I was suitably delighted to hear the first dire ‘what not to eat/drink if you don’t want to die’ prediction on last Friday morning’s news: there is no safe alcohol consumption and both men and women should not drink more than 14 units per week (previously men’s limit was higher).
It makes a great headline in January, a month which has now become ‘how-to-flagellate-yourself-every-which-way-month’. I’ve lost count of the number of people I’ve heard and overheard talking about what they are not doing right now; my least favourite was in the supermarket, where a small girl asked her mum why she wasn’t eating bread, as she had just said, in January. The reply? ‘Well, it’s sort of a tradition’. So from, ooh about six years of age, that child will believe, along with many other things, that cutting stuff out of her diet at the beginning of the year is normal behaviour.
I am not going to go on about what a sad culture we have become if that is the case. I’d rather counter it with some fascinating, and much more life-affirming information that may help you interpret these headlines and either take them, pretty much always, with a pinch of salt (unless that’s out too…) or, at least, be prepared to form your own opinion.
Back in November I went to a New Scientist Live event about Healthy Eating, subtitled ‘What science has to say’. I am, for both personal and professional reasons, more and more interested in the science, rather than the hearsay, of nutrition. Having proofread many diet books that offer different solutions (most of them, if you’re interested, tell you to cut carbs, dairy, fruit, sugar and alcohol), I thought it was time to learn something more concrete.
Presented by two exceptionally well qualified scientists, Dame Susan Jebb, professor of diet and population health at Oxford and Professor Bruce Griffin, professor of nutritional metabolism at the University of Surrey, this lecture steadily unveiled how nutritional studies are carried out and, in the process revealed how very little that we hear in the news is based on fact.
The first statement Professor Jebb made which, for me, underpinned everything else, is that the biggest problem with nutritional studies is ‘under-reporting’: those on the studies, unless they live in a hospital ward for the duration, do not necessarily tell the truth. So, because we are human, we may say that we only ate 10g of fat every day for two weeks, because it was what we were asked to do, but we may have eaten more, or less, and unless we say so, the study can’t measure the results accurately. This may be the case for both those in the study, and those in the control group since the latter, having been informed of what the study is about are sometimes motivated to change their diet anyway.
Second, for those involved, whether or not they are in a ward study, who’s to say that the fact that A does Y means that she loses weight? There may be other factors that have an effect, ones that are not monitored. I could go into great detail about the various examples given but the words I took away were that, in an observational study, you can find associations, but not causes.
Third, both scientists pointed out that the problem with cutting out, or trying to cut out a food group, or measure its effect on our health, is that humans eat food, not nutrients. We don’t, or rarely, eat spoonfuls of fat, carbohydrates, proteins or sugars; most foods are a combination and, again, to measure the effects of those combinations is extremely difficult.
Finally, what often happens when you see a headline is that the results of one study have been singled out, and that study doesn’t tell you whether all the other studies confirm or contradict it. Or what degree of error has been recorded in all of them. Which means that one study alone is not enough.
So, does this mean, most of the audience wanted to know, that there were no agreed guidelines on what to eat and not eat? No, it meant that there were very few and, interestingly, the ones we were told are mostly age-old and established: alcohol, saturated fat and refined sugar have been proven to be detrimental and oily fish is good for you, not just because of the oil but because of other elements in the fish. For you no-carbers, there is no proof that it improves your health and, for anyone obsessed with the likes of coconut oil, it has no proven benefits. And fruit, which is generally considered to be healthy, should be eaten whole whenever possible, not drunk as a juice because most of the goodness is in the fibre not in the liquid it becomes. And, if you want to lose weight, there is only one practice that is proven: eating fewer calories. In the picture below (apologies for the quality; it was taken on my phone) you can see Professor Jebb’s personal approach to what to eat, based on her research.
So it’s not about ‘no-carb’, it’s not about ‘clean’; our diet should be based around whole, as opposed to processed foods, with limited sugar and saturated fat, and plenty of oily fish and vegetables. Nothing else, not one little scrap, has, according to these experts, who I tend to trust more than a newspaper interpreting or reporting on possibly only one study, been proven.
And, yes, whilst we might all like to believe that red wine is good for us, those positive effects are even more difficult to prove. As Professor Jebb pointed out, if you think it’s hard to monitor and research the effects of eating certain foods, think how much harder it is to get people in a study to tell, or remember, the truth about what they have and haven’t drunk…