For many Americans, the convenience of pre-cooked and instant meals may make it easy to overlook the less-than-ideal nutritional information, but a team led by researchers at Tufts University and Harvard University hope that will change after recently discovering a link between the high consumption of ultra-processed foods and an increased risk of colorectal cancer.
In a study published Aug. 31 in The BMJ, researchers found that men who consumed high rates of ultra-processed foods were at 29% higher risk for developing colorectal cancer—the third most diagnosed cancer in the United States—than men who consumed much smaller amounts. They did not find the same association in women.
“We started out thinking that colorectal cancer could be the cancer most impacted by diet compared to other cancer types,” said Lu Wang, the study’s lead author and a postdoctoral fellow at the Friedman School of Nutrition Science and Policy at Tufts. “Processed meats, most of which fall into the category of ultra-processed foods, are a strong risk factor for colorectal cancer. Ultra-processed foods are also high in added sugars and low in fiber, which contribute to weight gain and obesity, and obesity is an established risk factor for colorectal cancer.”
The study analyzed responses from over 200,000 participants—159,907 women and 46,341 men—across three large prospective studies which assessed dietary intake and were conducted over more than 25 years. Each participant was provided with a food frequency questionnaire every four years and asked about the frequency of consumption of roughly 130 foods.
For the study in BMJ, participants’ intake of ultra-processed foods was then classified into quintiles, ranging in value from the lowest consumption to the highest. Those in the highest quintile were identified as being the most at risk for developing colorectal cancer. Although there was a clear link identified for men, particularly in cases of colorectal cancer in the distal colon, the study did not find an overall increased risk for women who consumed higher amounts of ultra-processed foods.
The Impacts of Ultra-Processed Foods
The analyses revealed differences in the ways that men and women consume ultra-processed foods and the prospective associated cancer risk. Out of the 206,000 participants followed for more than 25 years, the research team documented 1,294 cases of colorectal cancer among men, and 1,922 cases among women.
The team found the strongest association between colorectal cancer and ultra-processed foods among men come from the meat, poultry, or fish-based, ready-to-eat products. “These products include some processed meats like sausages, bacon, ham, and fish cakes. This is consistent with our hypothesis,” Wang said.
The team also found higher consumption of sugar-sweetened beverages, like soda, fruit-based beverages, and sugary milk-based beverages, is associated with an increased risk of colorectal cancer in men.
However, not all ultra-processed foods are equally harmful with regard to colorectal cancer risk. “We found an inverse association between ultra-processed dairy foods like yogurt and colorectal cancer risk among women,” said co-senior author Fang Fang Zhang, a cancer epidemiologist and interim chair of the Division of Nutrition Epidemiology and Data Science at the Friedman School.
Overall, there was not a link between ultra-processed food consumption and colorectal cancer risk among women. It’s possible that the composition of the ultra-processed foods consumed by women could be different than that from men.
“Foods like yogurt can potentially counteract the harmful impacts of other types of ultra-processed foods in women,” Zhang said.
Mingyang Song, co-senior author on the study and assistant professor of clinical epidemiology and nutrition at the Harvard T.H. Chan School of Public Health, added that, “Further research will need to determine whether there is a true sex difference in the associations, or if null findings in women in this study were merely due to chance or some other uncontrolled confounding factors in women that mitigated the association.”
Although ultra-processed foods are often associated with poor diet quality, there could be factors beyond the poor diet quality of ultra-processed foods that impact the risk of developing colorectal cancer.
The potential role of food additives in altering gut microbiota, promoting inflammation, and contaminants formed during food processing or migrated from food packaging may all promote cancer development, Zhang noted.
Analyzing the Data
With more than a 90% follow-up rate from each of the three studies, the research team had ample data to process and review.
“Cancer takes years or even decades to develop, and from our epidemiological studies, we have shown the potential latency effect—it takes years to see an effect for certain exposure on cancer risk,” said Song. “Because of this lengthy process, it’s important to have long-term exposure to data to better evaluate cancer risk.”
The studies included:
After an exclusionary process for past diagnoses or incomplete surveys, the researchers were left with prospective data from 159,907 women from both NHS studies and 46,341 men.
The team adjusted for potential confounding factors such as race, family history of cancer, history of endoscopy, physical activity hours per week, smoking status, total alcohol intake and total caloric intake, regular aspirin use, and menopausal status.
Zhang is aware that since the participants in these studies all worked in the healthcare field, the findings for this population may not be the same as they would be for the general population, since the participants may be more inclined to eat healthier and lean away from ultra-processed foods. The data may also be skewed because processing has changed over the past two decades.
“But we are comparing within that population those who consume higher amounts versus lower amounts,” Zhang reassured. “So those comparisons are valid.”
Changing Dietary Patterns
Wang and Zhang previously published a study that identified a trend in increased ultra-processed food consumption in U.S. children and adolescents. Both studies underscore the idea that many different groups of people may be dependent on ultra-processed foods in their daily diets.
“Much of the dependence on these foods can come down to factors like food access and convenience,” said Zhang, who is also a member of the Tufts Institute for Global Obesity Research. “Chemically processing foods can aid in extending shelf life, but many processed foods are less healthy than unprocessed alternatives. We need to make consumers aware of the risks associated with consuming unhealthy foods in quantity and make the healthier options easier to choose instead.”
Wang knows that change won’t happen overnight, and hopes that this study, among others, will contribute to changes in dietary regulations and recommendations.
“Long-term change will require a multi-step approach,” Wang added. “Researchers continue to examine how nutrition-related policies, dietary recommendations, and recipe and formula changes, coupled with other healthy lifestyle habits, can improve overall health and reduce cancer burden. It will be important for us to continue to study the link between cancer and diet, as well as the potential interventions to improve outcomes.
Research reported in this article was supported by awards from the National Institutes of Health’s National Institute on Minority Health and Health Disparities (R01MD011501), National Cancer Institute (UM1CA186107; P01CA087969; U01CA176726; U01CA167552; and R00CA215314), and a Mentored Research Scholar Grant in Applied and Clinical Research from the American Cancer Society. The content is solely the authors’ responsibility and does not necessarily represent the official views of the National Institutes of Health.
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
People
ARTICLE TITLE
Association of ultra-processed food consumption with colorectal cancer risk among men and women: results from three prospective US cohort studies
ARTICLE PUBLICATION DATE
31-Aug-2022
Food and health: the front-of-pack label is not enough, if the consumption of ultra-processed foods is not reduced
An Italian study, published in the British Medical Journal, analyses the combined health impact of the Nutri-Score front-of-pack labelling system and the degree of food processing according to NOVA
Peer-Reviewed PublicationISTITUTO NEUROLOGICO MEDITERRANEO NEUROMED I.R.C.C.S.
Foods are not only characterized by their nutritional composition, but also by the degree of processing, which is crucial to determine the overall food health potential. Its indication on the labels would therefore help consumers to choose with greater awareness.
These are the results of an Italian study by the Department of Epidemiology and Prevention at the I.R.C.C.S. Neuromed of Pozzilli in collaboration with the University of Insubria in Varese and Como, the University of Catania and the Mediterranea Cardiocentro of Naples. Published in the British Medical Journal, which also dedicated an editorial to this work, the study investigated what aspect of nutrition best defines the risk of mortality. The researchers followed for 12 years more than 22 thousand people participating in the Moli-sani Study, monitoring their health status and associating it with eating habits, taking into account both the nutritional composition of the diet and the degree of food processing.
"Our results - says Marialaura Bonaccio, epidemiologist of the Department of Epidemiology and Prevention at the IRCCS Neuromed of Pozzilli and first author of the study - confirm that the consumption of both nutrient-poor or ultra-processed foods independently increases the risk of mortality, in particular from cardiovascular diseases. However, when we jointly took into account both the overall nutritional composition of the diet and its degree of processing, it came out that the latter aspect was paramount to define the risk of mortality. Actually, over 80 percent of the foods classified as unhealthy by the Nutri-Score are also ultra-processed. This suggests that the increased risk of mortality is not due directly (or exclusively) to the poor nutritional quality of some products, but rather to the fact that these foods are mostly ultra-processed”.
“It is estimated that one in five deaths in the world is due to unhealthy diets, for a total of 11 million deaths a year - recalls Augusto Di Castelnuovo, researcher at the Mediterranean Cardiocentro in Naples - This is why improving eating habits is at the top of the priority list of public health agencies and governments around the world”.
A proposal to help people make healthier food choices is to use a front-of-pack labelling system for commercial products. Already used on a voluntary basis in some European countries, such as France and Spain, front-of-pack labels are now being examined by the European Commission in order to adopt a harmonised and mandatory nutrition labelling scheme in all Member States. The Nutri-Score, developed in France, is given as a favourite. This system shows nutritional quality of a food (on the basis, for example, of the content of fat, salt, fibre, etc.) by a five-colour scale (from dark green to dark orange) associated with letters, from A to E.
But nutritional composition is not the only factor to take into consideration when looking at diet-health relationship. The NOVA classification, in particular, instead of evaluating a food on the basis of nutritional characteristics, looks rather at how much that product has been processed, mostly at industrial level. NOVA specifically identifies the so-called ultra-processed foods, i.e. those foods made in part or entirely with substances not routinely used in the kitchen (hydrolysed proteins, maltodextrins, hydrogenated fats, etc.) and which generally contain various additives, such as dyes, preservatives, antioxidants, anti-caking agents, flavour enhancers and sweeteners. This category includes the usual suspects: sugary and carbonated drinks, pre-packaged baked goods and spreads. But also apparently innocent products must be regarded as ultra-processed. It is the case of rusks, some breakfast cereals, crackers and fruit yoghurt.
According to the NOVA system, proposed a decade ago by a team of Brazilian researchers, a slice of unprocessed meat is healthier than a vegan hamburger, simply because the former has not undergone industrial manipulation and possibly does not contain food additives, while the latter is the result of an articulated industrial processing at the end of which the percentage of whole food is negligible.
“The goal of helping people make healthier food choices is certainly a priority - comments Licia Iacoviello, Director of the Department and Professor of Hygiene at the University of Insubria in Varese and Como- However, the Nutri-Score, as well as other labelling systems, developed in Italy and in other countries, only partially transfer the message aimed at improving food choices. While the letters and colours of the Nutri-Score may help to quickly compare products belonging to the same category, allowing people to choose the best one from a nutritional point of view, they does not provide any indication on food processing degree. This is why we believe, in agreement with other researchers worldwide, that every nutritional labelling system should be integrated with information regarding the level of processing”.
"For a truly effective prevention strategy, we shall focus on those foods that the Nutri-Score classifies as healthy from a nutritional point of view but which are also highly processed - explains Giuseppe Grosso, associate professor at the University of Catania - This is the case, for example, of some beverages which, despite having a reduced sugar content, thus being adequate on a nutritional level, so as to earn a letter B in the Nutri-Score, are in fact highly processed. Or even some types of yogurt and cold desserts that are low in fat although containing a full-bodied list of food additives”.
"A weakness common to all front-of-pack labelling systems is that they isolate a single food from the overall diet - specifies Giovanni de Gaetano, President of the IRCCS Neuromed in Pozzilli - To really improve nutrition, we should go back to the ancient lesson of the Mediterranean diet, which is a lifestyle characterized by a wise choice of foods and the way to combine and consume them. It is not a shopping list, but it reflects a century-old history that risks disappearing if we consider food as atoms that do not communicate with each other. We must also remember that the diet of Mediterranean people is mainly based on fresh or minimally processed products. Therefore, an effective preventive strategy should pay attention also to industrial processing which, if excessive, represents a documented threat to our health".
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
People
ARTICLE TITLE
Joint association of food nutritional profile by Nutri-Score frontof-pack label and ultra-processed food intake with mortality: Moli-sani prospective cohort study
