Ignore the lazy headlines. Chips don’t ‘double your chances of death’

You can increase your chances of living forever by avoiding french fries, according to the Telegraph. Eating chips ‘doubles your chances of death‘, according to the newspaper. Step away from the deep fat fryer.

Epidemiological studies often take groups of people of a certain age and observe how many of them die over a certain number of years. This can be useful in identifying the causes of premature mortality, but it does not tell us anything about our ‘chances of death’ which remain 100 per cent despite the best efforts of the health lobby.

Should we avoid chips on the basis of this study? I wouldn’t be too hasty. Published in the American Journal of Clinical Nutrition, it is a fairly average study by the standards of nutritional epidemiology. It does not have any glaring flaws that set it apart from the others, but that is not high praise. Most epidemiological studies are useless and nutritional epidemiology, in particular, is a cesspool of contradictory findings and confounding factors.

This is not the fault of the researchers. Sending people a food survey once in a blue moon and then waiting for them to die is a weak methodology at the best of times, but what else can we do? One thing we could do is stop funding this junk science, but then newspapers would have nothing to print next to the cartoons.

So what does the study say? The researchers set out to find whether potato consumption increases the risk of premature mortality. The presumption is that it doesn’t because, as they note, a systematic review published last year did not find any ‘convincing evidence’ to link potato consumption with heart disease, diabetes or obesity.

The researchers used this website to find 4,000 people between the ages of 45 and 79. They only selected people who had knee osteoarthritis or were at high risk of developing knee osteoarthritis. It is not obvious why they focused on this disease, but obesity is a major risk factor for knee osteoarthritis so it is likely that the group contained a higher proportion of obese people than the national average.

These 4,000 people were sent a survey asking them about their diet, including questions about how often they ate fried or unfried potatoes. As you might expect, most of them ate potatoes at least once a week.

The researchers then waited to see how many of them died. After eight years, 236 of them – one in twenty – had joined the choir invisible. For some reason, the researchers were unable to ascertain what they had died of, but they nevertheless set about analysing the data.

It turned out that the death rate among those who ate potatoes three or more times a week was three times higher than among those who rarely or never ate potatoes. However, this was not the only difference between them. The potato enthusiasts also tended to be older, male, less well educated and less healthy. The apparent association between potato consumption and premature mortality disappeared when the researchers adjusted their model for age, sex, race, body weight, income, physical activity, alcohol consumption and other factors.

But when the researchers looked specifically at fried potato consumption, adjusting the model had less of an effect – the association fell from a threefold increase in risk to a twofold increase in risk. Or, if you prefer, it ‘doubled the chances of death’.

This might sound alarming but, as Nick Ross used to say, don’t have nightmares. As the authors note, ‘consumption of potatoes was very high’ among the 4,000 people in this study and yet 95 per cent of them were still alive by the time it was concluded. The authors also note that the kind of people who eat a lot of fried potatoes might also be the kind of people who eat a lot of ‘red meat, salty foods, and sugar-sweetened beverages, which may increase the risk of death’. This seems to me more than a mere possibility. It is highly likely, and yet the study was unable to control for it.

It is also likely that the people who never ate potatoes had different characteristics from those who regularly ate french fries. I would never be so rude as to describe people who abstain from potatoes as being odd, but they are clearly not average. The researchers did their best, given the limited information available to them, to control for such variables but, in the final analysis, the seriousness with which you take these findings depends on how confident you are that they have made the right adjustments to their model.


  • MX

    thank you Chris Snowdon !!! when i saw ‘doubles your chances of death’ yesterday i almost cried in disbelief how any newspaper could print that mathematical impossibility !! Your 1 line –

    our ‘chances of death’ which remain 100 per cent

    confirm that logic does prevail, and whether we eat chips or not one day we will all die !!!

  • Jason Victory

    These aren’t just potatoes – they are potatoes scorched in burnt oil. This is a poor article. It’s common sense that healthy eating is required on the part of the UK population otherwise the NHS is just not going to be able to cope with the burden of chronic disease. The meat and dairy industries will continue to promote the dissemination of articles like these. The big picture suggests we need to cut down drastically our meat, dairy and processed food intake. And fries are processed foods of the worst kind.

    • JonathanBagley

      The countries where the most milk, cheese and butter is consumed don’t in general have significantly lower life expectancies. See third column here for European dairy consumption.
      http://www.nature.com/bonekeyreports/2016/160629/bonekey201630/fig_tab/bonekey201630_T1.html
      The highest are Sweden , Finland, Denmark, Netherlands, Switzerland, then Norway and France – all above the UK. Austria is missing and has a very high dairy consumption. Now look at life expectancy
      https://en.wikipedia.org/wiki/List_of_European_countries_by_life_expectancy
      If dairy consumption has any effect, positive or negative, it is dwarfed by per capita income. If I were Swiss, French, Swedish, Austrian or Finnish, I wouldn’t be worried about dairy consumption.

      • JonathanBagley

        What do the Swiss worry about? At the moment it’s immigration, but previously?

  • Mr. Snowdon, I believe that as long as the potatoes are covered with a healthy and thick layer of dark chocolate that the tater munchers will live forever!

  • gray cooper

    It is the government,political brand tax funding of those Puritans that is so very wrong.Government lives lavishly off taxpayers yet expects the public to buy health quango rubbish . Morons.

  • Chris Oakley

    The person who wrote The Telegraph article has no knowledge of science but even so…. The MSM continues to believe that it can arrogantly ignore the need for at least some level of background understanding when writing about complex subjects. The MSM is wrong and in justifiable decline.