What Does Niacin Do for The Body? 7 Benefits and 5 Side Effects

Niacin is a member of the B-complex group of vitamins. Benefits of niacin include energy production and improved brain health and side effects include flushing and stomach problems.

Niacin is a member of the B-complex group of vitamins. These vitamins are all water-soluble vitamins, which means the body can't store much of them. They are excreted in the urine. Niacin is also known as vitamin B3. The two most common forms are nicotinic acid and nicotinamide. Both forms are biologically active and are found in nature as well as niacin supplements. 

Niacin deficiency causes a disease called pellagra, affecting the skin, brain, and intestines. 

Since this vitamin has many roles in the body, you must consume it regularly, though in safe amounts. Overdose can be harmful.

Like other B vitamins, niacin helps your body convert food into energy. After absorption from the intestines, it is converted to the amide form. This form of niacin is then used to make niacinamide adenine dinucleotide (NAD), which has a critical role in energy metabolism. It acts as a coenzyme for several processes that generate adenosine triphosphate (ATP). ATP is used for energy in various cellular processes.

This energy generation is at a cellular level. Your cells and tissues use ATP as an energy source for their various functions. Consuming large amounts of niacin won't instantly make you feel energetic.

Niacin, given in doses of 1 to 3 grams a day as nicotinic acid, lowered serum low-density lipoprotein (LDL) and raised the high density lipoprotein (HDL). Both these actions benefit heart and vascular health. Niacin reduces the risk of atherosclerosis (reduced thickening of arterial walls and less narrowing). The dose used for its action on serum lipids is high and causes unpleasant side effects in some people. 

Heart attacks are among the most common causes of death, illness, and disability. Niacin may have a role in the prevention of cardiovascular disease with long-term treatment at high doses. Nicotinic acid, taken for years at high doses, reduces blood lipid levels and the occurrence of heart attacks. 

Though niacin reduces serum LDL and triglyceride levels, it is not recommended as a preventative treatment for heart disease on its own. It is usually combined with other medicines like statins, bile acid binding resins, or reductase inhibitors.

Niacin is required to form nicotinamide adenine dinucleotide (NAD), a vital molecule in cellular functions. The amount of NAD reduces with aging. Low NAP levels lead to aging at the cellular level. Supplementation with NAD precursors like niacin might slow down cellular aging.

Niacin protects brain cells from stress and injury. The deficiency of this vitamin causes a decline in brain function, manifested as memory loss and dementia. Niacin intake is likely to be beneficial for brain health.

Niacin promotes the growth and development of brain cells (neurons). It also promotes the survival of the neurons, especially after injury or oxygen stress.

Alzheimer's disease is a disorder of brain function that affects about 50 million people worldwide. The brain cells die, and the affected person loses thinking and social skills, making day-to-day life difficult.

Niacin is very important for neurons: cells found in the brain. It promotes important biological processes like energy metabolism, calcium homeostasis, and mitochondrial functions. It plays a role in cell survival and death. The active form of niacin, NAD, prolongs the lifespan of nerve and brain cells. This enhances learning, memory, and neurotransmission. This makes niacin important in the prevention of Alzheimer's disease.

People taking higher amounts of niacin are protected against Alzheimer's disease and cognitive decline. Much research into the effect of niacin on brain health is ongoing.

This is a progressive brain disease causing the death of cells in a part of the brain called the substantia nigra. The brain is unable to produce dopamine, a vital chemical transmitter. Affected people have tremors, rigidity, and loss of movement and balance.

Niacin is a promising treatment for Parkinson's disease. It restores the optimal balance of NAD and other coenzymes needed for mitochondrial activity. Niacin can increase dopamine production and can alleviate some symptoms of this disease.

Niacin is required for DNA repair in the body. Deficiency of niacin makes it difficult for the body to repair ultraviolet-light-induced DNA damage in the skin. Defects of DNA repair are known to progress to cancer. Niacin supplementation reduces cancer occurrence.

Nicotinamide also has a role in the treatment of cancers. Given in high doses, it sensitizes tumors to both radiation and chemotherapy.

Niacin requirements

Daily niacin requirements are:

Niacin is present in poultry, beef, and fish. Animal sources provide this vitamin mainly as NAD and NADP. These are activated forms of the vitamin that are vital for cellular functions. Nuts, legumes, and grains also provide the vitamin, mainly as nicotinic acid. Bread, cereals, and infant formulas in the United States and many other countries contain added niacin as a measure to prevent deficiency disease.

Apart from dietary sources, your body can also get niacin by processing tryptophan, one of the amino acids, but dietary tryptophan is converted to niacin only when there is a surplus after meeting the protein synthesis requirements of the body.

Niacin deficiency causes the disease pellagra, which consists of diarrhea, dermatitis (skin inflammation), and dementia (brain dysfunction). Dermatitis consists of brown discoloration of the skin or a pigmented rash. Dermatitis becomes worse on sun exposure, and the skin develops a rough, sunburned appearance. The tongue might be bright red. Vomiting is common.

The nervous system symptoms are the most dangerous. They include loss of memory, hallucinations, apathy, tiredness, headache, and suicidal tendency. Nervous system symptoms often respond within hours of starting niacin treatment. Untreated, this disease can cause death.

Niacin deficiency is uncommon now. People living in poverty with limited diets may suffer from niacin deficiency. It is often seen in people with a diet based on corn and maize. Niacin in these grains is bound to carbohydrates and cannot be absorbed and used by the body. People with alcoholism may also have signs of niacin deficiency.

Several foods like cereals and bread are now fortified with this vitamin. Almost all people in the US consume more than the recommended daily allowance of niacin.

Niacin is a water-soluble vitamin, and excess amounts consumed are usually removed by the kidneys in the urine. The safe limit of niacin consumption is 35 milligrams a day. At this dose, niacin is safe. Side effects rarely happen. However, excessive amounts taken as supplements, or high doses used medically, can cause toxicity. 

1. Skin flushing, itching, and heat sensation. This can be unpleasant and can cause patients to discontinue the treatment. Skin effects can be reduced by using extended-release (ER) tablets, which release niacin slowly in the intestines over a period of several hours. Most people have a reduction in the skin effects after taking niacin for a few days.

2. Disorders of glucose control. People on high-dose niacin have high blood sugar levels. Diabetes is also seen in some people. High-dose niacin therapy should be avoided in people with diabetes or metabolic syndrome. Patients on oral antidiabetic drugs or insulin injections may have a loss of diabetes control. This can usually be addressed by increasing the dose of the drugs or insulin.

3. Stomach and intestinal problems. High doses of niacin, used for reducing serum lipids, cause dyspepsia, diarrhea, ulcers, and bleeding in the intestines.

4. Hypotension. Hypotension refers to a fall in your blood pressure. This can be severe enough to make you dizzy and fall.

5. Liver damage. Prolonged use of high-dose niacin may damage the liver. Liver dysfunction can cause tiredness, nausea, vomiting, and poor appetite. Later, hepatitis and liver failure may happen. Liver damage is more likely with extended-release (ER) forms of nicotinic acid.

Niacin-containing foods are safe to consume. They do not contain the amounts of niacin that cause such negative effects. If you are consuming supplements, you should be more careful. Some vitamin supplement tablets contain 500 milligrams of niacin. This vitamin is a nutrient, but if you are consuming more than a thousand milligrams a day, it is potentially hazardous. You should only take such quantities with your doctor's blessing.