Why we will NEVER know the truth about a healthy diet
Almost every day we get conflicting information from ‘experts’ about what foods can kill you, and what foods can keep you healthy. No wonder people are confused. Here Vicky Allan tries to make sense out of science
RED wine is good for you. Red wine is bad for you. Salt will kill you. No it won’t. Don’t eat red meat. Do eat red met. Go vegan. Don’t be daft. The latest mixed message when it comes to diet is “fat”. After decades of being told that fat is bad for us, we now “learn” that it is actually supposed to be good for us.
“Eating fat does not make you fat”, the health charity the National Obesity Forum and the Public Health Collaboration tell us – while other diet experts respond with outrage to advice which contradicts Government guidelines in place since 1983.
All the while nutritionists dismiss each other as having conflicts of interest, or being selective in their presentation of research.
When it comes to diet and nutrition, you could be forgiven for feeling totally and utterly bewildered. Is there any chance, in all this, that we, as consumers, can find answers we can be confident in?
In an attempt to find out, we talked to a range of Scottish health experts on the key issues. Some said there needed to be more research. Often they agreed with each other on some points – the benefits of eating more fruit and vegetables, for instance, seem universally accepted – but not on others.
So, what’s the truth?
FAT
Good: Professor Iain Broom, director of Centre for Obesity Research and Epidemiology at Robert Gordon University, Aberdeen
I support the National Obesity Forum report on fat. I think the Government needs to change its attitude. What happened in the late 1970s in the United States, and then in 1983 in the UK was a change in policy, which directed all of the major energy consumption into carbohydrate. Fat was vilified. At the time Professor Edward Ahrens, a cholesterol research pioneer, said if you do this (say fat is bad) you’re going to create an obesity epidemic and a type II diabetes epidemic. And that is what has happened since.
The Government needs to look at the actual data. The so-called experts are still living as though the world is flat and not round. They’re not looking at the research in an unbiased way. If you look at the Women’s Health Initiative Dietary Modification Trial in the United States, there is absolutely no evidence that a low-fat diet has any effect on cardiovascular disease, any effect on diabetes, any effectff t on strokes. Research from the Medical Research Council Epidemiology Unit at the University of Cambridge suggested fat from dairy produce was cardio-protective and also protected against type II diabetes. So I have no idea why the Government is still insisting on going with this attitude towards saturated fat and high carbohydrate intake.
The Government has to admit they’re wrong. They say you have to have more than 50 per cent of your energy intake from carbohydrates. I think a balanced diet would have carbohydrate intake of 26-40 per cent with the rest of the energy intake being made up by fat and protein.
Bad: Naveed Sattar, professor of metabolic medicine, Glasgow University
Headlines saying eat as much fat as you want could be dangerous. Some people may take that literally. We definitely know that saturated fat increases cholesterol and we also know that LDL cholesterol level increases heart disease. We know that saturated fat levels have come down in society over the last 30 years. As a result cholesterol levels have come down in society and that has been a contributing factor to the 80 per cent reduction in the risk of heart disease.
And we know from trial evidence that reducing saturated fat does reduce risk of heart disease. The other piece of evidence is that if you take people who are obese and want to lose weight, no matter what they eat – whether it’s low fat, high fat, Mediterranean, what diet you take – they all work as long as you stick to it. If you cut calories you will lose weight.
Mostly bad: Professor Mike Lean, chairman of human nutrition, Glasgow University
This is a difficult topic. A big worry is that this document has no declared authors, but was released with a list of supporters, all linked to the “paleo” diet craze, and to the current low-carb diet craze. It has ignored the two very major recent systematic reviews and meta-analyses of the evidence, which concluded that there is no benefit for
low-carb versus other weight loss diets, in terms of weight loss, blood pressure, cholesterol, or diabetes.
The evidence says fat contains nine calories per gram, compared with four for protein and 3.75 for carbohydrates (including sugar). So a wee bit extra fat gives you more than twice as many calories as a wee bit extra sugar. The evidence says that appetite is more readily shut down, to stop eating more, by protein and carbohydrate than by fat. The evidence says that not all saturated fats are equally hazardous for heart disease. The public health message that saturated fat is bad is too simple, and wrong. Saturated fats ... from processed meat products and many vegetable oils are indeed hazardous, and put up cholesterol, but the shorter-chain saturated fats found in dairy foods are not hazardous.
MEAT
Good: Dr Carrie Ruxton, public health nutritionist
If you look at the research that suggests that a vegetarian or vegan diet brings greater longevity than one with meat in, they’re not comparing like for like. When people are saying you should give up meat to be healthier, they’re not looking at “no meat” versus meat, they’re look at a diet which is rich in nuts and pulses and fruit and vegetables versus diets which contain less healthy ingredients – your pie and chips diet, compared with a vegan diet. And that is an unfair comparison. Because if you look at randomised control trials, of which there aren’t that many, where they’ve actually got a healthy balanced diet with meat and a healthy balanced diet without meat, and what they find is there’s no difference whatsoever in people’s health after eating those diets. You’re getting a benefit whether you’re having the meat or not.
We already have guidelines for meat in the UK, produced by the Scientific Advisory Committee on Nutrition. They said 70g cooked red and processed meat (per day). I would say go for that. And it’s processed meat we need to be careful of because of the salt and the preservative. But fresh, red meat cooked sensibly at home isn’t a problem, and the World Health Organisation emphasises that. What they’re worried about is more than 50g a day of processed meat. But average intake in this country of bacon and ham is only 17g so we are well below that. And, by the way, processed meat in our country is bacon and ham and salami, not sausages or burgers, which are not processed.
Possibly bad: Professor Paul Shiels, Institute of Cancer Sciences, Glasgow University
In our research we found there is an association between the frequency of red meat consumed (combined with low fruit and vegetable consumption) by the most deprived males and how fast they age and how well their kidneys work and that’s tied into the poor health of these men. We’ve not provided causal information. It’s just an association. But there is a direct link between ageing and nutrition and there’s strong correlation between levels of phosphates in the blood and longevity. Phosphate is present in basic foodstuffs – that’s meat, fish, eggs, vegetables. These men had higher levels of phosphates in their blood.
One thing we want to start investigating now is whether it’s not the red meat itself, but possibly some of the preservatives, whether it’s processed meat. Why are wealthy men not experiencing this? Possibly the wealthy are eating more fruit and veg, possibly there’s a difference in the type of meat they’re eating.
We don’t know. That’s the next step we need to investigate.