Yet another story came out over the past few days trying to demonise a real food. The Daily Mail ran the story “Eating just THREE eggs a week ‘increases chance of men getting prostate cancer’”
I have the following points to make:
1) Association vs causation:
This study makes the usual and unforgiveable mistake of assuming that association means causation. To give an example, we can observe that people in the bath may be singing. This means that we could say singing may be associated with being in the bath. However, we can no more say that bathing causes singing than we can say that singing causes bathing!
If the study had measured sock colour, these men may also have worn blue socks – would the headline then be “wearing blue socks increases the chance of men getting prostate cancer?” Yes, it really is as daft as that. To jump from observed association to causation and risk is the most outrageous bad science and yet studies do it every day and the media amplifies it every time.
2) How risk is calculated:
Notwithstanding that association can say nothing about risk or causation, here is how ‘risk’ is calculated between two studies… If in one study people ate no eggs and 1 in 100,000 people died and in another study people ate eggs and 2 in 100,000 people died – they will say “Eating eggs doubles your risk of dying”. They always ignore the denominator (the bottom number in the equation – in these cases the study size). The second group still only had a 1 in 50,000 chance of dying full stop and yet the headline tells you you’ve got twice the risk – this is indefensible scare tactics.
The summary of the original research article is here. The study followed 27,607 men over a 14 year period from 1994 – 2008.
The study looked at the 3,127 men initially diagnosed with what is called “non-metastatic prostate cancer” (“non-spreading” or localised prostate cancer) and then reviewed those who went on to develop, as they called it “lethal prostate cancer”. (I assume “terminal” would be a word we would more typically use). The findings were “we observed 199 events during 306,715 person-years”. That’s an incidence rate of 0.0649%. That’s a 1 in 1,541 incidence. To put this in perspective, our chance of dying in a car crash was put at 1 in 200 .
The summary stated: “Men who consumed 2.5 or more eggs per week had an 81% increased risk of lethal prostate cancer compared to men who consumed less than 0.5 eggs per week (HR: 1.81; 95% confidence interval (CI): 1.13, 2.89).”
There are three things wrong with this:
i) The completely unjustifiable leap from association to risk must be reiterated. For researchers to claim “increased risk” from an observed association is simply not valid. This is the kind of food survey that Harvard Public Health use in studies like this (if not the same one). This shows how many foods are being studied, in how many different quantities, relying on subject recall of what they have eaten – and that’s just the food, let alone other lifestyle factors – smoking, exercise, stress, location, marital status, financial circumstances etc.
ii) The study is claiming that in amongst the overall incidence of 0.0649%, those people eating 2.5 or more eggs per week had almost ‘double the chance’. As an example, those eating more than 2.5 eggs a week could have had a 0.09% incidence rate and the 0.5 egg group could have a 0.05% incidence rate (there’s a difference of 81% between those two percentages and the overall incidence can still be 0.0649%). Can you see the absolutely tiny number behind the 81% risk massive headline?
PLUS – this is critical and irresponsible not to have highlighted – after the number 1.81% the 95% confidence interval is given as 1.13 to 2.89. What this means is – the researchers are 95% confident that the observed differences between the higher and the lower egg consumption were somewhere in a range between 13% and 189% – that’s one heck of a range. This means that they cannot even establish an association within a fourteen fold range, let alone make a claim of 81% with any degree of accuracy.
iii) There is a very good NHS review here. This suggests that the NHS have obtained a full copy of the report (not just the summary) and they have been able to see that “Men who consumed more red meat or eggs tended to exercise less and have a higher BMI, and were more likely to smoke and have a family history of prostate cancer.”
Do you wonder if smoking, exercising less, having a higher BMI and having a family history of prostate cancer was more relevant that any egg consumption?!
Why would so called researchers mislead the public in this way? Academics have egos and they want their ‘research’ widely published and talked about. The headline “Smoking causes cancer” is not new; “Obesity causes cancer” has been said before (whether correct or not is immaterial – it’s not new news). How about “Family history of prostate cancer increases your risk of getting cancer” – hardly surprising. So, pick the one headline that would be new. “Wearing blue socks increases the chance of getting prostate cancer?” That would be new – but absurd, so let’s pick the one vague association that will get the Daily Mail headline – it must be the eggs!
Even if the eggs have any relevance at all – what else could be happening at the same time? Were the egg eating men Paleo dudes, or were they egg and soldier addicts (blame the bread), or egg and brown sauce addicts (blame the sugary gunge), or even egg and bacon addicts who hadn’t selected their bacon carefully enough (blame the processed meat).
3) Cholesterol is vital not evil:
The suggestion from the ‘experts’ that cholesterol could be the cause of harm is laughable. Cholesterol is protective – one of its most important functions is to repair cells – not attack them. The longevity facts associated with high cholesterol are related in major part to the protective benefits that cholesterol has for cancer (cell repair – it should be obvious). My book, The Obesity Epidemic: What caused it? How can we stop it?, has many studies showing the benefits for cancer and cholesterol. The body makes all the cholesterol it needs (cholesterol in food makes no difference), but you never know what survival signals the body could send out. Should the headline have been “men with prostate cancer crave eggs!”?
4) Common sense:
Would nature really put both the essential fats (omega-3 and omega-6), amino acids, complete protein and the most phenomenal range of vitamins and minerals in the tiny, humble egg if it were trying to kill us at the same time? By the way – the reason why eggs contain so much cholesterol is because it takes a lot of cholesterol to make a healthy chicken. It takes a lot of cholesterol to make a healthy human as well!
5) Conflict of interest:
Finally – always follow the money – remember who stands to gain if we demonise eggs – the sugary cereal companies. The Kellogg’s and General Mills who sponsor the American Dietetic Association , to make sure that dieticians are ‘on message’.
Eggs have only recently been exonerated for being harmful for cholesterol even though Ancel Keys, the man who started the war on fat and cholesterol declared years ago “Cholesterol in food has no impact on cholesterol in the blood and we have known that all along”. No sooner have eggs been let out of jail for containing cholesterol – they need to be put back in jail or (heaven forbid) people will start eating eggs again for breakfast and not coco-pops.
Andy and I have just had a three egg omelette each for breakfast. Enjoy whatever real food you guys have!