Under the Microscope/Prof William Reville:A dietician addressed a large audience, saying the following: "The material we put into our stomachs should have killed most of us sitting here, years ago. Red meat is awful.
A dietician addressed a large audience, saying the following: "The material we put into our stomachs should have killed most of us sitting here, years ago. Red meat is awful. Soft drinks erode your stomach lining. Chinese food is loaded with monosodium glutamate. Vegetables can be disastrous, and none of us realises the long-term harm caused by the germs in our drinking water.
"But there is one thing that is the most dangerous of all and we all have, or will, eat it. Can anyone here tell me what food it is that causes the most grief and suffering for years after eating it?" An old man stood up and said: "Wedding cake."
I tell this joke because the old man's advice may be just as useful as the dietician's. Nutrition is a very complex area because our bodies are so complex. The foods we eat undergo a huge number of interactions and transformations in our bodies so that it can be extremely difficult to disentangle the effects, for good or ill, of any individual food. Nevertheless, we are regularly treated to new nutritional advice as to what constitutes an optimal diet. But because of the complexity of the area, details of these recommendations must be regularly modified, or even reversed.
The latest example of this phenomenon concerns coffee. Up until now, nutritionists have viewed coffee with suspicion, generally advising that drinking more than a cup or two a day is not a good idea. Drinking too much coffee causes nervousness, increases the heart rate, causes trembling hands and may upset the stomach. However, the latest research claims that coffee is loaded with natural chemicals that protect us against many ailments.
We all must inhale oxygen which we use to chemically burn (oxidise) ingested food in order to generate energy. One of the downsides of using oxygen is that many biomolecules in our body cells can also become oxidised, producing dangerous chemicals called free radicals. Free radicals can move about the cell randomly attacking and damaging other chemicals. Because this is so dangerous, the cell is equipped naturally with protective mechanisms. These are in the form of chemicals called antioxidants and enzymes that prevent unwanted oxidations. The natural antioxidants in the cell must be supplemented by antioxidants in our food. Research shows that eating antioxidant-rich foods reduces damage from free radicals and may prevent, slow down, or even reverse certain diseases that result from cellular damage. Antioxidants may also slow down natural ageing.
Antioxidants are abundant in grains, tomatoes and in many other vegetables and fruits. But, recent research, including work by Prof Joe Vinson at the University of Scranton in Pennsylvania, has shown that coffee provides more healthful antioxidants than any other food or beverage in the US diet. Vinson analysed more than 100 different foods and used typical food consumption patterns to calculate how much antioxidant each contributes to a person's diet. The average adult consumes 1,300mg antioxidant daily from coffee. The closest competitors were tea (294mg), bananas (76mg), dry beans (72mg), corn (48mg).
This does not mean that we can substitute coffee for fruit and vegetables. Fruit and vegetables are very important because of their higher content of vitamins, minerals and fibre.
A team of Japanese researchers reported in the Journal of the National Cancer Institute in February 2006 that drinking coffee daily halves the risk of contracting liver cancer. The effect was greater in people who drank three to four cups daily as compared to one to two cups.
In 2005, the Harvard School of Public Health reported that drinking coffee reduced the risk of contracting type-two diabetes, the most common form of the disease. Man who drank more than six cups of coffee per day lowered their risk by 50 per cent and women lowered their risk by 30 per cent. Other research indicates that drinking coffee can lower the risk of contracting cirrhosis by up to 80 per cent and Stockholm's Karolinska Institute declares there is "strong epidemiological evidence" that drinking coffee can prevent Parkinson's disease in men.
It has further been reported that coffee drinking reduces the risk of gallstones by 50 per cent and colon cancer by 25 per cent. And Dr Tomas De Paulis of Vanderbilt University's Institute for Coffee Studies claims that "people who smoke and are heavy drinkers have less heart disease and liver damage when they regularly consume large amounts of coffee compared to those who don't". Italian researchers even report that coffee can prevent dental cavities!
So, what do we make out of all this? Lets be cautious. The coffee bean, like many plants, also contains many natural carcinogens. There is no known correlation between drinking coffee and getting cancer, but I think it is far too early in this coffee story to switch over to large-scale regular coffee-drinking. On the other hand, if you like to drink four or five cups a day, this latest research will be a great comfort to you.
Far too much is published about diet in the popular media. It mostly serves only to confuse. Choosing a healthy diet is simple: eat a wide variety of foods in moderation and take plenty of exercise. Food types to be eaten more liberally include wholegrain foods, plant oils, fruits and vegetables; in moderate amounts - nuts, beans, peas, fish, poultry and eggs; in conservative amounts - dairy products, white bread, red meat, butter, sweets and sweet drinks.
• William Reville is associate professor of biochemistry and public awareness of science officer at UCC - http://understandingscience.ucc.ie