The Healthspan Map · Nutrient

Vitamin C

Compiled by Aamir Malik, PhD, Professor of Neuroengineering at Brno University of Technology, from published studies. He is a researcher, not a physician. Last updated 21 August 2026.

Linked to getting too little

Where a shortfall of Vitamin C is linked: 19 sources.In the order the Map holds them: strongest evidence first. That is a statement about the evidence, not about what matters most.
Condition or system	Direction	Strength	Evidence type	What was found	Source
Anemia	Eat enough of	Moderate	Review / narrative	Vitamin C boosts non-heme iron absorption; deficiency can worsen iron-deficiency anemia.	Vitamin C & iron absorption (opens in a new tab)
Anxiety	Eat enough of	Emerging	Review / narrative	Vitamin C reduced anxiety in an RCT; high-dose vitamin C lowered cortisol and subjective stress.	de Oliveira et al. 2015; Brody et al. 2002 (opens in a new tab)
Anxiety	Eat enough of	Emerging	RCT / trial	Vitamin C reduced anxiety in an RCT; high-dose vitamin C lowered cortisol and subjective stress.	Brody et al., "A randomized controlled trial of high dose ascorbic acid for reduction of blood pressure, cortisol, and subjective responses to psychological stress", Psychopharmacology 2002 (opens in a new tab)
Brain fog & memory	Eat enough of	Moderate	Review / narrative	Adequate vitamin C status is associated with better attention, concentration and memory; deficiency impairs cognition.	Linus Pauling Institute; Travica et al. (opens in a new tab)
Brain fog & memory	Eat enough of	Moderate	Review / narrative	Adequate vitamin C status is associated with better attention, concentration and memory; deficiency impairs cognition.	Linus Pauling Institute — Vitamin C (opens in a new tab)
Chronic fatigue / low energy	Eat enough of	Moderate	Review / narrative	Vitamin C supports carnitine synthesis and energy metabolism; early deficiency presents as fatigue.	Micronutrients for energy/fatigue review (Tardy 2020) (opens in a new tab)
Depression / low mood	Eat enough of	Moderate	Established clinical	Depression is a recognized feature of scurvy.	NIH ODS – Vitamin C (opens in a new tab)
Insomnia / poor sleep	Eat enough of	Emerging	Cohort / observational	Low vitamin C intake is associated with short sleep; as an antioxidant it may buffer oxidative-stress effects on sleep.	NHANES 2005-2016 (opens in a new tab)
Muscle & joint pain / weakness	Eat enough of	Moderate	Systematic review	Vitamin C is essential for collagen synthesis (tendon/cartilage); deficiency is linked to lower muscle strength, especially in older adults.	Nutritional supplements & sarcopenia (opens in a new tab)
Osteoporosis / low bone density	Eat enough of	Moderate	RCT / meta-analysis	Vitamin C is required for bone-collagen synthesis and osteoblast differentiation; higher intake links to higher BMD and lower hip-fracture and osteoporosis risk.	Vitamin C & BMD/fracture meta (opens in a new tab)
Osteoporosis / low bone density	Eat enough of	Moderate	Established clinical	Vitamin C is required for bone-collagen synthesis and osteoblast differentiation; higher intake links to higher BMD and lower hip-fracture and osteoporosis risk.	NIH Office of Dietary Supplements — Vitamin C (opens in a new tab)
Reproductive & sexual health	Eat enough of	Moderate	Review / narrative	Vitamin C is the principal antioxidant in seminal plasma; adequate intake protects sperm from reactive-oxygen-species damage and recycles vitamin E.	Diet & men’s fertility (Fertil Steril 2018) (opens in a new tab)
Respiratory infections & airway health	Eat enough of	Moderate	Systematic review	Low vitamin C status raises pneumonia risk; regular intake shortens cold duration ~8% and halves cold risk (RR 0.48) under heavy physical stress.	Vitamin C for the common cold (Cochrane, Hemilä 2013) (opens in a new tab)
Skin, hair, nails & wound healing	Eat enough of	Strong	Established clinical	Vitamin C is essential for collagen hydroxylation; deficiency (scurvy) causes fragile skin, corkscrew hairs, poor wound healing and bleeding.	Vitamin C & collagen (scurvy) (opens in a new tab)
Sleep-disordered breathing	Eat enough of	Emerging	Review / narrative	OSA patients show lower antioxidant status; vitamin C/E supplementation restored glutathione and reversed endothelial dysfunction, though effects on AHI are unproven.	Dietary antioxidants & OSA study (PMC8916682) (opens in a new tab)
Stress	Eat enough of	Emerging	Review / narrative	Vitamin C reduced anxiety in an RCT; high-dose vitamin C lowered blood pressure, cortisol and subjective stress responses.	de Oliveira et al. 2015; Brody et al. 2002 (opens in a new tab)
Stress	Eat enough of	Emerging	RCT / trial	Vitamin C reduced anxiety in an RCT; high-dose vitamin C lowered blood pressure, cortisol and subjective stress responses.	Brody et al., "A randomized controlled trial of high dose ascorbic acid for reduction of blood pressure, cortisol, and subjective responses to psychological stress", Psychopharmacology 2002 (opens in a new tab)
Vision problems	Eat enough of	Moderate	RCT / meta-analysis	Vitamin C is an AREDS antioxidant contributing to reduced AMD progression.	AREDS formula review (PMC7015456) (opens in a new tab)
Weak immunity & chronic inflammation	Eat enough of	Moderate	Review / narrative	Vitamin C supports barrier integrity and phagocyte/lymphocyte function; among the strongest-evidence immune micronutrients (shortens common cold).	Vitamin C & immune function (opens in a new tab)

Linked to getting too much

Where an excess of Vitamin C is linked: 3 sources.In the order the Map holds them: strongest evidence first. That is a statement about the evidence, not about what matters most.
Condition or system	Direction	Strength	Evidence type	What was found	Source
Digestive discomfort	Don't overdo	Moderate	Established clinical	Vitamin C above bowel tolerance (~2 g) causes osmotic diarrhoea and cramping.	NIH Office of Dietary Supplements — Vitamin C (opens in a new tab)
Reproductive & sexual health	Don't overdo	Emerging	Review / narrative	Megadosing antioxidants such as vitamin C can create reductive stress detrimental to sperm function — more is not better.	Dietary antioxidants & male infertility – antioxidant paradox (PMC8003818) (opens in a new tab)
Liver, Kidney & Urinary	Don't overdo	Moderate	Cohort / observational	High-dose vitamin C (>=1000 mg/day) is metabolized to oxalate, raising the risk of oxalate kidney stones and, rarely, oxalate nephropathy.	Secondary hyperoxaluria from high-dose vitamin C (PMC11924107) (opens in a new tab)

The Healthspan Map is part of Fix the Floor, a book by Aamir Malik. About the book