Nutritional Advice El Mondo

Vitamin C

Scientific studies (review articles) on the relationship between vitamin C and disease prevention:
One swallow does not make a summer. A famous Dutch saying that could not be any more obvious. Just because one single scientific study about a certain topic makes certain claims, it does not necessarily mean it is true. On the other hand, a review article (a collection of scientific studies on a certain topic) of randomized, placebo-controlled double blind clinical trials (RCTs) will answer the following question:
"Do taking dietary supplements make sense?" Yes for a positive conclusion and no for a negative conclusion.

One swallow does not make a summer. A famous Dutch saying that could not be any more obvious. Just because one single scientific study about a certain topic makes certain claims, it does not necessarily mean it is true. On the other hand, a review article (a collection of scientific studies on a certain topic) of cohort studies or case-control studies will answer the following question:
"Should I change my diet?".

  1. Daily 150-200mg dietary vitamin C reduce gastric cancer 
  2. High circulating vitamin C level reduces metabolic syndrome
  3. Vitamin C supplementation does not reduce risk of COVID-19
  4. Vitamin C supplements improve triglyceride and cholesterol levels in patients with type 2 diabetes mellitus
  5. Vitamin B1 + vitamin C supplementation does not reduce mortality in patients with sepsis or septic shock
  6. Dietary intake of vegetables and vitamin C could reduce renal cell carcinoma
  7. Higher vitamin C dietary intake reduces breast cancer
  8. 400 mg/day vitamin C supplementation improves lung function of COPD patients
  9. A higher dietary intake of fruit, dietary fiber, fish and vitamine C reduce COPD in adults
  10. Post-diagnosis calcium, vitamin C, D or E decreases cancer mortality
  11. Higher circulating concentration of vitamin C, vitamin E and β-carotene reduce cardiovascular mortality
  12. Dietary intake of 5 mg/d vitamin A reduces age-related cataract
  13. Dietary intake of vitamin A, C and green leafy vegetables reduce glaucoma risk
  14. A diet with high antioxidant properties reduces all-cause mortality risk
  15. No association between vitamin A, C, D, E and lycopene and risk of non-Hodgkin lymphoma
  16. Dietary intake of vitamin C-rich foods reduces risk of osteoporosis
  17. 50 mg/day dietary vitamin C intake decreases hip fracture risk
  18. Vitamin C supplementation for at least 30 days reduces glucose concentrations in patients with type 2 diabetes
  19. A high serum vitamin C reduces blood pressure
  20. Vitamin C supplements during ≥6 weeks reduce blood pressure
  21. Oral vitamin C supplementation may improve glycemic control and blood pressure in people with type 2 diabetes
  22. Vitamin C and D reduce blood pressure in patients with type 2 diabetes
  23. Perioperative antioxidant supplementations with NAC, PUFA and vitamin C prevent atrial fibrillation after cardiac surgery
  24. Dietary intakes of vitamin C and E lower risk of Alzheimer's disease

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  • Vitamin C is cofactor in at least 800 enzymatic reactions in the human body.
  • Vitamin C is a water-soluble antioxidant. Being an antioxidant, vitamin C protects the body from the harmful effects of free radicals and pollutants.
  • Vitamin C enhances the immune system.
  • Vitamin C is required for the maintenance of normal connective tissue and wound healing. Vitamin C is also needed for bone remodeling because of the presence of collagen in the organic matrix.
  • Vitamin C is involved in the synthesis of collagen, neurotransmitters and carnitine. Vitamin C increases the gastrointestinal absorption of non-haem iron.
  • Vitamin C is involved in the regeneration of vitamin E and these two vitamins appear to work together in their antioxidant effect.
  • Vitamin C does not prevent the development of cancer.
  • Vitamin C does not reduce the incidence of the common cold but it may reduce the duration of illness.
  • Vitamin C, also known as ascorbate, ascorbic acid or E300, is synthesized by all animals except humans, monkeys, guinea pigs, bats and several bird species.
    Humans, monkeys, guinea pigs, bats and several bird species lack a key enzyme, L-3 gulonolactone oxidase, necessary for the biosynthesis of vitamin C from glucose.
  • Deficiency of vitamin C can lead to anemia, scurvy, infections, bleeding gums, muscle degeneration, poor wound healing, atherosclerotic plaques, capillary hemorrhaging and neurotic disturbances.
  • The best food sources of vitamin C are uncooked or raw fruits and vegetables, like oranges, kiwi and peppers.
  • Vitamin C in foods is irreversibly oxidized by exposure to light, oxygen, and/or heat.
    Cooking fuit and vegetables reduces their vitamin C content by around 30-40%.
  • 300 grams of vegetables and 5 servings of fruit a day provide average of 200 mg of vitamin C.
  • Plasma vitamin C concentration of less than 11 mmol/L (0.2 mg/dL) is indicative of scurvy.
    Below 30 mg vitamin C per day, plasma concentrations are around 11 mmol/L.
  • Hypovitaminosis C has been characterized as having a plasma concentration of vitamin C less than 23 mmol/L.
  • The recommended daily allowance can be determined through the bowel tolerance. The moment you get intestinal complaints after taking vitamin C, meaning that you took too much vitamin C than the body can handle. Too much vitamin C binds to water and gives symptoms, such as diarrhea.
  • Scurvy can be prevented by 10 mg of vitamin C daily.
  • Vitamin C administered by mouth or injection is effective for curing scurvy. In adults, 100-250 milligrams by mouth four times daily for one week is generally sufficient to improve symptoms and replenish body vitamin C stores.
    For scurvy or vitamin C deficiency in children, 100-300 milligrams of vitamin C daily by mouth in divided doses for two weeks has been used.
    Symptoms should begin to improve within 24-48 hours, with resolution within seven days. Treatment should be under strict medical supervision.
  • Clinical signs of scurvy appear when the whole body content falls below 300-400 mg, and the last signs disappear when the body content reaches about 1000 mg.
  • 100-200 mg of vitamin C per day are needed to saturate tissues concentrations. Nowadays, these values are used to set the RDA.
  • Optimal plasma vitamin C concentration is 70 micromol/L.
    This blood value would require a daily intake of about 400-500 mg vitamin C.
  • The WHO has set the RDA of vitamin C for adults on 45 mg.
  • The FDA has set the RDA of vitamin C on 90 mg for men and 75 mg for women.
  • The EFSA has set the RDA of vitamin C on 80 mg.