THERE’S nothing to brighten a dull session in general practice like a colourful bottle of vitamins, extracted from a bulging handbag and placed on the desk to invite closer inspection of the 57 ingredients.
Time to give thanks for my severe myopia and squint at the label for a while before smiling sagely and saying: “Well … you really don’t need these if you eat a healthy diet”.
I’ve always been suspicious of vitamin supplements. My mother found the very idea of them morally and nutritionally reprehensible, and never put a meal on the table without repeating her favourite dietary mantra: “Protein, starch, green vegetable, yellow vegetable”.
I knew I had passed on the mantle when I heard my son, at age 7, refuse a chewable vitamin C tablet on the grounds that it might cause kidney stones.
It seems the science, in the guise of the Iowa Women’s Health Study, is also on my side. Among almost 40 000 women aged in their early 60s at baseline and followed for more than 20 years, taking vitamin and mineral supplements did not confer a survival benefit and was actually associated with a slightly increased risk of death.
Of the many vitamins, minerals and combinations included, calcium was the only supplement that showed a small survival advantage, but the authors were cautious about this because it conflicted with other studies.
They also cautioned that, as an observational study, they couldn’t control for all the factors that might have led the subjects to take supplements.
The Iowan paradox is not an isolated finding. A Cochrane review published in 2010 identified 67 randomised trials with 232 550 participants (both healthy and with identified chronic diseases), to try to determine if antioxidant supplements such as beta-carotene, vitamin A, vitamin C, vitamin E, and selenium had any effect on mortality. There was no evidence of benefit from any of the supplements, and some indication that vitamin A, beta-carotene and vitamin E may have a negative effect.
The disappointing news on supplements sits in contrast to the long-established and increasingly refined evidence that a healthy diet supports a range of positive outcomes, including reduced mortality.
The biological mechanisms for this are also being untangled. A study published last month, for instance, sought to replicate the health benefits of broccoli and other cruciferous vegetables by giving a supplement of the phytochemical contained in these plants. When the chips were down, the supplements lacked an enzyme present in the real thing, rendering them much less healthy (and tasty) than a plate of lightly cooked broccoli.
Many of the 10 million or so Australians who take vitamin supplements are doing so on top of a diet that is already nutritionally replete. Their money is literally going down the toilet and may even be doing them harm.
But there are some groups, such as the frail elderly, children in poor social circumstances, and Indigenous and other Australians who live in remote locations, who have trouble accessing enough healthy food. Given what we now know about diet and health, this is an unacceptable situation.
And there are people who just don’t get that eating is for health. In the absence of a Jetsons-style food pill, they might just all have to wake up and smell the spinach.
So, until more evidence emerges, doctors who are asked about the potential benefits of nutritional supplements can probably put away their reading glasses and advise patients that, except in cases of proven deficiency, they are unlikely to benefit and may be harmed.
We should lobby for a secure healthy food supply for all Australians, and encourage our patients to behave like adults and eat a wide variety of nutritious food.
And, with a nod to my mother and a raspberry to former US president George Bush, taking a supplement won’t get you out of eating your broccoli.
Dr Ruth Armstrong is a medical editor with the MJA.
Posted 24 October 2011
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