Mirror mirror on the wall – What’s the healthiest diet of all?

Open any magazine or newspaper, scan any article online and you’d be forgiven for being confused as to what a healthy diet actually is. In the past few years, the best diet, or way of eating as I prefer to call it, has been hotly debated and has reached Brexit-level in terms of the emotions it can stir up. I dare you to search the LCHF (low carb high fat) hashtag on Twitter. Devotees of this way of eating get terribly under the collar if you so much as suggest that, for example, oats can form part of a healthy breakfast. Is there really an ideal way to eat for ‘optimum’ health?

This is not a diet for weight loss

Let’s get one thing straight from the start, I am not talking about the best diet for weight loss. I can cover that in the later blog (although in short, if you’re looking to lose weight, do so via small and sustainable changes that help you eat fewer calories than you burn, while still eating a balanced range of foods).

The subject of this post is whether there is a way of eating linked to reduced risk of disease and therefore a potentially longer and healthier life. There is no such thing as the elixir of youth. Our disease risk is a complex interplay of genetics and environment. We can’t do much about our genes but we can, to an extent, manipulate our environment (our lifestyle factors) to influence the genetic hand of cards we have been dealt. That is not to say that you can ever blame someone if they develop cancer or cardiovascular disease (and you’d be a pretty despicable person if you did). Our dietary choices and the amount we eat are, to an extent, within our control but they are also themselves influenced by genetics, psychological state and income, for example. And, in some cases, our genes can greatly increase the risk of some diseases. And some people are just lucky. No one is to blame if they get sick. End of.

Nutrition studies are hard

A bit about me. I like evidence. Proper science. I don’t do woo. I don’t do herbal shaman dances. I only make recommendations if they’re grounded in evidence. Now, if you want to test whether a pharmaceutical drug is safe and effective, it is (relatively) easy. You get a bunch of people who have the condition the drug is designed to treat and you give some of them the drug. You then give the rest of them a placebo treatment that looks identical and is taken in the same way and you see whether the drug is effective by comparing what happens. No one knows who gets the drug or the placebo until the end if it’s a well-designed trial. Simple! I mean, it’s obviously very complicated and this is a very simplified summary but the study design is fairly simple.

Now we don’t obtain our nutrition from a pill. We eat a huge diversity of foods, in different quantities, at different times. This makes testing whether one particular food or one nutrient, like broccoli, carbs or saturated fat is linked to better or worse long term health outcomes a lot more difficult. The drug trial design is a tricky one when it comes to nutrition. Unless you lock people up for long periods of time, like their whole life, and feed them a completely controlled diet, you’re stuck with recommending what to eat and hoping that they comply. And let me tell you, they rarely do. Just like when you go on your January diet, you’re good for the first week or two and then you want to faceplant a pizza. So you’re going to get a lot of noise in the study results. Which makes the data hard to interpret and even harder to reproduce. I swear, the more studies we do in nutrition, the less we know!

Add to this the fact that if you reduce the amount of saturated fat that someone eats, you have to replace it with something to ensure that the same calories are consumed so the subject maintains their weight, as weight loss over the course of a trial will affect the results! What the replacement food is may also affect results positively or negatively. Some research shows that if you replace saturated fats from butter, cheese and fatty meat with carbohydrates like sugary foods and refined starchy carbs (white bread, pasta etc), there is no benefit to health but if you replace them with unsaturated fats in foods like avocado, olive oil, seed oils or oily fish, there may be cardiovascular benefits.

But the bottom line is, what’s known as “intervention trials” where you actively change a person’s diet and test how it affects their health are very very difficult to conduct and it’s also very hard to interpret the results. You need a lot of people to account for the fact that some individuals won’t stick to their assigned diet and to deal with the fact that everyone is different in terms of their genetics, metabolism and overall lifestyle.

So we actually get much of our information on what way of eating is best for long term health from what’s known as observational studies. Researchers investigate a large number of people, often thousands of individuals, sometimes spread across the globe but more often in one country or region. They interview them to find out about their lifestyle, their eating pattern, their weight or body fat levels, their income, where they live, their medical and psychological state, how much they drink or smoke, how active they are and so on. Then, these populations simply carry on living how they’ve always lived, popping back for regular interviews, blood tests and other measurements, for many years. There is no dietary advice provided so there is no ‘intervention’ or influence on people’s lives. They are simply observed.

These studies provide us with an idea of whether an eating pattern like the Mediterranean diet is linked to better long term health. You’ll often see news articles saying that olive oil can reduce your risk of death by X% or eating bacon increases cancer risk by Y%. These kinds of studies can link food with health in this way but it’s important to remember that they are only associations not cause and effect. Again, interpreting the results is fraught with difficulty.

Firstly, people don’t always accurately recall what they ate yesterday when they are asked – you might ‘forget’ those biscuits or ‘accidentally’ overestimate the amount of broccoli you ate, or the previous day might have been atypical from most days. Another issue is that lifestyle habits tend to be clustered. So if you eat a lot of red and processed meat, you’re more like to drink lots of sugary drinks, over-consume alcohol, smoke, be overweight, take less exercise and so on. That means researchers have to control for this clustering using clever statistics. All of this makes it very hard to categorically say whether eating butter, for example, really is linked to a great risk of heart disease.

OK, you’ve spent a lot of time telling me how hard it all is. Poor you. What’s the best diet then?

Well, the UK Government and World Health Organisation recommends a diet based around vegetables, fruit and wholegrain carbohydrates, with smaller amounts of protein foods like pulses, meat, fish, eggs and some dairy foods as well as foods that are high in healthy fats like oily fish (salmon, mackerel, sardines, trout), nuts, seeds. They advise eating only small amounts of processed meat (like sausages, ham or bacon), foods high in sugar, foods high in saturated fat like butter, cheese or fatty meat, or highly processed foods.

These recommendations are much maligned in the press by some groups who associate all carbohydrate foods (including wholegrains and fruit) with ill health. We can all agree that eating too much sugar and potentially highly refined carbohydrate foods like white bread or white rice is probably not ideal for health but wholegrains (brown rice, wholemeal pasta and other relatively unprocessed grains) are a fantastic source of many essential nutrients like fibre and B-vitamins. I wouldn’t cut them out lightly. Plus, I love bread and baked potatoes.

Now, while it’s true that low carb diets may be effective for weight loss and are a potential line of management for type 2 diabetics, cutting out carbs is not to be undertaken without some thought as to where you’re going to find all those nutrients you’re missing out on and what you replace the carbs with. If you replace them with lots of high fat foods, you’re going to end up eating more calories and could then put on weight, which again, may have its own health implications.

What do the healthiest people in the world eat?

OK, out of all the ways of eating in all the studies we’ve done so far (I say all, I haven’t read them all but I’ve read a lot of reviews!) we can pull out some common themes:

• Plant-based foods are the main focus (whether whole fruit and veg, wholegrains, pulses)
• Most foods are relatively natural, whole and minimally processed
• Sugar and refined starches are limited
• Some fats are limited (always trans fats and, depending on the study, either saturated or omega 6 fats)
• Some of these ‘healthiest diets’ include lean meat, fish, oily fish and poultry but not exclusively. They can form part of a healthy way of eating but they are not always essential, depending on the population being tested.

Bear in mind, this is advice at a population level. Individuals should always eat what is right for them and their own circumstances. Active people, people with allergies, older people, people who eliminate foods for religious, cultural or ethical reasons or those with medical conditions will obviously need to modify parts of the above themes or seek specialist advice from a professional (and by professional, I don’t mean someone who looks good in a bikini on Instagram).

It’s not just about food

We are more than the nutrients that we eat and there is more to life than food, although when I eat cheese with a glass of red wine, I do wonder…

Think about the Mediterranean way of eating and you don’t just picture olive oil, tomatoes and fresh fish dishes, you think of siestas, sun and enjoying a leisurely lunch in a social or family setting. The whole lifestyle can influence long term health and the healthiest populations are usually the happiest, the least stressed, the ones who get plenty of sleep, stay active and have strong social networks (and I don’t mean lots of Instagram followers!)

Which brings me to my final point: one of the greatest risks to health, across the globe, is not how much quinoa or coconut oil you eat; it is whether you are poor. Being poor influences your health in so many ways beyond simply what food is on the table. There probably isn’t a table. Food is scarce and often the cheapest way to obtain calories is via refined carbs and fast food. Eating healthily is expensive and requires preparation, utensils and time. Educational outcomes are worse when you are poor, and children go to school hungry, perpetuating poverty from one generation to the next. The stress of the spiralling cost of living and debt outweighs the need for 5 a day. So add “don’t be poor” to the list of healthy lifestyle choices. Oh wait…

The bottom line is that there are many varied routes to health. There are several ways of eating that can benefit your health, albeit based on similar principles. But whatever and how much you eat, you must consider the wider context of your overall lifestyle. Above all, if you can, try to enjoy the ride!

Photo by Charlotte Karlsen on Unsplash