No scientific evidence to support dietary supplements

> There is no scientific evidence that dietary
> supplements (vitamins, minerals, antioxidants,
> herbs) can improve your health.

What a disasterous example of inarticulacy.

Vitamins are vital. If you are on a restricted diet, think sailor on old-time sailing ship, you may well end up with scurvy and supplementing your diet with vitamin C will save your life. This was controversial at the time, and I am confident that anyone familiar with the literature can dig up the scientific studies that prove the point.

Keren Ventii is clearly trying to say something else, but what? Vitamins are traditionally understood as having the same kind of dose/response relationship as the lubricating oil that you put in the engine of your motor car: while essential, an excess conveys no additional benefit.

A popular hypothesis is that super-dosing does produce health benefits. Karen say "No scientific evidence" which suggests that the hypothesis may turn out to be true. It is also a surprising claim; the hypothesis has been knocking around for decades, surely some-one would have done an experiment by now!

Indeed. as Karen goes on to say, people have tested super-doses of vitamin E, expecting to demonstrate protection against heart disease and cancer, and been disappointed.

As the common cliche has it "absence of evidence is not evidence of absence". This cliche is often used to promote health scares. Just because we don't have evidence of danger, we cannot assume that we are safe. But this cuts both ways. Once an experiment has been done, it is no longer correct to say "There is no scientific evidence ...".

There is no point super-dosing on vitamin E, hoping for protection from heart disease and cancer. The reason for believing this is not a negative reason based on there being "no evidence". The reason is a positive reason. We think the trials were well done and we will get the same answer if we repeat them. They put an upper bound on the health benefits we might hope for. The health benefits must be less than would have shown up in the trials already run.

Obviously the size of the trial is relevant here. A small trial can only demonstrate large, clear health benefits.

The "no evidence" meme is especially anoying in the controversy over whether power lines cause cancer. I keep seeing claims that there is "no evidence that power lines cause cancer". That is so strange because relevant experiments are easy to do. Indeed they are often done, and there is plenty of evidence that power lines don't cause cancer. Evidence is not the same as truth, perhaps power lines do cause cancer in some small, strange way that is consistent with evidence that seems to show that they are safe. But we need to circulate round the various hazards. Having checked out the risks from power lines we should leave it and check out something else or breath a sigh of relief and go party.

Karen, if you want to be a medical journalist, do the world a favour and develop a writing style that only says "no evidence" before the experiments are done. After the results are in you should give a positive presentation of what the results show, in this case that "scientific evidence refutes the main hypotheses about the health benefits of dietary supplements".

This reminds me of the old "I did not borrow your pot, your pot does not have a hole in it, and it most certainly had the hole when i borrowed it!". Each one of those might be convincing arguments on their own for why I wasn't the cause of the hole in your pot, but they are mutually exclusive. In other words, you cannot say :

"There is no scientific evidence that dietary supplements (vitamins, minerals, antioxidants, herbs) can improve your health."

and then say

"The best way to get one's vitamins, minerals and antioxidants is through a balanced diet."

What you COULD say, if you supported the latter, is that as yet there has been no pill that combines the right anti-oxidents to have a measureable good effect.

But then again, that would be false too. Pilot studies show a few things can be beneficial, and the lack of more evidence is mostly due to the repeated myth that supplementary nutrition doesn't matter. Maybe we should be drinking 8 glasses of water a day too, Mr. Expert. What other popular meme's can we repeat that hold no bearing?

A negative of evidence does not mean evidence to the negative. The whole fact that there is a controversy here in the first place explains most of the missing evidence, as no one wants to do studies that get them labelled as an orthomolecular MD. Try getting funding these days explaining Global Warming to anything except manmade CO2 gasses and you'll see my point. The orthodoxy has spoken.

Moreover you focus exactly on the negative studies and don't mention the same that are positive, skewing your viewpoint. What we now know is that vitamin E, A and C don't really help much in the cases it was used. But like you said yourself, there are over 20,000 different compounds, ruling out three does not make a very convincing case that the rest don't help at all in isolation either. Selenium for cancer patients, for example, or a multivitamin for pregnent people.

There is evidence both ways, thats all I'm saying.

To Alan Crowe:
Thank you for your comment

You make a good point about word choices and you are definitely entitled to your opinion about my choice of words.

You say- Vitamins are vital. If you are on a restricted diet, think sailor...supplementing your diet with vitamin C will save your life.

I am certainly not disregarding the importance of vitamins or antioxidants to overall health. The main point is that it is better to focus on getting these substances from a balanced healthy diet and that it is not enough to rely on dietary supplement pills to ward off disease or slow aging.

It seems we can both agree, however, that dietary supplements have not been shown to harbor any significant health benefits.