Reducing our carbon footprint will mean eating less meat and dairy. That’s a hard message for many to swallow, but we have to face the facts. In 2006 the Food and Agriculture Organisation of the United Nations estimated the carbon emissions associated with the livestock industry to be 18% of global emissions. That’s partly because cows burp methane (and cows in the highly industrialised meat industry in the US that are fed processed feed cake burp more methane than those that eat grass). But it’s also because of the fossil fuels that are used to grow grain to feed to cattle, to make processed feed cake for cattle to eat, to pump water for cattle to drink, to refrigerate meat, to transport refrigerated meat, and to sell meat in supermarkets in open fridges and freezers.

Of course some meat production creates higher greenhouse gases than others. If you eat meat products from grass fed cattle from your local farm, then the associated greenhouse gases are likely to be lower than those of the industrialised meat industry. And if you keep your animals indoors most of the time and capture the methane then you can reduce your impact (although there may be animal welfare implications here). But the best thing you can do is eat less meat. A recent Cornell University study concluded that animal protein production requires more than eight times as much fossil fuel energy as production of a comparable amount of plant protein. It would be a far better use of resources if we humans simply ate some of the vegetable protein directly.

On the health aspects we have known for some time now that what’s come to be known as the Western Diet – large amounts of meat and dairy – is a key factor in the obesity epidemic (particularly when the meat is fried). On present trends half of all British children will be clinically obese or overweight by 2020 because they eat too many poor quality burgers and other junk food, and because they do not do enough exercise.

There are other health issues to consider as well as obesity. A recent report by the World Cancer Research Fund argued that eating red meat and processed meat are “convincing or probable causes of some cancers.” The largest ever epidemiological study of older women — the Harvard Nurses Study — concluded that women drinking two glasses of whole milk a day had 67% more risk of heart disease than those drinking no whole milk.

Vegetables, fruit, seeds, nuts, grains and pulses can provide all the protein, vitamins and nutrients that humans need. Indeed for most of their existence the human race has primarily lived off this sort of diet. It is only in the last 50 years that we have massively increased the quantity of meat and dairy we consume. And of course we now eat poor quality meat, often stuffed with antibiotics, growth promoters and other chemicals, and we prepare it badly as well, usually by frying it. There is just no getting away from it – large quantities of cheese burgers and pepperoni pizzas are simply not good for you. That is one of the main reasons why in 1990 the World Health Organisation recommended a change in agricultural practices away from meat and dairy and towards plant foods.

It seems clear that eating less meat, but better quality meat, will help both the planet and our health.