Processed Foods and Health: What are they and can they fit in your diet?

This week our intern Debbie Malakan and I got questions about processed foods quite a few times, therefore we did a bit of research and felt the need to clarify a few things:

    What do you think about when you hear the term “processed foods?” A bag of potato chips? What about roasted veggies? Does eating them affect your health? Most people think negatively about processed foods, thinking they should be avoided at all costs. However, almost all foods are processed to some extent. Any food that has been purposefully altered mechanically or chemically for nutrition, taste, or shelf life is considered processed.  For example, peeling, drying, curing, or cutting are all forms of processing. So where does the term ultra-processed come from?

     The NOVA Food System classifies food according to the extent and purpose of the processing it undergoes. There are four groups:
●    Group 1: Unprocessed or minimally processed foods. Unprocessed foods are edible parts of plants such as seeds, fruits, or leaves or of animals such as muscle, eggs, and milk. Minimally processed foods are natural foods altered by processes such as removing inedible or unwanted parts, drying, crushing, roasting, freezing, pasteurizing, or vacuum packaging (dried fruits, legumes, milk, leafy and root vegetables, granola, nuts, and spices.
●    Group 2: Processed Culinary Ingredients. These are substances obtained directly from group 1 foods by processes such as pressing, grinding, and milling. (Salt, sugar, and molasses obtained from cane or beet, honey extracted from combs, and syrup from maple trees.) (Butter, oils)
●    Group 3: Processed foods. These are simple products made by adding sugar, oil, salt, or other group 2 substances to group 1 foods (salted nuts, freshly made cheese, pickled vegetables, canned tuna)
●    Group 4: Ultra-processed food and drink products. These are foods that typically have five or more ingredients (carbonated drinks, ice cream, breakfast cereals, energy drinks, cake mixes, sausages, and burgers).

There’s much controversy about whether food processing affects health and to what extent it significantly affects diet quality and health outcomes.

     Studies that have claimed an association between ultra-processed food consumption and various chronic diseases have not been controlled for other well-established factors that can affect our health, such as physical activity, stress, genetics, comorbidities, mental health, and our relationships with friends and family.   In addition, these studies that assess dietary patterns and health have always been observational studies.

     An observational study in human nutrition collects information on people’s dietary patterns or nutrient intake and looks for associations with health outcomes.  There is no treatment or intervention therefore these studies can only identify correlation and cannot show that one factor causes another. There are many limitations to these types of studies such as participants under or over reporting dietary intake, foods containing multiple nutrients and non-nutrient components, and the way foods are prepared and combined differently.  Furthermore, the way a person metabolizes food can vary greatly.

     A stronger study design is an interventional trial or randomized controlled trial. These studies are double-blinded, placebo-controlled, randomized, and have an intervention. They are known as the “gold standard.” In these studies, we can confirm a causal relationship between exposure and outcome. Although a randomized controlled trial is the strongest study design, it’s challenging to study humans in a controlled environment.

     The first, and only thus far, randomized controlled trial examining the effects of ultra-processed foods defined by the NOVA classification system was done by the NIH in 2019.    They were able to take 20 adult volunteers for 28 days in an inpatient facility of a metabolic ward to study ultra-processed foods.  The study participants were randomly fed an ultra-processed diet for two weeks (bagel with cream cheese and turkey bacon) then two weeks a minimally processed diet (oatmeal with bananas, walnuts, and skim milk).  The results of this study were “People eating ultra-processed foods ate more calories and gained more weight than when they ate a minimally processed diet.”  (Keep in mind this was two pounds). Based on this study they are reviewing, and considering putting limits on ultra-processed foods in the 2025 dietary guidelines.

     There are limitations to this study.  First and foremost, the study was very small and a short duration.  Secondly the inpatient environment of the metabolic ward makes it very difficult to generalize these results in the outside world, and in free-living conditions.  It is also difficult to measure energy intake outside of the laboratory as diets typically cannot be followed for a long period of time. In addition, most people do not only eat ultra-processed foods, but a variety of foods, when given the opportunity and learn how to eat intuitively.

It’s important to remember that one food or ingredient will not improve or worsen your health.

     Eating some “ultra-processed” food will not cause you to have heart disease or diabetes.  One food will not make you fat, nor thin, healthy, nor unhealthy, as we do not only eat one food.  If you only ate chicken, you would have some nutrient deficiencies as well as if you only ate spinach or ice cream. Other than what we eat, our genes, and lifestyle habits such as how we manage stress, our sleep, relationships, levels of physical activity and even geographic location/access to foods, can impact our health.  Nutrition is just one part of your health.

     I worry that warning people about ultra-processed foods and adding them to the Dietary Guidelines next year, will further increase the anxiety, stress, and shame around food many of my patients struggle with, and possibly lead to orthorexia.  I am already hearing this from many adolescents in my office.  We all know there are more nutritious and less nutritious foods, but if we aim for eating a variety, all foods can fit. We also know that when we allow all foods and do not place moral value on them, in addition to listening to our bodies,  we eat in a more balanced way.

Warmly,

Maddy and Debbie

 

 

References:

https://www.nih.gov/news-events/news-releases/nih-study-finds-heavily-processed-foods-cause-overeating-weight-gain
Astrup, A., & Monteiro, C. A. (2022). Does the concept of “ultra-processed foods” help inform dietary guidelines, beyond conventional classification systems? debate consensus. The American Journal of Clinical Nutrition, 116(6), 1489–1491. https://doi.org/10.1093/ajcn/nqac230 .
Monteiro, C. A., Cannon, G., Levy, R., Moubarac, J.-C., Jaime, P., Martins, A. P., Canella, D., Louzada, M., & Parra, D. (n.d.). Nova. the star shines bright. World Nutrition. https://www.worldnutritionjournal.org/index.php/wn/article/view/5