B3

Vitamin B3

Chemical structure of Niacin

Vitamin B3, also known as niacin, is an essential water-soluble vitamin that plays a critical role in the metabolism of carbohydrates, fats, and proteins. It is a member of the B vitamins group and is vital for maintaining healthy skin, nerves, and digestion.

Chemical Structure and Forms

Vitamin B3 exists in two main forms: niacin (nicotinic acid) and niacinamide (nicotinamide). Both forms are precursors to the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), which are essential for energy production and cellular metabolism.

Biological Functions

Vitamin B3 is crucial for several biological functions:

• Energy Production: It is a component of NAD and NADP, which are involved in redox reactions in the electron transport chain, a key process in cellular respiration.
• DNA Repair: NAD is involved in DNA repair mechanisms, helping to maintain genomic stability.
• Cholesterol Metabolism: Niacin can influence lipid metabolism by reducing low-density lipoprotein (LDL) cholesterol and increasing high-density lipoprotein (HDL) cholesterol.
• Antioxidant Defense: NADP is a precursor to NADPH, which is used in biosynthetic reactions and in maintaining the glutathione antioxidant system.

Dietary Sources

Vitamin B3 can be obtained from a variety of dietary sources, including:

• Animal Products: Chicken, turkey, beef, and fish such as tuna and salmon.
• Plant Sources: Peanuts, avocado, and whole grains.
• Fortified Foods: Many cereals and breads are fortified with niacin.

Recommended Dietary Allowance

The Recommended Dietary Allowance (RDA) for vitamin B3 varies by age, sex, and life stage:

• Adults: 16 mg/day for men and 14 mg/day for women.
• Pregnant Women: 18 mg/day.
• Lactating Women: 17 mg/day.

Deficiency

A deficiency in vitamin B3 can lead to a condition known as pellagra, characterized by the "three Ds": dermatitis, diarrhea, and dementia. If left untreated, pellagra can be fatal.

Toxicity

While vitamin B3 is generally safe, excessive intake can lead to toxicity, with symptoms such as flushing, itching, nausea, and liver damage. The Tolerable Upper Intake Level (UL) for adults is 35 mg/day.

Clinical Uses

Niacin is used therapeutically to manage dyslipidemia by lowering LDL cholesterol and triglycerides while raising HDL cholesterol. It is also being studied for its potential benefits in cardiovascular disease and neurodegenerative disorders.

Conclusion

Vitamin B3 is an essential nutrient with diverse roles in human health. Adequate intake through diet or supplementation is important for maintaining metabolic functions and preventing deficiency-related diseases.