Niacin (vitamin B3, niacinamide, and nicotinic acid):
Food Sources of Niacin include:
meats, salmon and tuna;
beans, green peas;
peanuts, and seeds;
avocado, mushrooms, green leafy vegetables;
grains, nixtamal flour, & fortified cereals;
milk, coffee and tea.
Symptoms of Niacin (Vitamin B3) Deficiency:
Digestive symptoms of less severe niacin deficiency may include nausea and vomiting and may also be able to be seen visibly as an unusually bright red tongue. Several B vitamins can cause changes in the appearance of the tongue as the cells all along the digestive tract need to be replaced frequently with new cells. The B vitamins work together as a group and many are essential for the growth of new cells. See the excerpt in the reference section for other B vitamins necessary for maintaining a healthy tongue.
Headache, apathy, memory loss, disorientation, and/or depression may be neurological symptoms that occur if niacin deficiency continues long term. Fatigue may also be a symptom of niacin deficiency.
Severe niacin deficiency is called pellagra. Symptoms of pellagra include skin rashes, (dermatitis), diarrhea, dementia, and eventually death if adequate niacin isn't provided to the patient.
The condition was discovered in groups of people who lived primarily on a diet of corn or sorghum. However the condition was not common in Mexico, in Central America, or for some groups of Native Americans. Corn in those areas was first soaked in an alkaline solution of lime or wood ash before being made into a type of flour called nixtamal. The alkaline soaking method makes more of the grain's niacin content available for absorption in the human digestive system.
Nixtamal flour is available to the home shopper and might be called tortilla or tamale flour. The ingredient list would include lime or wood ash if the product was made with the alkaline presoaking step.
See the comment by citicat in this Q/A forum about a commonly available brand that offers plain corn flour and the nixtamal type : https://www.chowhound.com/post/differences-maseca-masa-harina-products-1015479
The amino acid, tryptophan, can be converted to niacin within the body if adequate B6, folate and heme are available (an iron rich enzyme cofactor).
Background history regarding nicotinic acid, niacin, and nicotine:
Nicotinic acid and nicotine from tobacco cigarettes have similar names because they are similar chemicals but are not the same chemical and don't have the same function within the body. This is a content marketing issue, read more - including the comments in the following link.
A summary: Nicotinic acid is a chemically reasonable name for the form of the nutrient that was initially discovered, but the similarity of the word to nicotine made people fearful when it was first added to foods and food labels as a new nutrient fortification being added to help prevent and treat pellagra. The use of a different form with a name change to "niacin" may have been a move at that time towards a form with a more commercially successful name even though it is not as descriptive of the way the chemical is formed as the name "nicotinic acid."
See the following article and comments for the details: https://underdogsbiteupwards.wordpress.com/2013/12/17/nicotine-vs-nicotinic-acid-niacin/
Warning - non-harmful "Niacin flush" may occur with Nicotinic acid:
For some people, excessive supplementation with the nicotinic acid form of vitamin B3, but not the niacin form, may cause a temporary non-life-threatening reaction that may include symptoms of itching, a temporary flushing or reddening of the skin, nausea and vomiting. The reaction may be referred to as a "niacin flush." A holistic practitioner describes the reaction in the following article and mentions that it usually goes away after a week of taking the supplement and that drinking some extra water during the sensation might help ease symptoms. The practitioner suggests that the reaction may be helpful for multiple sclerosis.
See the article for links to more information on those topics (I just discovered the site & will have to read them myself): https://www.onlineholistichealth.com/the-niacin-flush/
Niacinamide is a form of niacin that does not help reduce cholesterol
Niacin can be converted to niacinamide in the body and both forms are available as supplements which could help prevent deficiency symptoms. However niacin may also be helpful with blood lipid (fats) levels. It may help reduce elevated levels of triglycerides which may help prevent high cholesterol levels. Niacinamide is a form that does not affect blood lipid levels and wouldn't be recommended over the niacin form if the goal is protecting cardiovascular (heart & blood vessel) health. http://www.webmd.com/vitamins-supplements/ingredientmono-924-niacin%20and%20niacinamide%20vitamin%20b3.aspx?activeingredientid=924&
B vitamins essential for health of the tongue (and Gastrointestinal tract):
Deficiency of several of the B vitamin group can cause changes in the appearance and surface texture of the tongue. B vitamins that can cause changes in the tongue are mentioned in the following excerpt and include "niacin (B3), riboflavin (B2), pyridoxine (B6), folic acid (folate/B9), and vitamin B12":
"Deficiencies of niacin, riboflavin, pyridoxine, folic acid, or vitamin B12, resulting from poor diet or from the administration of antagonists, may cause a sore, beefy-red tongue without a coat. In the chronic vitamin deficiency state, the tongue may become atrophic and smooth." - "The Tongue - Clinical Methods - NCBI bookshelf https://www.ncbi.nlm.nih.gov/books/NBK236/
See the post on Vitamin B6 for more information about how the group of B vitamins work together in energy metabolism and cell growth.
Reference used for food sources & symptoms of Niacin deficiency:
An Evidence-based Approach to Vitamins and Minerals: Health Benefits and Intake Recommendations, 2nd Ed., by J. Higdon & V. Drake, (Thieme, Stuttgart / New York, 2012) [Amazon]
A description and source for purchasing the text: http://www.thieme.com/books-main/complementary-medicine/product/1040-an-evidence-based-approach-to-vitamins-and-minerals
A review of the text: http://ajcn.nutrition.org/content/79/5/892.full
The text is produced in cooperation with the Linus Pauling Institute. He is a researcher who used large doses of vitamin C to cure cancer tumors. His work was met with skepticism. More recently research supports his work in that a specific type of cancer cells is very susceptible to vitamin C - while to the rest of the body it is water soluble and non-toxic at the level that was toxic to the cancer cells. http://www.sciencedirect.com/science/article/pii/S2213231716302634
Other References used for the food sources of Niacin:
Disclaimer: Opinions are my own and the information is provided for educational purposes within the guidelines of fair use. While I am a Registered Dietitian this information is not intended to provide individual health guidance. Please see a health professional for individual health care purposes.