Vitamin B3 (Niacin)
The disease pellagra had been known for centuries to be associated with diets using corn as the staple food, but the exact cause remained illusive. The first mention of pellagra was by the Spanish physician Casals in 1735. He described a dread disease that would go on to claim countless victims around the world among corneating populations for the next 200 years.
In the early 1900s, as pellagra continued to baffle scientists, it reached epidemic proportions in the southern United States. Scientists believed it was caused by an infectious agent or some toxin in corn until an American researcher, Goldberger, figured out that pellagra was caused by a still-unknown nutrient deficiency. A study in 1937 showed that nicotinic acid cured pellagra in dogs, and within a year doctors began using the compound to cure the disease in people.
Pellagra produces symptoms known as the three Ds: dementia, diarrhea, and dermatitis. Usually the final D, death, was the result. It's not surprising that early scientists couldn't figure out the corn connection. Although corn contains a fair amount of niacin, a protein in corn binds niacin, making it unavailable for absorption in the intestine. Soaking the corn in an alkaline solution releases the niacin, making it available for absorption.
This is the reason why Hispanic populations never were affected by pellagra, since they traditionally soak corn in lime water before making tortillas. But when Spanish explorers brought corn back to Europe from the New World, they weren't aware of the importance of the soaking step. This is what led to widespread niacin deficiency in Europe.
The term niacin is a generic name for two compounds, nicotinic acid and nicotinamide or niacinamide. Niacin functions as part of two important coenzymes that together help over 200 enzymes that depend on the vitamin to carry out chemical reactions. These coenzymes are contained in every cell of the body and are present whenever energy is released from chemical reactions. In addition, niacin is important in helping to make new compounds, especially those containing fat.
The U.S. diet provides more than adequate amounts of niacin. Good sources include whole grain or enriched grain products and meats. The units of measure are niacin equivalents (NE) which take into account the body's ability to convert the amino acid tryptophan into niacin. One NE, which is 1 mg of niacin, is equivalent to 60 mg of tryptophan. Surveys showed that most Americans had little difficulty meeting the 1989 RDA, and the new DR! is lower at 16 NE for men and 14 NE for women. However, some special groups who may be vulnerable include people who abuse alcohol and those who are poorly nourished. Pellagra is still a problem in Asia and Africa.
One of the most interesting facts about niacin is its cholesterollowering effect. Large doses of niacin (3,000 mg/day) had been shown in several studies to significandy lower blood cholesterol. One such study treated thirtyone subjects with 4 mg of nicotinic acid daily for six weeks in a highly controlled research environment, known as a metabolic ward. In all subjects, total cholesterol was significandy reduced, including the artery-clogging fractions, LDL and VLDL, which is a precursor to LDL. An added bonus was an increase in HDL. This helpful cholesterol carrier is notorious for the limited means by which it can be effectively raised.
The common side effect of large doses, anywhere from 3 to 9 grams a day, is an uncomfortable flushing of the skin, called "niacin flush," which is caused by the dilation of blood vessels. This could be more than just an annoying problem for people with asthma or ulcers. In several studies of niacin's cholesterol-lowering effect, subjects dropped out because of this side effect. A recent study in fortytwo men and women suggests that an aspirin regimen of 325 mg/day is effective in preventing this pesky reaction. Other studies indicate that only the nicotinic acid form causes the skin reaction, not the nicotinamide form. Another way to prevent side effects is to use a slow-release capsule.
An even more recent study supported a beneficial effect on HDL cholesterol. One hundred patients with heart disease and high cholesterol or low HDL started the study with a niacin supplement of 100 to 250 mg twice daily. They gradually increased the dose to 1,000 mg twice a day over four to eight weeks. The doses were split to minimize side effects. The group had a 13 percent reduction in total cholesterol, a 31 percent incr~ase in HDL, and a 32 percent decrease in the cholesterol-to-HDL ratio, a simple but effective calculation of heart attack risk.
A subgroup of thirtynine patients taking less than 1,000 mg per day had only a 5 percent reduction in total cholesterol, but still enjoyed a 29 percent increase in HDL and a 24 percent decrease in the cholesterol-to-HDL ratio. About a third of the patients reported side effects, and four decided to drop out because of them. The results were impressive, even in the lower-dose group, since low HDL may be more predictive of heart attack than an elevated total cholesterol.
The authors concluded that niacin is an effective and inexpensive treatment in improving the cholesterol-to- HD L ratio; splitting the dose cuts down on side effects. What about safety? Some researchers have cited other potential side effects besides the relatively innocuous skin tingling, including liver damage and stomach ulcers at extremely high doses. Some people using a high dose to lower cholesterol have also reported gastrointestinal side effects such as indigestion, nausea and vomiting, and diarrhea. But the potential for liver damage is by far the most serious side effect. Experts estimate that serious side effects probably only occur at doses of 2,000 to 6,000 mg. The potential benefit of niacin supplements in lowering cholesterol may warrant using it, but only under the supervision of a physician.