November 2019

In October earlier this year, revised clinical guidelines regarding the intake of red and processed meat has been published in Annals of Internal Medicine and is causing quite a stir among the scientific community, due to its conclusion that red meat may not actually be as bad as it has been made out to be.

The guidelines have been subject to extensive research based on 5 individual systematic reviews. All considering the harms and benefits of reducing red meat consumption on cardiometabolic occurrences and cancer incidence and mortality. However, unlike the eat-lancet report which is based on a sustainable diet, the environment and red meats impact on climate change has not been considered, in addition to animal welfare concerns also. The authors of these guidelines wanted to focus specifically on the individual health effects of red meat rather than focus on societal effects (such as animal welfare and climate change).

The current red and processed meat recommendations suggested by the NHS, state that if you consume more than 90g per day, then you should try to cut down to 70g (this recommendation is following advice from the Department of Health). This is due to the accumulated evidence suggesting that certain meats (including red meat) can contain high levels of saturated fats which can in turn, cause elevated cholesterol levels. Another reason for the 70g/day target is the associated link of red meat with bowel cancer. The World Health Organisation (WHO) states that processed meat should be considered as ‘carcinogenic’ and red unprocessed meat to be ‘probably carcinogenic to humans.

Processed meats have been subject to processing including smoking, curing or salting with the addition of chemical preservatives can include bacon, ham, sausages, salami, corned beef, jerky, canned meat and meat-based sauces. Whereas unprocessed red meat is either beef, pork of lamb which has not undergone any processing methods. This would include steak, joints and roasts.

The effects of red meat on health have long been debated and criticised for the quality of studies which have guided the advice for healthcare professionals and government policies. Therefore, this review investigated and assessed the quality of evidence to determine if red meat is really a risk to health or not.

Studies in which more than 20% of the sample was pregnant, had cancer, or a chronic health condition, other than cardiometabolic disease, were excluded. This would make it easier to identify a more direct association between red meat and its health effects in healthy people which out being influenced by other co-factors such as disease.

Panellists considered 3 servings a week to be a realistic reduction in meat consumption (e.g. Going from 7 to 4 portions or 4 to 1 portion per week). Risk estimates for cardiometabolic mortality were estimated based over a time frame of 10.8 years. For cancer mortality the effects were monitored over a lifetime.

The studies considered for review were either looking at the direct influences of red and processed meat on health or cohort studies addressing the effects of dietary patterns with varying amounts of red and processed meat. The researchers expected the direct studies to show a greater risk to health rather than the dietary patterns with varying amounts of meat (as direct studies will have fewer confounding variables e.g. other ‘unhealthy’ foods in the diet).

However, this was not the case as the results uncovered from the review showed that there is little ‘good-quality’ evidence to show this association.

The main findings show that if 1000 people were to cut down their portions of red or processed meats a week for:

  • A lifetime, only 7 fewer deaths would occur from cancer* 
  • 11 years, only 4 less deaths would occur from heart disease

*Based on reducing their unprocessed red meat intake (and with no significant difference between cancers: prostate, breast, colorectal, oesophageal, gastric and pancreatic).

It also suggests that if 1,000 people were to cut out three portions of red meat for 11 years, there would be six fewer incidences of type 2 diabetes, while if they did the same for processed meat, there would be 12 fewer cases.

Therefore, the guidelines have been based on the understanding that red and processed meat can neither be confirmed to directly cause cancer(s) and cardiometabolic incidences as well as increase the risk of these occurring.

Despite the results showing that red and processed meats are unlikely to be causal factors for cancer and cardiometabolic outcomes, this does not preclude the possibility that meat has a very small causal effect. It is also worth noting that although there is little difference in risk between unprocessed and processed meats, processed meats appear to have a slightly higher risk of causing cancer or cardiometabolic incidences. This could potentially be caused via the other ingredients which are in the meat (e.g. nitrites, nitrates and sodium).

Interestingly the study also brought up the potential evidence showcasing that red meat can enhance muscle development and reduce the risk of anaemia.

So, if reducing red meat intake by almost half of what the average person consumes weekly, doesn’t have a significant effect (or a very little and unlikely effect) on health, then why reduce the guidelines further? This is the main point of the review – to show that red meat can be included as part of a healthy diet and shouldn’t be excluded based on inconclusive evidence.