Niacin, a form of vitamin B-3, helps the body produce glucose from carbohydrates, aids in the metabolism of proteins and fats, improves circulation, reduces cholesterol, assists in the production of hormones and supports healthy functioning of your healthy liver, eye, hair, skin and nervous system. A common side effect of niacin supplementation, as well as signs of both niacin toxicity and deficiency, is diarrhea.
Niacin Deficiency
Diarrhea represents one of the "3-D syndrome" used to characterize a severe deficiency of niacin throughout the body often referred to as pellagra. The other "D's" are dermatitis and dementia. While these cases rarely occur in the United States, they can occur occasionally in alcoholics and people with gastrointestinal problems that prevent the absorption of niacin or tryptophan, which the body uses to make niacin when needed. Treatment for pellagra typically includes treatment of symptoms, niacin supplementation and a calorie-rich diet that promotes the consumption of niacin and tryptophan. Foods rich in niacin include poultry, fish, red meat, bran, eggs, peanuts, seeds and legumes. Foods containing the highest amount of tryptophan include peanuts, cottage cheese, sesame seeds, meat and brown sugar.
Niacin Side Effects
Expect to experience diarrhea when first starting treatment with a niacin supplement or prescription. While the diarrhea should go away within a week or two with continued use of niacin, keep an eye out for signs of dehydration, such as thirst, decreased urination and dark urine. Combat dehydration by increasing your intake of fluids, such as water, and decreasing your consumption of foods that irritate the bowels such as fried foods, foods high in fiber, fatty foods and sweets.
Other side effects of niacin include headaches, blurry vision, vomiting, heartburn, bloating, and skin problems such as tingling, burning, stinging, rash or itching. Most of these symptoms clear up with continued use of niacin. If you experience side effects that make breathing difficult, change your heart rate or last longer than a week or two, consult your physician.
Niacin Toxicity
High doses of niacin, especially those of 50 mg or more each day, may result in side effects or niacin toxicity. Symptoms of niacin toxicity include diarrhea, nausea, abdominal, rapid heartbeat, skin flush with dizziness or liver damage. Contact your health care provider if you experience any combination of these symptoms.
Considerations
The diarrhea you experience taking niacin may not have an association with niacin. Diarrhea occurring outside of the first two to three weeks of niacin supplementation or outside of dosage changes may be caused by bacterial infections, viral infections, parasites in the digestive tract, a form of inflammatory bowel disease or food intolerances. Contact your doctor anytime you experience severe diarrhea that lasts for longer than 2 days, have severe pain, experience a fever greater than 102 degrees Fahrenheit, see blood or pus in your stools, have black or tarry stools or experience signs of severe dehydration such as dry skin, fatigue, light-headedness or dizziness.
References
- University of Maryland Medical Center: Niacin
- "Santé : Cahiers D'étude Et De Recherches Francophones"; Pitche PTellagra; P. T. Pitche; July-September 2005
- The Franklin Institute: Nourish - Proteins
- MayoClinic.com: Niacin - Safety
- MayoClinic.com; Niacin Overdose: What Are the Symptoms?; Thomas Behrenbeck, M.D., Ph.D.; July 2008
- National Digestive Diseases Information Clearinghouse; Diarrhea; January 2011
