EXPERT REACTION: Stepping-up your red meat intake could be a step closer to the grave

The paper by Xheng et al in the BMJ is a classic dreadnought, all guns firing, that if you up your red meat intake in (on average) late middle age you run the risk of earlier death; lowering intake does not appear to be useful. The mortality numbers are very high - 8426 women and 5593 men, of total cohorts with almost twice as many women as men, and  with interesting differences in causes of death; women have lower levels of cardiovascular death, higher levels of daeth from cancer, and much higher levels of "neurodegenerative disease'' deaths. The data are subjected to the normal battery of statistical analyses, and it's all very convincing... except...

The data shows that processed meat (bacon, sausages) are more dangerous than non-processed meat; so far, so good, and not unexpected. What the study does not address head on is whether the findings can be generalised. Bacon in the USA is fine strips of pork fat with thin red lines of meat, maybe 20% or the total. Hamburgers fail to get a mention, in either category. Those of us that have been taken out to eat in the US know that feed lot beef is much more marbled than our grass-fed, pork served in lashings and lamb almost non-existent. What also gets only passing mention is that in previous studies non-processed meat was found to be associated with increased mortality in the US population, but not in those in Europe or Asia.

Possibly the most obvious omission is the possibility that what we eat with steak or pork chops may be a major contributor to the issue in the USA. Nobody orders French fries with the nuts they are urged to eat instead of meat; nobody wants to waste good wine on tofu. In Australia, moderation in all things - but to generalise from these particularly American data is to leap at shadows. Grass-fed beef, trim the fat off the pork chop, lose the fatty bits of the roast lamb - and enjoy what we are blessed to have.

This study is important because most cohort studies only measure people’s dietary patterns at one point, and assume diet does not then change over a person’s life.

Researchers in this study had data from about 80,000 adults. They asked about people’s dietary patterns very four years, using a food frequency questionnaire. Every eight years they divided people into five categories based on how much their intake of red meat had either increased, stayed the same or decreased. This change was then related to their risk of dying over the next 8 years. The analyses were adjusted for all the other factors that also influence risk of dying from diseases, including smoking and dietary factors such as intake of vegetables and wholegrains.

They found that increasing total red meat intake over an 8 year period, including both processed and unprocessed meat, was associated with a higher risk of dying over the subsequent 8 years. This relationship existed even when they took into account how much meat people ate at baseline and how healthy (or not) their lifestyle was. The association existed for both unprocessed and processed meat but was stronger for processed meat.

A decrease in total red meat intake over 8 years, while simultaneously increasing intakes of vegetables, wholegrains, nuts, fish, poultry without skin, dairy and eggs, was associated with a lower risk of death over the next eight years.

Although this data comes from an observational study, it represents a large number of adults over many years living their day to day lives. There will never be a randomised trial that goes for 16 years that allocates people to eating higher versus lower amounts of meat to assess the impact on death rates.

The key message  is to moderate your red meat intake, decreased your intake of processed meats such as bacon, hot dogs, sausages and salami, and increase your intake of vegetables, wholegrains, nuts, fish, poultry without skin, dairy and eggs, as a way to lower your risk of dying from heart disease, cancer, lungs disease and neurodegenerative disease like dementia.

This is an exceptional longitudinal study, which allows us to see how changes in dietary patterns might improve longevity.

They used an interesting statistical approach to estimate how replacing red meat with similar amounts of protein from sources such as nuts, chicken, fish or eggs would affect long-term mortality risk. Some caution will need to be taken when making individualised recommendations based on these replacement models as these relied on estimated overall effects across the whole population. However, from these statistical estimates we can gain some insights into how longevity might improve with positive dietary changes.

A particularly encouraging aspect with this study is, that it suggests benefits with reduced meat consumption regardless of the initial amount of meat consumed. This is of course good news, as it suggests that by making changes to our dietary patterns now, we may be able to positively affect our health regardless of whether our diet has been healthy or not in the past.  

The strongest benefits were seen with replacing a portion processed meat with a portion of fish or nuts, which in their modelling appeared to reduce mortality risk by 25-26%.

This study comes from two of the most well documented and log prospective cohort studies in the world. Although not able to draw conclusions other than identifying the association (confounding and reverse causation is acknowledged in the paper) between red meat intake and mortality (all cause included but not apparently cancer!), it is unlikely a RCT will be mounted beyond those already done (eg the Australian Polyp Prevention Study and the US Polyp Prevention Study) to provide higher level evidence.

The study underpins current recommendations that red meat, and especially processed meats, should be consumed in moderation. Importantly it demonstrates that the modest mortality risk from eating red meat can be mitigated by consuming proteins from plant sources - which is welcome news for the many of us interested to follow a well balanced diet including some red meat but a healthy portion of fresh fruit and vegetables, nuts and wholegrains.

This paper is an important one adding to the evidence that continues to build in support of plant-rich diet (note I don’t mean vegetarian or vegan, but any dietary pattern that includes lots of plant food). There are however I few points to be made around red and processed meat intake. The first is that the people who increased their meat intake, also had a worsening of their overall diet. Did their increased risk of death come from eating more meat, or from eating less of other foods, such as fish or plant food, that may have offered protection? A considerably larger number of people reduced their meat intake of the study period and at the same time they improved their overall diet quality. The reduction in meat did not associate with a lower risk of death, but when meat was replaced by known healthy foods such as wholegrains, legumes, vegies or fish then risk of death was reduced. This again shows us that ultimately it is the overall diet quality that counts.

Ultimately it matters whether you have an enormous fat-marbled steak with fries and a tiny salad, or a lean smaller steak with potatoes in their skins and a gorgeously generous salad dressed with extra virgin olive oil. The two meals are both red meat, but have very different effects on health!

Secondly this is a US study and meat production and how meat is consumed is different to the Australian setting. Our meat is not as intensively produced and there are considerable differences between our food supply and that in the US. It would be most helpful to replicate the study in Australia with our own data.

Nevertheless, there are known biological mechanisms for how red meat and especially processed meats may negatively affect our health. For Australians this reinforces the message that we should limit or cut out processed meats like bacon, salami and sausages, and watch the portion size and frequency of red meat. Crucially choose leaner cuts of meat and make sure you team it with plenty of vegies and other plant foods including legumes, wholegrains, nuts and seeds.

A new large US study published in The BMJ reports, for the first time, the impact on mortality of changing red meat consumption either up or down.

It involved tens of thousands of healthy middle-aged men and women whose diet and lifestyle factors were followed in detail for eight years. There were 14,019 deaths in the eight years that followed, mostly from heart disease, cancer, lung disease and dementia. Half a serving or more of red meat per day increased the risk of death by 10 per cent. An increase of one serving per day led to a 19 per cent increase in risk of death from cardiovascular disease and a 57 per cent increase in risk of death from neurodegenerative diseases. Risk was 13 per cent for processed meat. In contrast, reducing red meat consumption by one serving a day and replacing it with healthy protein sources such as fish and/or vegetable protein lowered death rate by 25 per cent.

Reasons suggested by the authors for the rise in cardiovascular deaths were increased atherosclerosis from meat fats, heme iron and other natural chemicals in red meat. This and the high sodium in meat would increase blood pressure, so causing stroke, heart attacks, heart failure and kidney failure. Cooking meat, especially by BBQ, generates chemical carcinogens, so increasing cancer risk. The increased cancer risk of processed meat is contributed by N-nitroso compounds. Constituents of meat, including fats, are also associated with Alzheimer’s Disease and Parkinson’s Disease.

This new study adds important fuel to the fire on the danger of red meat consumption. But the good news is that if people switch to non-meat sources of protein they can substantially reduce their risk of common diseases of ageing and premature death.

This study adds to the weight of evidence suggesting that dietary patterns are important in reducing the risk of a range of common health problems, especially cardiovascular disease. Many studies now show the value of increasing healthy plant-based food choices.

A number of potential mechanisms have been identified to underlie potential problems with a high intake of red – and especially processed – meats. This study adds to the body of evidence showing the value of decreasing red meat in favour of increasing vegetables, nuts and legumes, and substituting healthier animal foods, such as fish and, possibly, poultry and eggs.

The value, or problems, associated with any particular food depend on the quantity consumed. Where red meat makes up only a small part of the diet, as in some Asian countries and in some of the traditional Mediterranean dietary patterns, few problems can be identified. Equally important is the fact that in such dietary patterns, more vegetables are consumed, along with more nuts and legumes.

The unique aspect of this large, long-term study is the fact that the researchers have looked at changes in diet over time. Both men and women who have reduced their consumption of meats have shown benefits for all-cause mortality. We are not yet sure of the relative merits of reducing red and processed meat compared with increasing plant-based foods. However this study adds to the evidence that such changes in dietary patterns show benefits.

This study underpins the fundamental principle of balance  and moderation in dietary patterns for health. It adds strength to the Australian Dietary Guidelines which state ‘eat a wide variety of nutritious foods from core food groups’.

What is new is that an association with higher mortality rates emerged when US adults progressively ate more meat as years went by, in particular processed (cured, salted) meat. They found this changed if ‘theoretically’ other foods in that group were chosen instead, such as eggs, fish, and poultry and alternatives such as nuts, legumes wholegrains and vegetables.

The take-home message would be for adults in particular to be mindful of shifts in food choices away from Dietary Guideline recommendations (see www.eatforhealth.gov.au). Considering how meals are put together might be a starting point, and checking the frequency of consumption of different types of dishes would help.

This study has examined the red meat intakes of two large groups of people. The findings present a contemporary challenge for Australia, given the impact of red meat consumption on the food industry, farmers and climate change. As well as the prominence of red meat in current diet fads such as low carbohydrate or ketogenic diets.

It’s important to note that this study looked at change in meat intake, rather than actual intake, which means we can’t arrive at a clear answer on how much red meat we should eat to promote optimal health.

This study examined its statistics in a few different ways, and attempted to take into account original meat intake, which I think is the most important factor that could bias the results.

Unfortunately, they did not look at reasons for changing meat intake. For example, people who try and reduce energy intake to improve health do this by reducing their processed meat intake, amongst other foods. People who increased other forms of protein such as eggs and fish may have been making other lifestyle choices such as increasing their physical activity, which also reduces the risk of mortality.

Overall, this research seems to be adding to the evidence on the consequences of diets that are high in red meat. The research should be taken into account in future revisions of the Australian Guide to Healthy Eating, given its role as our national dietary guidance to help promote the health of all Australians.

These findings come from two well-respected, long-term cohort studies and some of the leading researchers in this field of nutritional epidemiology. These results add to a growing body of evidence over the last decade on the risks of red meat consumption, in particular processed meats.

Last year the World Cancer Research Fund released their latest report updating all the evidence on diet and cancer risk, and showed convincing evidence that processed meats are associated with risk of colorectal (bowel) cancer. This new research now shows how changes in red meat intake are associated with mortality and highlight very clearly the risk of processed meat consumption in particular.

This evidence is particularly relevant for us in Australia. Data from our latest national nutrition survey (2011-2012) showed that on average, Australians consumed about a half a serve of processed meat a day (primarily sausages and ham). However, data shows that intake is higher in children – intake of processed meat, on average, is around 25-30 grams per day in four- to eighteen-year-olds.
 
Findings from this new study confirm that plant-based foods are important for good health and longevity. Current popular, fad diets in Australia however, promote the intake of meat. While lean red meats are an important part of a healthy, well-balanced diet, intake should be limited to about three serves per week. This is also important from an environmental and sustainability perspective. The World Cancer Research Fund recommends that little, if any, processed meats are consumed. One small start is to look at what we are packing our kids for lunches, and find some alternatives to the ham sandwich.

The intake of red meat has been associated with a higher risk of chronic diseases, such as type 2 diabetes, cardiovascular death and certain types of cancer as well as increased risk of death. The association holds for all types of red meats (beef, lamb, pork and processed meats) but is strongest for processed meats. What has been lacking in the literature is whether changing your intake of these meats will led to changes in your risk of these chronic disease and death. This study, which followed over 80,000 people from the US over eight years, has shown that changing your intake of red meat will change your risk.
 
When people (white health professionals from US) in this study reduced their intake of red meat by one serve per day (85g) and increased their intake of other non-red meat and/or vegetable-based sources of protein (including nuts, whole-grains, chicken without skin, fish, dairy, eggs or legumes) there was a lower risk of death. Conversely those who increased their meat and processed meat intake over this time had increased risk of death.

More importantly, these changes were seen regardless of their initial intake of red meat and were observed in a wide range of people across different age groups, levels of physical activity as well those that smoked and drank alcohol. This is an important finding as it shows that relatively simple/easy dietary swaps, for example from red meat to chicken or fish, or more adventurous swaps to the vegetable sources of protein such as legumes, wholegrains and vegetables can significantly reduce your risk of death.

These swaps produce many changes in individual nutrients in your diet that could explain it. There is a decrease in the level of nutrients and food components that we know have negative health effects such as saturated fat, trans fats, the carcinogens that occur with cooking red meat (polycyclic aromatic hydrocarbons and heterocyclic amines) and cholesterol. And then there is an increase in the nutrients that provide known health benefits such as dietary fibre, phytonutrients, anti-oxidants, vitamins, monounsaturated and polyunsaturated fatty acids. The results seen in this study are likely due to favourable changes in both.

These results further support the importance of eating a wide variety of foods in your diet with a focus on non-red meats and plant-based sources of food.