Food is an emotional topic, which is part of the reason that the 'diet-of-the-day' story is one that returns to the media as regular as clockwork. Each time we are told that certain foods will either bring eternal health or certain damnation.
This week, Dr Michael Mosley tried to shed some more light on the health effects of meat as part of a well-judged BBC Two Horizon programme, in which I and colleagues at the University of Reading made an appearance. Meat is a food that produces strong opinions - loved by some, scorned by others. So what does the latest science say about eating meat?
There are many reasons to eat flesh: it is an excellent source of protein and micronutrients and humans have eaten it for a very long time. But there are also reasons against: meat consumption has been linked to an increased risk of a number of chronic diseases, such as heart diseases, diabetes and cancer, and to an earlier death.
In 2007, the World Cancer Research Fund published a report on diet and cancer based on all scientific evidence available. It found that there is convincing evidence that eating red or processed meat increases the risk of cancer. A new analysis by the National Cancer Institute in the US has confirmed this. In contrast, a large study in Europe with almost half a million participants found that only processed meat increases the risk for cancer, heart disease and an early death, whereas both red and processed meat increase the risk for type-2 diabetes.
The data available are quite clear: eating too much meat can have a negative effect on your health. And there is broad consensus that it is in particular processed meat, such as bacon and sausages, which have the strongest effect.
It is still not known how meat intake is linked with cancer risk, but there are some very good and convincing explanations. Processed meat contains nitrite which is an important preservative and helps to keep the meat safe. However, it also helps the formation of so-called nitrosamines in the gut, and some of these compounds are known carcinogens. Unfortunately, it is very difficult to remove the nitrite without putting consumers at risk of food poisoning, which can be fatal on a much quicker timescale.
So is this the end of the bacon sandwich? Not necessarily. At the moment, a big European research consortium called Phytome (of which I am a partner) is investigating alternatives to using nitrite preservatives in processed meat. The idea is to replace nitrite with natural plant extracts, without compromising food safety or taste, but while also reducing the risk of cancer.
And meat lovers should not be too depressed. There is clear evidence that meat, in all its forms (red, white and processed) is an important source of many nutrients. The protein in meat contains all the amino acids we need, and it also includes important micronutrients such as B-vitamins, iron and zinc which are crucial for good health. Meat still has a useful part to play in our diet.
Of course, many people are vegetarians, don't eat any meat at all and are still healthy. But from a health point of view, the science shows there is no reason not to eat meat. On this question, science is in step with common sense: eat everything in moderation.Suggest a correction