When good things are bad for you – are vitamins too much of a good thing? (10/14/11)
When Good Things Are Bad For You
Vitamin – the word itself conjures up healthiness, something vital for life. Without them we can’t live.
But can we have too much of them?
Yes. Just like we can have too much food.
The fat soluble vitamins A, D, E, and K – all have associated hypervitaminosis syndromes – we can store enough of them in our fat to make us sick. A recent study of vitamin E to prevent prostate cancer showed an increase in incidence, not the expected decrease. The Norwegian Vitamin trial, performed over many years, found that combined B vitamins probably increased cardiovascular risk – the opposite of what the researchers hoped to show.
If specific combinations of vitamins and minerals can harm our health what about the multivitamin hundreds of millions take every day?
Iowa Woman’s Health Study
Recently the University of Minnesota published data from the Iowa Woman’s Health Study, looking at women at or over the age of 62. Overall, those who claimed to take a multivitamin died early than those who did not. Almost every individual item taken, whether it was iron or folic acid – seemed to potentially increase mortality – with one exception – calcium supplements.
Do these results actually apply to everybody?
No. Here are some problems with generalizing the implications of the Iowa Woman’s Health Study:
1. There was no data on what the women ate.
2. The results were based on recall – which can be faulty.
3. The group looked at was only older women.
4. There was little opportunity to investigate volunteer bias – comparing the women who wanted to take multivitamins and those who did not.
As for calcium,
1. Other studies do not show taking more calcium improves overall mortality – even an improvement in bone fracture risk.
2. There is data that calcium may increase overall heart attack risk-though the “30% increased risk” seen in a recent study pooling of many studies might simply have picked up earlier diagnoses of heart attacks.
What This All Means
There are several take home lessons from recent studies of vitamins:
A. There’s precious little evidence taking multivitamins benefits everybody in the population.
B. Public health measures – what works for populations – gets short shrift in research.
There’s plenty of money to look at “medical breakthroughs” – like new cholesterol lowering drugs. But asking whether adding parks and green spaces does more than health care to keep people alive, or whether vitamins really work, become research stepchildren.
Because there’s little direct profit to companies and institutions in knowing the results.
The end game is that governments are needed to fund such studies – ones that look at what aids the overall health of a population. And without a public health constituency and with saddled budgets, don’t expect to find good answers to important questions:
Including who will best benefit from multivitamins. Are they good for kids? Pregnant women? There’s certainly positive evidence for these populations. Certain vitamins can also help people who are sick – as in those with kidney disease. The Iowa Women’s Study argues that they may not benefit older white women – but what about the rest of us?
Different populations have very different needs.
C. Without expensive longitudinal studies you’re shooting in the dark, because human biology is really complex.
Ask the drug companies. So many promising drugs have hit the skids because of unexpected side effects – results that did not show up in animal studies.
Ask the makers of thalidomide – who knew that a drug would cause disappearing limbs in newborns? Or be reborn decades later as an anti-cancer treatment.
Ask the supplement manufacturers – who claim healthful results for their products – like vitamins – without backing scientists and clinicians trust.
And there’s the rub.
Too Much Of a Good Thing
Ask a patient on first clinical examination to give you a list of your drugs, and you’ll often find the usual culprits – anti-hypertensives, statins, various jiggers of aspirin.
Yet many folks do not consider vitamins or supplements to be “drugs.” After all, they’re “natural.”
Probe a little further, and many patients – especially those who are health conscious – and frequently a laundry list of vitamins and supplements pops out.
In my practice, people are often taking 5-10 separate substances – together.
Ask how they take them, and the answers become more interesting. “If I feel blue, I take more complex Bs, because they give me a lift.” Or, “ I was worrying about my friend who was just diagnosed with melanoma, so I doubled my vitamin D dose for a few weeks.” (By the by, vitamin D is a hormone that a recent National Institute of Medicine panel argued – very controversially – should not be given in higher doses to the general population.)
Like food, people feel they can take such “non-drugs” with abandon.
The end results are still unknown – particularly from the many combinations of supplements and vitamins – often combinations of combinations. But the auguries, based on recent vitamin trials, are not good.
Most of us get enough vitamins from our diet and moving around outside.
So what will be the result of these many billions of individual experiments?
We’ll need research money to find out. And with only the population to profit, most of the time we won’t get it.
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