The Primary Alternate Name
Nicotinic acid is most commonly known as niacin. This name was adopted to dissociate the vitamin from the nearly unrelated and toxic compound nicotine, as the two are often confused by the public. Both nicotinic acid and its derivative, nicotinamide, are forms of the larger group known as niacin, or vitamin B3. While the names are often used interchangeably in general nutrition contexts, there are important chemical and physiological differences between the specific forms, especially concerning high-dose applications.
Nicotinic Acid vs. Niacinamide: A Key Distinction
Understanding the different forms of vitamin B3 is vital, as they have distinct effects on the body. The two primary forms found in foods and supplements are nicotinic acid and niacinamide (also called nicotinamide).
Nicotinic Acid
This form of vitamin B3 is famously known for causing a 'niacin flush,' a harmless but uncomfortable side effect characterized by warmth, redness, itching, and tingling of the skin. This occurs because nicotinic acid dilates small blood vessels. Medically, high doses of nicotinic acid have been used for over 40 years to treat dyslipidemia (abnormal lipid levels), effectively raising HDL ('good') cholesterol and lowering LDL ('bad') cholesterol and triglycerides. However, due to the side effects and recent studies questioning its incremental benefit over statins, its use for this purpose has declined.
Niacinamide (Nicotinamide)
Unlike nicotinic acid, niacinamide does not cause the 'flush' effect. It is the preferred form for treating pellagra (niacin deficiency) because it can be administered in higher doses without the flushing side effect. Niacinamide is also the form added to many fortified food products. While it shares the same vitamin B3 activity as nicotinic acid, it does not have the same pharmacological effects on blood lipid levels.
The Function of Niacin in the Body
Niacin, in both its nicotinic acid and niacinamide forms, is converted into the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). These coenzymes are indispensable for hundreds of enzymatic reactions throughout the body, including:
- Energy Production: They help transfer the energy from carbohydrates, fats, and proteins to adenosine triphosphate (ATP), the cell's primary energy currency.
- Cellular Communication: NAD is required for signaling between cells.
- DNA Repair: Both NAD and NADP are involved in maintaining the integrity of the body's genetic material.
- Antioxidant Function: NADP plays a crucial role in maintaining cellular antioxidant function.
Symptoms of Niacin Deficiency (Pellagra)
Severe niacin deficiency can lead to a disease called pellagra, which is rare in developed countries but still affects undernourished populations. The disease is classically defined by the 'four D's':
- Dermatitis: Rough, dry, and scaly skin, often resembling sunburn, especially in sun-exposed areas.
- Diarrhea: Often watery, bloody, and mucoid due to inflammation of the gastrointestinal tract.
- Dementia: Neurological symptoms that can include depression, apathy, memory loss, confusion, and, in severe cases, hallucinations.
- Death: If left untreated, pellagra can be fatal.
Food Sources of Niacin
Since the body does not store niacin, it must be consumed regularly through diet. Excellent sources of niacin include:
- Red meat, including beef and pork
- Poultry
- Fish, such as tuna and salmon
- Legumes
- Nuts and seeds
- Fortified cereals and breads
Additionally, the body can produce niacin from the amino acid tryptophan, which is abundant in protein-rich foods like milk, eggs, and turkey. However, this conversion is not very efficient.
Nicotinic Acid vs. Niacinamide: A Comparison Table
| Feature | Nicotinic Acid | Niacinamide (Nicotinamide) |
|---|---|---|
| Effect on Lipids | Effectively lowers LDL and triglycerides and raises HDL in high doses. | No significant effect on lipid levels. |
| Flushing | Often causes the 'niacin flush' (skin redness, tingling, itching). | Does not cause skin flushing. |
| Primary Use (High Dose) | Used historically to treat dyslipidemia and improve cholesterol levels, typically under medical supervision. | Preferred for treating pellagra and is the form used in many multivitamins. |
| Common Side Effects | Flushing, headache, gastrointestinal upset, can increase blood sugar and risk of liver issues at high doses. | Less severe side effects, mainly gastrointestinal issues at very high doses. |
| Supplement Labels | Often labeled as 'niacin' or 'nicotinic acid' and may specify 'immediate-release' or 'extended-release'. | Labeled as 'niacinamide' or 'nicotinamide'. |
Conclusion
Nicotinic acid is the chemical name for one form of niacin, also known as vitamin B3. While both nicotinic acid and its derivative, niacinamide, provide the essential function of this water-soluble vitamin, they differ significantly in their pharmacological properties and side effects. Nicotinic acid is noted for its ability to cause skin flushing and its historical use in treating high cholesterol, while niacinamide is the preferred form for supplementation to avoid the uncomfortable flushing effect. Understanding this distinction is important for anyone considering niacin supplementation for specific health purposes.
For more detailed information on niacin, its functions, and health considerations, consult the NIH Office of Dietary Supplements fact sheet: NIH Office of Dietary Supplements: Niacin
