You must be yolking! Controversial study finds one egg a day increases risk of stroke death by 17% but critics spot cracks in the findings. A new study claims eating an egg a day dramatically raises your risk of a heart attack or a stroke.
Many leading cardiologists say the study, which reignites a fierce and controversial debate over eggs, is the most rigorous ever published.
Assessing data on 30,000 people, the researchers found that people with dangerously high cholesterol were more likely to have eggs – crucially: with yolks included – as a stalwart of their diet.
Tallying it up, they conclude that a daily egg increases the risk of heart disease by 18 percent, and the risk of premature death from a stroke by 17 percent.
Those who eat two eggs a day increase their chances of dying early by 34 per cent and are 27 per cent more likely to have a heart attack or stroke.
But others warn we shouldn’t all leap to cut eggs from our diet: there are significant caveats to the study, which is based on old, self-reported data.
Crucially, after the researchers adjusted for total cholesterol intake (from red meat, cigarettes, and other sources) the egg connection flopped.
Experts on all sides largely agree that the study shows we should keep an eye on cholesterol – but it’s unclear that cutting out eggs is the best way to do that.
The egg-heart disease debate has been thriving for decades.
A handful of studies have looked into it – and many researchers have done ‘reviews’ of those same studies – coming up with all kinds of results.
They have found eggs are transformatively good for you, deadly for you, and everything in between.
The key issue is that nutrition studies are hard to carry out: it is very difficult to control what someone is eating, and to know that they followed your direction – particularly if it is over a long time.
Short of conducting the study in a prison, a nursing home, or the Big Brother house, there is a large margin for error.
The new study, published today in the Journal for the American Medical Association, was hailed in an accompanying editorial as ‘far more comprehensive’ than previous studies, ‘with enough data to make a strong statement that eggs and overall dietary cholesterol intake remain important in affecting the risk of [heart disease] and more so the risk of all-cause mortality.’
But Christopher Labos, MD, a cardiologist at McGill University, told DailyMail.com he is less convinced.
First, the research does not offer anything new.
‘This was a meta-analysis of six different cohorts summarized together,’ Dr Labos said.
‘The statistical analysis they used is certainly more complex than in previous cases, but at the end of the day you’re just synthesizing everything that’s already there. It doesn’t add anything.’
The biggest issue for Dr Labos – with this and all nutrition studies – is the unreliability of the data.
The studies involved just one interview with each of the 29,615 participants, asking them to remember how many days they had eaten eggs in the past year.
‘You’re asking people to remember how many eggs they had over the past month, year, two years, three years,’ Dr Labos said.
‘How many eggs have you eaten per day over the past two years? Any answer you give me is fundamentally going to be a guess.
‘That casts doubts on the results of the study.’
The only way to get around it is to do a randomized trial: get 100 people, tell half of them to eat eggs for three years, and half of them not to eat eggs.
But there is no guarantee that participants will perfectly follow the rules, so the only way to be certain is to conduct it in a place where all the food is provided direct to the participants – such as in a prison or a hospital.
‘For practical reasons and cost, I think it is very unlikely that this would ever happen,’ Dr Labos said.
‘I don’t think this question is important enough that we have to spend $10 million on answering it.
‘Does anyone want to invest the time and the money?
‘Nobody has, so I think the answer is no.’
The researchers at Northwestern University in Chicago insist there is merit to the research.
Egg yolks are some of the most cholesterol-rich foods we consume. Data suggest the average American eats three to four eggs a week.
US dietary guidelines say to consume no more than 300 milligrams of cholesterol a a day. Eggs contain 187 milligrams of cholesterol – and 184 of those milligrams come from the yolk.
However, there is a school of thought that says eggs contain ‘good’ cholesterol (HDL), which carries ‘bad’ cholesterol (LDL) away from arteries. Plus, eggs come with a good helping of vitamin E.
Dr Labos agrees that controlling cholesterol is important, and that this study reflects that.
But cutting out eggs will not be a silver bullet to preventing stroke deaths, he says.
Buried at the bottom of the study it says that after they adjusted for cholesterol intake overall, the egg-heart disease connection disappeared.
Co-corresponding author on the study, Norrina Allen, concedes: ‘The take-home message is really about cholesterol, which happens to be high in eggs and specifically yolks. As part of a healthy diet, people need to consume lower amounts of cholesterol. People who consume less cholesterol have a lower risk of heart disease.’
Dr Labos said: ‘It’s not eggs, it’s more about your overall dietary cholesterol. Whether eggs make much of a difference, it’s not clear.
‘At the end of the day, it’s probably more the cholesterol in your blood than in your food.
‘You’re better off just eating healthy if you’re concerned about cholesterol.
‘I wouldn’t stress too much about this, I would worry about smoking, exercise, and controlling blood pressure and diabetes.
‘I won’t change my behavior based on this study.’
Last year an Oxford University study of 400,000 people in China found an egg a day reduced stroke risk by more than a quarter.
A daily glass of fruit juice could cut the risk of life-threatening strokes by almost a quarter, a study by the Dutch National Institute for Public Health has found.
Just two portions of mushrooms a week could halve the risk of abnormal brain decline in old age.
Researchers found over-60s who eat 300g (10.5oz) or more of cooked mushrooms – or a medium-sized punnet – were 50 per cent less likely to show mild cognitive impairment. The team at the University of Singapore polled 600 pensioners on their consumption of mushrooms, which are rich in nutrients, and assigned them a ‘dementia rating’.
Co-author Feng Lui said the correlation was ‘surprising and encouraging’. The study appears in the Journal of Alzheimer’s Disease.