Take the one on today's front pages: "Eating too much meat and eggs is as deadly as smoking." Really? Taken at face value this should be a public health emergency. Warnings on plates used to serve the full English breakfast ought to be introduced, we might even call for an ingestion charge on meat and eggs! But probably what will happen is that we will forget the headline by tomorrow certain in the knowledge there will always be another story this time telling us that too much fat or sugar or carbohydrate or this or that is bad. Confused about what the best diet is? Of course you are who wouldn't be? With so much conflicting information it is difficult to know what to believe.
So what of the study reported today? Should we worry about meat and eggs? Are they really as dangerous as smoking?The story comes from a paper published in Cell Metabolism. This is a "good journal" with a very high impact factor. In other words you would be proud to have your research published there. The study followed 6.381 adults, 50 years old and over for 18 years. So far so good, a large study sample with long follow up. They found that people with diabetes were more likely to die from diabetes if they had a high protein intake.
They assessed protein intake using a diary card for 24h at the start of the study ie about 20 years ago. Are you still eating the same diet as you were 20 years ago? I thought so but anyway not to worry the authors assumed that the people's diet remained unchanged for 20 years. When the results were analysed there were no differences in death rates overall, cancer or cardiovascular deaths. Now this ins interesting because the group eating a lot of protein had a much higher proportion of diabetic patients and you would have though that the cardiovascular death rate would be higher in that group.
Then if you look at the data more carefully you notice that the death rate from diabetes in the study is very low indeed (about 1in 100). Most people died of cancer or cardiovascular disease as expected
The proportion of diabetics in the high protein group was 17% whereas it was only 2.6% in the low protein group. Presumably this reflects the advice given previously by diabetes specialists to recommend high protein diets to diabetics as it was thought that the blood sugar levels were easier to control. So this group has far higher numbers of diabetics and if you look at the proportion of diabetics in each group which died of diabetes then it is 7.7 for the low, 8.7 for the intermediate and 11.8 for the high protein groups. Not so different and because the numbers are small the accuracy is low.
Not withstanding this the investigators analysed the data some more and managed to find an association between age, protein consumption and cancer mortality. If you are 50–65 years you get benefit from a low protein intake but once you are over 65 then it is harmful. Is this biologically plausible?
So that's just one headline on one day. But there is a message there: Meat and eggs are as deadly as smoking. This is confusion at best and harmful at worst as this study really doesn't support that conclusion. In the end it is likely that the public, seeing so many stories which apparently contradict each other, will decide that no-one really knows what the best diet is and carry on eating their usual food.