Vitamin C

What Is Vitamin C?

Vitamin C (ascorbic acid) is a water-soluble vitamin that humans cannot synthesize — we must get it from food or supplements. It’s one of the most important antioxidants and plays critical roles in immune function, collagen synthesis, and protecting cells from oxidative damage.

Despite being the most commonly supplemented vitamin, true vitamin C deficiency (scurvy) is rare, but suboptimal levels are common. Requirements increase significantly during illness, stress, and exposure to pollutants.

Benefits

Primary Benefits

• Immune Support: Supports function of various immune cells
• Antioxidant Protection: Neutralizes free radicals; regenerates vitamin E
• Collagen Synthesis: Essential for skin, joints, blood vessels
• Iron Absorption: Enhances absorption of non-heme iron

Secondary Benefits

• Supports adrenal function and stress response
• Important for wound healing
• May reduce duration of colds
• Supports cardiovascular health
• Protects eye health
• May support mood (cofactor in neurotransmitter synthesis)

How It Works

Vitamin C functions through several mechanisms:

• Electron donor: Provides electrons to neutralize free radicals
• Enzyme cofactor: Required for 8 enzymes, including those making collagen
• Immune cell support: Enhances neutrophil and lymphocyte function
• Regenerates antioxidants: “Recycles” vitamin E and glutathione
• Gene expression: Influences hundreds of genes

Dosage Recommendations

Bowel tolerance: The dose at which you experience loose stools indicates tissue saturation. During illness, this threshold increases dramatically (the body uses more vitamin C).

RDA is 75-90 mg — this prevents scurvy but may not be optimal for health.

Best Forms

Liposomal Vitamin C

Liposomal delivery wraps vitamin C in phospholipid spheres:

• Higher blood levels than regular vitamin C
• Better tolerated at high doses (less GI upset)
• More expensive
• Ideal for those needing therapeutic doses

When to Take

• Split doses: Vitamin C is water-soluble and excreted within hours. Taking 500mg twice daily is better than 1,000mg once.
• With meals: Reduces potential stomach upset
• With iron-rich foods: If you need to enhance iron absorption
• Throughout illness: Increase frequency during acute illness

Vitamin C and Immunity

Despite being the “cold vitamin,” vitamin C’s effects are nuanced:

What Research Shows

• Prevents colds: Modest effect in general population; significant effect in those under physical stress (athletes, soldiers)
• Shortens colds: Consistent evidence for modest reduction (8-14% shorter duration)
• Reduces severity: Some evidence for reduced symptoms
• High doses during illness: Taking high doses at symptom onset may help more than chronic supplementation

How It Works for Immunity

• Supports epithelial barrier function
• Enhances neutrophil chemotaxis and phagocytosis
• Supports B and T cell function
• Reduces oxidative stress during infection

Vitamin C and Skin

Vitamin C is essential for collagen production:

• Wrinkle reduction: Topical and oral vitamin C support skin structure
• Wound healing: Accelerates tissue repair
• Sun protection: Antioxidant protection (not a substitute for sunscreen)
• Brightening: Reduces melanin production

Combination of oral and topical vitamin C provides best results for skin.

Side Effects

• Digestive upset: Nausea, cramps, diarrhea at high doses
• Kidney stones: Theoretical risk with very high chronic doses (>2,000 mg)
• Iron overload: Can worsen hemochromatosis
• False positive tests: May affect certain blood/urine tests

Upper limit: 2,000 mg/day is considered safe for most adults.

Drug Interactions

Who Benefits Most

• Smokers: Have 35% higher vitamin C requirements
• Those under stress: Physical or mental stress depletes vitamin C
• Athletes: Increased oxidative stress and immune demands
• Elderly: Often have lower dietary intake and absorption
• Those with poor diet: Limited fruit and vegetable intake
• During illness: Requirements increase dramatically

Food Sources

Note: Vitamin C is sensitive to heat, light, and air. Fresh, raw sources retain most vitamin C.

Vitamin C + Vitamin E Synergy

These antioxidants work together:

• Vitamin E protects cell membranes (fat-soluble)
• Vitamin C regenerates vitamin E after it neutralizes free radicals
• Together, they provide comprehensive antioxidant protection

Research Summary

• Immunity: Meta-analyses show consistent modest benefits for cold duration and severity
• Cardiovascular: Associated with lower cardiovascular risk; mechanism includes blood pressure reduction
• Collagen: Well-established role; deficiency causes scurvy
• Cancer: IV vitamin C studied in cancer care (not oral supplementation)
• Mortality: Higher vitamin C levels associated with lower all-cause mortality

Myths and Controversies

“Megadose vitamin C cures everything”

Linus Pauling promoted very high doses. While vitamin C is important, megadose claims are often exaggerated. Evidence supports moderate supplementation.

“You just pee out excess vitamin C”

Partly true — you do excrete excess. But higher doses can maintain higher plasma levels, and during illness, excretion decreases as body uses more.

“Natural vitamin C is better than synthetic”

Synthetic ascorbic acid is chemically identical to natural. “Whole food” vitamin C contains cofactors but at much lower doses.

Bottom Line

Vitamin C is a foundational supplement with strong evidence for immune support, antioxidant protection, and collagen synthesis. While most people can get adequate amounts from food, supplementation provides insurance — especially during stress, illness, or with suboptimal diet.

Key takeaways:

• Take 500-1,000 mg daily, split into 2 doses
• Increase during illness (up to bowel tolerance)
• Ascorbic acid is effective; liposomal is best for high doses
• Essential for smokers and those under stress
• Works synergistically with zinc and vitamin E