In 1747, James Lind conducted what may well be the first documented controlled clinical trial in the history of medicine. He treated a small group of healthy sailors with a range of different remedies to see whether one of these regimen might be effective in preventing scurvy. The results showed that lemon and lime juice – effectively vitamin C – did the trick. This trial changed the world: it saved tens of thousands of lives, gave Britain the advantage at sea needed to become a dominant empire, and set medicine on the track to eventually become evidence-based.

Of course, Lind did not know that the effective principle in his lemon/lime juice was vitamin C. The Hungarian physiologist Albert Szent-Gyorgyi discovered vitamin C only ~200 years later and received the Nobel Prize for it in 1937. Since then, research has been buoyant, and vitamin C has been advocated for almost every condition one can think of. Looking at some of the claims made for it, I get the impression that more charlatans have jumped on the vitamin C band-waggon than the old vehicle can support. In alternative medicine, high-dose IV vitamin C is a popular variation of Lind’s concept, not least for the treatment of cancer.

Researchers from the NIH in the US surveyed attendees at annual CAM Conferences in 2006 and 2008, and determined sales of intravenous vitamin C by major U.S. manufacturers/distributors. They also queried practitioners for adverse effects, compiled published cases, and analyzed FDA’s Adverse Events Database. Of 199 survey respondents (out of 550), 172 practitioners had administered IV vitamin C to 11,233 patients in 2006 and to 8876 patients in 2008. The average dose was 28 grams every 4 days, with a mean of 22 treatments per patient. Estimated yearly doses used (as 25g/50ml vials) were 318,539 in 2006 and 354,647 in 2008. Manufacturers’ yearly sales were 750,000 and 855,000 vials, respectively. Common reasons for treatment included infection, cancer, and fatigue. Of 9,328 patients for whom data was available, 101 had adverse effects, mostly minor, including lethargy/fatigue in 59 patients, change in mental status in 21 patients and vein irritation/phlebitis in 6 patients. Publications documented serious adverse events, including two deaths. The FDA Adverse Events Database was uninformative.

The authors of this paper conclude that high dose IV vitamin C is in unexpectedly wide use by CAM practitioners. Other than the known complications of IV vitamin C in those with renal impairment or glucose 6 phosphate dehydrogenase deficiency, high dose intravenous vitamin C appears to be remarkably safe. Physicians should inquire about IV vitamin C use in patients with cancer, chronic, untreatable, or intractable conditions and be observant of unexpected harm, drug interactions, or benefit.

I find these results somewhat worrying. Desperate cancer patients are constantly being told that they can fight the disease with high-dose vitamin C, for instance on the >9 million (!) websites on this subject. One site, for instance, leaves little doubt about the efficacy of vitamin C as a treatment for cancer: First shown to be a powerful anti-cancer agent in 1971, it wasn’t until 20 years later that vitamin C started to be accepted by the mainstream medical profession. Eating a vitamin C-rich diet substantially reduces the risk of cancer, and high intakes – above 5000mg a day (the equivalent of 100 oranges) – substantially increases the life expectancy of cancer patients.

Statements like this one give false hope to cancer patients which is unethical and cruel and might hasten the death of many. The reality is quite different and provides little reason for such hope. Here are just a few conclusions from recent scientific analyses on this or closely related topics:

post-diagnosis vitamin C supplementation at the level observed in our population was not associated with survival

Evidence is insufficient to prove the presence or absence of benefits from use of multivitamin and mineral supplements to prevent cancer and chronic disease

We could not find evidence that antioxidant supplements prevent gastrointestinal cancers. On the contrary, they seem to increase overall mortality. The potential cancer preventive effect of selenium should be studied in adequately conducted randomised trial

The question whether the regular intake of high doses of vitamin C have a preventative effect for certain cancers is currently open. But there is no good reason to suggest that high dose IV vitamin C is an effective treatment for any cancer. To pretend otherwise, as so many alternative practitioners seem to do, is less than responsible – in fact, it is a hallmark for cancer quackery.

Antioxidant vitamins include vitamin E, beta-carotene, and vitamin C. They are often recommended and widely used for preventing major cardiovascular outcomes. However, the effect of antioxidant vitamins on cardiovascular events remains unclear. There is plenty of evidence but the trouble is that it is not always of high quality and confusingly contradictory. Consequently, it is possible to cherry-pick the studies you prefer in order to come up with the answer you like. That this approach is counter-productive should be obvious to every reader of this blog. Only a rigorous systematic review can provide an answer that is as reliable as possible with the data available to date. Chinese researchers have just published such an assessment.

They searched PubMed, EmBase, the Cochrane Central Register of Controlled Trials, and the proceedings of major conferences for relevant investigations. To be eligible, studies had to be randomized, placebo-controlled trials reporting on the effects of antioxidant vitamins on cardiovascular outcomes. The primary outcome measures were major cardiovascular events, myocardial infarction, stroke, cardiac death, total death, and any adverse events.

The searches identified 293 articles of which 15 RCTs reporting data on 188209 participants met the inclusion criteria. In total, these studies reported 12749 major cardiovascular events, 6699 myocardial infarction, 3749 strokes, 14122 total death, and 5980 cardiac deaths. Overall, antioxidant vitamin supplementation, as compared to placebo, had no effect on major cardiovascular events (RR, 1.00; 95% CI, 0.96-1.03), myocardial infarction (RR, 0.98; 95% CI, 0.92-1.04), stroke (RR, 0.99; 95% CI, 0.93-1.05), total death (RR, 1.03; 95% CI, 0.98-1.07), cardiac death (RR, 1.02; 95% CI, 0.97-1.07), revascularization (RR, 1.00; 95% CI, 0.95-1.05), total CHD (RR, 0.96; 95% CI, 0.87-1.05), angina (RR, 0.98; 95% CI, 0.90-1.07), and congestive heart failure (RR, 1.07; 95% CI, 0.96 to 1.19).

The authors’ conclusion from these data could not be clearer: Antioxidant vitamin supplementation has no effect on the incidence of major cardiovascular events, myocardial infarction, stroke, total death, and cardiac death.

Few subjects in the realm of nutrition have attracted as much research during recent years as did antioxidants, and it is hard to think of a disease for which they are not recommended by this expert or another. Cardiovascular disease used to be the flag ship in this fleet of conditions; not so long ago, even the conventional medical wisdom sympathized with the notion that the regular supplementation of our diet with antioxidant vitamins might reduce the risk of cardiovascular disease and mortality.

Today, the pendulum has swung back, and it now seems to be mostly the alternative scene that still swears by antioxidants for that purpose. Nobody doubts that antioxidants have important biological functions, but this excellent meta-analysis quite clearly and fairly convincingly shows that buying antioxidant supplements is a waste of money. It does not promote cardiovascular health, it merely generates very expensive urine.

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