People reading some of today’s alarming headlines will be relieved to learn that – for the vast majority of people – eating protein isn’t “as bad for you as smoking”.
Tobacco is the single biggest cause of preventable disease and early death in the UK.
It’s difficult to overstate the harm that tobacco causes – half of all long term smokers die as a result of their habit, and half of them in middle age.
If you smoke, even if you are partial to the odd cheeseburger, the best thing you can do for your health and cancer risk is to quit smoking.
Today’s media stories were triggered by an interesting but far from conclusive study, published in the scientific journal Cell Metabolism.
The study asked around 6,400 US adults, aged 50 and over, what they’d eaten over a 24 hour period along and other questions about their lifestyles.
The researchers then ‘followed up’ these people over a period of up to 18 years to see, essentially, which people died and what of.
The most striking finding was that people who were aged 50-65 when the study began and who said they ate a diet with high levels of animal protein – as a proportion of their total calorie intake – were four times more likely to die from cancer than people who said they ate a low-protein diet.
But when the researchers looked at people aged 66 and over, they found the opposite – the people who ate the highest amounts of protein were less likely to have died from cancer during the study than people who ate only a little.
On the face of it, this is quite a strange finding – why would protein be seemingly so bad for you at one point, but then protective a few years later? So it’s worth considering whether factors in the study design, or just pure chance, could help to explain the findings.
There are several reasons why we think caution is required when interpreting the results of this study:
- 6,400 people may seem like a lot, but by the time the researchers were looking at deaths from cancer the numbers were in the hundreds. We’d really like to see many more people than this to be more confident in the results.
- The conclusions are based on a single survey of what people reported eating in the preceding 24 hours. It’s a big leap to presume that people’s diets didn’t change in the following 18 years.
- It’s not clear how accurately the researchers adjusted for other things such as whether people smoked in the past.
- Because this research looked at deaths from cancer, not cases of cancer, we can’t know whether protein was linked with people’s chance of surviving cancer, developing the disease in the first place, or both.
- The study didn’t compare the risks of smokers versus people who ate lots of animal protein, so it’s not accurate to say that high protein diets are as deadly as smoking.
Does protein still have a place in a healthy diet?
Yes, but it’s not quite that simple.
There’s good evidence linking diets high in red and processed meat – including beef, pork, lamb, and sausages and bacon – with a moderate increased risk of cancer, particularly bowel cancer, as well as heart disease. So if you’re a self-confessed meat fiend – and eat piles of red and processed meat – then we would encourage you to cut down to help reduce your risk of cancer.
Because this study looked at animal protein as a whole, we can’t tell whether the links the researchers saw were driven by red and processed meats, rather than fish, poultry and dairy.
But they did note that vegetable proteins – from things like beans and other pulses – didn’t seem to be associated with an increased risk.
This fits with what we already know about food groups and health – beans and pulses are also usually high in fibre, plus a serving counts as one of your five-a-day. Getting plenty of fibre, fruit and veg – and swapping other protein sources for red and processed meat – are all good ways to make your diet better for you…Read Sarah’s blog here.