Some compounds in mango skin help fight diabetes and some forms of cancer
MY FATHER was fond of mangoes. During the summer season, he would polish off two mangoes at each meal time - juice, pulp and skin - with relish. My wife, who is from Gujarat, wondered why he would eat the skin too, while she did not. When asked, he would say: "You North Indians are missing out a good part of the fruit." I, the son and husband, would take the safe midcourse and eat it from time to time.
On to a good thing
Now I know that my father was on to a good thing in eating the mango skin. Recent work, presented at the Australian Health and Medical Research Congress at Melbourne, by Ashley Wilkinson and Sarah Roberts-Thomson of Queensland University, show that some compounds in the mango skin help fight some metabolic diseases such as diabetes and some forms of cancer.These compounds modulate some receptor molecules called PPARs in our cells. These receptors help in controlling the levels of cholesterol and related fatty compounds in the blood stream on one hand, and the levels of glucose on the other. Thus, mangoes might have positive benefits for diabetes and heart conditions. Since PPARs are also related to some cancers, the substances in the mango may also have anti-cancer effects. But note: these compounds are more abundant in the mango skin than in the pulp. We do not yet have a full catalogue of all the compounds in the skin, but some of them are already well known and found elsewhere too. One is quercetin, an antioxidant molecule that helps our cells from "cellular overburn" or oxidative damage. It is found in several other fruits, in some greens and also in onion. The other is mangiferin, found in the mango skin, which, as the name implies, quarantines away excess free iron in the body and thus offers protection against iron-caused oxidative damage. The third is a by-product of mangiferin called norathyriol, which too is an antioxidant.
It is likely that the mango skin also has resveratrol, which also lowers cholesterol levels. The skins of blue grapes are rich in resveratrol, which finds its way into red wine. Wines and juices from all dark-coloured berries are good sources of resveratrol. Hence the recommendation of red wines as health aids. Green grapes are not high on this score; hence neither is white wine. Incidentally, the pinkish skin of peanuts (groundnuts) is another rich source of resveratrol and other health-aiding agents. Here my wife evened up to my father. She would bring roasted, salted peanuts with (skins intact) from Baroda, and my father would remove the skin from them by rubbing the nuts off his palms and eat the nuts. She would then pip in: "You Tamilians don't know a good thing when given to you." Eating mango skin and peanut skin might thus be useful against diabetes, a disease that has become a pandemic across India. But is eating the mango pulp a good idea? After all it contains high amounts of sugar. While sugars such as glucose are the fuel for the body and give us energy, not using them up efficiently and having them lying around in the cells and blood stream is harmful. Glucose is `burnt' or oxidized in our cells to yield energy, but too much of it can lead to `overburn' and oxidative damage. Glucose also chemically combines with proteins and alters their properties and functions. This leads in time to impaired eyesight, neuromuscular function, kidney damage and so on. In discarding the skins of many fruits, we throw away useful health aids. Other, herbivorous, mammals such as cows, goats, horses and elephants eat the whole fruits with skins intact, and gain health benefits.
Benefits of apple skin
Apple skin is a good source of calcium and vitamin A. The vitamin content is reported to be five times higher in the skin than the flesh. So, throw away not the apple skin but the apple-peeler, and eat the fruit, skin and all. The same goes for the potato too. Pomegranate skin is rich in a variety of antioxidants and cell-protectants. Indeed, some claim that it tops the list of all fruits on this score. While we normally eat only the beautifully coated and tasty seeds, commercially available pomegranate juice is healthier, since it is made by crushing the whole fruit, skin included.Traditional medicine men use the pomegranate skin as a treatment against diarrhoea. The skin is boiled with a small amount of cloves or cinnamon, and the solution drunk thrice daily for a few days. It would appear from this that the skin has some antibiotics. What about the banana skin? While cows and goats eat them, monkeys and men do not. The banana skin is useful in other ways. Some use it to treat rashes from shrubs such as poison ivy, by rubbing the skin inside out. It is also useful to treat bruises. Taping the banana skin around the bruise helps in healing.
It is not necessary to avoid fruits in diabetes, but it is wise to choose the fruits. A parameter called the glycemic index (GI) gives a measure of how fast carbohydrate foods are converted in the body to glucose. It is best to choose fruits not high in this index. Nutritionists suggest that diabetics avoid dates and canned fruit cocktails, which are high in GI. Apple, cherries, grapefruit and oranges, with their low GI values, are good. Mangoes, papaya and banana are of medium GI and are thus OK. But mangoes - eat them in moderation and eat them with their skins. I for one eat mangoes and peanuts with their skins, thus meeting the approval of my genes and my love. I have learnt the wisdom of the middle path. D. BALASUBRAMANIAN