# Vitamin B3 (Niacin): Metabolism and Cardiovascular Health

B Vitamins & Longevity | By Longevity Futures Research Team | Updated November 2025

Vitamin B3, commonly known as niacin, is one of the most fascinating B vitamins due to its profound effects on metabolism, cardiovascular health, and—most excitingly for longevity research—its role as a precursor to NAD+ (nicotinamide adenine dinucleotide), a molecule central to cellular aging.

Niacin exists in several forms: nicotinic acid, nicotinamide (niacinamide), and nicotinamide riboside (NR). Each form has unique properties and applications, making understanding the differences essential for optimizing your supplementation strategy.

The NAD+ Connection: NAD+ is required for over 500 enzymatic reactions in your body and is essential for energy production, DNA repair, and sirtuin activation—the "longevity genes." As we age, NAD+ levels decline significantly, contributing to many aspects of aging. Niacin and its derivatives help maintain and restore NAD+ levels.
16 mg
RDA for Men
14 mg
RDA for Women
500+
NAD+ Dependent Enzymes
50%
NAD+ Decline by Age 50

## Forms of Vitamin B3

### Nicotinic Acid (Niacin)

The original form of vitamin B3, nicotinic acid is famous for its cardiovascular benefits—particularly its ability to raise HDL cholesterol. However, it also causes the "niacin flush," a temporary reddening and warming of the skin due to blood vessel dilation.

### Nicotinamide (Niacinamide)

This form doesn't cause flushing and is popular in skincare for its anti-inflammatory properties. It's an effective NAD+ precursor but doesn't have the same lipid-modifying effects as nicotinic acid.

### Nicotinamide Riboside (NR)

A newer form that efficiently converts to NAD+ without flushing. NR has become popular in longevity circles due to research showing it can effectively boost NAD+ levels in humans.

### Nicotinamide Mononucleotide (NMN)

Another NAD+ precursor that's one step closer to NAD+ in the biosynthetic pathway. Research on NMN for longevity is rapidly expanding.

## Energy Metabolism and NAD+

NAD+ is indispensable for cellular energy production. It serves as an electron carrier in the metabolic processes that convert food into ATP:

- Glycolysis: NAD+ accepts electrons during glucose breakdown
- Citric acid cycle: Multiple steps require NAD+
- Electron transport chain: NADH donates electrons for ATP synthesis
- Fatty acid oxidation: NAD+ is essential for burning fat

Aging Connection: Research published in Cell Metabolism demonstrated that NAD+ levels decline by approximately 50% between ages 40 and 60. This decline correlates with reduced mitochondrial function, decreased energy levels, and accelerated aging. Restoring NAD+ levels through niacin derivatives may help counteract these effects.

## Cardiovascular Benefits

Nicotinic acid (immediate-release niacin) has powerful effects on blood lipids that no other vitamin can match:

- Raises HDL cholesterol: Can increase "good" cholesterol by 20-35%
- Lowers LDL cholesterol: Modest reductions of 10-20%
- Reduces triglycerides: Can lower by 20-50%
- Lowers Lp(a): One of few interventions that reduces this atherogenic particle
- Reduces VLDL: Decreases very-low-density lipoprotein production

Important Note: While niacin's lipid effects are impressive, recent clinical trials (like AIM-HIGH and HPS2-THRIVE) didn't show cardiovascular event reduction when niacin was added to statin therapy. However, niacin may still benefit those who can't tolerate statins or have specific lipid abnormalities like low HDL or high Lp(a).

## Sirtuins and Longevity

Perhaps the most exciting aspect of niacin for longevity is its role in activating sirtuins—a family of proteins that regulate cellular health and aging:

- SIRT1: Regulates metabolism, inflammation, and stress resistance
- SIRT3: Critical for mitochondrial function and energy production
- SIRT6: Involved in DNA repair and metabolic regulation

Sirtuins require NAD+ to function. By maintaining NAD+ levels through niacin intake, you support sirtuin activity and potentially slow aspects of cellular aging.

Research Highlight: David Sinclair's lab at Harvard has shown that boosting NAD+ levels in aged mice reversed many markers of aging, including improved muscle function, better insulin sensitivity, and enhanced exercise capacity. Human trials with NR and NMN are ongoing with promising early results.

## Best Food Sources of Niacin

#### Chicken Breast

14.4 mg per 3 oz serving. One of the richest sources—provides nearly 100% of daily needs.

#### Tuna

11.3 mg per 3 oz serving. Excellent source with omega-3 fatty acids.

#### Turkey

10.0 mg per 3 oz serving. Another excellent poultry option.

#### Beef

7.6 mg per 3 oz serving. Good source alongside protein and B12.

#### Peanuts

4.4 mg per 1/4 cup. Top plant source with healthy fats.

#### Fortified Cereals

Variable—check labels. Many provide 25-100% of daily needs.

## The Niacin Flush

Taking nicotinic acid often causes "niacin flush"—a harmless but sometimes uncomfortable reaction involving:

- Reddening of the face, neck, and chest
- Warmth or tingling sensation
- Itching that typically resolves within 1-2 hours

The flush is caused by prostaglandin release and vasodilation. Strategies to minimize it include:

- Take with food: Reduces absorption speed
- Start low, go slow: Gradually increase dose over weeks
- Take aspirin: 325mg taken 30 minutes before niacin blocks prostaglandin
- Use extended-release forms: Slower absorption reduces peak flush (but monitor liver function)
- Choose nicotinamide: Doesn't cause flush (but no lipid benefits)

## Who May Benefit from Extra Niacin?

- Those seeking NAD+ restoration: For longevity and cellular health
- People with low HDL: Niacin remains effective for raising HDL
- High Lp(a) levels: One of few options to lower this risk factor
- Aging individuals: To counteract age-related NAD+ decline
- Those with pellagra risk: Alcoholics, those with malabsorption

## Safety Considerations

While niacin at food levels is completely safe, high-dose supplementation requires some caution:

- Liver monitoring: Extended-release niacin can affect liver enzymes; periodic testing recommended
- Blood sugar: High doses may affect glucose tolerance in diabetics
- Uric acid: Niacin can raise uric acid levels; caution with gout
- Muscle problems: Rare when combined with statins

Nicotinamide (niacinamide), NR, and NMN don't typically cause these issues and are generally well-tolerated at higher doses.

## Recommended Niacin Supplement

### Thorne B-Complex #12

A comprehensive B-complex with active B12 and folate. Contains all eight B vitamins including niacin for metabolism and cardiovascular health. Uses bioactive forms for maximum absorption. NSF-certified for sport and third-party tested for purity.

$42.87
View on Amazon

## Related Articles

- NMN: NAD+ Booster for Longevity
- Nicotinamide Riboside (NR): NAD+ Booster
- Vitamin B1 (Thiamine): Energy Metabolism
- Vitamin B12: Nerve Function and Red Blood Cells