Just how unhealthy is it to eat meat?

    22 October 2015

    We’ve become rather used to categorising foods as good or bad. It’s simpler that way. Some foods are easy — sugar is the most recent pantomime villain (boo!) while kale and coconut water are the latest heroes (hurrah!) — but what happened to red meat, which used to be a baddy, is it still worthy of a big boooo?

    The vilification of red meat began in earnest in the 1960s following landmark postwar research entitled the Seven Countries Study, which established a link between meat consumption and cardiovascular disease. It was believed that saturated fat raised cholesterol levels, in turn increasing the incidence of coronary heart disease, and as red meat (along with butter and eggs) is a common sources of saturated fat, it was directly implicated. More recently, we have understood that saturated fat intake alone is unlikely to raise cholesterol compared to that of sugars and carbohydrates — but does that mean meat is off the hook?

    Historically, many of the dietary studies have researched the outcome of eating ‘meat’, a term that encompasses red and processed meat. The resulting reports included increased incidence of colorectal cancer as well as heart disease — and so challenging this strong belief has been a task. But processed meats are quite different from the fresh variety as they contain sodium nitrate, a preservative that is converted into a nitrite on contact with saliva or enzymes in the digestive system. Nitrites can then be further converted into nitric oxide or nitrosamine, the former being beneficial, the latter less so. Nitrosamines are created when nitrites are combined with amino acids (present in protein) and heat. In other words, fresh meat when cooked and preserved increases numbers of nitrosamines, which have been linked to colorectal cancer.

    Concentrating on fresh unprocessed red meat (beef, lamb etc), there are distinct nutritional benefits on offer in the form of iron, together with zinc and the B group of vitamins including B12. But the concentration of nutrients is somewhat dependent on the type of feed used in rearing the animal. Some herds are fed with corn to bulk them up while others graze naturally on grass. Meat derived from grass-fed animals is generally nutritionally superior in terms of essential fats as it offers over four times the amount of omega 3 than grain-fed. Omega 3 is noted for its anti-inflammatory potential while omega 6, the prevailing fat in grain-fed meat, can encourage inflammation. Grass-fed also tends to be higher in iron, zinc, vitamin E and beta-carotene and is a worthy source of protein.

    How the meat is cooked is a factor, too. Exposing fresh red meat to direct flames or allowing it to burn produces heterocyclic aromatic amines and polycyclicaromatic hydrocarbons. These increase the incidence of some forms of cancer and so overbarbecuing even the finest organic grass-fed red meat from a herd raised by nuns, massaged by professionals and certified kosher by the Chief Rabbi will turn it into the nutritional equivalent of a slice of iffy ham from some discount value range.

    Although eating processed meat carries more of a risk than red meat, does that make the latter ‘safe’? A meta-analysis of studies published in the British Journal of Nutrition last year considered data from 13 studies involving over 1.6 million individuals. This concluded that those eating the most processed meat had a 22 per cent increase in mortality from any cause and 18 per cent increase from cardiovascular disease. Even small amounts of processed meat might carry risk, as eating an extra 50g a day showed a positive association with mortality rates, while eating an extra 100g of red meat showed only a weak positive, but nonetheless a positive. Bear in mind that eating x means we don’t eat y, and so eating large amounts of processed or red meat means that we are likely to eat fewer vegetables and so less fibre, fewer antioxidants etc and to some extent this will affect the outcome.

    In short, processed meat intake carries increased risk of mortality, cancer and cardiovascular disease while red meat intake showed a slight increase in risk. Where does this leave us? All things considered, I think that processed meats should be a rare occurrence. A slice of ham or bacon here and there when added to a decent diet shouldn’t result in ending up on an NHS waiting list. Nor should 200/250g of red meat twice a week as long as it is cooked carefully and not burnt. Ideally, the red meat would be grass-fed but that can cost anything from 25 per cent upwards more. (Grain-fed is still a decent enough choice).

    To my mind, the joy of eating a rib-eye steak, medium rare, with some fiery horseradish sauce once a week is a pleasure, which means that red meat, enjoyed sparingly, is a nutritional hero. Hurrah.