Thinking Nutrition

Making sense of nutrition confusion

• Dr Tim Crowe • Episode 1

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If you want to be less confused about just how to make sense of conflicting nutrition messages that you hear about each day then you’ve come to the right place. In today’s podcast, I’ll unpack what makes nutrition appear to be such a confusing area. But importantly, I’ll help set you straight in knowing how to make sense of it all.

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If you want to be less confused about just how to make sense of conflicting nutrition messages that you hear about each day then you’ve come to the right place. In today’s podcast, I’ll unpack what makes nutrition appear to be such a confusing area. But importantly, I’ll help set you straight in knowing how to make sense of it all. 

What is it about nutrition that seems to breed so much confusion and controversy? Surely something as simple as ‘healthy eating’ can’t be that complex to study and communicate? But there’s the rub: nutrition is about eating. And as humans, we are incredibly diverse creatures. There are a multitude of factors that influence what goes into our mouths. Mix in a dash of conflicting science and is it any wonder that people are so confused?

To explain this confusion, let’s start with the science first. Nutrition is a young science. The first vitamin was only isolated and chemically defined in 1926. Fast forward to today where an understanding of the role that nutrition plays in major non-communicable chronic diseases such as heart disease, type 2 diabetes and cancer is accelerating at a rapid pace. But despite so much attention, the quality of research that informs it is not always the best quality. This is not an indictment on the researchers; it is more a statement on the tools available to them to study the links between diet and health.

Want to answer the big questions about how diet can alter a person’s risk of cancer? Good luck with that if you want to answer it by running randomised-controlled trials where people dutifully adhere to their assigned diet for years on end as we wait for the disease incidence to ramp up. Instead, researchers need to turn to observational studies which is where large groups of people have their diet, lifestyle and health measured at different times and they just go about their normal daily business. So many inherent flaws, biases, confounders and ‘unknown unknowns’ with doing this, but it is the next best option if you can’t do the big randomised controlled trials.

The tools available to measure what someone eats over the long periods of time that observational studies run are imprecise to say the best. Hands up who can answer what they ate on the Monday evening of 6 weeks ago? Many dietary assessment tools rely on self-reporting, using instruments like food-frequency questionnaires. The bias here is well described: people over-report eating ‘healthy foods’ such as fruits and vegetables and under-report how much discretionary foods they eat. It’s no different to how we may add a centimetre or two to our height and drop the odd kilo or two from our weight when we have to give this information.

Even with the best di et assessment tools, nutrition research is dealing with people - each with their own unique food preferences and physiology. This has been elegantly demonstrated by Israeli scientists in 2015 who tracked the influence of the same foods on blood glucose levels in 800 people for a week. Not unexpectedly, each person had vastly different blood glucose responses to the same foods and even meals. Use of a specially designed machine-learning algorithm that considered a person’s body type, physical activity, and even their unique gastrointestinal microbiome fingerprint was more powerful in predicting their blood glucose response to food than knowing what the nutritional characteristics of the food were. Yes, our gut microbes really do control us in more and more surprising ways.

Finally, we have the presence of vested interests. It is all too easy to go after the low-hanging fruit such as ‘big food’ for funding research. But industry groups will do what best helps their industry and that is fund research that may be more likely to reflect a positive outcome. Be it meat. Or soft drinks. Or dairy. Or broccoli. Or avocados. Big plant plays the game just as well as big animal I assure you. The end result is the same: the balance of a body of knowledge can be tipped in a particular direction purely because of the industry funding dollars it attracts.

How concerned should we be in evaluating industry influence on nutrition research? Here’s one analysis. Research that has financial conflicts with companies that make sugar-sweetened beverages is less likely to find links between sugary drinks and obesity or diabetes-related outcomes.3 Then there was a 2007 review of 206 studies that looked at the health benefits of milk, soft drinks and fruit juices which found that those sponsored entirely by a food or beverage company were many times more likely to show positive health effects from consuming those products. And for those studies that reported unfavourable conclusions, no industry funded studies were present here. I’ll pop a link to this study in the show notes. https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.0040005#s3

Before you think that researchers are lining up to be paid off by industry so they can produce fraudulent research in the pursuit of upgrading to a bigger yacht, take a step back. There are very, very few bad apples in the research community – most researchers are good people who want to do good work regardless of who funds it, but they also have the reality of needing research grants to develop their research program.

So it could be that research that attracts industry funding is already helping to confirm prior positive work in the field so the outcome is already pretty assured. It also could be that a study is designed to report a positive outcome by using a battery of outcomes where if any one lights up as positive, it gets the focus of the study conclusion. Or maybe, only positive research is allowed to be published and such industry funding contracts do exists. They are ones I would never, ever sign, but some researchers may.

It doesn’t stop at the influence of ‘big food’ though. Researchers tied to a narrative with their research program (and maybe a large social media following and the odd best-selling book on Amazon or two) may find it difficult to do an about face when conflicting evidence presents itself. As humans, we are all susceptible to this. The scientific method helps to reduce it, but it cannot eliminate it entirely.

So by way as an example, let’s touch on a few of the perennial controversial areas. And for the first one, we don’t have to look much further than carbohydrates. COI declaration to start with: I love carbs and a life without bread makes me sad.

Low-carbohydrate diets are hardly a new thing with these diets coming into and out of popularity for decades just like fashion trends. Can we blame carbohydrates for growing waistlines? No. The simple explanation is that the amount of food (kilojoules) eaten has increased over time. 

Well-controlled weight loss studies find very little difference between low- and high-carbohydrate diets for long-term weight loss success or sustainability.5 It is the energy deficit created by restricting carbohydrates, fat or the volume of food that drives weight loss – not any metabolic superiority of one diet over another. The key predictor in these studies for weight loss is simply adhering to the diet that someone is following. Controversial stuff I know.

 Health problems linked to carbohydrates only start when we rely too heavily on overly refined, highly processed carbohydrate foods. Foods like cakes, muffins, confectionery and soft drinks are over-represented in the western diet at the expense of minimally processed plant foods such as wholegrains and legumes. Wholegrains are linked to a lower risk of type 2 diabetes, obesity, cancer and cardiovascular disease. Yet these are the very foods that are advised to be turfed out of the diet when the latest advocate for a low-carbohydrate diet captures the public’s attention.

 Want another example of polarised debate and opinion? Then look no further than saturated fat. For decades, saturated fat has been implicated as a major dietary culprit for heart disease but reading the popular press could have one believe that this has now been upturned. Even Time Magazine in 2016 proclaimed on their front cover: ‘Eat Butter’. Depending on what camp a person sits in, there is evidence to both support or debunk such a claim.

It is true that saturated fat raises cholesterol levels, particularly the more harmful LDL-cholesterol. But what is lost in this general statement is that there are different types of saturated fat, and their effects on cholesterol differ. So, it is complicated. And this explains why that even with changes in cholesterol caused by saturated fat consumption, it does not always appear to equal a greater risk of heart disease.

Despite all the debate, it loses sight of this one simple fact: nobody eats ‘saturated fat’ – people eat food. Food contains a broad range of nutrients. Even heart-healthy olive oil contains some saturated fat. Sure, it’s not a lot, but it is still there. Dietary messages framed around nutrients lose sight of the bigger picture of foods. The forest is lost among the trees.

Here is why it is important to focus on foods rather nutrients and why studies can give different conclusions. When saturated fat is replaced by wholegrain foods, heart disease risk goes down. But replace the same saturated fat with highly refined carbohydrate foods and risk stays the same. Likewise, replacing saturated fat with plant-based monounsaturated fat from foods like olive oil and avocados is associated with a reduced risk of heart disease. Whereas if the source of the monounsaturated fat is animal-based then no benefit on heart disease risk is seen.

 A declaration that ‘butter is back’ losses sight of this. Butter can be a part of any diet, but it is not some miracle heart health superfood. Neither is coconut oil for that matter.

Don’t blame the guidelines

With growing rates of obesity and type 2 diabetes, the Dietary Guidelines have received a lot of undeserved attention as the ‘smoking gun’ to explain this. If only public health nutrition was so simple: ‘Build the Guidelines and they will come’. If you believe that, then I have a bridge in Sydney to sell you. What the Guidelines say and what the typical person in a country like Australia eats are as far apart as the shores of Sydney Harbour.

In 2017, only half of adult Australians met the recommended two serves of fruit per day. And the news on vegetables was worse: just seven percent met the guidelines of that being five serves each day.

So, if we are eating so few fruits and vegetables, what are they being replaced with? Look no further than the discretionary foods list. Fully one-third of daily kilojoules come from foods such as cakes, biscuits, alcohol, soft drink and chips – none of these foods are core recommendations in Dietary Guidelines.

The cognitive dissonance of anyone blaming dietary guidelines for weight and health problems when so few people follow them is writ large as a gateway into promoting an alternative dietary paradigm. We’re ‘fat and sick’ as a population because we eat too much rubbish and not enough healthy food and almost no one follows the Guidelines. Sure, they could be sexed up a bit and the promoters of them certainly could learn a thing or two from those promoting fad diets such as Paleo and products such as coconut oil, but anyone maintaining that it is the Guidelines fault for our weight and health problems is ignorant at best, and making the health of the population worse, not better, with the counter advice they give.

Dietary patterns for the win

Amongst the conflict and confusion, there is common ground that most camps can agree on. The need to eat more minimally processed plant-based foods and less processed foods high in sugar is one such theme. Rather than a nutrient focus, nutrition research is now turning its attention to dietary patterns. This makes perfect sense. We eat a whole range of foods, not just nutrients.

One of the largest ever scientific reviews looking at associations between food and beverages and the risk of diet-related disease has reinforced the fundamental dietary patterns for good health. The review looked at diet and chronic disease risk from 304 reviews published in the last 7 decades. Type 2 diabetes, overweight and obesity, cancer and cardiovascular disease together accounted for most of the links found. This was a big study and I’ll link to it in the show notes. https://academic.oup.com/nutritionreviews/article-lookup/doi/10.1111/nure.12153

From the review, it was plant-based foods that were most protective against the risk of developing disease compared to animal-based foods. For plant foods, it was wholegrain-based foods that seemed to have a small edge over fruits and vegetables. So much for the anti-grain sentiment that is popular at the moment.

For animal-based foods, dairy products were considered neutral on health while fish was considered protective. Red and processed meats were linked to higher disease risk as too were sugar-sweetened beverages and highly refined low-fibre grains.

The findings from this major review are close to a carbon copy of existing dietary guidelines that have changed little over the decades. Eat more plant-based foods than animal foods, choose wholegrains over refined grains, limit red and processed meat and choose other beverages in preference to soft drinks. Such recommendations may not get media attention or help sell books in numbers like the latest fad diet, but they are the cornerstone of long-term health in preventing and managing many chronic health conditions. Get the core of these guidelines right, and you can hit the snooze button when the next nutrition controversy surfaces.

So, in summary, here are my tips on applying everything I’ve covered today both for yourself and for clients you may work with.

  1. Firstly, acknowledge the diversity of reasons that determine what we eat. Food choice is a personal matter and is based on much more than just following scientific evidence
  2. And secondly, there is no one ‘best’ way to eat – think more dietary patterns: fruits, vegetables, wholegrains, nuts and legumes for the win.
  3. And yes, nutrition research is conflicting and that is unlikely to change anytime soon so in seeking out good quality information, look for work that is based on a systematic review which includes lots of research as these are best to refer to for higher quality evidence. Feelpinions and Insta-influencers are the polar opposite to this.
  4. Ask yourself if the advice you’re reading is also repeated consistently by the voices of credible nutrition professionals, researchers and peak health bodies? If no, raise the skeptical flag
  5. Is the end result of following the advice you read pointing you in the direction of eating more plant-based foods and less highly processed foods and added sugar without banning any foods or food groups or labelling certain foods as toxic? If no, then strongly consider doing it anyway.
  6. And finally for someone that finds themselves on the latest fad diet or trendy superfood merry-go-around, rather than beat yourself up for falling for it again, look at the positive changes you’ve made for being more conscious of what you’re eating. Few people maintain any diet to the letter after a few months so aim for getting 80% right most of the time – we’re all humans trying to do the best we can.

 Research Update

For the last part of the show, I like to do a quick research update about a study that has grabbed my attention recently. So avocado lovers, sit tight, you’re going to lover this one.

A new study has found that eating one avocado each day can significantly reduce the levels of a harmful oxidised form of LDL cholesterol.

A bit of backstory. Avocados have long been considered a healthy food owing to their high levels of monounsaturated fat and antioxidants. They are considered a heart-healthy food because they have been shown to help lower the more dangerous LDL-cholesterol levels in the blood. LDL comes in different ‘flavours’ though with both the oxidised form of LDL as well as the small, dense LDL particle size form being more likely to progress atherosclerosis.

Could avocados then have an additional heart-health benefit outside of lowering LDL-cholesterol by also decreasing the oxidised form of LDL? That was the question posed by United States researchers from Penn State University. And the work was published in October 2019 in the Journal of Nutrition – see the show notes for the study details. https://pubmed.ncbi.nlm.nih.gov/31616932

Forty-five adults who were overweight took part in a randomised-controlled trial that ran for 5 weeks. Now a RCT is where one group of people are randomly allocated to the study intervention while another group are randomly allocated to receive a placebo. They are powerful studies to do because they help to balance out all the inherent differences that exist between us as humans.

The diets followed were either a low-fat diet, a more moderate-fat diet, and finally a moderate-fat diet that also included one avocado each day (big win for those that were randomly allocated to that group). An important point was that the moderate-fat diet alone also included additional monounsaturated fat to match that found in the avocado so that kept the fat content similar between the two diets.

What did the research team find? It was the avocado diet that was the most effective in lowering oxidised LDL with a fall of almost 9 percent seen. Blood levels of the antioxidant lutein were also higher when following the avocado diet. Lutein belongs to the vitamin A family, and avocadoes are a great source of it.

So it could be the lutein that was helping to protect the LDL from oxidation, and this seems valid to conclude. The reason being that the moderate-fat diet alone also had monounsaturated fat added to it to match that found in avocados, but no other bioactive compounds naturally found in avocados.

Avocados are a heart-healthy food and this benefit comes not just from their high levels of monounsaturated fat, but also their unique mix of bioactive compounds.

Whether smashing your avo releases more of these bioactive compounds is a vital question for future studies to address I feel 

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

If you find this podcast of value, then please consider sharing it with your friends and colleagues. Or maybe even leave a review. This all helps increase the ranking and reach of the podcast which means a big win for credible evidence-based nutrition messages while helping to dilute out the crazy and making the world a slightly less confusing place.

I’m Tim Crowe and you’ve been listening to Thinking Nutrition.

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