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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Latest Article

Can Plant-based Diets Be Unhealthy?

Posted September 10, 2019 by Dr. Steve Chaney

Do Plant-Based Diets Reduce Heart Disease Deaths?

Author: Dr. Stephen Chaney

 

plant-based diets vegetablesPlant-based diets have become the “Golden Boys” of the diet world. They are the diets most often recommended by knowledgeable health and nutrition professionals. I’m not talking about all the “Dr. Strangeloves” who pitch weird diets in books and the internet. I am talking legitimate experts who have spent their life studying the impact of nutrition on our health.

Certainly, there is an overwhelming body of evidence supporting the claim that plant-based diets are healthy. Going on a plant-based diet can help you lower blood pressure, inflammation, cholesterol and triglycerides. People who consume a plant-based diet for a lifetime weigh less and have decreased risk of heart disease, diabetes, and cancer.

But, can a plant-based diet be unhealthy? Some people consider a plant-based diet to simply be the absence of meat and other animal foods. Is just replacing animal foods with plant-based foods enough to make a diet healthy?

Maybe not. After all, sugar and white flour are plant-based food ingredients. Fake meats of all kinds abound in our grocery stores. Some are very wholesome, but others are little more than vegetarian junk food. If you replace animal foods with plant-based sweets, desserts, and junk food, is your diet really healthier?

While the answer to that question seems obvious, very few studies have asked that question. Most studies on the benefits of plant-based diets have compared population groups that eat a strictly plant-based diet (Seventh-Day Adventists, vegans, or vegetarians) with the general public. They have not looked at variations in plant food consumption within the general public. Nor have they compared people who consume healthy and unhealthy plant foods.

This study (H Kim et al, Journal of the American Heart Association, 8:e012865, 2019) was designed to fill that void.

 

How Was The Study Done?

plant-based diets studyThis study used data collected from 12,168 middle aged adults in the ARIC (Atherosclerosis Risk in Communities) study between 1987 and 2016.

The participant’s usual intake of foods and beverages was assessed by trained interviewers using a food frequency questionnaire at the time of entry into the study and again 6 years later.

Participants were asked to indicate the frequency with which they consumed 66 foods and beverages of a defined serving size in the previous year. Visual guides were provided to help participants estimate portion sizes.

The participant’s adherence to a plant-based diet was assessed using four different well-established plant-based diet scores. For the sake of simplicity, I will include 3 of them in this review.

  • The PDI (Plant-Based Diet Index) categorizes foods as either plant foods or animal foods. A high PDI score means that the participant’s diet contains more plant foods than animal foods. A low PDI score means the participant’s diet contains more animal foods than plant foods.
  • The hPDI (healthy plant-based diet index) is based on the PDI but emphasizes “healthy” plant foods. A high hPDI score means that the participant’s diet is high in healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) and low in animal foods.
  • The uPDI (unhealthy plant-based diet index) is based on the PDI but emphasizes “unhealthy” plant foods. A high uPDI score means that the participant’s diet is high in unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) and low in animal foods.

For statistical analysis the scores from the various plant-based diet indices were divided into 5 equal groups. In each case, the group with the highest score consumed the most plant foods and least animal foods. The group with the lowest score consumed the least plant foods and the most animal foods.

The health outcomes measured in this study were heart disease events, heart disease deaths, and all-cause deaths. Again, for the sake of simplicity, I will only include 2 of these outcomes (heart disease deaths and all-cause deaths) in this review. The data on deaths were obtained from state death records and the National Death Index. (Yes, your personal information is available on the web even after you die.)

 

Do Plant-Based Diets Reduce Heart Disease Deaths?

plant-based diets reduce heart deathsThe participants in this study were followed for an average of 25 years.

The investigators looked at heart disease deaths over the 25 years and compared people with the highest intake of plant foods to people with the highest intake of red meat and other animal foods. The results were:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

What Else Did The Study Show?

The investigators made a couple of other interesting observations:

  • The association of the overall diet with heart disease and all-cause deaths was stronger than the association of individual food components. This underscores the importance of looking at the effect of the whole diet on health outcomes rather than the “magic” foods you hear about on Dr. Strangelove’s Health Blog.
  • Diets with the highest amount of healthy plant foods were associated with higher intake of carbohydrates, plant protein, fiber, and micronutrients, including potassium, magnesium, iron, vitamin A, vitamin C, folate, and lower intake of saturated fat and cholesterol.
  • Diets with the highest amount of unhealthy plant foods were associated with higher intake of calories and carbohydrates and lower intake of fiber and micronutrients.

The last two observations may help explain some of the health benefits of plant-based diets.

 

Can Plant-Based Diets Be Unhealthy?

plant-based diets unhealthy cookiesNow, let’s return to the question I asked at the beginning of this article: “Can plant-based diets be unhealthy?” Although some previous studies have suggested that unhealthy plant-based diets might increase the risk of heart disease, this study did not show that.

What this study did show was that an unhealthy plant-based diet was no better for you than a diet containing lots of red meat and other animal foods.

If this were the only conclusion from this study, it might be considered a neutral result. However, this result clearly contrasts with the data from this study and many others showing that both plant-based diets in general and healthy plant-based diets reduce the risk of heart disease deaths and all-cause deaths compared to animal-based diets.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

There is one other subtle message from this study. This study did not compare vegans with the general public. Everyone in the study was the general public. Nobody in the study was consuming a 100% plant-based diet.

For example:

  • The group with the highest intake of plant foods consumed 9 servings per day of plant foods and 3.6 servings per day of animal foods.
  • The group with the lowest intake of plant foods consumed 5.4 servings per day of plant foods and 5.6 servings per day of animal foods.

In other words, you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet.

 

The Bottom Line

A recent study analyzed the effect of consuming plant foods on heart disease deaths and all-cause deaths over a 25-year period.

When the investigators looked at heart disease deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

A more subtle message from the study is that you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet. The people in this study were not following some special diet. The only difference was that some of the people in this study ate more plant foods and others more animal foods.

For more details on the study, 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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