Personalized Nutrition: Ready for Prime-time?

Welcome to 2018, everybody - a time where we can hand-select everything from the ingredients in our fast-casual salad to the patterns we get in our Sock of the Month Club, all from the comfort of our own homes and offices. With customization as king, the demand for a more personal approach to health is growing stronger. In parallel, the science community has become increasingly aware that “healthy” doesn’t mean the same thing to everybody (and is pretty hard to define).

In a world where we can throw down a few C-notes for direct-to-consumer tests of our ancestry and health risks, it only seems logical that from that information, we’d be able to design diets adapted to our genetics, exercise habits and lifestyles. But what do we really know about the field of personalized nutrition? Let’s take a look at this rapidly evolving – though still hazy – area of research. 

Why personalized nutrition?

For decades, nutrition recommendations have followed a one-size-fits-all template. Eating at least five servings of fruits and vegetables a day and making half your grains whole grains have been the central guidelines aimed at improving the eating patterns of large groups of people. Despite their importance for public health, many people struggling with their health may feel that generic suggestions to improve their condition aren’t very helpful, and our consumer research shows that confusion about food choices and nutrition is all too common. Removing some of the guessing game from what a “healthy diet” means is an enticing prospect.

What exactly is personalized nutrition?

A personalized nutrition approach is based on the idea that by customizing nutrition advice, we may be more motivated to make dietary changes to improve our health and lower risk of conditions like obesity, type 2 diabetes and heart disease. Personalized nutrition is at the heart of what registered dietitians have been doing since the advent of the profession: delivering tailored nutrition advice that fits the physical, clinical and emotional needs of their patients.

But recently, things have become much more specific. Now, personalized nutrition involves a more in-depth approach, assessing a person’s genetics, dietary habits, physical activity, sleep behaviors,  microbiome, and even the metabolome, which is a term describing the small molecules produced by our body that may have effects on the way we function.

Exciting research on understanding the relationship between food, genes and lifestyle is underway as we speak, and we’re already seeing interesting results. In one study, researchers monitored the blood sugar, diets, microbiome and other traits of over 800 people, which allowed them to build an algorithm to predict how a person’s blood sugar levels would spike after eating a meal. Using this information, they were able to design customized dietary plans to control blood sugar – and the computer algorithm worked slightly better than a dietitian’s advice (gulp). Over in Europe, the Food4Me Project and the PREDIMED study have demonstrated clear evidence that individualized dietary advice can be a key element of disease prevention.

Sounds pretty good. Are there any limitations?

The main drawback is this: There’s still a huge gap between what we know about the relationship between our eating patterns and our genes (and vice versa) and the interplay with our behaviors and environments. Diseases like obesity and diabetes are complex – we can’t just flip one switch and solve the problem. There are multiple genetic pathways that could predispose a person to gaining weight or having trouble controlling their blood sugar. And this doesn’t even begin to consider a person’s lifestyle habits, gut microbiome composition or environment. There’s so much to be done before we can hone in on what’s right for any given person.

Another major shortcoming of personalized nutrition is its reliance on understanding exactly what a person eats, which is important in determining how our bodies respond to different foods and nutrients. Let’s say that you find out about a genetic variation that affects your dietary fat metabolism, and your doctor recommends eating more heart-healthy omega-3s to make up for it. They’d probably want to track how much salmon or olive oil you were eating to see how these foods affected your health.

The problem? Study after study has demonstrated that reporting dietary intake is full of omissions and inaccuracies. After all, who wants to tell the registered dietitian that they didn’t actually eat any fish last week, and by the way, an accidental three (…was it four?) margarita happy hour was essentially Tuesday’s dinner? Even if a person tries their hardest to be an open book, our methods for accurately assessing dietary intake are notably flawed. Once we find ways to better capture what we’re eating and drinking, health professionals will be able to deliver better recommendations.

Despite a clear lack of readiness for prime-time, there are already multiple companies hawking personalized diets based on simple blood and saliva tests. Little is known about how well they work, if at all, and many are based on information that’s not grounded in science. A 2015 meta-analysis found the evidence behind these tests to be minimal and full of conflicting information, and concluded that they “cannot be presently recommended”, which aligns with the Academy of Nutrition and Dietetics position on direct-to-consumer nutritional genomics tests.

Putting personalized nutrition into perspective

As our knowledge and skill in personalized nutrition continues to evolve, let’s not forget about the basics of a healthy eating pattern: a diet rich in fruits, vegetables, whole grains and lean protein, along with keeping total calories in check. These recommendations may not be flashy, but they’ve withstood the test of time.