A week ago, I read about another really interesting “personalized nutrition” study[i] again looking at the differences in the way people respond to food. 34 participants kept a record of everything they ate for 17 days, while the researchers looked at stool samples over these 2+ weeks to see how their microbiomes responded to these foods.
While individual biomes did change depending on food choices, the actual nutritional content of food seemed to have little relationship to these changes. As these researchers point out, we currently have very little information on nutrients that affect gut bacteria. They used a database that provided information about 50 macro and micro nutrients (fats, carbs and proteins=macro; vitamins and minerals=micro) yet, as they point, “…these nutrient profiles ignore hundreds of additional chemical compounds present even in a single piece of fruit…and many other non-nutritive components of foods such as preservatives and food additives.”[ii] Really it comes as no surprise that there was little consistency in microbiome changes between people. That is, microbiome responses to food were completely individualized: I eat a banana, you eat a banana – our gut bacteria respond completely differently. Since microbiomes appear to be as individual as fingerprints, and we have no idea how each species reacts to this vast number of substrates (which is essentially defined as the food that makes things grow), this only makes sense.
One more items of particular note: firstly, two of the people in the study drank only a liquid meal replacement product during the study and yet their microbiomes varied day to day anyway, emphasizing this individuality as well as potentially demonstrating that food is not the only factor to affect our microbes. (Think about stress, or sleep, etc.!) In fact, a more varied diet actually led to greater biome stability!
As you all know, I love coincidences, so I was delighted when, directly after reading this research, I found another article from the same day about personalized eating.[iii] I’ve actually covered this topic before, in February 2018, looking at research out of the Weizmann Institute in Israel on how people have completely different glucose responses to the same food. It’s so darn interesting, though, and so pertinent to this blog post, it’s more than worth (briefly) repeating.
In 2015, these Israeli researchers conducted a 3-part study looking at how people respond completely metabolically differently to food. First, they tested glucose levels in 800 participants and confirmed that indeed, glucose levels varied considerably after eating the same food. They took this information (along with other factors like age and weight, etc.) and created an algorithm to try to predict this glucose response. They then confirmed the algorithm’s validity in a double blind randomized study in which they created customized diets for the participants using microbiome profiles and their algorithm…and by successfully lowering glucose responses in the participants, provided proof that the algorithm works.
This 2nd article I read that day was about another proof of concept study that was conducted this year, again using the algorithm to predict glucose response to food in 293 people. The results were actually pretty amazing. For example, “…serum glucose levels after eating a bagel with cream cheese rose by a low of 6 mg/dL in some individuals (low responders) to a high of 94 mg/dL in others (high responders). And some findings were counter intuitive to commonly held nutritional guidance, as evidenced by blood glucose levels that rose higher after eating a banana than after eating a cookie.” What’s also quite remarkable is that sometimes, combining foods lowers glucose response. One of the lead authors of this study points out that, “Sometimes a few almonds added into a certain food mitigated the glycemic response.”
In my previous post on this, I mentioned the company Day Two who is using this algorithm to test personal responses to foods. Unfortunately, the kit is $499, which I simply cannot afford at the moment. Otherwise, I’d be more than willing to act as a guinea pig. If any of you do give it a try, please share! I’d love to hear from you!
[ii] Johnson AJ, et al. Cell Host and Microbe 2019;25(6):789-802. doi.org/10.1016/j.chom.2019.05.005.