Trusting a news headline blindly is a bad idea, with so much “fake news” being spread out there. 

And often headlines tell just part of a story. They hype up the stats without explaining possible limitations of the research they are quoting. So for this post, I have read the actual journal article for you. And will give you some key details from the paper to help you understand the story behind the headlines.

Not long ago, I dissected the breakfast study (find video link HERE) that made headlines across the globe. It was great to see so many of you discussing and sharing your thoughts on nutrition research. And I feel that it important to know that researching nutrition and diets is complicated for many many reasons.

Firstly, how do you collect information about what people are actually eating?

Do you ask them what they ate yesterday? Well then you may not get an accurate picture of their usual patterns over the course of weeks and months. Ask them how they ate over the past year? Well, then they may forget some important information about their habits from a few months ago. Ask people to fill out a food diary, and they are likely to eat differently because they know you’re watching.

You can check blood and urine samples for evidence of what they ate recently. However this only gives you information about key nutrients rather than foods and diets. Lock people in a room and feed them a specific diet you hope to study, and you may end up getting sued…

And if I, a dietitian, asked you to tell me about your eating habits. Would you tell me the full truth? Or would you be more likely to tell me what you think I would want to hear? Maybe you would play up the healthy foods a little, maybe forget to mention some of the treats?

If you participate in a study about doughnuts, and I ask you to list off just in general what you eat on a normal day… Would you possibly give me the information you think I want to hear, and tell me about your favourite doughnuts?

For all these reasons, and more, collecting accurate information about people’s nutritional intake is tough.

You can use 24 hour recalls and miss out on usual eating trends. You can do a food frequency questionnaire or test urine and blood samples, and miss out on the detail you need. Food diaries are known to cause people to change their eating patterns. And the moment you ask someone about their eating habits, you are at risk of collecting information that they think you WANT to hear. And you are also likely to miss out on information they feel less eager to share.

Another example of difficulties in studying nutrition may be when you may want to study the effect that certain diet habits might have on our health.

You can for example collect information about what people eat using some of the methods we discussed before. Then you can follow them up for several years to assess what happens to their health. Here you are possibly measuring the effect that their diet has on their health. However it is very difficult to rule out whether other behaviours such as smoking, physical activity and stress levels are causing those conditions.

You can also tell one group of people to eat a certain way, and then another group to continue eating the way they always do. Then you follow up what happens to their health. If one group has different health effects than the other group, then maybe this was because of their dietary changes. But how can you be certain that they eat the way you told them to, without locking them up in a room and literally feeding them. Again, we do not want expensive lawsuits to get in the way of our research!…

So realistically, studying the effect of diet on our health is tough. It is complicated and in many ways, it is simply carefully guided guess work.

But that doesn’t mean that we should simply give up on studying the important links between our diet and our health. No matter how complicated it is to study, there is no denying that our health is affected by our eating habits. And in many ways a very carefully calculated guess is hugely valuable in improving the diets of our people.

Meanwhile many research teams across the globe are providing us with their best estimates of the effect of diet on health. And we can start looking at patterns in those estimates. Based on groups of experts meeting together to discuss these studies, we can start to produce nutrition recommendations, and healthy eating guidelines.

Yes, there is a lot of guess work, and the research communities are very aware of these limitations. But we know action needs to be taken globally to improve dietary habits. And we need to find a place to start.

Cue, the recent Lancet study that we will be discussing today.

The paper in question is titled: Health effects of dietary risks in 195 countries, 1990-2017: a systematic analysis for the Global Burden of Disease Study 2017. It was published in the Lancet, a reputable medical journal, online on 3rd April 2019.

The study hopes to provide a picture of the possible impact that a suboptimal diet may have on human health, across the globe. It worked on collecting as much data as possible on the dietary intakes of countries across the world and the risks that certain elements of our diet may have on our health. It then looked at the size and diversity of the populations across the planet. It took into account age, gender and many other factors.

Based on all this data, it tried to calculate the potential risk that different diet behaviours pose on our health.

Ofcourse, the study can only give you their best guess. However, their best guess here is based on information provided to them from as many sources as possible. And having even a rough understanding of what diet behaviours are posing the greatest threat to our health is incredibly useful when trying to improve global eating habits on a limited budget!

So how did the researchers carry out this study?

Well first they identified 15 different dietary risk factors that were known through strong evidence to have a negative effect on our health. They made sure that for each of these risk factors, they would have enough evidence available to then quantify the risk that they posed on our health.

The 15 different dietary risk factors that they looked at were:

Diet low in fruits, in vegetables, in legumes, in wholegrains, in nuts and seeds, in milk, in fibre, in calcium, in seafood omega-3 fatty acids and in polyunsaturated fatty acids. And then diets that are high in red meat, in processed meat, in sugar-sweetened beverages, in trans fatty acids and in sodium.

For each of these risk factors, they were able to estimate an amount of that food that was considered a healthiest amount to take. For example, for fruits, they were said that people would be healthiest if they took 250g of fruits a day. For processed meats, a healthiest intake was 2g (so almost none).

They then looked at all the information available on national intakes of these 15 dietary risk factors.

They were able to collect information on how much of each of the foods or nutrients were consumed each day by each country. To collect this information, they mostly tried to look at 24-hour food recalls and food frequency questionaires. However, they also looked at food sales information and national food availability data. For sodium (salt) they collected information on urinary sodium levels if this information was available.

They then gathered information about the demographics of each country. This included the number of people living there and the age distribution within each country.

Once they had all this information gathered:

• The amounts consumed of these 15 different foods.
• The risk that consuming these foods posed on our health.
• The amount of people in each country.

They were able to do some very complicated maths. They were then able to estimate the amount of deaths that may have occurred because of a suboptimal intake of each of these foods. When I say suboptimal intake, I mean eating too much of foods that were deemed unhealthy foods and too little of foods that were considered healthy.

So, what did the study find?

Well firstly, they found that globally, people mostly ate too little of the healthy foods.

People only ate 12% of their recommended amount of nuts and seeds, 16% of the recommended amount of milk and 23% of the recommended amount of wholegrains.

Meanwhile, across the globe, people ate too much of the unhealthy foods.

People drink 16 times more of sugar sweetened beverages than recommended, ate 90% more processed meat than recommended and took 86% more salt than considered healthy.

When looking then at the risk that this unhealthy balance of foods poses on our health, they calculated that 11 million deaths globally were contributable to dietary risks each year.

This means that 22% of deaths each year are likely related to unhealthy diets. 10 million of these diet-related deaths are suggested to be due to cardiovascular disease.

These results are where those headlines such as “1 in 5 deaths due to poor diet” come from.

When looking at the results in more detail, it found that more than half of all diet-related deaths are likely due to a diet that is high in sodium, low in fruits and low in wholegrains.

Although I am not going into the results in much more detail today, the study did give more specific information. It was able to base recommendations on different regions of our globe, different age groups and different socioeconomic groups. It was also able to break down the various diet-habits that posed the greatest risk for each of these groups.

So lets take a step back, and look at what value a study such as this may add to what we already know about nutrition:

Firstly, it again highlights that improvements in our diets across the globe can possibly prevent unnecessary deaths. Having a big study such as this, published in a reputable journal, making such a statement is vital when pushing nutrition to the forefront of policy making.

And secondly, the main focus of global policies on healthy eating has been on reducing salt, fat and sugar intakes. Thankfully, this study pushes two new focus points into the light. A need to increase the consumption of fruits and wholegrains. So often, health-promotion is focussed on things to give up. Eat less fat, cut that sugar intake, and watch your salty foods. So it is refreshing to see a possible opportunity to promote people to take ON a habit, such as more fruit and wholegrains.

So although this research is based on guesswork, as is most nutrition research, it is very carefully reviewed and calculated guesswork. And it is some of the best evidence we have at this point in time when it comes to guiding global policy making to reduce diet-related disease-risk factors.