Niacin
Niacin, also known as vitamin B3 or nicotinic acid, is a water-soluble vitamin that plays a vital role in various bodily functions, including skin health, metabolism, and nerve function. It is found naturally in many foods such as milk, eggs, fish, poultry, and legumes, and can also be synthesized by the body from the amino acid tryptophan. Niacin is available as a dietary supplement, particularly in higher doses for individuals with specific health conditions, though these require a physician’s prescription.
While niacin contributes positively to health—such as improving cholesterol levels and supporting the circulatory system—excessive intake can lead to significant side effects, including niacin flush, liver damage, and gastrointestinal issues. Deficiencies, though rare in developed countries, can occur in specific populations and lead to conditions like pellagra, characterized by severe digestive and mental health issues. For those considering niacin supplementation, medical guidance is strongly advised due to the potential for adverse effects and the availability of adequate dietary sources. Understanding the balance between adequate intake and the risks of excess is crucial for maintaining overall health.
Subject Terms
Niacin
Niacin, also known as vitamin B3 or nicotinic acid, is a water-soluble vitamin that serves a key role in several body systems. Niacin occurs naturally in many foods and is added to certain foods and daily multivitamins as a dietary supplement. Niacin supplements are available in higher concentrations for people who need them for health reasons, but they require a physician's prescription. Although niacin occurs naturally and is important to several body systems, excessive amounts of niacin can have serious, and even life-threatening, side effects.
Sources of Niacin
Many common foods, including milk, eggs, rice, yeast, fish, poultry, lean meats, legumes, and peanuts, contain niacin. Niacin is added to some enriched breads and cereals. In addition, the human body can manufacture niacin from the amino acid tryptophan, which occurs in many of the foods that contain niacin as well as seeds, tofu, dairy products, lentils, and beans.
The niacin in supplements is synthesized in a laboratory either chemically or through microbial fermentation, a process by which bacteria or other microbes digest or process one substance to produce another.
Benefits
Niacin is necessary for healthy skin and proper nerve function. It helps in digestion and metabolism, the process by which the body breaks down protein, carbohydrates, and fats to generate energy. The presence of niacin helps the adrenal glands in the production of hormones and aids the liver in processing harmful chemicals and other substances so they can be removed from the body.
The circulatory system also benefits from the presence of niacin. Prescription-strength niacin may be used to regulate cholesterol levels in the blood. Studies have shown that niacin can increase high density lipoprotein (HDL)—"good cholesterol"—by as much as 30 percent. HDL collects and transports low density lipoprotein (LDL) to the liver, where it is removed from the blood stream. LDL is considered "bad cholesterol" because it clogs arteries and leads to cardiovascular disease. Niacin is known to help with migraine headaches and dizziness, both of which can be related to circulation issues. In addition, niacin’s beneficial effects on the circulatory system can help some men with erectile dysfunction.
Niacin also has been shown to help some skin disorders. Acne patients who use a topical gel containing niacin have shown improvement in their condition. Nicotinamide, a form of niacin, has been shown to help prevent some forms of skin cancer, especially in patients who already have had skin cancer.
Side Effects
Niacin is water soluble, so excessive amounts are generally excreted in the urine and not stored in the body. However, some people do experience side effects when taking niacin and can have serious problems if too much is consumed.
The most notable and common side effect is known as niacin flush. Niacin flush can occur even with normal levels of the vitamin, such as those found in a supplemented cereal, especially if consumed close to the same time that a multivitamin or other source of the vitamin is taken. A person experiencing niacin flush will feel warm and experience redness, itching, and/or tingling of the face, neck, and arms, which eventually subsides on its own. Niacin flush is not dangerous, but it can be uncomfortable or frightening, especially if the person does not realize that it is caused by excess niacin and is not a symptom of a more serious reaction. Consuming hot beverages or alcohol can worsen niacin flush and should be avoided when taking niacin. For those who take prescription-strength niacin on a regular basis for a health problem, the issue of flushing may lessen with time.
Taking too much niacin can cause liver damage, high blood glucose (sugar) levels, gout, stomach ulcers, and skin rashes. However, too little niacin can cause problems, too. Deficiencies are uncommon in developed countries but can result from alcoholism, prolonged diarrhea, and liver disorders such as cirrhosis. A deficiency can make the skin especially prone to damage from the sun. It also may be a factor in the development of Type 1 diabetes mellitus.
The most severe result of niacin deficiency is pellagra, a disorder characterized by digestive problems including diarrhea, skin inflammations, and dementia, or impairment of mental processes. Pellagra occurs often in poor populations that rely on corn as a food staple. Corn contains significant amounts of niacin but not in a form that can be absorbed through normal human digestion. The niacin does become digestible—or bioavailable—if the corn is first treated in an alkaline solution, such as the lime solution used for the preparation of corn tortillas in Mexico. The digestive issues caused by pellagra often lead to other nutritional issues as well, and the condition can be fatal. Pellagra is treated through the administration of niacin and by supplementing nutrition to overcome other deficiencies caused by the condition.
Supplements
While niacin supplements are readily available, many physicians do not recommend taking them, especially without medical direction or supervision. As previously noted, deficiencies are uncommon in developed countries because natural sources of niacin are readily available through diet. Many physicians say supplementation is not necessary and may cause uncomfortable side effects such as flushing, nausea, and stomach upset. It also can alter liver test results and lead to muscle breakdown.
Bibliography
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