The Copenhagen team reviewed more than 815 clinical trials into the benefits of vitamins A, E, and C, alongside beta-carotene and selenium – all commonly-used supplements. They selected 68 whose methods were more likely to produce an accurate picture of vitamin benefits … [and] eliminated a further 21 trials which had a slightly higher possibility of producing a skewed result, … While the risk of death was unchanged among selenium and vitamin C users, a statistically significant increase in risk emerged for the other three supplements. Beta-carotene produced an approximate 7% increased risk, vitamin E a 4% increase and vitamin A, a 16% increase.
I posted an explanation of why this study was complete garbage about a year ago, here.
Short explanation: They used linear regression to fit curved data. The mean values of vitamin A and E in their study were dosages already known to be toxic. They included people taking up to 10 times that much. Some of them died. The authors concluded that taking any amount of vitamins is dangerous.
You could do the same study with water, or oxygen, or vegetables, and you would get the same results. Anything kills you in large enough doses. That doesn't mean small amounts are harmful.
Of course, even with all the information, you still cannot be sure of what to do. You may know all the statistics, but still not know how the presence or absence of the supplements will affect you, with your individual physiology.
But unless you have reason to believe you're atypical in some specific way that would predictably change the effect of the supplements, you should act as if the statistics apply to you.
(BTW, names appear below comments. The comment about sight was from Larry Sheldon. And it is a very good point.)
When people read stories like this, they wonder what to do: keep taking the supplements, change their diet, or whatever. There is a great danger of such decisions themselves being biased by incomplete information.
We are told that different supplements increase the risk of early death by different percentages (such as 4%, 7% and 16%). Those figures may look high enough to justify action. But if the risk of early death is low to start with, they might not be. If the supplements have advantages when they do not kill you, for example in preserving your sight to quote Caledonian's example a few comments ago, but they only raise the probability of an early death from, say, 3% to 3.5%, they may still be worth taking.
Just for an incredibly crude and unscientific measure, do you feel better when you take supplements? When you don't take them?
My point is that other than the well-established micronutrient deficiency diseases there is precious little evidence to suggest that the composition of your diet matters significantly to your health.
Avoiding the the micronutrient deficiency diseases is nearly trivial and can be accomplished by almost any kind of dietary composition. No one in developed nations needs to be counseled on their diet to avoid scurvy - and they aren't. Nutritionists don't suggest a "well-balanced diet" to avoid deficiency diseases, they do it to avoid cancer, heart attack, stroke, diabetes, and morbidity and mortality in general. So far, the evidence is not on their side that any of their recommendations make any difference.
The people taking supplements in the meta-analysis studies weren't doing it to avoid pellagra, they were doing it "to be healthy", i.e. to avoid general morbidity and mortality. The meta-analysis suggests the supplements weren't helping with that goal. The nutritionists interviewed for the BBC report said, in effect, "don't take supplements to be healthy, just eat a well-balanced diet." I'm predicting that someday their advice will be shown not to be helpful either. I may be wrong, but there's no basis for saying that they are right.
I don't know why you're having such a problem understanding this.
We don't know that we've identified all of the important nutrients, and it would be extraordinarily difficult to manage the ones we do know about through supplements. We also know beyond doubt that eating a sufficiently varied diet avoids deficiency diseases, maintains the ecology of the digestive system, and results in health.
Why would you even want to artificially replicate the benefits of a proper diet, when it's far easier just to eat a proper diet in the first place?
Besides avoiding nutritional diseases like scurvy and pellagra?
It doesn't take eating "a wide range of foods" to prevent the basic nutritional diseases. Supplements will prevent such illnesses just fine. I doubt the people in the study were dying from rickets or beriberi.
diets are considered 'balanced' if they provide the right nutrients in the proper amounts
Once upon a time, diets were considered 'balanced' if they had roughly equal amounts of the "four food groups". More recently, diets are considered 'balanced' if they conform in content and proportion to the "food pyramid". Both the food groups and the food pyramid have nothing to do with health or micronutrient adequacy and everything to do with agricultural influence over the federal bureaucracy.
Eating a varied diet is just a good way to hedge your bets...
So is Pascal's Wager. The evidence is still lacking, though.
The Opthamologist tells me to take the SREDS Formulation to slow the progress of macular degeneration.
Comes down to this. I like to read. I like to watch the birds. I like sight seeing. Should I be blind, or should I be dead?
Not sure I can see the difference from here.
I wonder what meta-analysis has been done to demonstrate that eating "a wide range of foods in a balanced diet" has any benefit over other kinds of diets?
Eating a varied diet is just a good way to hedge your bets... and diets are considered 'balanced' if they provide the right nutrients in the proper amounts. Imbalanced diets are thus necessarily unhealthy.
And now that there are so many better sources of technical information, does a blog with this caliber of author and reader really need to link to a broadcaster or a big newspaper for any scientific information -- but particularly news-you-can-use health stories?
What Tim Tyler said. I am inclined to believe that most medical articles even in the most prestigious journals are useless or worse than useless (for the purpose of improving or preserving health) because of an agenda. The agenda is usually profit motive. This particular JAMA article smells like its agenda is to protect drug revenue from competition from superior alternatives from the supplement industry.
This is not an endorsement of the supplement industry which markets many, many actively harmful products, but rather an assertion that a small fraction of supplements are superior to certain very profitable drugs as interventions on certain very common conditions. I am also not necessarily saying that carotene, retinol or vitamin E is a superior interventions for any condition: perhaps publishing on them is a convenient way to smear supplements in general.
I would not be at all surprised if a lot of the nutritional articles out of Harvard have an (unconscious) religious puritanical agenda rather than a proft agenda. More precisely that the principals get a high from imposing their will in the public or political sphere like political progressives do.
The medical and pharmaceutical industries are among the most unethical or destructive industries. The information-technology or oil industries for example are pure white in comparison.
I've been saying for years that supplements are ineffective at best and dangerous at worst.
You also need to consider what the peak plasma levels for these chemicals are. Mega-dosing is pointless and may be dangerous unless you know how much your body can absorb and metabolize at a time.
It would be useful to know what are the quantities involved. Some vitamin supplements, especially the single-vitamin supplements, deliver a dose many times larger than what will be found in a typical multivitamin. Does this result apply to typical multivitamins which give much more modest doses of a large number of vitamins and minerals?
From the article:
[N]utritionists said [the meta-analysis] reinforced the need to eat a balanced diet, rather than relying on supplements.Dr Frankie Phillips, a nutritionist at the British Dietetic Association, said food contained a complex matrix of different components which could not be replicated by supplements."Our advice is to eat a wide range of foods in a balanced diet which can provide all of the nutrients the body needs to protect itself and combat diseases."
I wonder what meta-analysis has been done to demonstrate that eating "a wide range of foods in a balanced diet" has any benefit over other kinds of diets? Supplements may be nutritional nonsense, but I'm not confident the advice of nutritionists is any better.
This news article is from over a year ago. Even back then it was well known that retinol, synthetic beta carotene and selenium were easy to overdose on -so my guess is that this study chose its targets in order to find problems.http://jama.ama-assn.org/cg...
It's probably not an accident that β-carotene, vitamin E, and vitamin A are all fat-soluble, whereas C and selenium compounds are water-soluble. It's much harder to overdose on water-soluble substances.