Pellagra

Related Topics:
Pellagra

Pellagra is a vitamin deficiency disease caused by dietary lack of niacin and protein, especially proteins containing the essential amino acid tryptophan. Because tryptophan can be converted into niacin, foods with tryptophan but without niacin, such as milk, prevent pellagra. However, tryptophan is also a precursor for protein, so if there is a deficiency in niacin and protein, then tryptophan production will be diverted into protein, leading to a deficiency of niacin.

Some sources also claim a relationship between lysine and pellagra, but this position does not have nearly as much support.

Symptoms

The symptoms of pellagra include:

Epidemiology

This disease can be common for persons who obtain most of their food energy from corn, as corn is a poor source of tryptophan. Therefore this disease can be common amongst people who live in rural South America where corn is a staple. Usually the symptoms show during spring, worsen in the summer due to sun exposure,and then return the next spring, after another long winter. It is also one of several diseases of malnutrition common in Africa, and was endemic in northern Italy, Spain, and southeastern Europe.

Prognosis

If left untreated the disease can kill within 4 or 5 years.

History

The traditional food preparation method of corn, nixtamalization, by native new world cultivators, who had domesticated corn, required treatment of the grain with lime, an alkali. It has now been shown that the lime treatment makes niacin nutritionally available and reduces the chance of developing pellagra. When corn cultivation was adopted worldwide, this preparation method was not accepted because the benefit was not understood. The original cultivators, who often depended heavily on corn, did not suffer from pellagra. Pellagra became common only when corn became a staple that was eaten without the traditional treatment.

Pellagra was first described in Spain in 1735. It was an endemic disease in northern Italy where its name originated by Francesco Frapoli of Milan who named it "pelle agra" (pelle, skin; agra, sour). Because pellagra outbreaks occurred in regions where maize was a dominant food crop the belief was that the maize carried a toxic substance or was a carrier of disease for centuries. However, it was not until later that the question of why pellagra outbreaks did not occur in Mesoamerica where maize is a major food crop and is processed that the causes of pellagra may not be due to toxins but to alternative reasons.

In the early 1900s, when pellagra appeared in the American South, the scientific community held that pellagra was probably caused by a germ or some unknown toxin in corn. However, in 1915 Joseph Goldberger, assigned to study pellagra by the Surgeon General, showed that pellagra was linked to diet by inducing the disease in prison volunteers. By 1926, Goldberger established that a balanced diet or a small amount of baker's yeast prevented pellagra. Still, skepticism in the medical community persisted until in 1937 Conrad Elvehjem showed that the vitamin niacin cured pellagra (manifested as black tongue) in dogs. Later studies by Tom Spies, Marion Blankenhorn and Clark Cooper established that niacin also cured pellagra in humans, for which Time Magazine called them its 1938 Men of the Year in comprehensive science.

There has been speculation that the legend of vampires may have been furthered in the 1700's during pellagra outbreaks in Europe.

References

External links