That’s what I am often asked, and I can’t blame anyone, because it really is confusing. It is in fact one of the reasons why I decided to study nutrition: I wanted to be able to wade through it all and make up my own mind.
The reasons are varied and complicated, I’m sure books have been written about it, but I’ll try and outline some reasons why.
1. Nutrition Research is difficult
People aren’t lab rats, so it is hard to control their diets. Many so called ‘feeding studies’ rely on participants to be compliant with the diets they have been assigned as part of the study. Compliance, especially over a long period of time, can be difficult. Short-term trials may not be long enough for the results to be representative, long-term trial results may be inaccurate due to insufficient compliance. Some studies use questionnaires and ‘diet recall’, so participants are asked to write down what they ate. Such accounts, too, can be unreliable, because people may not remember exactly, forget all the ‘small bites’ in between or feel embarrassed and may drop an item here and there.
2. There is a lot we do not yet know and new discoveries are made all the time
There isn’t very much money to be made with pure nutrition studies. You cannot patent food. You can patent drugs though, obviously, and there are considerably more funds for studies that explore new drug treatments. Still, research is being done all the time and our knowledge on nutrition is slowly growing. As our knowledge about the human body and what goes on at a molecular level increases, it often turns out that what we believed to be true for decades is actually wrong. Or it is not quite wrong, but not as simple as we thought.
When researchers design a study, they start out with a hypothesis and a expectation of what they are going to find. One would hope that they would keep an open mind and run with what they actually DO find, but that doesn’t always seem to be the case. Probably the most famous case of misinformation due to bias is the ‘Seven Countries Study’ conducted by Ancel Keys, starting in 1956, published in 1970. The researcher from the University of Minnesota wanted to find the reason why heart conditions were on the rise in the United States and his hypothesis was that this was connected to the high consumption of saturated fats from meat and dairy. He collected data from 22 countries, comparing their fat consumption to their rates of heart disease. The result was first a presentation given at Mount Sinai Hospital, New York, in 1952 - ‘6 Countries’, which ‘proved’ that, yes, indeed: Countries with high consumption of saturated fat also had high rates of heart disease. Case closed. But the attentive reader will have noticed something here: Why did he report on just 6 countries out of 22? It appears that the data from 16 of the 22 countries did not confirm Keys’ hypothesis, so he left it out. If you think this is unethical and unscientific, you'd be right. Two researchers, Yerushalmy & Hilleboe disputed Keys' findings in a paper dated 1957. Keys had the data of 22 countries in 1952, and after 1957 at the latest he couldn't have denied this. Yet he still published the "7-countries study" based on just a fraction of the data he had. This then formed the basis of the ‘low-fat’ recommendations we have been following for the last 60 years. It’s a long story. If you want to read more, read Nina Teicholz (“The Big Fat Surprise”) or Robert Lustig (“Fat Chance”).
As I said above, it is harder to get funding for research into diet and nutrition than it is to fund expensive drugs. However, some studies are sponsored by the food industry, and again you’ll have to be vigilant of bias. An institution whose whole reason to be is to further the consumption of sugar or a manufacturer of fizzy drinks will expect a certain outcome. Studies sponsored by such industries are not necessarily flawed, but you should take a very close look at them.
As consumers, we are often given incomplete, misinterpreted or simplified information. We tend to get our updates from the mainstream media and rarely read the actual studies – not least because the media hardly ever reference, which makes it quite difficult to even find the original publication. But when you read an attention-grabbing headline it is worth trying to track down the actual article and see what it actually says.
Where the conclusions really clear? Was the result significant? How many people took part: 6 or 60 or 6,000? How long did it run for: 3 weeks? 3 months? 3 years? Which supplements were used? Which form, which strength, for how long? Who paid for it?
It is very difficult to be completely unbiased, and it is my impression that experts will always find research to back up their own personal views, no matter how opposing views of different experts might be. There seems to be solid research to back up the Paleo Diet and the Atikins-type LCHF (low-carb/high-fat) diet as much as there are good studies to support vegan and vegetarian diets and so on. No wonder the public is getting confused. At the end of the day, we still have to make up our own minds!
Also, different things work for different people. We are all individuals and what might be brilliant for one, doesn’t work so well for another. There is a bit of trial and error involved in finding what works for you.
It seems wise to look at all the different advice and first check what they actually have in common – and that’s quite a lot! You may find some (usually industry-sponsered) studies that say that the consumption of sugary and processed foods is fine, as long as they are part of “a healthy balanced diet”. However, the vast majority of research promotes natural foods: fruit, vegetables, nuts, seeds, healthy fats. Opinions then diverge: meat, fish, eggs, dairy, beans, pulses? Some want to include all of these, some exclude some of these. The bottom line is: Eat Real Food. That’s something almost everyone agrees on. Try and see what works for you, but eat real foods, cook your own meals, plan and carry your own snacks and packed lunches and save money along the way. You can’t really go very far wrong then.