nameless, on Nov 21 2007, 02:26 AM, said:
I'm a bit too lazy to check pubmed right now, but have there ever been any high dose vitamin C studies that show either a heart benefit, or any health benefit at all?
By high-dose, I mean at least several grams/day, spread out at 4-5 hour intervals per dose. Most studies that get media attention tend to choose amounts in the 250mg-1 gram range/day, quite often with a single or double dose/day.
Till now saw only one with many grams a day, but various interesting others:
The effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infections.
RESULTS: Overall, reported flu and cold symptoms in the test group decreased 85% compared with the control group after the administration of megadose Vitamin C. CONCLUSION: Vitamin C in megadoses administered before or after the appearance of cold and flu symptoms relieved and prevented the symptoms in the test population compared with the control group.
Effect of ascorbic acid on plasma cholesterol in humans in a long-term experiment.
During the period of a low vitamin C intake (approximately equal to 20 mg per day) ascorbic acid in a dose of 2 x 500 mg per day was administered to 82 men and women aged 50-75 years. A correlation of plasma cholesterol levels determined before and after a three months' administration of ascorbic acid showed the effect of vitamin C to be dependent on the starting concentration of plasma cholesterol: the higher the initial cholesterolemia, the greater the hypocholesterolemic effect of ascorbic acid. On restricting the experimental group to subjects with an initial cholesterolemia above 230 mg%, the effect of the same dose of ascorbic acid on cholesterolemia was followed in three-month periods for a further 9 months. In all these time intervals, ascorbic acid was found significantly to depress cholesterolemia and its effects persisted 6 weeks after termination of the experiment. The administration of 2 x 500 mg ascorbic acid daily during one year resulted in an abrupt increase of ascorbemia and a marked accumulation of ascorbic acid in the leucocytes. Six weeks following interruption of ascorbic acid intake, vitamin C concentration in the leucocytes significantly declined but still continued to be twice higher than in the control receiving no ascorbic acid supplement.
Antioxidant vitamins and coronary heart disease risk: a pooled analysis of 9 cohorts.
RESULTS: Dietary intake of antioxidant vitamins was only weakly related to a reduced CHD risk after adjustment for potential nondietary and dietary confounding factors. Compared with subjects in the lowest dietary intake quintiles for vitamins E and C, those in the highest intake quintiles had relative risks of CHD incidence of 0.84 (95% CI: 0.71, 1.00; P=0.17) and 1.23 (1.04, 1.45; P=0.07), respectively, and the relative risks for subjects in the highest intake quintiles for the various carotenoids varied from 0.90 to 0.99.
Subjects with higher supplemental vitamin C intake had a lower CHD incidence.
Compared with subjects who did not take supplemental vitamin C, those who took >700 mg supplemental vitamin C/d had a relative risk of CHD incidence of 0.75 (0.60, 0.93; P for trend <0.001). Supplemental vitamin E intake was not significantly related to reduced CHD risk.
CONCLUSIONS: The results suggest a reduced incidence of major CHD events at high supplemental vitamin C intakes. The risk reductions at high vitamin E or carotenoid intakes appear small.
Vitamin C in the control of hypercholesterolemia in man.
(500mg - 1g/d)
The activity of the cholesterol 7 alpha-hydroxylating system containing cyto-chrome P-450 is depressed in the liver of guinea-pigs with chronic marginal vitamin C deficiency. Slowing-down of this rate-limiting reaction of cholesterol transformation to bile acids causes cholesterol accumulation in the liver, blood plasma and arteries, increase in the index total: HDL cholesterol, prolongation of plasma cholesterol half-life, increase in the index cholesterol: bile acids in the gall-bladder bile, cholesterol gallstone formation and atheromatous changes on coronary arteries in guinea-pigs with long-lasting marginal vitamin C deficiency.
The most effective means for preventing these changes are vitamin C doses ensuring maximal steady-state levels of ascorbate in the tissues. In most of hypercholesterolemic persons with a low vitamin C status, the administration of ascorbic acid in doses 500-1000 mg per day lowers total cholesterol concentration in blood plasma.
This effect may be reinforced through a simultaneous administration of bile acids sequestrants, such as cholestyramine or pectin. In every form of hypercholesterolemia therapy (dietary and/or pharmacological), an adequate vitamin C supply should be ensured in doses capable of creating maximal steady-state levels of ascorbate in human tissues.
Plasma lipids, lipoproteins and atherogenic index in men and women administered vitamin C.
The aim of the study was to establish whether it is possible, in a group of deliberately selected subjects with hyperlipidaemia, to modulate cholesterol levels by ascorbic acid administered at a dose of 500 mg/day. The authors assessed the levels of vitamin C, total and HDL cholesterol, triacylglycerols in the blood serum of 140 probands assigned to an 83-member experimental group, and to a 57-member control group. The experimental group was provided Celaskon effervescens Spofa at a dose of 500 mg/day/person. The experiment lasted for 18 months. Blood collections were made in the whole cohort at six-month intervals. Administration of L-ascorbic acid led to a highly significant decrease in the levels of total and LDL cholesterol. After 12 months of study, a highly significant decrease in atherogenic index and an increase in HDL cholesterol levels were found persisting until the end of the experiment.
US: vitamin C and stomach cancer
But when the researchers examined the blood levels of vitamin C they found a strong protective effect. That is: they found that those subjects with the highest level of vitamin C in their blood had a 60 percent lower risk of stomach cancer than those subjects with the lowest levels.
Vitamin C and risk of coronary heart disease in women.
After adjustment for age, smoking, and a variety of other coronary risk factors, we observed a ?modest? significant inverse association between total intake of vitamin C and risk of CHD (relative risk [RR] = 0.73; 95% confidence interval [CI] 0.57 to 0.94).
Among women who did not use vitamin C supplements or multivitamins, the association between intake of vitamin C from diet alone and incidence of CHD was weak and not significant (RR = 0.86; 95% CI 0.59 to 1.26).
In multivariate models adjusting for age, smoking, and a variety of other coronary risk factors, vitamin C supplement use was associated with a significantly lower risk of CHD (RR = 0.72; 95% CI 0.61 to 0.86).
CONCLUSIONS: Users of vitamin C supplements appear to be at lower risk for CHD.
Vitamin C Transforms Mouse Stem Cells Into Heart Muscle Cells
Lee and his colleagues tested 880 bioactive substances – including drugs and vitamins – approved by the U.S. Food and Drug Administration (FDA) to see if they stimulated the mouse stem cells to become heart muscle cells. The cells were genetically altered to give off a fluorescent bright green color when viewed under a microscrope if they had become heart muscle cells.
"We only got 1 out of the 880 to light up, and that was from ascorbic acid, the chemical commonly known as vitamin C," says Lee, an associate professor of medicine at Harvard Medical School and Brigham and Women's Hospital in Boston, and a lecturer in biological engineering at the Massachusetts Institute of Technology in Cambridge, Mass.
Edited by pamojja, 18 October 2009 - 04:24 PM.