We’ve long been told that eating red meat is bad for us. But is the science really that unanimous? Dr Michael Mosley investigates – and spends a month eating twice the recommended amount.
Do you walk round the shops thinking about what to slap on the barbecue, pause by the burgers, pick them up, put them back and go in search of something healthier? In a restaurant do you order fish though you would secretly prefer steak?
Eating meat, which used to be an innocent pleasure, is now a guilty one. If you believe the headlines, then eating meat will stop your heart, give you cancer, shorten your life and destroy the planet. Vegetarianism is the healthy, moral option. Or is it?
My wife, Clare, who is a GP, has been trying for years to persuade me that we should reduce our consumption of red and processed meat. She chooses chicken over beef, fish over steak. She complains about the amount of salami our children eat and looks disapproving when I return home with bacon.
I was sceptical, but until recently I was not convinced enough about my facts to put up much resistance. So I was delighted when Horizonasked me to make a two-part series on meat. The first part would look at the science behind the headlines; find out, the editor said, how much truth there is to the claims that eating meat is a sure way to an early grave. When it comes to meat, what are “safe” levels? Are the risks greatly overblown?
Once we’d established, as far as we could, the effects of eating meat on the human body, I was to investigate the effects of meat-eating on the planet. Can you be an ethical, environmentally sound carnivore? If so, what sort of meat should you eat and how much?
In recent years I’ve made a number of programmes for Horizon on health topics, ranging from The Truth about Exercise, in which I tested the unlikely claim that you can get many of the benefits of exercise from just three minutes a week, to Eat, Fast and Live Longer, my experiment with different forms of intermittent fasting.
In each of these programmes, as well as investigating the science, I make myself the subject, a self-experimenter in the grand old traditions of medicine.
For Should I Eat Meat?, my producer, Dan Barry, thought I should go on a high-meat diet to see what effects that had. Not a crazy amount, but about twice the recommended daily levels.
The meat which is said to be a threat to health is not white meat such as chicken. It is red meat: steak, lamb, pork and mince. It is also processed meat: bacon, sausages, salami, ham.
Red meat looks darker thanks to higher levels of haemoglobin and myoglobin, the iron and oxygen-binding proteins you find in blood and muscle. On average Brits eat about 70g of red and processed meat every day, a figure that doesn’t include chicken or any other poultry.
A quarter of British men eat almost twice as much, which is why I decided to aim at 130-140g of red and processed meat. For those who think in pre-metric terms (ie, me), that equates to 4-5oz of meat. Doesn’t sound a lot.
Since the most popular meat products in the UK by volume purchased (excluding chicken) are bacon, sausages, pork cooked meats (ie, ham and salami) and beef mince, those are the ones I would mainly devour.
So what does 130g of meat actually look like? Well, it could be a couple of bits of bacon in the morning for breakfast and a burger in the evening. A small steak or a pork chop for your evening meal. On another day, perhaps a sausage for breakfast and a couple of slices of ham for lunch.
Because my wife dictates our diet, I normally eat mainly chicken and fish. This would be a red meat fest. I was looking forward to it.
Instead of my normal porridge or eggs I would have bacon butties for breakfast, with mustard and lashings of ketchup. When I arrived at Marylebone station on my way home, late at night, instead of a miserable tuna sandwich I now planned to head over to Burger King and go for something juicier and far more illicit. I started reading recipes with fresh enthusiasm, new ways to cook steak and prepare beef.
But before I could properly indulge these meat-fuelled fantasies, I needed to get myself checked out, assess the “before” in anticipation of the “after”.
So I popped over to the food and nutritional sciences department at the University of Reading where they gave me a thorough health check. As well as taking blood to assess things such as cholesterol, they measured my weight, body fat and blood pressure.
Then I went downstairs for a quick chat with dietician Dr Orla Kennedy. She’d assembled beef mince, bacon and sausages alongside some popular vegetarian foods – tofu, cheese – to do a head-to-head comparison.
As she pointed out, on the plus side, red meat is a good source of protein. Beef, whole or minced, is also an excellent source of micronutrients such as iron and vitamin B12, which are vital for producing healthy blood cells. Vitamin B12 is also an essential nutrient for the developing brain, one of my favourite organs.
If you don’t eat meat you can get vitamin B12 by eating fish, dairy products or supplements, but you are still at greater risk than meat-eaters of deficiency. A study by Oxford University, Serum concentrations of vitamin B12 and folate in British male omnivores, vegetarians and vegans, in which they compared the blood levels of 689 men (226 meat-eaters, 231 vegetarians and 232 vegans), found that 52 per cent of vegans and 7 per cent of vegetarians were vitamin B12 deficient – but only 1 omnivore.
B12 deficiency matters because it can lead to anaemia, fatigue and loss of memory; in the long term, it can cause permanent brain damage.
The vegetarians and vegans in this study did have higher levels of folate (found in dark green vegetables, but also eggs and dairy products), but only two omnivores (one per cent of the sample) were actually deficient.
Although meat is a surprisingly rich source of vitamins it is also, of course, rich in saturated fat. Bacon and sausages have about 16 times more saturated fat per gram than tofu.
If you are a cheese-eating vegetarian then you can hardly point the finger. Cheese is, gram for gram, an even richer source of saturated fat than burgers.
But is saturated fat as bad for us as is often claimed? Another question I decided I would need to try to answer.
The trouble with just looking at the content of food is that it is hard to predict what impact any particular ingredient will have on the human body in the long run.
There are 46 different chemicals in coffee that have been shown to cause cancer in rats, but does that mean drinking coffee causes cancer? No. Does it mean that drinking coffee will shorten your life? At the moment the evidence is that it actually adds to life expectancy, mainly by improving mood.
Another way you can try to assess the impact of particular types of food on our health is by doing case control studies. You take two groups of people and compare them. If you do that with vegetarians and meat-eaters you almost always find the vegetarians are healthier and live longer.
The problem is, you have to adjust for “confounding variables”. Vegetarians tend to be much more health conscious than meat-eaters. They drink less alcohol, eat fewer calories, do more exercise and rarely smoke. These factors are much more important when it comes to health than eating meat.
The belief, once widely held, that drinking soya milk will reduce your risk of prostate cancer, was based largely on studies that failed adequately to take into account these confounding variables.
To establish properly the long-term impact of the different components of a diet, what you would really like to do is take a large group of children, randomly allocate them to different diets and then follow them for a lifetime. Not very practical.
Instead, what scientists try to do is find populations of meat-eaters and vegetarians that are as well matched as possible, assess their health, then follow them for decades to see who drops dead and of what. One such study is based in Loma Linda, a town in California near Los Angeles.
Stopping only for a quick ham sandwich, I headed for the airport with the film crew.
The man I went to see was Dr Gary Fraser of Loma Linda University and the group he studies are Seventh-day Adventists.
Seventh-day Adventists are a Protestant group, created in the aftermath of what’s called “the Great Disappointment”. In the 19th century, a group of American Christians who had been promised the Second Coming of Jesus Christ in 1844, were naturally enough Greatly Disappointed when it didn’t happen. In the years that followed, Ellen G White, a prolific author, had a series of visions that eventually led to the formal creation of the Seventh-day Adventist Church in 1863.
These visions also led Ellen to emphasise the importance of fresh air, sunshine, exercise and healthy eating on spiritual development. The result is that Seventh-day Adventists tend to abstain from smoking, drinking and eating meat.
Fortunately for scientists like Fraser, not all Adventists follow these commands. Most are vegetarians, but many eat some meat. That makes them an extremely interesting group to study.
When I met Fraser for lunch (he ate salad; I had pulled pork and chips), he ran me through some of the highlights of his research on Adventists.
I started by asking him if the meal I was eating (around 110g or 4oz of pork) would, in his terms, count as high.
“In our studies, this would be in the high-meat group. Yep,” he replied. When I confessed I had also had a couple of rashers of bacon for breakfast, his response was a laconic, “I hope you survive this experiment.”
Fraser almost never eats meat and thinks neither should we.
If you want the numbers, then his latest study showed that men who ate beef three times a week or more had double the risk of fatal heart disease compared with the vegetarians. And this apparently massive risk to health was in people eating less than 60g (2oz) a day, which is less than your average Brit and half what I was currently eating.
“I think there is little doubt that when it comes to cardiovascular risk factors, diabetes, hypertension, being overweight, having increased blood lipid levels, that the vegetarians are doing better than the non-vegetarians,” Fraser said.
“If you compare what I’m eating with what you’re eating, where I’ve replaced the meat with nuts and wholegrain bread and so forth, our evidence suggests that you’re looking at a difference of four to five years of life expectancy.”
He doesn’t expect us carnivores to give up meat without a fight. What he recommends is trying a couple of meat-free days a week and cutting back from there.
Fraser was convincing, but his studies have their critics. Although the vegetarians and meat-eaters were well matched, the meat-eaters were still, as a group, generally less healthy (they drank more, smoked and did less exercise). He tried to allow for this in his calculations, but he may not have succeeded. As he himself put it, “You can allow for the variables you know about, but not the ones you don’t.”
Then there is the question of mechanism. All Fraser’s studies can test are associations; people who eat more vegetables tend to be healthier than people who eat more meat. Why? The obvious answer is “saturated fat”, but is it true?
Putting his research papers in my bag and munching, reluctantly, on a burger, I headed for San Francisco.
There I met Dr Ronald Krauss, one of the world’s most respected nutrition researchers. Krauss is based at the Children’s Hospital Oakland Research Institute, just across the bay. He has spent his professional life investigating the link between saturated fat and heart disease and has personal reasons for his research.
“My father had a heart attack when I was very young,” he explained over breakfast in a Jewish deli (no bacon, but excellent pastrami). “This had such an impact on me that I decided when I was six years old that I was going to try to do something about heart disease.”
He trained as a doctor, then immersed himself in cholesterol research. Because of his family history he was concerned about his own health, so naturally he followed the dietary advice of the time, going on a low-fat diet and shunning cholesterol-rich eggs.
He also put his patients and research subjects on this diet. The trouble was, it didn’t produce the results they were expecting.
“We thought that everybody would get better on this diet, that their cholesterol profile would improve. What we found was that, in many cases, they actually got worse.”
The problem is that when you go on a low-fat diet you have to eat something else. The “something else” was often carbohydrates, such as bread, pasta, potatoes. Krauss discovered that eating carbohydrates increases levels of a particularly damaging form of cholesterol known as small particle LDL (low-density lipoprotein).
Yet almost everyone else in the medical community believed that saturated fat was the enemy. So, together with colleagues, he decided to do a meta-analysis, to pull together as many high-quality studies as could be found.
When, in 2010, the findings – Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease – were published in The American Journal of Clinical Nutrition, they proved to be something of a bombshell.
“We found heart attack risk was slightly higher but not significant. Stroke risk was actually reduced. So overall if you took it across the entire range of disease, heart disease and stroke, there was absolutely zero effect.”
Other more recent meta-analyses, such as one from Cambridge University published in March this year, have come to similar conclusions.
Krauss doesn’t see any harm in eating lean red meat a couple of days a week, although he is wary of processed meat – “When I see my granddaughter going for the hot dogs, I hope she doesn’t maintain that.
“I stay away from potatoes as much as possible but my real weakness is bread. I have half a bagel most days, because I cannot resist them. Sugar almost never. My main indulgence is a small piece of chocolate after dinner because I consider chocolate an essential nutrient.”
So far I had met two experts with very different opinions. I was also rather confused. Although I have sympathy withthe anti-meat lobby I couldn’t help feeling that by just focusing on health they were missing something. Meat, it seems to me, is more than simply food. It is part of our culture, part of our inheritance. Some would argue that it was meat that liberated us from our primate past, gave us the easily digestible calories that allowed our massive brains to grow.
I spent an enjoyable evening in Boston travelling around with the Boston Burger Bloggers, seeking out the ultimate meat patty and fries. We ate some exceptional food, but for them this was not really about the meat, it was an opportunity for guys to get together and talk about guy things. They weren’t just eating animal flesh; they were metaphorically gathering round the campfire.
But I hadn’t gone to Boston to find better burgers. I was there to meet Dr Walter Willet, who is based at the Harvard School of Public Health.
Willet heads a team who have been tracking the diets of more than 100,000 people for 2 decades.
“We found that those who consumed higher amounts of red meat had higher risk of total mortality, cardiovascular mortality and cancer mortality,” he told me in the Harvard cafeteria, while I nonchalantly ate steak. Eating red meat did have an impact: 85g a day – an average burger – was associated with a 13 per cent increased risk of premature death.
This just about convinced me until I read Meat consumption and mortality, the most recent findings of EPIC, the European Prospective Investigation into Cancer and Nutrition.
In this truly epic study, European researchers have followed around 500,000 people in 10 countries for more than 12 years. And their conclusions are very different to the American studies that are normally quoted.
The researchers found that eating moderate amounts of red meat had no effect on mortality; in fact, it seemed to be protective. The lowest overall mortality rates were in those eating up to 80g a day.
Although there was a small increase in overall risk for those eating more than 160g, there was also a higher all-cause death rate amongst the non-meat-eaters.
The researchers concluded that “a low – but not a zero – consumption of meat might be beneficial for health. This is understandable as meat is an important source of nutrients, such as protein, iron, zinc, several B vitamins as well as vitamin A and essential fatty acids.”
In other words, the vegetarians and vegans in this study may not have been getting enough essential micronutrients such as vitamin B12 in their diet.
Now, before meat-eaters go off rejoicing, there’s a significant sting in the tail. The EPIC study, like almost every other study that’s been done, found that eating processed meat did have a negative effect on health. Anything over 40g a day and deaths from heart disease and cancer began to climb.
“In this population, reduction of processed meat consumption to less than 20g per day would prevent more than 3 per cent of all deaths,” it concluded.
Bad news considering that three of the UK’s top five favourites – bacon, pork sausages and ham – all fall into the processed meat category.
By now I’d been on my high-meat diet for four weeks. I had eaten a couple of rashers of bacon most mornings (adding up to more than 2kg of pork) and got through at least 30 burgers. My wife looked on indulgently as I cooked myself and the kids yet more sausages, but I could tell she was looking forward to this particular experiment being over.
I had also begun to notice that my trousers felt tighter. Slightly anxious, I returned to the University of Reading where a month earlier I had had my health check.
The first thing I was told was that my cholesterol had gone up by ten per cent, mostly because of a rise in levels of LDL – the bad cholesterol.
Not great. Then I had my body fat measured. It had risen by a stonking 3kg, much of it settling down around my gut. This was particularly unfortunate because visceral fat, fat laid down close to your internal organs, greatly increases your risk of become insulin-resistant and diabetic.
Then I had my blood pressure taken. Yet more bad news. When I first went to Reading University it had been 114/69 mmHg, which is excellent for my age (57). Now it was 141/81 mmHg, heading towards stage 1 hypertension.
So what happened? Well, eating all those salty slices of bacon, ham and burgers, plus the weight gain, almost certainly pushed my blood pressure up. In addition to the burgers I had eaten far more than I normally would of the accompanying burger buns and chips. Together with all the added grease, they may have accounted for the fat gain and the cholesterol rise.
What I’ve learnt is that nutritional science is really complicated and there are few clear-cut answers. Making this documentary was more like attending a criminal court case than a dispassionate search for the truth. Expert witnesses hold radically different views, disagree vehemently over the strength of the evidence and offer up startlingly different solutions. The science is fascinating, but in the end where the truth lies is something only you can decide.
After assessing all the evidence I’ve made my own decisions. I’m going to cut back on the processed stuff, buy less bacon and fewer sausages, which will make my wife happy. But I also think that a nice bit of red meat, around 110g or 4oz, is fine. Which makes me and the kids happy.