Welcome to Straight Talk on Health, I’m your host Dr. Chet Zelasko. Straight Talk on Health is a joint production with WGVU in Grand Rapids MI. I examine the world of health. Whether it’s research that makes the news, another miracle diet, or a new food fad, I look at the science behind them, and let you know whether it’s real or not. You can check out other things that I do on my website drchet.com and sign up for my free emails.
Ultra-processed food has been in the news again. Sometimes it seems like it's just one constant news cycle but in reality, this look at the foods we eat extends over several research papers published in the last few months. I read the press releases as well as several articles by health columnists. I found and read the research papers and other supporting research. I’ve narrowed it down to a few questions about UPFs. Let’s see what I found to answer them in the research.
Let's begin with a working definition of ultra-processed foods (UPF). UPFs are substances extracted from foods that are altered chemically or mechanically, combined with flavor enhancers and other additives, and formed into consumer products that are highly palatable. What are the key words in that part of the definition?
Altered chemically can mean a natural process like using water or enzymes typically found in the body or using chemicals like alcohol, vinegar, or other chemicals to extract the desired substance. Mechanically altered can mimic the type of action in chewing or drying the food and chopping it up using sort form of blade or grinder. Flavor enhancers can run the gamut from sweeteners to artificial flavors. Additives can be binders to keep the new shape or preservatives like citric acid to prevent spoilage. The problem is that the finished products are usually high in calories and appeal to every taste sensation humans possess: salty, sweet, and umami.
Before I continue, I have to try to define umami. Everyone knows it when they taste it but getting a handle on it seems elusive. If we look at the Merriam Webster definition, it is the taste sensation that is produced by several amino acids and nucleotides (such as glutamate and aspartate) and has a rich or meaty flavor characteristic of cheese, cooked meat, mushrooms, soy, and ripe tomatoes. The Wikipedia definition adds the terms savory or savory-ness characteristic of soups or broths. Beyond that, there are no words that accurately define it; I just know it when I taste it and you probably do too. Because it's a desirable taste sensation, it can make foods seem addictive.
Back to ultra-processed foods. The manufacturing techniques themselves can change the structure of the original component and include extrusion, molding and preprocessing by frying. Simply stated, UPFs are designed to be irresistible to eat and keep eating.
The first question is simple: Do UPFs in the diet contribute to an increase in calorie intake? The answer is yes. Population studies of nutritional intake have demonstrated that Westernized countries where UPF are available result in additional caloric intake when compared with people who have low intakes of UPF. These studies are based on food frequency questionnaires which, as I've said repeatedly are not my favorite way to analyze diets.
However, the increase in caloric intake in well controlled studies where people are offered an ad lib UPF based diet versus a low UPF diet showed that people will eat up to 500 calories per day more on a UPF diet then on a diet that doesn't contain UPF foods. It seems clear that eating UPF foods can result in eating extra calories.
The next question to consider with UPF is this: Do you absorb more calories from UPF than you would from minimally processed food? The answer appears to be yes but requires some explanation. Keep in mind that UPF has been mechanically and chemically altered during the manufacturing process. The original grains of wheat, corn, or even something like carrots bear no resemblance to its original form. The components, especially the fiber, has been decimated.
What's the big deal? The normal chemical bonds that make up the food matrix are no longer in the same form as they were. Therefore, they require less digestion and can be potentially absorbed much faster starting in the small intestine.
That can mean a couple of things. The higher the proportion of UPF in the diet, the more calories from carbohydrates can enter the bloodstream faster. Blood sugars increase more quickly. The extra calories can be converted into fat for storage if they are not used.
It also means that the food that could have fed our microbiome is no longer present. We've got plenty of calories but our microbiome is starving. What nutrients are missing? Fiber and resistant starch. What does it resist? Digestion and absorption. Those probiotics that make up the microbiome? That’s their food and without it, our microbiome is starving and not as healthy as it could be.
This all leads to a final question in my mind: is a calorie still just a calorie? Many today would probably say that no, it isn’t. The body doesn’t make more calories from the foods that we eat than they contain. If there were a study, on a group of overweight people on a calorie-restricted diet, one following the high UPF diet while the other a low UPF diet with more fiber and other nutrients, we could see if there were differences in weight loss and other health markers between the two groups. If that were done, then we would find out whether there were any real differences in the type of calories.
I said more than once in a STOH podcast that when it comes to losing weight, it was, it is, and it always will be about the calories. I always go back to the Minnesota Starvation Diet. In that study, the subjects were given only the foods that would available after WW II in war ravaged Europe. Bread. Potatoes and other root vegetables. Little to no protein and little fat. Normal weight men lost weight and continued to do so for the entire 6 months of the study. If it is just about the calories, then substituting UFP for the starvation diet and adjusting it on a weekly basis would get the same results today. I don’t see that study happening in normal weight subjects but in overweight and obese subjects? Sure, because as of this date, calorie restriction is not considered harming an individual who needs to lose weight.
Even though the clinical trials have had low numbers of subjects, they have given us some important information. UPFs expose us to more calories because we crave them more and eat more of them. They are also absorbed sooner and, while they haven't demonstrated that results in eating more of the UPF, the result is starving our microbiome that resides in our large intestine. That alone may have more of an impact than we realize at this point in time.
So the research will continue and I will stay on top of it. Until next time this is Dr. Chet Zelasko saying health is a choice people. Choose wisely today and every day.
1. Food Funct. 2016 May 18;7(5):2338-46. doi: 10.1039/c6fo00107f.
2. Food Funct 2017 Feb 22;8(2):651-658. doi: 10.1039/c6fo01495j.
3. https://doi.org/10.1016/j.cmet.2019.05.008
