By Krista Scott-Dixon, PhD

You may remember at some point during childhood being encouraged to eat your carrots "to help you see better." Despite what you thought at the time, this was not totally kooky advice.

Carrots contain beta-carotene, which belongs to a nutrient class called carotenoids, and it is one of the many forms of a family of nutrients collectively known as vitamin A, or provitamin A. Some forms are able to be vitamin A all on their own; others are known as "provitamins" because they have to graduate to be vitamin A through a few steps. (We bet you thought that a vitamin was a vitamin was a vitamin right? Nuh uh.) Vitamin A in general is important for promoting healthy eyesight along with a number of other good things such as a robust immune system and nice glowing skin. Beta-carotene is found in orange fruits and vegetables such as carrots, pumpkin, peppers, cantaloupe, apricots, and yams, but also in leafy green vegetables such as spinach and kale.

Betacarotines: good for you or not?

There is now pretty good evidence that (surprise) eating fruits and vegetables is good for you, and this appears to be due in part to the role played by antioxidants such as beta-carotenes. Beta-carotene has shown some provocative possibilities for the prevention and treatment of aging and chronic diseases such as cancer and cardiovascular disease.

Except here is the funny thing about nutrients: They do not always behave the way one expects. It seems like a pretty simple idea on the surface: If eating a food high in vitamin X shows good effects, then cutting out the middle man and feeding people vitamin X on its own should be more efficient, right? Unfortunately, not always.

Also, just because people's lab tests show them to be low in vitamin X does not mean that feeding them more vitamin X will help. Perhaps there is some reason they can't absorb and use vitamin X, for example. Or perhaps vitamin X does not travel well through the body on its own, and so it is better to put it in some other form.

Questions about low beta-carotene levels

So here's the conundrum. People who are not very healthy may show lower levels of beta-carotene and other antioxidants. Does this mean that low beta-carotene is the cause of them not being healthy? Does this mean we should give them more? Or do low levels really mean something else--perhaps that low levels occur in the presence of disease? Does low beta-carotene signify that people do not eat their fruits and veggies, and it's all the other good stuff in the produce that does the work? We don't know just yet, but it is clear that unlike eating beta-carotene in food form, supplementing beta-carotene on its own does not seem to work very well, and in fact may be actively harmful.

Beta-carotene and cardiovascular disease

Studies of beta-carotene's effect on cardiovascular disease, for example, suggest that supplementing beta-carotene actually increases the risk of premature death slightly, particularly among smokers (although all things considered, beta-carotene probably should not be smokers' biggest health worry). Researchers are not yet sure why supplementing beta-carotene has this negative effect.

"May make you die a little early" is not exactly what you want to read in the small print of your supplement label! So for now, give beta-carotene supplements a pass and eat them along with the big happy carotenoid family the way Mother Nature and Bugs Bunny intended. (Sadly, this probably does not include carrot cake.)