As I mentioned on Wednesday, a common defence of arbitrary nutritional targets is that they can't do any harm. In Velvet Glove, Iron Fist, I gave the example of George Lundberg, former editor of the Journal of the American Medical Association, who published a junk science article which showed that eating fish halved the risk of coronary heart disease. When the study was exposed as garbage, he glibly replied: "People are told that eating fish once a week is not a bad thing. What harm can it do?" That, in a nutshell, is the problem with the public health crusade. The harm, surely, is to science and to the truth. You would hope the editor of a medical journal would appreciate that.
Sometimes, however, the harm is more tangible. In the case of dietary advice, it seems that parents have been giving their children the kind of meals that would be more appropriate to a food faddist on detox. From the BBC:
"Parents are aware of the importance of ensuring their child eats healthily to avoid obesity and health problems in later life, but this can sometimes lead to parents making requests that their child follows a strict diet, such as skimmed milk and low-fat foods," says [the National Day Nurseries Association's] chief executive Purnima Tanuku.
It is the madness of public health to paint some foods as good and some as evil. Against this background of fear, parents can hardly be blamed for avoiding 'evil' foods such as fat and carbohydrates while turning to trendy alternatives. But they really shouldn't...
"Children under five have specific needs, and should not have low-fat diets as their growing bodies need fat and carbohydrates."
Growing rapidly, this age-group needs a diet which is - proportional to their size - much higher in calories than that of an adult.
An obvious point, that. Children are not adults. They need calories and plenty of them. But while a small number of parents allow their children to grow fat, many other parents have gone in the opposite direction, giving their kids meals that are only suitable for an office worker on a diet. Just as the 'evil' foods are essential for children, the 'good' foods are nothing of the sort.
Studies have shown that children burn fat much faster than adults - and so skimmed milk and other low-fat dairy products should remain off the menu until they are much older.
"And parents really shouldn't feel too anxious about puddings - sponge and custard is a good dessert to offer, surprising as that may sound," says Jessica Williams, a paediatric dietician.
And don't listen to the vegans and quacks, give them some meat.
"There have also been problems with the messages about red meat. It's a shame some parents feel so worried about it as it really is the best source of iron, and iron deficiency anaemia among toddlers in particular is common."
And what about the totally arbitrary 5-a-day target?
"And while the five-a-day message must certainly still be there, a child's portion does need to be smaller so they have room for the other, more substantial items on their plates. They simply won't get the calories they need from fruit and vegetables, even in large quantities."
The risks of following public health dogma are very real. More real, indeed, than the hysteria about childhood obesity.
There are in fact concerns that the plight of the underweight child has been forgotten amid the intense focus on childhood obesity.
Studies have shown that being persistently underweight as a child can cause problems over a lifetime, from cognitive impairment to skeletal disorders."Poor nutritional status in toddlerhood can be linked to permanent cognitive damage and a child never reaching their full potential, as well as shorter stature in adulthood."
But isn't all this based on sound science?
"I think that we are in danger of overlooking these children in the obsession about obesity - and I am not convinced that we have good measures of bodyweight in small children in terms of later risk," says City University's Helen Crawley, director of the Caroline Walker Trust which promotes good diet. "We should be much more careful."
As is revealed time and again, the people who issue advice about diet make it up as they go along, often swayed by their own obsessions (primarily vegetarianism). No sooner has policy been based on one study when another study comes along and says the opposite. At the very least, there should be a recognition that the available data are a mass of contradictions and that the diet which has made us the longest-living people in history remains the best bet.
Public health has become hopelessly corrupted by the idea that 'strong messages' need to be sent out. It willfully misleads people and then refuses to take the blame for pandering to people's neuroses. In the case of diet, that means demonising some types of food (salt, fat, carbohydrates, sugar) and glorifying others (wholemeal bread, skimmed milk, broccoli). It may not be their intention to terrify parents into feeding their kids rabbit food, but it is such an obvious consequence of their actions that it can barely be called unintended.
If you want to know what to feed your children, listen to your grandmother before you listen to anything from the zealots, quacks and food faddists who now dominate the public health movement.