Vitamin C
By Dr Davis
Vitamin C, or ascorbic acid, has been a topic of controversy for many years. There is no dispute regarding its necessity for basic health, since vitamin C deficiency of vitamin C causes serious disease. But the health benefits of higher doses of vitamin C have been vehemently argued for years. Conservatives argue that the minimum daily requirement (30 mg) is required for health with no additional benefit obtained from greater quantities. At the opposite extreme are arguments like that of Nobel laureate (for physics) Dr. Linus Pauling , who argued that mega-doses of vitamin C could cure people of atherosclerosis, based on the premise that coronary atherosclerosis represented a lesser version of scurvy (vitamin C deficiency). Where does the truth lie?
First of all, doses of vitamin C of 1000-2000 mg per day tend to modestly lower LDL cholesterol, usually 5 -10 points. Not a huge effect, but still helpful. Similar doses tend to lower systolic blood pressure by a modest several points. Vitamin C has a relaxing effect on arteries, particularly if there is abnormal constriction, an effect somewhat similar to that of l-arginine (though by a different mechanism).
Does vitamin C have measurable effects on inhibiting coronary plaque growth, or reducing heart attack risk? Probably not to any substantial degree. There have been claims made (by Drs. Linus Pauling and Mathias Rath) that mega-doses of vitamin C (up to 10 grams, or 10,000 mg) lower Lp (a) and thereby reduce plaque growth, but attempts to reproduce their efforts have failed. Is the anti-oxidant effect of vitamin C helpful? The final answer remains unclear on this question, too. Large trials have included vitamin C as part of a mixture of anti-oxidants (often with vitamin E, selenium, and beta-carotene), and not as a single agent, and these trials have shown no beneficial effects on reducing risk of heart attack.
Some authorities have proposed that the lack of clear-cut benefit in clinical trials is due to the exclusion of other naturally-occurring flavonoids that normally accompany vitamin C in whole foods. More work is needed before the answers become clear. In the meantime, vitamin C in doses of 1000-2000 is a good idea, with potential for modest benefits. If you have a history of kidney stones, you should not exceed a dose of 500 mg and should discuss this with your doctor first. Ideally, the vitamin C preparation you use should include some of the other flavanoids which may be listed on the label, such as bioflavonoid complex, hesperidin , and rutin. Some authorities have proposed that vitamin C and other anti-oxidants express their real benefits when combined with l-arginine.
References:
Kim MK, Sasaki S, Sasazuki S, Okubo S, Hayashi M, Tsugane S. Long-term vitamin C supplementation has no markedly favourable effect on serum lipids in middle-aged Japanese subjects. Br J Nutr. 2004 Jan;91(1):81-90.
Clarke R, Armitage J. Antioxidant vitamins and risk of cardiovascular disease. Review of large-scale randomised trials. Cardiovasc Drugs Ther. 2002 Sep;16(5):411-5.
Wilburn AJ, King DS, Glisson J, Rockhold RW, Wofford MR. The natural treatment of hypertension. J Clin Hypertens (Greenwich). 2004 May;6(5):242-8.
Regensteiner JG, Popylisen S, Bauer TA, Lindenfeld J, Gill E, Smith S, Oliver-Pickett CK, Reusch JE, Weil JV. Oral L-arginine and vitamins E and C improve endothelial function in women with type 2 diabetes. Vasc Med. 2003;8(3):169-75.
Block G. Ascorbic acid, blood pressure, and the American diet. Ann N Y Acad Sci. 2002 Apr;959:180-7. |
