Personalized Nutrition: There Is No One

It seems everyone has an opinion on nutrition these days. It's not even so much of an opinion anymore but a sort of dogma. "Thou shalt eat this way or risk ones health irreparably." You read it all over the internet and magazines every day. There is always someone spouting the "real" healthy diet we should all be eating. For the average person, these diet wars are frustrating and confusing. To make matters worse, some of these seemingly healthy diets can be downright harmful, especially if someone is already at high risk for chronic disease.

The truth is, we are learning more and more about biochemistry every day, and what we are finding is that everyone's body responds differently to different foods. Part of this is genetics, part of it is diet, and part of it is a host of other factors such as lifestyle, environment, and even a person's particular microbiome.

A recent study published in Cell Magazine provided great insight into this (1). Entitled "Personalized Nutrition by Prediction of Glycemic Response," it looked at the glycemic response among subjects eating similar food items. They had 800 non-diabetic participants who agreed to eat a particular breakfast containing 50g of carbohydrate every morning for a week while having their blood glucose continuously monitored. The researchers look at post-prandial (post meal) glucose in the morning but also evaluated their blood glucose levels the rest of the day while eating their normal diets.

Surprisingly, many subjects responded very differently to the exact same breakfasts. When it came to other foods later in the day, there were stark differences as well. Some saw huge spikes in glucose after high carb foods such as ice cream or bread, while others showed only a modest increase.

While it was interesting that so many differences could be seen between the participants with the very same foods, it was also interesting to note that the glucose response within a particular individual remained constant, ie if they ate the same meal the next day, their blood glucose response would be roughly the same. The researchers could even start to predict what their post-prandial blood glucose would be based on the choices they made.

This really got me to thinking. For years we've been told by the American Diabetes Association how to educate Diabetics on their diet. If you've ever been in my office you may have heard me talk about carb counting, glycemic index, and balanced meals. It is a one-size-fits-all approach. Diabetics can have 45-60 grams of carb per meal, for example, and we usually talk about healthy ways to stay within those guidelines. While these still have their place, it's clear the particular foods one chooses to meet those guidelines, and in fact even the guidelines themselves, are not set in stone.

That point has been made to me many times sitting in my office, listening to clients tell me how one bite of rice sends their glucose levels through the roof. Then another client tells me rice is fine, but heaven forbid if they have even a smidge of potatoes. First off, despite what my training told me, I believed them. I believed that for one of my clients rice was a huge no-no while for others it was not. While the standard ADA guidelines were no doubt helpful, I started to realize my approach had to change. I needed to understand my clients better to know how to direct them. I also needed them to understand their bodies so they could tell me what foods worked for them and what foods weren't right, despite what the "rules" said.

I'm glad I believe this before there was solid scientific proof to make the case, as going by intuition has helped me help my clients make better choices. Now thankfully we are starting to see the science bear this out, explaining why one person reacts a certain way to particular foods or nutrients while another reacts the exact opposite. While much of this is genetic, we are also seeing that a person's unique microbiome plays a huge role in how nutrients are utilized, even to the point of affecting body weight. Then of course there is stress, environment, exercise, and other lifestyle factors that play a role. It is so complex, and we have just scratched the surface.

Apart from Diabetes, there are also other conditions affected in varying ways by diet and lifestyle. Cardiovascular Disease is one such example. One particular way of eating may raise unhealthy cholesterol in one individual but have no negative effect in another. Exercise might improve lipid profiles in one person but do nothing for another. Again, the one-size-fits-all diet approach has to be re-thought.

Admittedly I am still learning a lot about this as well, especially in regards to testing and corresponding diet recommendations. There are more and more tests coming on the market claiming to decipher your genetics and make diet-based recommendations for you. The challenge lies in understanding which tests are of value and worth the hefty price tag that often come with them.

For now, if you feel a particular diet is not for you, listen to your body. What your neighbor or coworker or family member eats may not be the best plan for you. Tell those Paleo fanatics to pipe down. Continue to keep tabs on your health (regular check ups, routine exams, etc) and if anything negative turns up, pay careful attention to your diet as a first step. You may want to consider additional testing as well to help guide that diet. A Functional Dietitian, such as myself, can be a great help in that area.

Clearly personalized nutrition is here. The idea of diets that work for everyone is on its way out. Healthy diet is still key, but how that looks may vary. Make the best educated choice for yourself and tune out the rest.

1. http://www.cell.com/cell/fulltext/S0092-8674(15)01481-6