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In our never-ending quest to get healthy, there's a constant, nagging hope that we'll find a hidden key to fitness — some trick or piece of information that finally makes it easy to look and feel how we want.
That's why bizarre diets take off and nutrition "breakthroughs" tend to go viral (even though these findings rarely change what we know about eating healthy).
Recently, dieters and investors alike have started betting on companies offering "personalized nutrition": dietary advice supposedly based on our own genes or even the bacteria living in our guts.
The pitch from such companies goes something like this: We're all unique, and we know that our genes and bacterial populations have a huge impact on our health — so harnessing that information can give us a tailored guide to healthy eating.
But there's reason to believe modern science may not be up to this task just yet.
The promise of personalized nutrition
"No two humans are alike and no two diets are good for everyone," says Naveen Jain, the founder of a company called Viome, which monitors its clients' microbiomes (specifically, their gut bacteria) and other biomarkers and uses that data to give dietary advice. Viome charges its customers $99 a month (or $1,000 a year).
"We test you every 3 months to see how your body is reacting to carbs, protein, and fat, and we adjust your diet based on what is going on in your metabolic system," Jain says.
Personalized or precision dietary advice, like precision medicine, is based on the realization that what works for one person doesn't necessarily work for another — a perspective shift that could transform the way we think of health in general. People with certain genetic variants thrive on high fat diets, while others are much more sensitive to the effects of consuming dietary cholesterol. That's the reason why so many companies are offering these DNA- and now also microbiome-based dietary services.
But Ginger Hultin, a registered dietitian nutritionist and spokesperson for the Academy of Nutrition and Dietetics, tells Business Insider that microbiome testing doesn't yet have any proven practical applications.
"It's too early," she says. "Right now, the science is still up and coming on dietary interventions for supporting the microbiome."
Our gut bacteria influence our metabolism, immune system, and other aspects of health, John Mathers, the director of the Human Nutrition Research Center at Newcastle University, tells Business Insider. But those complex interactions and relationships are not yet fully understood by health scientists.
"So far, we have limited evidence of how particular nutrients, foods or dietary patterns influence the gut microbiota and vanishingly little evidence of how knowledge of the gut microbiome influences nutritional needs," Mathers says.
According to Hultin, the current scientific understanding of our gut suggests that the more diversity of bacteria in there, the better. And we know that a high-fiber, plant-based diet is associated with diverse gut flora. But that knowledge basically backs up the idea that vegetables are good for you — standard advice that any dietitian or nutritionist could provide. Beyond that, Hultin says, we don't know enough to tell people how to eat based on their gut bacteria.
ViomeBusiness Insider asked Jain if he could provide evidence that Viome's dietary advice (based on the microbiome and other metabolic biomarkers found in the gut and blood) improves health. He responded, "that's a question you should be asking 6 months or a year from now."
Jain also acknowledged that for now, Viome can't diagnose disease based on their analyses of customers' microbiomes. The company is instead hoping that it will learn to do so as technology advances.
Jain did, however, provide Business Insider with a number of studies indicating that the microbiome is connected to various chronic health conditions, ranging from obesity to Alzheimer's.
"Papers are showing that every single chronic disease — from Parkinson's to asthma — is directly linked to the microbiome," he says. "If you can balance your gut and remove chronic inflammation ... if we can do that, we can create a world where no one will ever get sick."
The problem, however, is that even if Viome does succeed in figuring out how to diagnose clients with certain conditions, no one has figured out how to cure any diseases by modifying the microbiome (with perhaps the exception of giving people a fecal transplant to fight off a Clostridium difficile infection). We're far from being able to "create a world where no one will ever get sick" based on treating the microbiome, good as that may sound.
"I don't think we know nearly enough about the microbiome to understand the significance of test results for dietary advice," Marion Nestle, a professor of nutrition and public health at New York University, tells Business Insider.
Dieting based on your DNA
In addition to personalizing dietary advice based on the bacteria in your gut, for years many companies have offered dietary services based on DNA tests — based on a science known as nutrigenomics.
"Our groundbreaking DNA test will change the way you think about fitness and nutrition forever," reads the website of one such company, called DNAFit. "Whether you're looking to shape up, build muscle or just want to eat a little healthier, your genetics hold valuable information about the best way to do this, just for you."
In certain cases, a dietitian or genetic counselor can find useful information in a DNA test — certain genes may indicate a basic intolerance for foods like lactose or caffeine, and genes that are common among people with obesity might help explain why a person struggles to regulate their eating (though for the most part, genetic explanations for conditions like obesity are complex and not fully understood).
But this type of genetic information is most likely to be helpful in specific cases involving some kind of unsolved food sensitivity mystery, a rare occurrence since most people are already aware that they react poorly to certain foods.
Mike Nudelman/Business InsiderHultin says that so far, nutrigenomics "is actually further along [than microbiome research] and there's some really interesting things going on there."
But Nestle is skeptical.
"I suppose that DNA testing could turn up evidence of inborn metabolic errors" that make it hard for people to process certain foods, she says, "but most adults with them have figured out what they have to do to avoid symptoms."
A position paper from the Academy of Nutrition and Dietetics concurs: "The use of nutrigenetic testing to provide dietary advice is not ready for routine dietetics practice," it states.
Are any of these services worth the money?
So is a DNA test or microbiome analysis worth it as a way to help you eat healthier? So far, most experts seem to think the answer is not yet.
Several reviews of existing research have found no evidence that genetic information, including the data gathered by several existing companies, improves dietary health. In other words, even if there's useful information hidden in our DNA, we haven't learned enough about genetics to use information successfully.
"I am skeptical about many of these products because of the slender — or nonexistent — scientific basis for them," John Mathers told Vox.
Hultin also points out that there are many things people can attempt to test or change before shelling out for one of these dietary services.
"Is there some work that needs to be done on your diet, lifestyle, stress, or sleep?" she asks. Genetic testing is likely only useful after you've dealt with the obvious issues and gotten professional advice, she says. And even then, any information you gain is probably best put into context by a medical professional.
Mathers warns consumers to beware of the initial excitement that usually surrounds new dietary trends.
"In my view, there are been a lot of hype about links between the microbiome and health and, based on current evidence, the idea that knowledge of our microbiome can be used to tell us what we should eat is part of that hype," he says.
This doesn't mean that personalized nutrition services can't offer useful guidelines. Many of the companies that offer these products pair their testing results with advice from a nutritionist or other professional. Plus, much of their advice tends to be "eat more vegetables," which is a good suggestion for most people, even if they are charging a lot for that advice.
If nothing else, it might be fun to learn what's in your DNA or microbiome — though these are expensive ways to get that information. But don't expect them to solve some mystery of dietary health.
"The tests are fun but their usefulness has yet to be shown," says Nestle. "I'd rather spend the money on good dinners."