Vitamin C (ascorbic acid) is a household name mostly for its function in boosting the immune system, but it plays many other roles. Over the years I’ve read numerous studies on ascorbic acid and effects on the body and was always amazed that something as “simple” as vitamin C can produce such effects. Further investigation revealed these studies were using what is called therapeutic amounts or those amounts greater than the RDA (recommended dietary allowances). Currently the RDA for adults ranges from 90-155mg/day depending on your sex, pregnancy status, or if you smoke or not.VITAMIN-C-FOODS

Interestingly enough the human body cannot synthesize vitamin C. Vitamin C is formed from breaking down glucose. We are missing the last enzyme, L-gulonolactone oxidase, in the bioconversion process, which means vitamin C becomes essential (or must be obtained from the diet). Our diets currently lack in vitamin C due to premature harvesting of fruits and vegetables. We are also mis-informed by the media – that push oranges and citrus fruits as high in vitamin C while ignoring those with greater concentrations such as dark green and color veggies, which in my opinion are a superior choice due to their low sugar content.



A gross deficiency in vitamin C will lead to some bleeding disorders, joint and bone pain, muscle weakness, fatigue, swelling/edema, and osteoporosis. We have even begun to see mood and emotional states change due to deficiency. One of the uses of vitamin C you may not know about is its anti-histamine effect. I pick on the brand “Benadryl” because it is the most well know but what we are looking at is the active ingredient, diphenhydramine.

The immune system is a complex orchestration of inflammatory chemicals, messages and reactions. Histamine is a protein that is released during allergic reactions and manifest as itchy skin, hives, nasal congestion, and red, watery and itchy eyes. Once your body is exposed to sensitivities, for example a blade of grass, basophils and mast cells are called in a part of your immune response. Basophils and mast cells both release histamine.  The best way to stop the release of histamine is to limit your exposure to the sensitivity. Of course, there are times when it un-avoidable or too late (consumed a food you did not know you were sensitive to). Administration of 2,000mg ascorbic acid for 2 weeks dropped histamine levels in the blood by 38%, noted one study published in the Journal of the American College of Nutrition. High levels of histamine are also found in subjects with atherosclerosis. The ability for vitamin C to lower plasma histamine levels could be one of the mechanisms that make it cardio protective.

Table taken from textbook, Nutritional Medicine.

Table taken from textbook, Nutritional Medicine.

High dose vitamin C can be antibacterial and antiviral. Once the body reaches its saturation point (or renal re-sorption point) in the blood, ascorbic acid will then be excrete in the urine and possibly through the sweat glands. This can make vitamin C therapy very useful in patients with urinary tract infections (UTIs) and skin conditions/rashes. In fact, many chronic diseases are caused and perpetuated by oxidative damage. Vitamin C is a well-known, powerful antioxidant which can help quench free radical damage.

Dosing Vitamin C

Vitamin C is what is considered fractionally absorbed. Dr. Alan Gaby published Nutritional Medicine where he explains. “When 15–30 mg of vitamin C was administered, approximately 90% was absorbed. In contrast, less than 50% was absorbed when the dose was increased to 1,250 mg. Clinical observations suggest that the capacity to absorb vitamin C increases during acute illness.  Vitamin C is excreted primarily in the urine, and urinary excretion increases with increasing vitamin C intake.”

Vitamin C leg

The RDA of 90-155mg per day is too low and laboratory testing can be somewhat unreliable unless severe deficiency is present. Vitamin C loading is often performed to assess each individual saturation point. Commonly we increase the amount of vitamin C per day until the patient has begun to have lose bowel movements. This is considered “bowel tolerance” dose. At this point some practitioners will continuing the loading phase and continue with “therapeutic diarrhea” thus creating a gastric lavage – clearing the gut of possible hazardous microbes. This is very beneficial in patients with chronic diseases to rapidly decrease their microbial load but is not suggested unless under the care of a physician as there is a risk of dehydration or exacerbation of pre-existing conditions or interactions with certain pharmaceuticals. Toxicity of vitamin C is extremely low. The most common adverse effects from high dose vitamin C are GI distress which can be ameliorated by consuming vitamin C with food or certain forms of vitamin C such as magnesium ascorbate. A dose around 3,000mg/day for adults divided over 2-3 doses is customary in practice. Intravenous vitamin C may prove to be an alternative to very high dosages of Vitamin C while avoiding GI complaints.


Singh D, Chan W. Cardiomegaly and generalized oedema due to vitamin C deficiency. Singapore Med J 1974;15:60– 63.
Shafar J. Rapid reversion of electrocardiographic abnormalities after treatment in two cases of scurvy. Lancet 1967;2:176–178.
Johnston CS, Martin LJ, Cai X (April 1992). “Antihistamine effect of supplemental ascorbic acid and neutrophil chemotaxis”. J Am Coll Nutr 11 (2): 172–6. PMID 1578094.
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