For November we return to the B vitamins. We've already discussed B1 and B2, then we skipped ahead to B12. Now we'll go back to Vitamin B3, also known as niacin. For you chemistry buffs, here's a picture of niacin as a chemical structure. For the rest of us, it's good to know it
has as structure, but let's talk about what makes niacin important to me!
History of Niacin. As with many vitamins, it was the
lack of niacin that first made us aware that there was something that would eventually be called niacin. Pellagra, the disease caused by niacin deficiency, was known in the 1700s. Niacin was partially prepared in 1867, then isolated from rice polishing in 1911. But there was much confusion about its role in pellagra. In fact, in the early 1900s in the U.S. there was a research team promoting - and many people buying - the idea that pellagra was caused by an infectious microbe. A man named Joe Goldberger (hired in 1917 by the US Bureau of Public Health to investigate pellagra) was convinced, however, that pellagra was not infectious, but caused by a deficiency of something. He made a dramatic scene to prove his point - eating the red scales of pellagra sufferers and making a solution of them and injecting that solution into himself and his family! No one became ill from that, but it still wasn't until 1937 that it became crystal clear that niacin was a necessary nutrient for human health. And yes, the PR stunts have been around a long time, haven't they?
Niacin in the Body. Niacin is the shortened, generic term for nicotinic acid and nicotinamide, which is also known as niacinamide (which is actually the chemical structure in the picture above). In animals, including humans, most niacin is found as NAD and NADP (nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate)
. One of the reasons there was such difficulty in determining the relationship between niacin and pellagra is that our body makes NAD in the liver from the amino acid tryptophan. So if that production is working well, with enough tryptophan to begin with and all the co-factors required (Vitamins B1, B2 & B6 in part), then dietary niacin may be less critical. Only a small percentage of our total tryptophan is used in the NAD production pathway and it takes 60mg of tryptophan to make 1 mg of NAD. There are a number of other factors that influence the efficiency of this pathway, so it's still a good idea to get some dietary niacin!
In the body, NAD and NADP is required by at least 200 enzymes in many reactions in nearly every cell of the body. These reactions assist in the synthesis of fatty acids, cholesterol, proteins and steroid hormones, in the metabolism of glucose in the Krebs cycle, the oxidation of alcohol, in reactions involving conversions of Vitamin B6, folate and Vitamin C.
Deficiency of Niacin. We've already discussed that pellagra is the deficiency disease associated with lack of niacin. A common hook to remember niacin deficiency is the 3 (or 4, depending on your source) D's - Dermatitis, Diarrhea, Dementia - and Death if you're going with the 4th "D"! That's a pretty severe case - and it probably had some or all of the first 3 Ds prior to getting that bad!
Besides the obvious dietary deficiency of niacin, other things can contribute to a deficiency as well. Some drugs, including alcohol, increase risk of deficiency. Some diseases impair the absorption of niacin and/or tryptophan. And some conditions of life (prolonged stress, trauma, and prolonged fever) may increase the need for niacin.
Recommended Intake & Sources. It's hard to determine an amount of straight niacin that's required in a day, because it depends on how much the body is making out of tryptophan already. The basic recommendation ranges from 13-18mg/day. The average American gets at least that in a typical diet. Chicken, turkey, eggs, milk, salmon, peanuts, sunflower seeds, almonds and grains are all decent sources of niacin. As with all the B vitamins, if you decide to supplement niacin outside the diet, it's best to do this in combination with the other B vitamins in a B-Complex or multivitamin formula.
Cautions and Side Effects of Niacin. Doses higher than 1 gram/day cause a release of histamine that triggers flushes of heat and can aggravate existing symptoms of asthma or peptic ulcers. In sensitive individuals, this flushing may occur at much lower doses. High doses of niacin can also cause liver damage, may increase uric acid levels (contributing to gout) and may cause itching
. It should be used with caution with diabetes as it may cause increased glucose intolerance. Niacin may also cause stomach upset in higher doses. Also note that while niacin in extended release form tends to have less flushing, it has a higher tendency for liver toxicity.
Therapeutic Uses of Niacin. If you skipped right to this section to find out what niacin is good for, you MUST go back and read the previous section, Cautions and Side Effects! Niacin has been successfully used for some things, but it is IMPORTANT that higher daily doses be monitored by a health professional.
I stress this because a common use of high dose niacin is to lower cholesterol - and with the huge numbers of people who are currently concerned about this issue - it's important to know that this intervention must be used with care and with regular monitoring of liver health. Only niacin, not niacinamide, has this action - lowering LDL and raising HDL cholesterol. There is another form of niacin, inositol hexaniacinate, that doesn't flush, but has been inconsistent in having the cholesterol-lowering effect.
Most other therapeutic indications can successfully use niacinamide and avoid the flushing complication. It is used in osteoarthritis, various nervous system disorders, skin conditions and psychiatric disorders.
Summary Suggestions. As always, it's best to get your nutrients from your food! Whole grains, nuts and healthy proteins will provide you the niacin you need for your basic everyday functions. If you have a particular health issue that may benefit from additional Vitamin B3, please consult your health care professional.
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