Variation in Availability of Niacin in Grain Products

o RECENT OUTBREAKS of pellagra-the disease caused by deficiencies of the vitamin niacin and resulting in dermatitis, diarrhea, dementia, and death-have been reported in the starving droughtand war-torn nations of the Sahel and Southeastern parts of Africa. Thus, although pellagra can be easily and economically treated by niacin supplementation and moderately good diet, political, social, and economic conditions in developing nations can make supplementation and adequate nutrition difficult or even impossible. Of course, food supply is the major problem, but one complication is the nutritional unavailability of endogenous niacin in mature cereal grains, which are the mainstay of the diet in developing nations and the main component of donated relief programs. We are seeking to understand more about how this vitamin exists in cereal grains and other foods, and how native American Indians who lived on high-corn diets resolved the problem of its nutritional unavailability. In this work, employing new methods of analysis based on animal feeding or chromatography, we found that established chemical methods of analyzing niacin in foods are not always accurate and may need modification. Pellagra was a serious problem in Italy and Romania, where corn was a major component of the diet, in the middle of the 19th century. Goldberg et al. (1918) correlated the occurrence of pellagra in the United States with dietary deficiencies among people who also subsisted on a diet consisting mainly of corn meal. Improvement of the diet with a variety of fresh vegetables, dairy products, and some meat alleviated the disease. Warburg and Christian (1935) demonstrated that nicotinamide (Fig. 1) was a constituent of the coenzymes nicotinamide adenine dinucleotide (NAD) (Fig. 1) and nicotinamide adenine dinucleotide phosphate (NADP), which are essential in cellular metabolism. Elvehjem et al. (1937) demonstrated that nicotinamide and nicotinic acid (Fig. 1) were effective cures for blacktongue, a disease in dogs given a pellagragenic diet. Shortly thereafter, Fouts et al. (1937) showed the effectiveness of nicotinic acid and nicotinamide in the treatment of pellagra in humans. A small amount of the vitamin can be synthesized from the dietary amino acid tryptophan (Fig. 1), but most of the daily requirement must be met by external sources of niacin (Krehl et al., 1945). In plants, niacin is synthesized from quinolinic acid (Fig. 1), which is converted to quinolinic acid adenine dinucleotide, next to nicotinic acid adenine dinucleotide (NAAD) , and then to NAD (Wagner and Wagner, 1985).