1 June 2010

Food for Thought

Why supplements are not a substitute for fruits and vegetables

Professor Walter Willett
Professor Walter Willett

‘There is no way that taking a pill can replace eating fruits and vegetables,’ writes Prof Walter Willett Chairman, Department of Nutrition, Harvard School of Public Health in Eat Drink and Be Healthy. ‘So far, no one has found a magic bullet that works against heart disease, cancer and a host of other chronic diseases as well as fruits and vegetables seem to do. In theory, one could cram all the good things that plants make – essential elements, fiber, vitamins, antioxidants, plant hormones, and so on – into a pill. But it would have to be a very large pill, and no one can honestly say what should go into such a pill. Or in what proportions. The benefits of eating fruits and vegetables probably come from combinations of compounds that work together.

Take the antioxidant pigments known as carotenoids, for example. When you eat a tomato or carrot, the different carotenoids it contains eventually get into different types of cells and different parts of each cell. This offers antioxidant protection throughout the cell and to a wide variety of cell types. When eaten in the proportions usually found in foods, carotenoids and other phytochemicals probably work together and protect cells at different levels. But when delivered in unnatural proportions – say via a poorly designed supplement – an oversupply of one carotenoid or phytochemical could block the activity of others. This isn’t to say vitamin and mineral supplements are worthless … [they] are excellent insurance. But they aren’t a substitute for a healthy diet.

Boy eating apple
Credit: The Low GI Family Cookbook
Photograph by Ian Hofstetter

Health issues aside, the biggest drawback is that a pill would always taste like a pill. It can’t give you the earthy smell and taste of a fresh ear of corn, the sweetness of a juicy tomato still warm from the afternoon sun, the crunch of an apple, the festive green of a snap pea or broccoli floret, or the smooth nutty taste of an avocado. Stick with real fruits and vegetables – they taste better and contain a bounty of phytochemicals that don’t come in capsules.
Eat Drink and Be Healthy is available from major bookstores and Amazon

Eat Drink and Be Healthy

How much fruit do you need a day?
This depends on your energy (calorie/kilojoule) needs, which is of course determined by age, sex and activity level. Check out Fruits and Veggies: More Matters to find out what you should be tucking into.


Anonymous said...

I enjoy reading the GI news, but I wonder why you are referring readers to an American website about recommended intakes for fruit and vegetables? In Australia we have different guidelines to the US and you should refer readers to the appropriate Australian Guidelines (the Australian Guide to Healthy Eating).


GI Group said...

Thanks for the Australian link. Based on our visitor stats, the majority of our readers are from North America. Hence the US link. In addition, this particular Food for Thought piece is by Prof Walt Willett from Harvard, so it seem appropriate to have the US link. But point taken and we will investigate simple ways of having different national links for these sorts of stories.