Chop up and boil some purple cabbage. Take some of the juice, and add a little vinegar. It turns a bright red. Now add some baking soda and watch the juice turn blue. What’s going on? The color of purple cabbage is due to compounds called anthocyanins. In this case, we are looking at anthocyanins that absorb wavelengths of light other than purple, which they reflect. The addition of an acid or a base to these molecules slightly alters their structure and changes their light absorption pattern. But the really neat thing about this experiment is that it can benefit more than your mind. It can benefit your health. All you have to do is eat the cabbage after you’re through ogling the color changes. Those anthocyanins not only absorb light, they also have antioxidant properties, meaning that they can neutralize some of the potentially health damaging free radicals that are a byproduct of inhaling oxygen. The deeper the colour of a fruit or vegetable, the more anthocyanins it contains. That’s why researchers are interested in berries, grapes and even blue corn. Blackberries, being particularly rich in anthocyanins and antioxidant activity, are excellent candidates for health benefits. Researchers at Ohio State University fed diets laced with freeze-dried blackberries to rats after injecting them with azoxymethane, a chemical that causes colon tumours. The results were impressive. The more berries a rat ate, the fewer tumours it had. And the more berries it ate, the less 8-hydroxydeoxyguanosine, a marker for oxidative damage, was found in its urine. But, and it is a pretty big but. To duplicate the cancer protection seen in rats, a human would have to eat about four cups of fresh blackberries a day.
But blackberries are not the only foods with anthocyanin activity. Grapes, chokeberries, bilberries, blueberries, strawberries and purple corn all owe their color to these compounds. And in test tube experiments and animal feeding studies all of these have shown anti-cancer activity. For example, extracts were added to cultured human cancer cells and the amount of anthocyanin extract needed to reduce cancer cell growth by 50% was determined. Purple corn led the field. Again, this doesn’t mean that tortillas made with blue corn should be promoted as an anti-cancer food, although if there is a choice, one could argue for their consumption instead of regular tortillas. Interestingly, it even turns out that blue tortillas have a lower glycemic index than regular tortillas, and are more suitable for diabetics. It is clear that anthocyanins have some interesting potential benefits. But a lot more research has to be done before we can make specific recommendations, especially when we take into account that more than 600 anthocyanins have been identified and undoubtedly anti-cancer activity is related to specific aspects of their molecular structures. Perhaps in the future we will avail ourselves of anthocyanin pills, but for now the best idea is to include as many deep colored fruits and vegetables in the diet as possible. What we need is a recipe that involves a blue tortilla, purple cabbage and a good dose of blackberries.