The Guardian gives us the bad news that "red and processed meat can shorten life", while The Daily Telegraph provides the good news that "swapping one portion of red meat a day for fish or nuts could cut risk of early death by almost a fifth".
Both headlines are prompted by a major new study into diet and health outcomes. Researchers looked at changes in diet for more than 50,000 women and 27,000 men in the US, over 16 years.
They found that those who had changed their diet to include more red meat were around 10% more likely to die during the study. While reducing red meat alone did not result in lower risk of death, swapping red meat for another protein source such as fish or nuts did slightly reduce the risk of death.
Previous studies have found that higher red meat consumption, and especially processed red meat such as bacon and sausage, is linked to poorer health including increased risk of cancer and cardiovascular disease. But this is the first study to try to assess whether changing your diet to include more or less red meat makes a difference to how long you live.
We still need to be cautious about the findings. This study cannot tell us for sure that red meat or changes in red meat consumption are the direct cause of changes in length of life. But the results support existing healthy eating advice to limit red and processed meat, and to eat plenty of vegetables, fruit and other protein sources such as nuts and legumes.
Find out more about a balanced, healthy diet.
Where did the story come from?
Most of the researchers came from the Harvard TH Chan school of public health in the US, with one researcher from Huazhong University of Science and Technology in China. The study was funded by the US National Institutes for Health and the Boston Obesity Nutrition Research Center. It was published in the peer-reviewed British Medical Journal on an open access basis so it is free to read online.
Most of the media coverage in the UK focused on the potential benefits of switching from red meat to other protein sources. The coverage of the study was largely accurate.
But The Independent misinterpreted the findings, stating that "eating red meat 3 times a week increases the risk of early death by 10%". The 10% increased risk is related to eating 3.5 additional portions of red meat a week, not 3 portions overall.
What kind of research was this?
This research used data collected from 2 long-term cohort studies of US health professionals and combined the results.
Cohort studies are a good way to find out whether risk factors (such as increased or decreased red meat consumption) are linked to outcomes (such as death). But they cannot prove that the risk factor directly causes the outcome. Other factors may be involved.
What did the research involve?
Researchers used dietary and lifestyle information recorded as part of the Nurses' Health Study (mostly female nurses), which began in 1976, and the Health Professionals Follow-up Study (mainly male doctors), which began in 1986.
In both studies, people completed questionnaires at the start of the study and then every 2 years, including a food frequency questionnaire that asked how often they ate different types of food.
The researchers focused on information from a 16-year period, from 1994 to 2010. They looked at how people's diets changed during the first 8 years (1994 to 2002) and how that related to people's chances of dying during the following 8 years (2002 to 2010). They excluded people who had a history of cancer, heart disease or stroke.
They calculated the risks of death from any cause for people who:
- increased their red meat (including processed meat) by 1 or more serving a week
- reduced their red meat (including processed meat) by 1 or more serving a week
- did not change their red meat consumption by at least 1 serving a week
They took account of confounding factors including:
- family history of heart attack, diabetes or stroke
- aspirin use
- multivitamin use
- consumption of red meat at the start of the study
- body mass index (BMI)
- menopausal status and hormone therapy use
- smoking history
- physical activity
- alcohol consumption
- total energy intake and intake of other food groups
What were the basic results?
Of the 53,553 women in the study, 8,426 died during the 16 years of follow-up (15.7%). Of the 27,916 men, 5,593 died (20%).
Average age at the start of the study was around 60 years. The main causes of death were cardiovascular disease, cancer, respiratory disease and dementia.
Men and women who increased their red meat consumption by more than 3.5 servings a week (or more than half a serving a day) had a 10% increased risk of death from any cause (hazard ratio [HR] 1.10, 95% confidence interval [CI] 1.04 to 1.17).
The risk increase for people who increased their red meat consumption by less than 3.5 servings a week was too small to be sure it wasn't down to chance.
Eating less red meat in itself had no effect on people's chance of death. However, when the researchers looked at the impact of swapping 1 portion of red meat per day with 1 portion of nuts, chicken, fish, dairy products, eggs, legumes, wholegrains or vegetables, they found the risk did go down. The change in risk ranged from a 19% reduction with nuts (HR 0.81, 95% CI 0.79 to 0.84) to 6% with legumes (HR 0.94, 95% CI 0.9 to 0.99).
When breaking down by type of meat, the links to risk of death seemed slightly stronger with processed meat than unprocessed meat (HR 1.13, 95% CI 1.04 to 1.23 for an increase of more than 3.5 servings of processed meat a week).
How did the researchers interpret the results?
The researchers said: "Increases in red meat consumption, especially processed meat, over 8 years were associated with a higher risk of death in the subsequent 8 years in US women and men. Increased consumption of healthier animal or plant foods was associated with a lower risk of death compared with red meat consumption."
They added: "Our analysis provides further evidence to support the replacement of red and processed meat consumption with healthy alternative food choices."
This study provides additional evidence to support previous studies that have found a link between eating more red meat, and particularly processed meat, and higher chances of cardiovascular disease and some types of cancer.
However, as with all observational studies, we need to remember that the results do not prove conclusively that eating more red meat increases your risk of death.
Even though the researchers adjusted for various health and lifestyle factors, they still may not be able to fully account for their effect and other factors could be having an influence. It's always difficult to quantify exactly how much of a difference a single change, such as swapping a portion of red meat with a portion of nuts, will make.
Changes in risk of death in the study were quite small. It may be that a single dietary change alone only makes a small difference when combined with the multitude of other factors that affect our health and disease risk.
Also we don't know why people in the study changed their diets. It's possible that some people might have chosen to eat more or less meat as a result of being diagnosed with a health condition. This may further cloud the picture.
The studies mostly included white health professionals from the US. We don't know how applicable the results are to other populations. As the average age of participants was around 60 at the start of the study, the study can't really tell us about the effect of consuming more or less processed meat over a lifetime.
However, the results are broadly in line with what we already know about eating well. Current advice is to limit consumption of red meat and processed meat, and to eat plenty of vegetables, fruit, pulses, beans and wholegrains.
If you eat more than 90g of meat a day, you are advised to cut down. This study suggests that replacing one portion of meat with other, healthier food might help you live a little longer.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
The Guardian, 12 June 2019
The Independent, 12 June 2019
The Daily Telegraph, 12 June 2019
Mail Online, 13 June 2019
The Times (subscription required), 13 June 2019
Links to the science
BMJ. Published online June 13 2019