Meat and death – mortality figures

Is there a relationship between what you eat and how long you live? Is bacon as bad for you as smoking? What should you be eating if you want a long and healthy life?

Deaths from circulatory diseases, cancers and neoplasms, respiratory diseases, digestive diseases, mental and behavioural disorders, diseases of the nervous system, genitourinary disease, endocrine, nutritional and metabolic diseases, infectious and parasitic diseases or dying as the result of an accident are collectively referred to as all-cause mortality – all the deaths that occur in a population, regardless of the cause. It is measured in population studies and clinical trials as an indicator of the safety or danger of a specific activity, such as eating meat.

Several studies suggest that vegetarians and vegans have a greater longevity compared with meat-eaters. Substantial evidence from epidemiological studies shows that meat intake, particularly red and processed meat, is associated with an increased risk of premature death from diabetes, heart disease, stroke and certain cancers (Pan et al., 2012). Numerous large prospective studies have also found that meat intake is linked to all-cause mortality. However, the relationship between meat, disease and mortality has been challenged by the meat industry.

In 2012, a large-scale study from Harvard School of Public Health reported how red meat consumption is associated with an increased risk of early death (Pan et al., 2012). The study warned that each daily serving of red and processed meat increases the risk of dying prematurely. This study was widely reported in the media with headlines such as: “Red meat death study”, “Will red meat kill you?” and “Red meat ‘kills’”.

The research analysed data from two large US studies including 37,698 men from the Health Professionals Follow-up Study (1986-2008) and 83,644 women from the Nurses’ Health Study (1980-2008), giving a total of 121,342 participants. Over 22 years of follow-up, there were 23,926 deaths (including 5,910 from CVD and 9,464 from cancer). Results showed that a higher intake of both red and processed meat was associated with a significantly increased risk of all-cause mortality:

One 85g serving of red meat a day (equivalent to the size of a deck of cards) was associated with a:

• 13 per cent increased risk of early death
• 18 per cent increased risk of death from CVD
• 10 per cent increased risk of death from cancer

One serving of processed meat (one hot dog or two slices of bacon) a day was associated with a:

• 20 per cent increased risk of early death
• 21 per cent increased risk of death from CVD
• 16 per cent increased risk of death from cancer

Source: Pan et al., 2012.

The authors estimated that substituting one serving of red meat a day for a healthier source of protein (they suggested poultry, fish, nuts, pulses or wholegrains) would reduce the risk of early death by between 7-19 per cent. Furthermore they suggested that 9.3 per cent of early deaths in men and 7.6 per cent of early deaths in women could be prevented if they consumed just under half a serving (around 42g) a day of red meat.

The authors suggest that saturated fat and haem iron in red meat might partly explain the increased risk of CVD, while the presence of sodium and nitrites might explain the additional risk associated with processed meats. They also point out that some compounds generated in red meat by high temperature cooking are potential carcinogens. This was the first large-scale prospective longitudinal study showing that consumption of red and processed meat is associated with an increased risk of early death.

The findings of this large study were challenged by Dr Carrie Ruxton from the Meat Advisory Panel, a body funded by the meat industry. Ruxton said: “This US study looked at associations between high intakes of red meat and risk of mortality, finding a positive association between the two. However, the study was observational, not controlled, and so cannot be used to determine cause and effect. The authors’ conclusion that swapping a portion of red meat for poultry or fish each week may lower mortality risk was based only on a theoretical model.”

Whereas Dr Rachel Thompson, Head of Research Interpretation at the WCRF said: “This study strengthens the body of evidence which shows a link between red meat and chronic diseases such as cancer and heart disease. The research itself seems solid and is based on two large scale cohort studies monitored over a long period of time.”

Seventh-day Adventists are a conservative religious group that includes more than 13 million members worldwide. The Adventist church promotes a healthy lifestyle; members are expected to be non-smokers, not drink alcohol and are encouraged to eat a vegetarian diet. Studies among Adventists in California have shown the advantages of a meat-free diet (Butler et al., 2008). Adventists adhere with these recommendations to varying degrees which makes them an ideal group for prospective studies; seeing the relationship between diet and disease over time either within the Adventist group, or comparing them with the general population.

The Adventist Mortality Study (1960-1966) and the first Adventist Health Study (AHS-1) (1974-1988) showed that vegetarian Adventists had a lower risk for most cancers, CVD and diabetes. They also lived longer compared with the general California population; vegetarian Adventist women lived 4.4 years and men 7.3 years longer (Fraser, 2003).

More recently, in an attempt to resolve uncertainty in the literature, the Adventist Health Study 2 (AHS-2) set out to evaluate the link between vegetarian and vegan diets, disease and death (Orlich et al., 2013). The study included 73,308 participants amongst which there were 2,570 deaths during a period of almost six years. Results showed that, compared to meat-eaters, all-cause mortality was 12 per cent lower in vegetarians and 15 per cent lower in vegans. The authors concluded that the evidence that vegetarian and vegan diets may be associated with a lower risk of death should be considered carefully by individuals as they make dietary choices and by those offering dietary guidance. Health professionals, take note!

Another large-scale systematic review of nine prospective studies (from the US, China and Europe including a total of 1,330,352 individuals and 137,376 deaths), was conducted to quantify the association between red and processed meat and all-cause mortality (Larsson and Orsini, 2014). Results also found that a high consumption of red meat, in particular processed meat, is associated with an increased risk of early death. Those with the highest intake of processed meat and total red meat had a 23 per cent and 29 per cent increased risk of death respectively, compared to those with the lowest.

What this study showed was that for both total meat and processed meat intake, the increase in risk of death rises steeply at the lower end of consumption then continues to rise in a dose-response fashion as intake increases. In other words, the increase in risk of early death associated with red and processed meat is not linear; the risk increases rapidly at relatively low intakes. The authors said that the results from their analysis add to the increasing evidence that consumption of red and processed meat should be limited. They point out how this research falls in line with the WCRF report which says that the public health recommendation with regard to cancer risk is to eat no more than 500g per week of red meat like beef, pork and lamb and to avoid processed meats such as ham, bacon, salami, hot dogs and sausages (WCRF/AICR, 2007).

Another study, this time from the US, investigated meat intake and mortality among 322,263 men and 223,390 women enrolled in the National Institutes of Health (NIH)-AARP (formerly known as the American Association of Retired Persons) Diet and Health Study (Sinha et al., 2009). During 10 years of follow-up, 47,976 men and 23,276 women died. Again, results showed that those who ate the most red and processed meat had an increased risk of all-cause mortality, compared to those who ate the least. The authors of this study estimated that 11 per cent of deaths in men and 16 per cent of deaths in women could be prevented if they reduced their red meat intake to the lowest level of intake in this study (14.4g per 1,000 calories).

The UK government says men need around 2,500 calories a day and women around 2,000. The average daily intake of calories per person in the US in 2009 was 3,652 (FAOSTAT, 2015). Based on these figures, people in the NIH-AARP study eating 53g of red meat per day could still be classed in the lowest intake group! In case you are wondering, the highest consumers were eating up to 320g of red and processed meat per day, almost five times what the Department of Health advises people to limit their intake to.

The authors list the potential culprits linking meat to mortality: NOCs, HCAs and PAHs, haem iron (increasing oxidative damage and increasing the formation of NOCs) and saturated fat (associated with breast and bowel cancer). Curiously, in contrast, higher white meat consumption was associated with a small decrease in mortality (more on this to follow).

Studies of UK vegetarians have yielded mixed results. The EPIC-Oxford study was established in the 1990s and included about 65,000 participants. In 2009, they compared mortality rates in vegetarians and meat-eaters among 64,234 participants of which 2,965 died (Key et al., 2009). Results showed no statistically significant differences between vegetarians and meat-eaters. There are a number of possible explanations why the vegetarians did not show a reduced risk. The EPIC-Oxford cohort is not representative of the wider UK population. Recruited through vegetarian societies, health food shops and magazines, they appear to be more health-conscious; they smoke less, weigh less and the meat-eaters consume less meat. The death rates of all participants in this study were much lower than average for the UK and this may have obscured differences in the wider population between vegetarians and meat-eaters. Also, although fruit and vegetable intake was higher among vegetarians than meat-eaters, the difference was small. The authors say that the relatively low meat intake and high fruit and vegetable intake of the meat-eaters in this UK cohort may have reduced the chance of observing lower mortality rates among vegetarians. Also, this study grouped vegetarians and vegans together so the animal protein (dairy products and eggs) consumed by vegetarians may have masked the harmful effects of meat. Later work has revealed that compared to US Adventist vegetarians, UK vegetarians consume relatively more animal protein and less fibre and vitamin C (Appleby et al., 2016; Orlich et al., 2013).

In 2013, a larger EPIC study investigating the association between meat consumption and early death, combined data from 10 European countries (Rohrmann et al., 2013). There were 448,568 individuals and 26,344 deaths (5,556 died of CVD, 9,861 of cancer, 1,068 of respiratory diseases, 715 of digestive tract diseases and 9,144 of other causes). Initial results showed that high-meat consumers (more than 160g of red meat per day) were 14 per cent more likely to die early than low-consumers (eating 10.0-19.9g per day) and for processed meat, the figure was even higher at 44 per cent. There was no association with mortality and the consumption of poultry (see more on this below). After correction for measurement error (a statistical procedure designed to strengthen the reliability and precision of the results), the risk of early death remained significantly higher only for processed meat; 50g a day of processed meat was associated with an 18 per cent increased risk of early death.

Again, the authors list the usual suspects pointing out how compared to red meat, processed meats tend to contain more saturated fat, cholesterol, salt and additives (some of which are carcinogenic or precursors to carcinogenic substances: NOCs, HCAs and PAHs). They point out that haem iron also links meat consumption to cardiovascular risk but that this is not limited to processed meat. They estimated that three per cent of premature deaths each year could be prevented if people ate less than 20g of processed meat a day and concluded that as processed meat consumption is a modifiable risk factor, public health guidelines should include specific advice on lowering processed meat consumption.

The EPIC-Oxford cohort was revisited more recently in a study comparing mortality rates in vegetarians and meat-eaters. This study also included data from another prospective study; the Oxford Vegetarian Study. Taken together, they included a total of 60,310 people and 5,294 deaths before the age of 90 (Appleby et al., 2016). Like the 2009 EPIC-Oxford study, the results suggested that UK vegetarians and vegans have a comparable risk of all-cause mortality to meat-eaters. However, when analysing deaths before the age of 75 and excluding participants known to have changed diet group at least once during follow-up, vegetarians and vegans had a 14 per cent lower all-cause mortality than meat-eaters. The decision to switch diet during the study may have occurred in response to the onset of illness, for example, people warned about weight or blood sugar levels going vegetarian or vegan to avoid diabetes and/or heart disease. So it seems logical that excluding individuals who switched diet may give a truer picture of how beneficial a meat-free diet can be. This may not match the substantive evidence seen in US studies, but it shows there is a beneficial effect associated with avoiding meat.

Another possible reason for the discrepancy between the US and UK studies may be the type of vegetarian diet followed. The authors suggest that the perceived healthfulness of vegetarian diets is a major motivating factor for Adventist vegetarians, whereas UK vegetarians may be motivated by other factors that are not health-related (animal welfare and/or the environment), possibly making them less likely to adopt a healthy vegetarian diet (Appleby et al., 2016). Furthermore, the amount of animal protein (dairy products and eggs) in the UK vegetarian diet was significantly higher than that in the vegetarian Adventists’ diet.

The authors of AHS-2 agree that the lack of similar findings in UK vegetarians is interesting and suggest this difference deserves careful study. In both cohorts, the meat-eaters are a relatively healthy reference group, healthier than the general population. In both cohorts, the vegetarians (especially the vegans) consume less saturated fat and more fibre. However, UK vegetarians and US Adventist vegetarians appear to eat somewhat differently. For instance, the Adventist vegetarians consumed even more fibre and vitamin C than those in the EPIC-Oxford cohort (average dietary fibre in EPIC-Oxford vegans was 27.7g per day in men and 26.4g per day in women compared with 45.6g per day in men and 47.3g per day in women in AHS-2 vegans; the average vitamin C in EPIC-Oxford vegans was 125mg per day in men and 143mg per day in women compared with 224mg per day in men and 250 mg per day in women in AHS-2 vegans).

People choosing to follow a vegetarian or vegan diet for ethical or environmental reasons may eat differently from those who choose vegetarian or vegan diets primarily for health reasons. It seems likely that the potential health benefits of a vegetarian diet is a major motivator of Adventist vegetarians. The authors of AHS-2 say that other large cohort studies have linked increased red and processed meat consumption to higher mortality and that their findings build on this work by demonstrating reduced mortality in those consuming low-meat diets. Notably, the findings of AHS-2 are similar to those of previous North American Adventist cohort studies, demonstrating a consistent association over several decades and replicating prior results in a population with great geographic and ethnic diversity (Orlich et al., 2013).

A different approach was taken by researchers from the Oxford Martin Programme on the Future of Food (Springmann et al., 2016). They estimated both the health and climate change impacts of a global move toward a more plant-based diet. The researchers from the University of Oxford predicted what the effects of four different types of diet would be by 2050. The four different diets were as follows:

• No change
• One that follows health guidelines for meat, fruit and vegetables
• A vegetarian diet
• A vegan diet

Results suggest that dietary change across the globe could have multiple health, environmental and economic benefits; more than five million premature deaths could be avoided globally by 2050 if health guidelines on meat consumption were followed. On a vegetarian diet, the figure rises to more than seven million, on a vegan diet more than eight million premature deaths could be avoided. The report suggests the monetary value of health improvements could be comparable with, and possibly larger than, the environmental benefits of the avoided damages from climate change. Lead author, Dr Marco Springmann said: “Unbalanced diets are responsible for the greatest health burden around the world”.

The scientific consensus is that both red and processed meats increase the risk of a premature death. Research regarding white meat is somewhat varied, it may decrease mortality when it replaces red meat in the diet but that may just mean that it is just not quite as bad for you as red meat. Avoidance of red and processed meats (and poultry) and a diet rich in plant-based whole foods including fruits, vegetables, wholegrains, nuts and pulses remains a sound, evidence-based recommendation (Fields et al., 2016).