The origins of maize: the puzzle of pellagra
03 August 2001
The spread of maize as a staple food from the fifteenth century resulted in a devastating nutrient-deficiency disease called pellagra. The causation of pellagra posed a medical puzzle for centuries until twentieth century scientists unravelled the mystery.
The spread of maize
Columbus discovered maize in the New World in 1492 and brought it back to Spain, from where it spread throughout Europe, to North Africa, the Middle East, India and China. Maize (Zea mays, or corn as it is known in some countries) is the only cereal crop that has an American origin and which is now a principal cereal crop in tropical and subtropical regions throughout the world. The increasing use of maize as a staple food reflected the much higher yields per hectare, compared with wheat, rye and barley. Because maize was cheap, it became the dominant food and main source of dietary energy and protein for poor people, particularly those in rural and underprivileged segments of society.
Pellagra or "the sour skin" disease
Unfortunately, wherever maize went, a disease called "pellagra" was sure to follow. The connection between maize and pellagra was first described by Casal in Spain in 1735.When it became an endemic disease in northern Italy, Francesco Frapoli of Milan named it 'pelle agra" (pelle, skin; agra, sour). Clinically, the disease is identified by the three Ds-dermatitis, diarrhoea and dementia-and if untreated, pellagra typically leads to death in four or five years.
For years, the lack of medical knowledge and the earlier suspicion that pellagra was caused by some hypothetical toxin in maize, or as a result of infectious agents or a genetic condition, led to major pellagra epidemics in Europe and the United States.
The puzzle started to be solved when it was noted that pellagra was rare in Mexico despite widespread consumption of maize. The reason appeared to lay in the different way in which the grain was prepared in Mexico. The people of the Aztec and Mayan civilisations softened the corn to make it edible with an alkaline solution-limewater. This process liberated the bound niacin (also known as niacytin) and the important amino acid tryptophan, from which niacin can be formed, making both "bioavailable" for digestion.
The ancient practice of soaking the maize meal overnight in lime water before making tortillas was never transferred to those countries in the Old World to which maize travelled or to communities subsisting largely on maize as a staple food. This almost invariably led to the niacin deficiency disease, pellagra.
The knowledge of the chemistry of this process ultimately explained a long-standing nutritional puzzle. Much of the credit for demonstrating that pellagra is a nutrient deficiency disease belongs to Goldberger and his colleagues, who between 1913 and 1930 proved that the disease in humans and 'black-tongue' (a niacin-deficiency disease in dogs) could be cured by the pellagra-preventing (P-P) factors nicotinic acid and niacin.
Pellagra and vampires?
There are many who think that the development of beliefs in vampires was associated with pellagra. Just as folklore states that vampires must avoid sunlight to maintain their strength and avoid decay, sufferers from pellagra are hypersensitive to sunlight. Clinical symptoms of pellagra include insomnia, aggression, anxiety, and subsequent dementia, all of which may have contributed to the vampire legends and European folklores of the 1700.
Fortunately today, pellagra is rare and maize exists in a large variety of forms. Everyone is familiar with cornflour, maize meal cooked into cakes called tortillas, corn breads, 'pop corn', 'corn on the cob', and, the familiar breakfast cereal, cornflakes. Science has certainly progressed a long way since the days of widespread niacin deficiency. Today we can look at the new varieties of high-yielding maize as one of the most significant advances in agriculture.
- Hampl, J. S. and Hampl, W. S. (1997) Pellagra and the origin of a myth: evidence from European literature and folklore. J. Roy. Soc. Med. 90 636-639
- Latham, M. C. (1973) A historical perspective. In Nutrition, National Development and Planning. Edited by Berg, A., Scrimshaw, N. S. and Call, D. A. The MIT Press, Cambridge, Massachusetts, pp. 313-328