Over half a century ago, we discovered that high blood cholesterol and high blood pressure greatly increased the risk of heart disease.
We soon learned that by moderating our intake of saturated fats, we could better control our blood cholesterol. In the case of high blood pressure, we learned that reducing salt intake helped control this condition.
We would go on to discover more links between nutrition and disease, such as maternal iodine intake and childhood IQ, folic acid and spina bifida, and micronutrients and age-related blindness. We can directly link the nutrient in question to biological pathways to explain their role in disease. For every one of those nutrients we can identify their main sources in the food chain and we can advise on how to make better food choices.
The food industry can also help us. In Ireland, our intake of saturated fats has fallen by one third, largely due to the advent of low-fat spreads and margarines rich in unsaturated fatty acids. For the last 15 years, the salt levels in soups, bread and cereals has been reduced by food manufacturers under a programme initiated by the Food Safety Authority of Ireland. The Department of Health has established a food reformulation programme to incentivise the industry to improve the nutritional value of manufactured foods. Whilst all of this effort at improving our diets using the best science available takes place, it sadly has to compete with all sorts of celebrities who write books on some wonder diet.
Popular targets emerge such as fast foods or added sugars, and the most popular target these days are the so-called ultra-processed foods (UPFs). The advocates of UPFs insist that our dietary problems have nothing to do with nutrients or even with foods, but rather that the root of the problem is food processing. They define which foods are classified as UPFs and they advocate that UPFs should be avoided. That would be an enormous food policy challenge since their definition of UPFs account for 60pc of our daily calories.
When people hear of UPFs, they immediately think of foods that are very fatty, high in salt and sugar and usually highly coloured and flavoured. But the problem is that the definition of UPFs includes bread, spreadable fat, baby foods, flavoured yoghurts, breakfast cereals and flavoured milk, all of which are important sources of our nutrients.
I have examined the many scientific papers on UPFs, and two important things emerge. The first is that as the intake of UPFs increases, there is no change in the intake of either total fats, saturated fats or salt. So reducing our intakes of UPFs won’t help us control the intake of these key nutrients. Secondly, across the many scientific papers on UPFs that I have reviewed, almost all focus on their impact on food choice and nutrient intake. This is hard to fathom since the UPF advocates declare that our health is not linked to either foods or nutrients but to processing. And yet they focus on foods and nutrients and ignore processing.
Several studies have shown a link between UPF intake and obesity. But not all do so. Both French and UK studies find a zero association between UPFs and either being overweight or obese. A recent US study showed that subjects living in metabolic wards under strict supervision gained weight on a high-UPF diet but not on a diet which did not include UPFs. The subjects were offered foods at each meal and the researchers devised the two diets to be nutritionally identical. However, among those offered the UPF dishes and foods, their free choice ended up with a much higher (40pc) quantity of calories per gram. This is almost certainly why they ended up with a higher overall calorie intake and consequent weight gain.
There is a mountain of evidence that we can improve our health through better nutrient intake and we have ample evidence of which foods we need to target to improve health. It would be a massive set-back to abandon all that knowledge in favour of a policy which simply blames food processing without as much as a shred of supporting evidence.
Mike Gibney, Professor Emeritus of Food and Health, University College Dublin
Health & Living