(Niacin, niacinamide, nicotinamide, inositol hexaniacinate)
Vitamin B3 is required for proper function of more than 50 enzymes. Without it, your body would not be able to release energy or make fats from carbohydrates. Vitamin B3 is also used to make sex hormones and other important chemical signal molecules.
Vitamin B3 is needed for healthy skin and proper circulation of the blood throughout the body. As with other B vitamins, it also aids in proper functioning of the nervous system and in the metabolism of proteins, fats and carbohydrates. The secretion of bile and stomach acids requires niacin. Niacin lowers cholesterol and helps with the synthesis of hormones, including estrogen and testosterone. It is often used to enhance memory.
Similar to riboflavin, vitamin B3 is used in energy production by the cell. It is an integral part of nicotinamide adenine dinucleotide phosphate and nicotinamide adenine dinucleotide. These enzymes are also used to transfer hydrogen ions (which are supplied by sugars and fatty acids in the diet)to the cytochrome and hydrogen ion transfer systems to supply energy to the body.
Tryptophan metabolism is intrinsically linked to niacin (niacin may also be synthesized from dietary tryptophan if the diet is low in niacin and adequate tryptophan is available). In cats, however, one of the intermediate compounds formed during tryptophan metabolism to niacin is quickly utilized by another pathway; therefore, cats cannot convert tryptophan to niacin. Thus cats, unlike dogs, have a strict dietary requirement for niacin.
Vitamin B3 comes in two principal forms niacin (nicotinic acid) and niacinamide (nicotinamide). When taken in low doses for nutritional purposes, they are essentially identical. However, each has its own particular effects when taken in high doses. High-dose niacin is principally used for lowering cholesterol. High-dose niacinamide may be helpful in presenting type I (childhood-onset) diabetes and reducing symptoms of osteoarthritis in people. However, these are concerns regarding liver inflammation when any form of niacin is taken at high dosages.
There is no question that niacin (but not niacinamide) can significantly lower total cholesterol and LDL cholesterol and raise HDL cholesterol in people. However, unpleasant flushing reaction and the risk of liver inflammation have kept niacin from being widely used. According to numerous studies, niacin can lower cholesterol and LDL (“bad”) cholesterol by 15 to 25 percent, lower triglycerides by two to 50 percent, and raise HDL (“good”) cholesterol by 15 to 25 percent. Furthermore, longterm use of niacin has been shown to significantly reduce death rates from cardiovascular disease.
Intriguing evidence suggests that regular use of niacinamide (but not niacin) may help prevent diabetes in children at special risk of developing it. Risk can be determined by measuring the ratio of antibodies to islet cells (ICA antibody test). Niacinamide may improve blood sugar control in both children and adults who already have diabetes.
Exciting evidence from a huge study conducted in New Zealand suggests that niacinamide can prevent high-risk children from developing diabetes. In this study more than 20,000 children were screened for diabetes risk by measuring ICA antibodies. It turned out that 185 of these children had detectable levels. About 170 of these children were then given niacinamide for seven years (not all parents agreed to give their children niacinamide or stay in the study for that long). About 10,000 other children were not screened, but were followed to see whether they developed diabetes.
The results were impressive. In the group in which children were screened and given niacinamide if they were positive for ICA antibodies, the incidence of diabetes was reduced by as much as 60 percent. These findings suggest that niacinamide is a very effective treatment for preventing diabetes. (It also shows that tests for ICA antibodies can very accurately identify children at risk for diabetes.)
At present, an enormous-scale, long-term trial called European Nicotinamide Diabetes Intervention Trial is being conducted to definitely determine whether regular use of niacinamide can prevent diabetes.
If a child has just developed diabetes, niacinamide may prolong what is called the honeymoon period. This is in the interval in which the pancreas can still make insulin, and insulin needs are low. A recent study suggests that niacinamide may also improve blood sugar control in type II (adult-onset) diabetes, but it did not use a double-bind design.
According to several good-size, double-bind studies involving a total of over 500 individuals, a special form of niacin, inositol hexaniacinate, may be able to improve walking distance in intermittent claudication (severe leg cramps caused by hardening of the arteries). For example, in one study, 120 individuals were given either placebo or 2 g of inositol hexaniacinate daily. Over a period of three months, walking distance improved significantly in the treated group. (Other treatments that may help intermittent claudication include carnitine and ginko.)
Preliminary evidence (one small double-bind study) suggests that insoitol hexaniacinate niacinamide may be able to reduce symptoms of Raynaud’s phenomenon as well. This condition includes a response to cold, usually most severely in the hands. The dosage used in he study was 4 g daily, again a dosage high enough for liver inflammation to be a real possibility.
Preliminary evidence suggests that niacinamide may be able to reduce symptoms of osteoarthritis. There is some evidence that niacinamide may provide some benefits for those with osteoarthritis. In a double-bind study, 72 individuals with arthritis were given either 3,000 mg daily of niacinamide (in five equal doses) or placebo for 12 weeks. The results showed that treated patients experienced a 20 percent improvement in symptoms, whereas those given placebo worsened by 10 percent. However, at this dose, liver inflammation is a concern that must be taken seriously.
Very weak evidence suggests one of the several forms of niacin may be helpful in bursitis, cataracts, and pregnancy.
Niacin was discovered to be the specific chemical that cured black tongue (pellagra) in dogs fed niacin-deficient diets. Niacin deficiency (pellagra) causes dermatitis, diarrhea, dementia and death.
Niacinamide has been recommended for the treatment of several disorders in pets, including discoid lupus erythematosus and pemphigus erythematosus in dogs. When combined with tetracycline, niacinamide (at a dosage of 500 mg of tetracycline and 500 mg of nacinamide per dog given every eight hours for dogs weighing more than 10 kg) has been found to show an excellent response in 25 to 65 percent of cases. While no studies support the use of niacinamide for dogs with atopic dermatitis, since niacinamide works by inhibiting antigen-IgE-induced histamine release, it may be an option for atopic dogs.
Good food sources of niacin are seeds, yeast, bran, peanuts (especially with skins), wild rice, brown rice, whole wheat, barley, almonds, liver, brewer’s yeast, broccoli, carrots, cheese, eggs, fish, milk, pork, potatoes, and peas. Tryptophan is found in protein foods (meat, poultry, dairy products, and fish). Turkey and milk are particularly excellent sources of tryptophan. Other sources include green alfalfa and the herbs catnip, cayenne, chamomile, chickweed, licorice, mullein, nettle, peppermint, raspberry leaf, red clover, rose hips, slippery elm, and yellow dock.
The AAFCO recommends 11.4 mg/kg of niacin daily for dogs and 60 mg/kg of niacin for cats.
In people, when taken at a dosage of more than 100 mg daily, niacin frequently causes annoying skin flushing, especially in the face. This reaction may be accompanied by stomach distress, itching and headache. In studies, as many as 43 percent of individuals taking niacin quit because of the unpleasant side effects.
A more dangerous effect is liver inflammation. Although most commonly seen with slow-release niacin, it can occur with any type of niacin,when taken at a daily dose of more than 500 mg. Regular blood tests to evaluate liver function are therefore mandatory when using high-dose (or niacinamide or inositol hexaniacinate). This side effect almost always goes away when niacin is stopped. People with liver disease, ulcers (presently or in the past), gout, or diabetes should not take high-dose niacin except on medical advice.
Maximum safe dosages for young children and pregnant or nursing women have not been established. Pets are not routinely treated with niacin. However, similar precautions are probably warranted if your pet is prescribed niacin.
As in the case in human medicine, if your pet is taking cholestrol-lowering drugs in the statin family, he should probably not take additional niacin. Pets taking older choslestrol-lowering drugs such as cholestyramine or colestipol should take niacin at a different time of day to avoid absorption problems based on the recommendation in human medicine. Pets taking the antituberculosis drug isoniazid may need extra niacin. However, because niacin can interfere with INH, doctor supervision is necessary.
Shawn Messonnier, DVM
Dr. Messonnier, a 1987 graduate of Texas A& M College
of Veterinary Medicine, opened Paws & Claws Animal
Hospital in 1991. His special interests include exotic pets,
dermatology, and animal behavior.
Dr. Messonnier is a well-known speaker and author.