coronary heart disease
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.
Still in the spirit of ACUPUNCTURE AWARENESS WEEK, I have another critical look at a recent paper. If you trust some of the conclusions of this new article, you might think that acupuncture is an evidence-based treatment for coronary heart disease. I think this would be a recipe for disaster.
This condition affects millions and eventually kills a frighteningly large percentage of the population. Essentially, it is caused by the fact that, as we get older, the blood vessels supplying the heart also change, become narrower and get partially or even totally blocked. This causes lack of oxygen in the heart which causes pain known as angina pectoris. Angina is a most important warning sign indicating that a full blown heart attack might be not far.
The treatment of coronary heart disease consists in trying to let more blood flow through the narrowed coronaries, either by drugs or by surgery. At the same time, one attempts to reduce the oxygen demand of the heart, if possible. Normalisation of risk factors like hypertension and hypercholesterolaemia are key preventative strategies. It is not immediate clear to me how acupuncture might help in all this - but I have been wrong before!
The new meta-analysis included 16 individual randomised clinical trials. All had a high or moderate risk of bias. Acupuncture combined with conventional drugs (AC+CD) turned out to be superior to conventional drugs alone in reducing the incidence of acute myocardial infarction (AMI). AC+CD was superior to conventional drugs in reducing angina symptoms as well as in improving electrocardiography (ECG). Acupuncture by itself was also superior to conventional drugs for angina symptoms and ECG improvement. AC+CD was superior to conventional drugs in shortening the time to onset of angina relief. However, the time to onset was significantly longer for acupuncture treatment than for conventional treatment alone.
From these results, the authors [who are from the Chengdu University of Traditional Chinese Medicine in Sichuan, China] conclude that “AC+CD reduced the occurrence of AMI, and both acupuncture and AC+CD relieved angina symptoms and improved ECG. However, compared with conventional treatment, acupuncture showed a longer delay before its onset of action. This indicates that acupuncture is not suitable for emergency treatment of heart attack. Owing to the poor quality of the current evidence, the findings of this systematic review need to be verified by more RCTs to enhance statistical power.”
As in the meta-analysis discussed in my previous post, the studies are mostly Chinese, flawed, and not obtainable for an independent assessment. As in the previous article, I fail to see a plausible mechanism by which acupuncture might bring about the effects. This is not just a trivial or coincidental observation – I could cite dozens of systematic reviews for which the same criticism applies.
What is different, however, from the last post on gout is simple and important: if you treat gout with a therapy that is ineffective, you have more pain and eventually might opt for an effective one. If you treat coronary heart disease with a therapy that does not work, you might not have time to change, you might be dead.
Therefore I strongly disagree with the authors of this meta-analysis; “the findings of this systematic review need NOT to be verified by more RCTs to enhance statistical power” — foremost, I think, the findings need to be interpreted with much more caution and re-written. In fact, the findings show quite clearly that there is no good evidence to use acupuncture for coronary heart disease. To pretend otherwise is, in my view, not responsible.
There might be an important lesson here: A SEEMINGLY SLIGHT CORRECTION OF CONCLUSIONS OF SUCH SYSTEMATIC REVIEWS MIGHT SAVE LIVES.