Does red and processed meat increase the risk of dying from cancer?

The carnivores among us may have been taken aback by this morning’s headlines, warning of the health risks of eating too much red meat.

These claims come from a meaty new report (freely available online) looking at the effects of different types of meat on our risk of dying from various causes.

The report is the latest to come from a huge American study called the NIH-AARP study. With over 545,000 people, it is one of the largest on diet and health ever conducted, rivalled only by the European EPIC study.

What did they do?

The researchers asked their half-a-million-strong sample about what they ate, using a questionnaire including over a 100 different types of food. They tracked the group’s health for over a decade to see what happened to them and how it related to their food choices.

The NIH-AARP study has reported on many other links between lifestyle and cancer. In this study, they focused on red, processed and white meat.

Red meat includes all fresh, minced and frozen beef, pork and lamb. White meat includes chicken and turkey. Processed meat includes ham, bacon, salami, sausages and luncheon meats.

What did they find?

By the end of the study, the researchers found that people who ate the most red or processed meat were more likely to die of cancer, heart disease, and all causes combined than those who ate the least.

For example, men and women who ate the most red meat had 20-22 per cent higher risk of dying from cancer than those who ate the least. However, people who ate the most white meat were less likely to die of cancer and all causes combined than those who ate the least.

The table below shows how different types of meat increase the risk of dying from different conditions by gender.

To put things in perspective, the people who ate the most meat in the study were eating about 160g a day – about the size of a six-ounce steak. Those who ate the least meat were getting just 25g a day – about a small rasher of bacon.

The increase in risk of dying from different conditions by type of meat and gender. All the figures compare people who ate the most meat to those who ate the least.

But what about other weight, age and other things?

Obviously, many other things can cause cancer and affect our health. In the past, some people have said that the connection between meat and cancer reflects nothing more than the fact that heavier people eat more meat, and heavier people are more likely to get cancer.

Fortunately, the NIH-AARP researchers took that into account. All of their results have been adjusted for a large number of other things that can affect the risk of cancer and other diseases – age, smoking, physical activity, educational level, marital status, family history of cancer, ethnicity, body mass index, alcohol, calorie intake, fruit and vegetable consumption, use of hormonal replacement therapy and use of vitamin supplements.

Despite these adjustments, the results were still statistically significant. This means that they were unlikely to have come about by chance.

Does this fit with what we know already?

Yes. Certainly for cancer, other large studies have found that red and processed meat can increase the risk of some cancers. Several years ago, the large EPIC study showed that bowel cancer is more common in people who ate the most red or processed meat.

And more recently, the World Cancer Research Fund’s panel of scientific experts concluded that these types of meat are “convincing” causes of bowel cancer.

We also have an idea about the many ways in which these meats could affect our risk of cancer, and Henry has laid these all out in a previous blog post.

The fact that white meat seems to lower the risk of dying from cancer is a new result from this study. In the past, most other studies have found no link between these meats and cancer – they don’t increase the risk, but they don’t lower it either.

It’s certainly possible that they have a protective effect simply by replacing red and processed meat in our diet, rather than having any special beneficial properties of their own. And actually the people in the study who ate the most white meat were also those who ate the least red or processed meat.

So what does this mean?

As we’ve said to the BBC, meat-lovers need not take this as a call to abandon bacon or burgers completely. Studies like this shouldn’t be seen as a wagging finger telling people to avoid meat. This sort of research is carried out by scientists to find out how our behaviour affects our health – it shouldn’t be seen as a dictat issued to persecute meat eaters, as some commentators imply.

That said, if you’re worried about your cancer risk, cutting down your meat consumption is a good idea.

We’re now in a position where two of the world’s largest studies on diet and health have found that people are more likely to develop some cancers, if they eat too much red or processed meat.

The evidence tells us that eating less of these foods can reduce the risk of dying from cancer and other diseases.

Ed

• Find out more: How does red meat increase the risk of bowel cancer?

Reference:

Sinha, R., Cross, A., Graubard, B., Leitzmann, M., & Schatzkin, A. (2009). Meat Intake and Mortality: A Prospective Study of Over Half a Million People Archives of Internal Medicine, 169 (6), 562-571 DOI: 10.1001/archinternmed.2009.6