in circulating levels of key female hormones-and consequently a disturbance in the menstrual routine-begins within weeks of starting a weight-reduction regime (2). Chronic dieting may maintain this suboptimal hormonal state and thus ex­ plain the infertility demonstrated by some dieting women of reproductive age. Other dietary factors may be responsible for im­ paired fertility. A diet excessively high in carotene(s) is one example (3, 4). In women whose diets are ex­ ceptionally rich in carotene-containing foods (e .g., carrots), high circulating levels of carotene in the blood have been reported (but not proven) to be associ­ ated with amenorrhea. Use of carotene-containing tan­ ning pills by women in Europe has also been reported to lead to infertility (5). Reducing the intake of caro­ tene from either source reportedly leads to normaliza­ tion in the menstrual cycle (3). Whether other dietary factors are associated with similar effects has yet to be determined.