Does Processed Food Cause Cancer?

Written by Dr. Steve Chaney on . Posted in Processed Food and Cancer

What Are Processed Foods Doing To Your Health?

Author: Dr. Stephen Chaney

 

does processed food cause cancerDoes processed food cause cancer?

We Americans have a love, hate relationship with processed foods. We love how they taste. We love the convenience. All our friends eat them, so it is the socially acceptable thing to do. But, we also worry about them. We know they aren’t good for us.

We know they increase our risk of becoming obese. We have been warned that they may increase our risk of heart disease, diabetes, and hypertension. But, what if they also increased our risk of cancer? A new study strongly suggests that ultra-processed foods significantly increase our cancer risk.

What Are Ultra-Processed Foods?

udoes processed food cause cancer ultra processed foodsUntil recently it had been very difficult to determine the effect of processed foods on our health because there was no uniform system for classifying the processed food content of our diet. With no consistent classification system, the outcomes varied from one study to the next. That changed around 2016 with the development of the NOVA food classification system. The NOVA system divides foods into four categories:

 

  • Ultra-processed foods.
    • These are foods most Americans would consider junk foods.

 

  • Commercially Processed foods.
    • These are commercially processed foods using natural ingredients like salt, sugar, and fats. For example, frozen peas would be considered a minimally processed food (category 4). Frozen peas with added salt or frozen creamed peas would be considered a commercially process food.

 

  • Restaurant Foods.
    • These are foods processed in a kitchen (either in people’s homes or a restaurant) using salt, sugar, and/or fats to produce a culinary masterpiece (As you might suspect from the emphasis on culinary masterpiece, this is a European classification system).

 

  • Unprocessed or minimally processed foods.
    • These are foods that most Americans would consider whole foods. They are either raw or minimally processed.

 

Intuitively, you have probably already guessed that foods in category 1 are likely to be bad for us and foods in category 4 are likely to be good for us. Categories 2 and 3 start with healthy foods but often end up with foods that are higher in salt, sugar, and/or fat than most experts would consider to be healthy.

With this classification system in mind, the next step was to classify every food in large food databases into one of these four categories. In this case the 3,300 item French NutriNet-Santé food composition database was used.

 

How Was The Study Performed?

does processed food cause cancer studyThis study (T. Fiolet et al, British Medical Journal, 2018;360:k322 doi: 10.1136/bmj.k322) was performed as part of the 8-year NutriNet-Santé web-based program launched in France in 2009 with the objective of studying the associations between nutrition and health. This study enrolled 104,980 participants who were 18 or older. The average age of participants was 42.8 years. There were 82% women and 18% men enrolled in the study.

Dietary intake was assessed using an online 24-hour dietary recall survey administered every 6 months over a two-year period. The survey was administered on random days so that every day of the week was covered in the survey. On average, participants completed 5 diet surveys during the study. The validity of these dietary surveys has been established in other studies that were part of this project.

Over an average 5-year follow-up, cancer incidence was assessed via a check-up questionnaire for health events that was administered every three months.  Participants were also encouraged to self-report health events at any time. Any time a cancer diagnosis was received, a physician from the study team contacted the participant and requested their medical records, which were provided in 80% of the cases. Finally, French death records were also screened to identify any study participants who died from cancer during the study.

In short, this was a very well-done study.

 

Does Processed Food Cause Cancer?

 

does processed food cause cancer junk foodsUsing the NOVA classification system, this question is concerning ultra-processed food.

Here is what the study showed:

  • Every 10% increase in the proportion of ultra-processed foods (junk foods) in the diet was associated with a 12% increase in overall cancer and a 11% increase in breast cancer.
  • No association was seen between commercially processed foods or restaurant foods in the diet and cancer.
  • Every 10% increase in the proportion of unprocessed foods in the diet was associated with a 9% decrease in overall cancer and a 58% decrease in breast cancer.

Just in case you might be tempted to say that a 12% increase in cancer risk is insignificant, remember it is the cancer risk associated with just a 10% increase in ultra-processed foods in the diet. Recent studies have suggested that ultra-processed foods contribute from 25% to 50% of the calories consumed by most Americans.

The authors concluded “[The] rapidly increasing consumption of ultra-processed foods may drive an increased burden of cancer and other non-communicable disease.”

 

What Does This Study Mean For You?

does processed food cause cancer unprocessed foodsBecause the NOVA classification system for identifying the processed food composition of the diet is a recent introduction, this is the first study of its kind. While it is a very good study, it needs to be confirmed by further studies in different population groups.

It would be tempting to ascribe the higher cancer incidence to secondary consequences of ultra-processed food consumption. For example, consumption of ultra-processed food is associated with:

  • Obesity which, in turn, is associated with increased cancer risk.
  • Increased intake of fat, saturated and trans fats, and sugar and decreased intake of fiber and essential nutrients. The effect of these dietary changes is uncertain but could be associated with higher cancer risk.
  • Decreased intake of fruits, vegetables, and whole grains which would result in increased cancer risk.
  • Increased intake of neoformed contaminants (a fancy term for contaminants formed during processing such as acrylamide, heterocyclic amines, and polyaromatic hydrocarbons). These are all carcinogenic compounds. They are usually present in very small amounts, so their effect on cancer risk is uncertain.
  • Increased consumption of food additives of uncertain safety.

While this is an interesting area for future research, it represents a danger and shows that we will try to “have our cake and eat it too.”  Let me explain what I mean by that.

  • does processed food cause cancer restaurant foodWe love our junk foods. Food manufacturers will be only too happy to provide us with “healthier junk foods” by removing salt, sugar, and/or fat and replacing them with a chemical smorgasbord of artificial ingredients. They will reduce calories (again by adding artificial ingredients) so they can claim their junk foods won’t make us fat. They can reduce neoformed contaminants like acrylamide and claim their junk foods are now healthy. But, are they really any healthier? Not necessarily, according to this study.
  • The investigators performed a very sophisticated statistical analysis. The 12% increase in cancer they reported had already been adjusted for differences in age, sex, BMI (a measure of obesity), physical activity, smoking habits, alcohol intake, family history of cancer, and educational level. They also adjusted for fat, salt, and sugar content of the diet.
  • Some supplement companies may tell you that it’s OK to eat junk foods as long as you take the supplements they are trying to sell you. I have head dietitians say it’s OK to eat junk foods as long as you “balance” your diet with lots of fruits and vegetables. The results of this study suggest those approaches won’t be much help either.
  • Further analysis of their data by the investigators showed that the 12% increase in cancer risk was independent of overall fruit and vegetable consumption and supplement use.

The only variables left were increased intake of food additives and neoformed contaminants, and it is unlikely that those would have been sufficient to cause a 12% increase in cancer.

So, does processed food cause cancer?

Once again it appears to be the foods we eat rather than the individual components in those foods that are either good for us or bad for us. The inescapable conclusion from this study is that we are more likely to be healthy if we eat fewer processed foods and more unprocessed foods. Who would have guessed?

 

The Bottom Line:

 

A recent study looked at the effect of ultra-processed foods (otherwise known as junk foods) on cancer  risk. This was a very well-designed study, and it showed.

  • Every 10% increase in the proportion of ultra-processed foods in the diet was associated with a 12% increase in overall cancer and a 11% increase in breast cancer.
  • Every 10% increase in the proportion of unprocessed foods in the diet was associated with a 9% decrease in overall cancer and a 58% decrease in breast cancer.

Just in case you might be tempted to say that a 12% increase in cancer risk is insignificant, remember it is the cancer risk associated with just a 10% increase in ultra-processed foods in the diet. Recent studies have suggested that ultra-processed foods contribute from 25% to 50% of the calories consumed by most Americans.

This is the first study of its kind. While it is a very good study, it needs to be confirmed by further studies in different population groups.

When you look at the details of this study it appears to be the foods we eat rather than the individual components in those foods that are either good for us or bad for us. The inescapable conclusion from this study is that we are more likely to be healthy if we eat fewer processed foods and more unprocessed foods. Who would have guessed?

For more details, read the article above:

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Comments (1)

  • Kathryn Farries

    |

    Dr Chaney,

    Thank you. Again!
    This information is very well explained. And it should be confirmation that what you don’t know can/might kill you.

    Regards,
    Kathryn

    Reply

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Is Our Microbiome Affected By Exercise?

Posted November 6, 2018 by Dr. Steve Chaney

Microbiome Mysteries

Author: Dr. Stephen Chaney

is our microbiome affected by exerciseIn a recent post,  What is Your Microbiome and Why is it Important,  of “Health Tips From The Professor” I outlined how our microbiome, especially the bacteria that reside in our intestine, influences our health. That influence can be either good or bad depending on which species of bacteria populate our gut. I also discussed how the species of bacteria that populate our gut are influenced by what we eat and, in turn, influence how the foods we eat are metabolized.

I shared that there is an association between obesity and the species of bacteria that inhabit our gut. At present, this is a “chicken and egg” conundrum. We don’t know whether obesity influences the species of bacteria that inhabit our gut, or whether certain species of gut bacteria cause us to become obese.

Previous studies have shown that there is also an association between exercise and the species of bacteria that inhabit our gut. In particular, exercise is associated with an increase in bacteria that metabolize fiber in our diets to short chain fatty acids such as butyrate. That is potentially important because butyrate is a primary food source for intestinal mucosal cells (the cells that line the intestine). Butyrate helps those cells maintain the integrity of the gut barrier (which helps prevent things like leaky gut syndrome). It also has an anti-inflammatory effect on the immune cells that reside in the gut.

However, associations don’t prove cause and effect. We don’t know whether the differences in gut bacteria were caused by differences in diet or leanness in populations who exercised regularly and those who did not. This is what the present study (JM Allen et al, Medicine & Science In Sports & Exercise, 50: 747-757, 2018 ) was designed to clarify.  Is our microbiome affected by exercise?

 

How Was The Study Designed?

is our microbiome affected by exercise studyThis study was performed at the University of Illinois. Thirty-two previously sedentary subjects (average age = 28) were recruited for the study. Twenty of them were women and 12 were men. Prior to starting the study, the participants filled out a 7-day dietary record. They were asked to follow the same diet throughout the 12-week study. In addition, a dietitian designed a 3-day food menu based on their 7-day recall for the participants to follow prior to each fecal collection to determine species of gut bacteria.

The study included a two-week baseline when their baseline gut bacteria population was measured, and participants were tested for fitness. This was followed by a 6-week exercise intervention consisting of three supervised 30 to 60-minute moderate to vigorous exercise sessions per week. The exercise was adapted to the participant’s initial fitness level, and both the intensity and duration of exercise increased over the 6-week exercise intervention. Following the exercise intervention, all participants were instructed to maintain their diet and refrain from exercise for another 6 weeks. This was referred to as the “washout period.”

VO2max (a measure of fitness) was determined at baseline and at the end of the exercise intervention. Stool samples for determination of gut bacteria and concentrations of short-chain fatty acids were taken at baseline, at the end of the exercise intervention, and again after the washout period.

In short, this study divided participants into lean and obese categories and held diet constant. The only variable was the exercise component.

 

Is Our Microbiome Affected By Exercise?

is our microbiome affected by exercise fitnessThe results of the study were as follows:

  • Fitness, as assessed by VO2max, increased for all the participants, and the increase in fitness was comparable for both lean and obese subjects.
  • Exercise induced a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise increased fecal concentrations of butyrate and other short-chain fatty acids in the lean subjects, but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production were largely reversed once exercise training ceased.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent of diet, and contingent on the sustainment of exercise.” [Note: To be clear, the exercise-induced changes in both gut bacteria and short-chain fatty acid production were independent of diet and contingent on the sustainment of exercise. However, only the production of short-chain fatty acids was dependent on obesity status.]

 

What Does This Study Mean For You?

is our microbiome affected by exercise gut bacteriaThere are two important take home lessons from this study.

  • With respect to our gut bacteria, I have consistently told you that microbiome research is an emerging science. This is a small study, so you should regard it as the beginning of our understanding of the effect of exercise on our microbiome rather than conclusive by itself. It is consistent with previous studies showing an association between exercise and a potentially beneficial shift in the population of gut bacteria.

The strength of the study is that it shows that exercise-induced changes in beneficial gut bacteria are probably independent of diet. However, it is the first study to look at the interaction between obesity, exercise and gut bacteria, so I would interpret those results with caution until they have been replicated in subsequent studies.

  • With respect to exercise, this may be yet another reason to add regular physical activity to your healthy lifestyle program. We already know that exercise is important for cardiovascular health. We also know that exercise increases lean muscle mass which increases metabolic rate and helps prevent obesity. There is also excellent evidence that exercise improves mood and helps prevent cognitive decline as we age.

Exercise is also associated with decreased risk of colon cancer and irritable bowel disease. This effect of exercise has not received much attention because the mechanism of this effect is unclear. This study shows that exercise increases the fecal concentrations of butyrate and other short-chain fatty acids. Perhaps, this provides the mechanism for the interaction between exercise and intestinal health.

 

The Bottom Line

A recent study has reported that:

  • Exercise induces a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise causes an increase in the number of gut bacteria that produce butyrate and other short-chain fatty acids that are beneficial for gut health.
  • These effects are independent of diet, but do not appear to be independent of obesity because they were seen in lean subjects but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production are largely reversed once exercise training ceases.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent on diet, and contingent on the sustainment of exercise.”

For more details and my interpretation of the data, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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