Behind the scenes of nutrition science

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Behind the scenes of the messy, beautiful, and complex world of nutrition science

science nutrition spoons of spices

Nutrition science is . . . messy! And complex! We’ve all heard the updates that coffee is good/bad for you, protein will help/hurt your bones, stop taking/take more multivitamins, etc.

There is a ton of conflicting information about what we should and shouldn’t eat (it’s messy). There are a lot of reasons for this (it’s complex). But, there is also some beautiful research being done that is amazing!

Because of its complexity, science—and nutrition science, in particular—is difficult to do. Some studies answer our questions better than other ones, so we’re bound to get “interesting” (messy) results sometimes. (I’m going to share two recent “beautiful” high-quality studies on metabolism and nutritional psychiatry).

Don’t get me wrong, continuing to conduct scientific research is 100 percent the best way to understand and learn more about ourselves, other species of plants and animals, our world, and our galaxy. It’s most definitely the best method we’ve got and it improves every day.

And let’s add another layer of “messy” to the pile. Because it’s messy and complex, many studies are miscommunicated in the media and on social media simply because it’s difficult to translate messy complexity into something audiences will click, read, understand, remember, and action.

Science is difficult to do

In fact, most areas of science are challenging—and the science of nutrition is one of the more challenging ones when it comes to biology (the study of living things).

The simple fact is that designing and conducting high-quality studies, and properly analyzing and interpreting the results takes time, care, and expertise; and is still kinda “messy.” Here’s why: There are so many different ways to study one thing. For example:

  • You could look at that one thing from the perspective of a compound, a cell, an organ, a body system, the entire body of an animal/person, or a group of animals/people.
  • If doing studies with people, do they have any conditions that can skew the results, are they taking any medications or supplements, do they represent your demographic?
  • What you measure matters, too. You can measure biomarkers (e.g., gut microbes), symptoms (e.g., gut pain/nausea/diarrhea/constipation), or outcomes (e.g., IBS diagnosis).

HINT: Most nutrition outcomes take years and decades to occur (how much broccoli do you have to eat for how many years to see any measurable change in health?).

Studies are also designed in many different ways:

  • Observational studies observe what’s going on without actually changing anything. We can observe things as they are right now (e.g., a snapshot in time), dive into the past (e.g., What did people previously do that *may* have led them to their current situation?), or look forward into the future (e.g., following people’s lifestyles over weeks, months, or years to find out what’s going to happen to their health).
  • Clinical trials are experiments (not observations) where researchers change one or two things about someone’s diet or supplement regime, etc. Then they measure a pre-set list of certain things over time to see what—if anything—changes (e.g., randomized controlled trials). (I talk about two recent nutrition clinical trials below.)
  • Review studies and meta-analyses take several previously done studies on one topic and look at all the results together to get an overall “big-picture” answer.

PRO TIP: If you’re going to look at studies directly to research a topic, opt for review studies first. You’ll get a good overview without first diving too deeply into any single study.

Even after you collect and analyze the data from your study, the answer is rarely: true/false or 0 percent/100 percent. It’s shades of somewhere in-between (e.g., 10 percent risk reduction). What I found while doing my Master’s research was that as you answer one question, you end up with two (or more) new questions. The more you learn the more you see how much more there is to learn. And this is especially true when studying something like human health.

Plus, each type of study provides a valuable piece of the puzzle when understanding something so complex as the science of nutrition. Clinical studies that control a few factors are excellent at understanding cause/effect. Observational studies are important to understand things from a population level. Studies that look a compounds/cells/animals are a great way to understand microscopic and biochemical mechanisms behind what we see happen. All of them have their inherent “messy” factor to them. That’s why we need all of them.

Let’s admit it: Science is fascinating for the intellectually curious, but most people want a simple, credible answer. Amirite?

science nutrition spoons of spices

Nutrition science is (more) difficult to do

You’d think that studying people eating food—such a common thing we’ve done for millennia—might be simple, right? It’s really not. In fact, it’s far easier to study how one drug compound affects our bodies than it is to study the health effects of a single natural food. And this is even more difficult when you’re looking at an entire eating style, like the Mediterranean diet, for example.

For one thing, this is because nature is infinitely complex. A whole food doesn’t contain just one or two compounds—it contains hundreds! In fact, mangoes have over 270 volatile compounds. Studying so many compounds at once is even more difficult and “messy” because you don’t know which compound has what (if any) effect. Not to mention the fact that two mangoes can have different levels of those hundreds of compounds based on: soil fertility, freshness, processing, and cooking.

Just as human biochemistry is mind-bogglingly complex, natural products are far more complicated than a one or two ingredient drug. #Complex

Plus, due to its very nature, the vast majority of nutrition studies aren’t experimental, they’re observational. A true experimental study would change what people eat, measure it very accurately, and see what happens over time—a clinical trial. As nutrition pros, it’s hard to help clients change what they eat and to sustain that long-term. So, you can imagine how difficult (and expensive) that kind of study would be and how much monitoring would have to be done to get accurate results!

So nutrition scientists most often have to ask participants what they eat, maybe test a few biomarkers, ask what their symptoms or diagnoses are and make “educated estimates” called correlations (not causation) based on that.

Having said that, in the past couple of years there have been a few experimental studies done on food’s effects on people, and they’re pretty impressive! Here are two examples from Dr. Kevin Hall and Dr. Felice Jacka.

science nutrition woman eating sandwich

Dr. Hall’s metabolism research

Dr. Kevin Hall at the National Institutes of Health has recently done some great clinical (experimental) research in the area of metabolism.

In one study he wanted to see if there are any differences in how much people eat depending on what they eat. In other words, do people tend to eat more when they’re eating ultra-processed foods or minimally processed foods? Or does the type of food even make a difference in how much people eat?

He took two groups of people and offered them food for two weeks: ultra-processed or minimally processed. They could eat as much as they wanted and that was measured. To reduce some of the variables that might skew (bias) the results, they kept the calories, sugar, sodium, fat, and fibre the same for both diets.

After those two weeks, they switched it up and offered the participants the other option for two more weeks (this is called a “crossover” study for fellow research nerds. 🤓 Each group of people crosses over to the other option half-way through. In this case, it means two-weeks eating ultra-processed foods, then two-weeks eating minimally-processed foods—and vice versa for the other group.)

You’ll never guess what happened . . .

(OK, maybe you will.)

The people who were offered the ultra-processed foods ate more calories each day. 500+ more calories!

And, guess what happened to the participants’ weight when they were eating the ultra-processed foods (and inadvertently 500+ more calories per day)?

They gained 1 kg in those two-weeks!

So then, what happened to participants when they ate the minimally-processed foods?

In this case, even though they could eat however much they wanted to, they took in fewer calories and lost 1 kg during those two-weeks!

There is more to this story than just calories (nutrition is complex, right?). While eating the ultra-processed foods for two-weeks (and eating more calories), people also ate faster and took in slightly less protein. Plus, they had lower levels of the appetite-suppressing hormone PYY and higher levels of the appetite-stimulating hormone ghrelin.

Conclusions: Ultra-processed foods = more calorie intake = weight gain; and while that may be the bulk of the effect, it seems there are other factors that play a role as well. More research will shed more light on this area.

Here are a couple of articles to learn more about this study:

Find out more about this study and what makes it strong, how many calories and weight were lost and gained on each diet; and what *exactly* are processed, unprocessed, and natural foods. Have a listen to my podcast episode all about it right here (for all rEATsearch episodes, click here):

science nutrition bowl Mediterranean diet

Dr. Jacka’s nutritional psychiatry research

Dr. Felice Jacka is a Professor at Deakin University, Director of the Food and Mood Centre, and Founder and President of the International Society for Nutritional Psychiatry Research.

In the past few years, she led breakthrough studies of how changing what people with depression ate (so you see, this study was an experiment, not an observation because people made a change) and the effect that had on their moods. Not only was this a clinical trial, but was done on people with depression (as opposed to healthy people—this means the results can apply to people with depression).

Dr. Jacka’s randomized, controlled clinical trial (the SMILES trial: “Supporting the Modification of lifestyle In Lowered Emotional States”) split people into two groups. One group received seven nutritional consultations about the “ModiMedDiet,” while the other group got seven social support or “befriending” sessions instead (a person to talk to and hang out with).

Guess what?

Conclusions: The improved diet helped with depression symptoms. In fact, 32 percent of the group who had dietary counselling felt better, versus just 8 percent of those who got the social support.

Here are some resources so we can all benefit from the power of nutritional psychiatry:

Find out more about the SMILEs trial—what makes it such strong nutritional research and some of the other amazing results it had. Have a listen to my podcast episode all about it right here (for all rEATsearch episodes, click here):

How are you going to help your clients and patients benefit from this high-quality nutrition science?

Get a done-for-you health article on the microbiome-gut-brain connection and mood foods. It’s fully researched easy-to-read pre-written article about microbiome-gut-brain axis and the power of mood foods.

*Note there is a limited quantity of this (and all) the done-for-you articles in the Credible Health Blog Shop.

Industry influence on nutrition science

No one can deny that massive industries influence what we know about nutrition.

Does this mean that we should immediately dismiss any study funded by industry?

No . . .  but, be aware that these studies may suffer from publication bias. This means that industry will most often fund studies they think will benefit them, and if studies are done that don’t, they are less likely to get published.

Does this mean the researchers and their research are biased or poor quality?

Not necessarily. Many of these funding contracts have clauses that the company/industry will not control any of the day-to-day research. And that the source of funding for the research must be disclosed.

NOTE: Scientists have to apply for grant money to conduct their research. These often come from governments, research panels (like NSERC) and the universities themselves. They can also come from industry.

Another thing to look out for here is that the study results are put into an industry-funded marketing and public relations spin machine. This can take positive results and make them look even more positive than the science suggests. (More on the problems with how research makes it to the media and social media below.)

One recent example of how food and nutrition recommendations have ditched industry influence to be based on the research itself is Canada’s new Food Guide. In this case, no industry lobby was allowed, unlike in the past. During this process, industry was treated like any other citizen—they had no more leverage than you or I. This resulted in stronger recommendations for plant-based foods, merging of the “dairy” and “meat and alternates” into one category now called “protein,” and an entire section for consumers to understand how food marketing can influence their choices.

Bottom line with funding is yes, be aware and skeptical of studies funded by industry. But, don’t dismiss them altogether. Instead look at the quality of the study and how it fits into everything else we know on the topic.

The future of nutrition research

The studies you see today are certainly not the “be all and end all” of nutrition research. New, even better, studies will be coming out over time. We are going to continue to learn more and more and as this happens we update our knowledge. The nutrition claims we now believe to be true are based on the best information we have right now. But none of this is guaranteed to be the same in ten or even five years.

This is why it’s important to keep an eye out for better and stronger studies because they continue to test what we know, answer more questions . . . and come up with even more questions to answer in the future.

science nutrition open magazine

Nutrition science is difficult to communicate

(and often gets misrepresented in the media and social media)

Everything mentioned so far is based on the scientific research processes, but that’s not where the vast majority of people hear about—and get confused by—the latest study. People hear about the latest study via traditional media, social media, and other websites and blogs (and their friends and family that share these updates with them). They’re not hearing the new research directly from the people who do it or even experts in those fields. And sometimes those nutrition science experts aren’t expert at science communication, either (I 100 percent sucked at this when I first left industry and I’m continuously improving my #SciComm skills).

There is often a “broken telephone” phenomenon when it comes to how that research is communicated to people en mass.

Here’s how it works:

  1. Researchers design a study to answer a question, get funding, conduct the study, analyze the results, and then write about it (in the language of “expert-only science-ese”). That study is then reviewed by other experts in the field (“peer review”). These peers analyze and critique the study to see if it’s high enough quality to publish in a reputable medical journal like those in PubMed (not all studies pass this test!).
  2. The study is published and the university sends out a press release summarizing it for the media. This summary is meant to relay the important points and be easier to understand than understanding and interpreting the study itself.
  3. The media, often not trained in health science, takes that simplified summary, simplifies it further, spins it for their target audience, and creates a clickworthy headline and image. Why? They work for a media company or website who needs to maximize clicks and traffic to their site. These articles can stretch nutrition claims so they’re not *entirely* true anymore. Plus, they’re experts at knowing what hot button words and feelings are most likely to “go viral.” Sometimes they include expert interviews and comments, but that’s not always done in the most credible fashion (have you heard of “false balance“?). Don’t get me wrong—there are some amazing health journalists out there (like Julia Belluz, for example)—but as with everything, there is a range of quality online, so beware of overly simplified or sensationalized clickbait!
  4. Now we’re at the fourth step in the “broken telephone” phenomenon. Others (health websites, some professionals, or even anyone online with an interest in health and wellness, etc.) take that information from step 3 and use it to create their own content (blog or social media posts). Again, any benefits may be further embellished and there may be additional spin and clickbaity headlines and images to maximize traffic to their website.

Few people go straight to the original source of information in step 1 (that’s why it’s so important to link to your references—whatever they are!). Let’s be honest, not everyone has the time or is even versed enough to understand the “expert-only science-ese.” And sometimes there is a race to be the first to bring “breaking news” to the world.


Below is an example of this process shared by Dr. Yoni Freedhoff (an obesity doc that you should follow if you do anything at all regarding weight loss).

You can see how the media headline (very simple and “clickbaity”), differs from the press release (simplified into English), which differs from the actual study (written in “expert-only science-ese”):

green tea study vs headline science nutrition


Science is complex which makes it messy. It’s still 100 percent the best way to learn about and understand things like nutrition. Every day we find out something new by looking at it in new ways. Research continues to get closer and closer to the truth. And more, higher-quality studies continue to help us get closer to really understanding the complexity of the human body.

Signing off and toasting: To looking forward to new (and beautiful) research results!

Over to you

How frustrated do you feel when you hear conflicting nutrition information? How much of it is from the studies themselves vs. media/social media reporting? How impressive are Dr. Hall’s and Dr. Jacka’s studies?

I’d love to know (in the comments below)!

Want a fairly constant flow of credible health information (and content marketing/blog strategy)? Follow me on Twitter.

Originally published Feb 2020; updated with even more awesomeness Nov 2020.


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I’m Leesa Klich, MSc., R.H.N.
Health writer – Blogging expert – Research nerd.

I help health and wellness professionals build their authority with scientific health content. They want to stand out in the crowded, often unqualified, market of entrepreneurs. I help them establish trust with their audiences, add credibility to their services, and save them a ton of time so they don’t have to do the research or writing themselves. To work with me, click here.

Behind the scenes of nutrition science

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