Why nutrition research is so messy

https://www.vox.com/2016/1/14/10760622/nutrition-science-complicated

There was a time, in the distant past, when studying nutrition was a relatively simple science.

In 1747, a Scottish doctor named James Lind wanted to figure out why so many sailors got scurvy, a disease that leaves sufferers exhausted and anemic, with bloody gums and missing teeth. So Lind took 12 scurvy patients and ran the first modern clinical trial.

The sailors were divided into six groups, each given a different treatment. The men who ate oranges and lemons eventually recovered — a striking result that pointed to vitamin C deficiency as the culprit.

This sort of nutritional puzzle solving was common in the pre-industrial era. Many of troubling diseases of the day, such as scurvy, pellagra, anemia, and goiter, were due to some sort of deficiency in the diet. Doctors could develop hypotheses and run experiments until they figured out what was missing in people's foods. Puzzle solved.

Unfortunately, studying nutrition is no longer that simple. By the 20th century, medicine had mostly fixed scurvy and goiter and other diseases of deficiency. In developed countries, these scourges are no longer an issue for most people.

Today, our greatest health problems relate to overeating. People are consuming too many calories and too much low-quality food, bringing on chronic diseases like cancer, obesity, diabetes, and heart disease.

Unlike scurvy, these illnesses are much harder to get a handle on. They don't appear overnight; they develop over a lifetime. And fixing them isn't just a question of adding an occasional orange to someone's diet. It involves looking holistically at diets and other lifestyle behaviors, trying to tease out the risk factors that lead to illness.

Nutrition science has to be a lot more imprecise. It's filled with contradictory studies that are each rife with flaws and limitations. The messiness of this field is a big reason why nutrition advice can be confusing.

It's also part of why researchers can't seem to agree on whether tomatoes cause or protect against cancer, or whether alcohol is good for you or not, and so on, and why journalists so badly muck up reporting on food and health.

To get a sense for how difficult it is to study nutrition, I spoke to eight health researchers over the past several months. Here's what they told me.

1) It's not practical to run randomized trials for most big nutrition questions
burger
(Vetreno/Shutterstock)

In many areas of medicine, the randomized controlled trial is considered the gold standard for evidence. Researchers will take test subjects and randomly assign them to one of two groups. One group gets a treatment; the other gets a placebo.

The idea is that because people were randomly assigned, the only real difference between the two groups (on average) was the treatment. So if there's a difference in outcomes, it's fair to say that the treatment was the cause. (This was how James Lind figured out that citrus fruits seemed to have an effect on scurvy.)

The problem is that it's just not practical to run these sorts of rigorous trials for most important nutrition questions. It's too difficult to randomly assign different diets to different groups of people and have them stick with those diets for enough time to find clues about whether certain foods caused certain diseases.

"IN AN IDEAL WORLD, I WOULD TAKE THE NEXT 1,000 CHILDREN BORN, RANDOMIZE THEM INTO TWO DIFFERENT GROUPS, AND HAVE HALF OF THEM EAT NOTHING BUT FRESH FRUIT AND VEGETABLES FOR THE REST OF THEIR LIVES"
"In an ideal world," said the British physician and epidemiologist Ben Goldacre, "I would take the next 1,000 children born in Oxford Hospital, randomize them into two different groups, and have half of them eat nothing but fresh fruit and vegetables for the rest of their lives, and half eat nothing but bacon and fried chicken. Then I'd measure who gets the most cancer, heart disease, who dies the soonest, who has the worst wrinkles, who's the most clever, and so on."

But, Goldacre adds, "I would have to imprison them all, because there’s no way I would be able to force 500 people to eat fruits and vegetables for a life.’"

It's undeniably a good thing that scientists can't imprison people and force them to stick to a particular diet. But it means that real-world clinical trials on diet tend to be messy and not so clear-cut.

Take the Women's Health Initiative, which featured one of the biggest and most expensive nutrition studies ever done. As part of the study, women were randomly assigned to two groups: One was told to eat a regular diet and the other a low-fat diet. They were then supposed to follow the diet for years.

The problem? When researchers collected their data, it was clear that no one did what they were told. The two groups basically had followed similar diets.

"They spent billions of dollars," says Walter Willett, a Harvard physician and nutrition researcher, "and they never tested their hypothesis."

Conversely, it is possible to conduct rigorous randomized control trials for very short-term questions. Some "feeding studies" keep people in a lab for a period of days or weeks and control everything they eat, for example.

But these studies can't measure the effects of specific diets for decades — they can only tell us about things like short-term changes in cholesterol. Researchers then have to infer what long-term health effects might result. There's still some educated guesswork involved.

2) Instead, nutrition researchers have to rely on observational studies — which are rife with uncertainty
coffee
(Vetreno/Shutterstock)

So instead of randomized trials, nutrition researchers have to rely on observational studies. These studies run for years and track very large numbers of people who are already eating a certain way, periodically checking in to see, for example, who develops heart disease or cancer.

This study design can be very valuable — it's how scientists learned about the dangers of smoking and the benefits of exercise. But because these studies aren't controlled like experiments, they're a lot less precise and noisy.

An example: Say you wanted to compare people who eat a lot of red meat with fish eaters over many decades. One hitch here is that these two groups might have other differences as well. (After all, they weren't randomly assigned.) Maybe fish eaters tend to be higher-income or better-educated or more health-conscious, on average — and that's what's leading to the differences in health outcomes. Maybe red meat eaters are more likely to eat lots of fatty foods or smoke.

Researchers can try to control for some of these "confounding factors," but they can't catch all of them.

3) Another difficulty: Many nutrition studies rely on (wildly imprecise) food surveys
kiwi fruit
(takiwa/shutterstock)

Many observational studies — and other nutritional research — rely on surveys. After all, the scientists can't hover over every single person and watch what they eat for decades. So they have subjects report on their diets.

This poses an obvious challenge. Do you remember what you ate for lunch yesterday? Did you sprinkle nuts or dressing on your salad? Did you snack afterward? Exactly how many potato chips did you eat?

Chances are you probably can't answer these questions with any certainty. And yet, a lot of nutrition research today rests on just that kind of information: people's self-reporting from memory of what they ate.

When researchers examined these "memory-based dietary assessment methods," for a paper in the Mayo Clinic Proceedings, they found that this data was "fundamentally and fatally flawed." Over the 39-year history of the National Health and Nutrition Examination Survey — which is a national study based on self-reported food intake — the researchers found that the alleged number of calories consumed by 67 percent of the women in the study was not "physiologically plausible" given their body mass index.

"I WANT A CAMERA, A STOMACH IMPLANT, A POOP IMPLANT, AND A THING IN THE TOILET THAT GRABS YOUR PEE AND POOP BEFORE YOU FLUSH IT AWAY AND ELECTRONICALLY SENDS INFORMATION OFF ABOUT WHAT WAS IN THERE"
This may be because people lie about what they eat, offering answers that are more socially acceptable. Or it may be a simple failure of memory. Whatever the cause, this leaves researchers in a tricky place, so they've developed protocols to account for some of those errors. (For more on the problems with nutrition surveys, see this FiveThirtyEight story.)

Christopher Gardner, a Stanford nutrition researcher, says in some studies he provides food for people. Or he has dietitians go over people's diet in detail, checking it against their bodyweight and health outcomes to make sure it seems valid. He builds in margins of error to account for potential problems in recall.

But he conceded that he and others in his field dream of having better tools, like chewing and swallowing monitors or wrist motion detectors that track "plate-to-mouth motion."

Even better, said Gardner: "I want a camera, a stomach implant, a poop implant, and a thing in the toilet that grabs your pee and poop before you flush it away and electronically sends information off about what was in there."

4) More complications: People and food are diverse
As if the problems with observational studies and survey data weren't enough, researchers are also learning that different bodies have really different responses to the same food. That makes nutrition research even more difficult, introducing another confounding factor.

In a recent study published in the journal Cell, Israeli scientists tracked 800 people over a week, continuously monitoring their blood sugar levels to see how they responded to the same foods. Every person seemed to respond wildly differently, even to identical meals, "suggesting that universal dietary recommendations may have limited utility," the researchers wrote.

"It's now clear that the impact of nutrition on health cannot be simply understood by assessing what people eat," said Rafael Perez-Escamilla, a professor of epidemiology and public health at Yale, "as this is strongly influenced by how the nutrients and other bioactive compounds derived from foods interact with the genes and the extensive gut microbiota that individuals have."

burger comparison
A hamburger at a fast-food restaurant (left) will have different fat and salt content compared with one made at home. (Shutterstock)

Making things even more maddeningly complicated, seemingly similar foods can differ wildly in nutrition profile. A local, farm-fresh carrot will probably be less diluted in its nutrients than a mass-produced baby carrot that's been bagged in the grocery store. A hamburger at a fast-food restaurant will have different fat and salt content compared with one made at home. Even getting people to better report on every little thing they put into their bodies can't completely address this variation.

There's also the issue of food replacement: When you chose to eat something, you're usually eating less of something else. So if a person decides to stick to a diet mostly composed of legumes, for example, that means he's not eating red meat or poultry. This raises a question in studying his health outcomes: Was it the legumes he ate lots of or the meat he didn't eat that made the difference?

The last problem is nicely illustrated by studies of dietary fat. When researchers followed people who ate low-fat diets, they realized that health outcomes were really affected by what study participants replaced the fat with. Those who replaced fat with sugary, refined carbohydrates ended up having obesity and other health issues at least as frequently as those eating higher-fat diets.

5) Conflict of interest is a huge problem in nutrition research
carrots vegetables
(takiwa/shutterstock)

There's one final problem with nutrition research that adds to the confusion. Right now, nutrition science is horribly underfunded by government — leaving lots of space for food companies and industry groups to sponsor research.

This means, quite simply, that food and beverage makers pay for many nutrition studies — with sometimes dubious results. More troubling: The field of nutrition research hasn't quite caught up to medicine when it comes to building in safeguards to address potential conflicts of interest.

"So much research is sponsored by industry," wrote nutrition and food policy researcher Marion Nestle in a recent issue of JAMA, "that health professionals and the public may lose confidence in basic dietary advice,"

Industry-funded studies tend to have results that are more favorable to industry. Between March and October last year, Nestle identified 76 industry-funded studies. Of those, 70 reported results that were favorable to the industry sponsor. (To read more about corporate sponsorship of nutrition research, check out this Eater feature.)

"In general," she wrote, "independently funded studies find correlations between sugary drinks and poor health, whereas those supported by the soda industry do not."

6) Even with all those faults, nutrition science isn't futile
pizza2
(Vetreno/Shutterstock)

The problems with nutrition research may make it seem impossible to know anything about diet and nutrition. But that's not true. Researchers have used all these imperfect tools to learn some important things over the years. Slow and careful science can pay off.

"Without nutritional research," said Frank B. Hu, a professor of public health and nutrition at Harvard, "we would not know that folate deficiency among pregnant women causes birth defects; we would not know trans fat is bad for heart disease; and we would not know drinking too much soda increases risk of diabetes and fatty liver disease."

I asked the researchers about what nutrition science they trust. Generally, they said, you should always consider all the available research on a question, and not just single studies. (For this, systematic reviews or meta-analyses are helpful.)

They also look to see if different types of studies on a question — clinical trials, observational data, lab studies — were all pointing in the same direction, toward a common conclusion. Different studies in different settings with different methodologies that come to similar results on the same question give a reasonably good indication that there's a link between a particular diet and a certain health outcome.

Paying attention to the source of funding behind the research is key, too. "Research funded by independent government agencies or foundations tends to be more credible than industry-funded research," says Nestle, "mainly because the study designs tend to be more open-ended."

On questions of how to eat, none of the researchers talked about seeking out specific foods or cutting others. They didn't make bold claims about the effects of particular fruits or vegetables or meats beyond simply suggesting that a "dietary pattern" could be "healthy."

This broad advice was reflected by a consensus statement from a very diverse group of nutrition researchers, who recently got together to discuss what they agree on about food and health.

Here's what they came up with:

A healthy dietary pattern is higher in vegetables, fruits, whole grains, low- or non-fat dairy, seafood, legumes, and nuts; moderate in alcohol (among adults); lower in red and processed meats; and low in sugar-sweetened foods and drinks and refined grains.

Additional strong evidence shows that it is not necessary to eliminate food groups or conform to a single dietary pattern to achieve healthy dietary patterns. Rather, individuals can combine foods in a variety of flexible ways to achieve healthy dietary patterns, and these strategies should be tailored to meet the individual’s health needs, dietary preferences and cultural traditions.

Anyone who tells you it's more complicated than that — that particular foods like kale or gluten are killing people — probably isn't speaking from science, because, as you can see now, that science would actually be near impossible to conduct.

You have to listen to YOUR body and be YOUR OWN scientist, use intuition, experiment, safety, logic and reason

Nutrition Science isn't that complicated. This is a credible source:

https://NutritionFacts.org/

Nutrition is, however, complicated by industry funded studies, bro scientists ... and crappy websites like Vox

I created this forum at least in part because of industry sponsored research compromising our health.

In most "health food markets" many packaged, pro-healthy implied products usually are made with canola oil (health enemy, pro-inflammatory and anti-hair).

Also prior to this forum, I received a lot of flak from "pharma bros" or reductionist types presuming that anything natural was akin to snake oil. Many did not want to hear that saturated fat was and is pro-health and pro-hair (regardless if its derived from vegetable or animal sources).

That's just the very tip of the iceberg, because so many truths have been obscured by deep conditioning from misinformation in text, ads, media, etc.

I've read countless studies from the last century and the current. The further back you go, the more genuine the writing and language is. Let's say if you're reading something in the early 1900's or before, it will be easy to understand, thoughtful and inquisitive. As you read into the 1970's, 80's and beyond, and especially post 2000, the technical-ese increases and similar phrases begin to appear, such as ("X" item does some amazing things, but because we are looking for drug targets that will mimic certain pathways, receptors of said plant, substance or "X," we will state the more research is needed to confirm that it works).

Therefore, no conclusion is ever drawn on anything actually working (if there's no patent).

Also, nutritional research is filled with bias and the JOURNAL OF ORTHOMOLECULAR MEDICINE is intentionally not indexed in the National Institute of Health. Furthermore, Academia is dependent on heavy grants from food and chemical industry, who has a way of silencing progress or at least obscuring the truth.

Also, last but not least is that 'educated' dietitians are programmed to believe industry fabrication. Things that should be taught or known about are simply long forgotten.

Nutritionfacts.org is biased, Vox interviewed actual researchers in the fields and the points they brought up are legit. Animal Studies, short term studies are just the tip of the Iceberg.

I use to go to Nutritionfacts.org, but realized he is biased towards a vegan/vegetarian studies and cherry picks data

CausticSymmetry wrote:I created this forum at least in part because of industry sponsored research compromising our health.

In most "health food markets" many packaged, pro-healthy implied products usually are made with canola oil (health enemy, pro-inflammatory and anti-hair).

Also prior to this forum, I received a lot of flak from "pharma bros" or reductionist types presuming that anything natural was akin to snake oil. Many did not want to hear that saturated fat was and is pro-health and pro-hair (regardless if its derived from vegetable or animal sources).

That's just the very tip of the iceberg, because so many truths have been obscured by deep conditioning from misinformation in text, ads, media, etc.

I've read countless studies from the last century and the current. The further back you go, the more genuine the writing and language is. Let's say if you're reading something in the early 1900's or before, it will be easy to understand, thoughtful and inquisitive. As you read into the 1970's, 80's and beyond, and especially post 2000, the technical-ese increases and similar phrases begin to appear, such as ("X" item does some amazing things, but because we are looking for drug targets that will mimic certain pathways, receptors of said plant, substance or "X," we will state the more research is needed to confirm that it works).

Therefore, no conclusion is ever drawn on anything actually working (if there's no patent).

Also, nutritional research is filled with bias and the JOURNAL OF ORTHOMOLECULAR MEDICINE is intentionally not indexed in the National Institute of Health. Furthermore, Academia is dependent on heavy grants from food and chemical industry, who has a way of silencing progress or at least obscuring the truth.

Also, last but not least is that 'educated' dietitians are programmed to believe industry fabrication. Things that should be taught or known about are simply long forgotten.

I agree 100 percent

Hairbeback wrote:Nutritionfacts.org is biased, Vox interviewed actual researchers in the fields and the points they brought up are legit. Animal Studies, short term studies are just the tip of the Iceberg.

I use to go to Nutritionfacts.org, but realized he is biased towards a vegan/vegetarian studies and cherry picks data

... Why don't you give us a few examples of cherry picked studies?

All his studies on eggs and meat are cherry picked. He never cites any studies on that show positive results for eating eggs or meats, he always does video on the negative one. I was subscribed to his channel for a year, but caught on to his vegan/vegetarian agenda.

He has his bias he's human I get it. Do I like factory farming? No, Do humans each too much meat? IMO yes. Do I think eating meat is necessary for some people? yes. My mother became anemic and her blood pressured lowered after stopping eating meats, She was Vegan for 5 years.....she got pale one day, almost fainted and had to bring her to the doctor. She didn't have enough iron in her blood. Maybe she could of ate more food rich in iron like beets? I don't know.

Is Mcgregor wasn't biased he would post positive studies on eating eggs and certain meats

Hairbeback wrote:All his studies on eggs and meat are cherry picked. He never cites any studies on that show positive results for eating eggs or meats, he always does video on the negative one. I was subscribed to his channel for a year, but caught on to his vegan/vegetarian agenda.

He has his bias he's human I get it. Do I like factory farming? No, Do humans each too much meat? IMO yes. Do I think eating meat is necessary for some people? yes. My mother became anemic and her blood pressured lowered after stopping eating meats, She was Vegan for 5 years.....she got pale one day, almost fainted and had to bring her to the doctor. She didn't have enough iron in her blood. Maybe she could of ate more food rich in iron like beets? I don't know.

Is Mcgregor wasn't biased he would post positive studies on eating eggs and certain meats

A Vox link and an anecdote about your mother. Nice.

Vox interviewed scientists who preformed actual research if you actually read the actual article. The fact you think nutrition research is easy says a lot about your grasp of the big picture.
You can enjoy all the Vegan propaganda you want, I do my own research and way both sides.
My favorite Dr Greger video is when he said Fish causes type 1 diabetes

Hairbeback wrote:
My favorite Dr Greger video is when he said Fish causes type 1 diabetes

Greger publicised the findings of 6 meta-analysis. He didn't conduct those studies.

So you have an elaborate conspiracy theory. Why don't you break down why this video is wrong:

What conspiracy theory? Are you being fragile? Is your ego dent that I don't worship the drop out doctor Greger?

The video is awful, and a very poor analysis, he did a great job of cherry picking a few parts of these meta studies and making the possible claim that fish or maybe chemicals in the fish cause type 1 diabetes.

On top of that his anaylisis mentions nothing about the long term effects of eating meat and not eating meat.


What type of fish are Americans eating? Fish sticks? Fish sandwiches? It doesn't specify, the video is totally lacking I could go on and on, but I don't want to make you think to much. Just buy your priest books and fill his pocket books.

Only redeeming thing about the video was possible contaminants in fish that might be a problem. A lot of cultures live off fish and have lower type 2 diabetes rates than americans

Here's your conspiracy theory:

Hairbeback wrote:
You can enjoy all the Vegan propaganda you want, I do my own research and way both sides.

Vegan Propaganda. Biased. Priest, etc. Your posts are rife with rhetoric but little substance.

Central to claims meat -- and animal products in general -- are unhealthy is the evidence that saturated fat and dietary cholesterol are unhealthy. That isn't too hard to understand. For most.

Anyway. Let us all know when you actually have a cohesive argument to make.

I'm not looking to argue. Especially with a guy who can't interpret the studies he reads, its your health...I could care less what happens, enjoy the vegan propaganda

Hairbeback wrote:I'm not looking to argue. Especially with a guy who can't interpret the studies he reads, its your health...I could care less what happens, enjoy the vegan propaganda

Compelling debate based on an anecdote about your Mum and some guy called Mcgregor? Nice.

Go out and buy yourself a Big Mac Dirty Hairy. Enjoy yourself ; )

Like I said you can't comprehend what you read, the video is suspect and I willing to bet most people on the board would agree. Enjoy your day hopefully you spend it learning how to interpret studies

Hairbeback wrote:Like I said you can't comprehend what you read, the video is suspect and I willing to bet most people on the board would agree. Enjoy your day hopefully you spend it learning how to interpret studies

Most people would agree that multiple meta-analysis from independent researchers deserve a better counter-argument than "My Mum". You want fries with that?

What meta research? it was never presented in depth with the video. He pulled a few sentences out of 6 meta studies and then went on about agent orange. 6 studies are not enough to declare the science is finished, it would go up against hundreds of other studies on fish. The video also failed to mention if they were eating farmed raised fish which is processed or wild fish caught in the ocean. There is so many things wrong with the video I can go on and on. I'll take some fries and a burger.....now go tell everyone who doesn't care how your're a vegan

Hairbeback wrote:What meta research? it was never presented in depth with the video. He pulled a few sentences out of 6 meta studies and then went on about agent orange. 6 studies are not enough to declare the science is finished, it would go up against hundreds of other studies on fish.

Dirty Hairy here doesn't understand what a meta-analysis is ... Why is your Nutrition Research So Messy?

... I wonder.

Its a statistical method of combining multple studies, your vegan prophet only used 6 out of hundreds of studies and failed to state many variables

Hairbeback wrote:Its a statistical method of combining multple studies, your vegan prophet only used 6 out of hundreds of studies and failed to state many variables

You just Googled that didn't you?

And now we're making progress ...

Perhaps I could cite key passages of the studies in question and challenge your comprehension of them? You're not nearly entertaining enough and I don't have time for 1 to 1 tuition.

More broadly, it's a shame this forum isn't a place to exchange good research and the results of blood tests, deficiencies, trial and error. If it were we might hone in on critical bio-markers. But ya Mum.

Yea I googled it, when my whole point the whole time was how studies possibly conflicting with hundreds of other studies and the variable greger never mention (farmed fish/wild caught fish) length of studies, processed fish like fish sticks and mcdonald fish sandwiches.

You'll get there one day vegan nazi

Here read this and when you are done get back to me. We need to refine your scientific knowledge or more commonly known as pseudo skepticism

https://theethicalskeptic.com/tag/anecdote/

Get busy SON

Aww. Looks like someone's a bit triggered.

Take it easy, Hairy. Me and you both have better things to do.