Niacin – an important water-soluble vitamin
Niacin (Vitamin B3) is one of the many water-soluble B-vitamins required for maintaining basic bodily functions. Niacin serves as a coenzyme, supporting other enzymes in activating various chemical reactions within the body. It is involved in converting carbohydrates, fats, and proteins into ATP for energy as well as for synthesizing cholesterol and fat.
DNA synthesis and cognition
Niacin also supports the creation and repair of DNA and plays an important antioxidant function within the body. It has been found to be potentially protective against Alzheimer’s Disease and enhances cognitive function. Conversely, niacin deficiency has been linked to memory loss, dementia and cognitive decline.
Tryptophan as a source of niacin
The amino acid tryptophan may be converted into niacin in the liver and serves as an additional source of niacin in the diet. About 60 mg of tryptophan will generate 1 mg of niacin.
Niacin deficiency
Individuals who are highly deficient in niacin may develop a disease known as pellagra, which results in a dark, scaly rash on skin areas that are exposed to sunlight. Other common symptoms of pellagra include redness of the tongue and constipation/diarrhea. In the most severe cases, niacin deficiency may lead to depression, headaches, fatigue, memory loss, hallucination, and even death.
At risk populations
Niacin deficiency is very rare, especially in developed countries, as a variety of foods contain abundant amounts of niacin. Deficiencies most commonly occur in cases of extreme poverty where access to food variety is limited. Deficiency has also been seen in communities where corn and corn-based products serve as the primary food source, since niacin binds to the carbohydrates in corn making it difficult to absorb in the body. Other individuals who may experience niacin deficiency include individuals with eating disorders, alcohol abuse, AIDS, irritable bowl disease, and liver cirrhosis which reduce the absorption of niacin and limit the conversion of tryptophan into niacin. Certain diseases, including Hartnup Disease and Carcinoid Syndrome, may also lead to niacin deficiency due to the way these diseases interfere with the absorption and conversion of tryptophan into niacin. Certain medications, such as medications to treat tuberculosis, may also interrupt the production of niacin and result in potential nutrient deficiency.
Food sources
Niacin is found in many different foods; however, it is most abundantly found in meat including beef, pork, poultry, and fish as well as nuts, seeds and legumes. Peanut butter and sunflower seeds are good sources of niacin for individuals who are vegetarian or vegan. While niacin is found in a variety of grains, it binds to the carbohydrates in the grains making it more difficult for the body to absorb. Typically grain products are enriched with niacin to increase the absorbable content.
Niacin and cardiovascular disease
One unique benefit of niacin is that it has been shown to improve lipid profiles, including increasing good HDL cholesterol, lowering bad LDL cholesterol, and lowering triglycerides. As a result, several studies have been conducted on using niacin supplementation to prevent cardiovascular disease. However, while most water-soluble vitamins are minimally stored in the body with low risk of causing toxicity, extremely high levels of niacin have been shown to result in toxicity and adverse side effects. Studies conducted on the use of niacin for preventing cardiovascular disease have found that while it does improve lipid profiles, it does not actually reduce the instance of cardiovascular disease. In fact, consuming large doses of niacin has been found to result in other diseases and health problems including glucose intolerance and insulin resistance, leading to type 2 diabetes, as well as digestive issues, ulcers, blurred vision, flushed skin, low blood pressure, fatigue, and inflammation of the liver.
Recommended dietary allowance and toxicity
While niacin is a vital nutrient for supporting a variety of functions within the body, most individuals consume sufficient levels of niacin from food alone, and supplementation is not typically necessary. The recommended dietary allowance for niacin is 14-16 mg for adults over 19, but the average adult actually consumes 21-31 mg, with only about 1% of the population found to have niacin levels below the recommended amount. Toxicity with red flushing of the skin has been shown to occur at levels as low as 35 mg. Therefore, most studies recommend obtaining niacin from the diet alone, and only supplementing with niacin under the guidance and recommendation of a medical professional.
