The Townsend Letter's Curmudgeon Corner recently looked at processed foods and their link to cancer
Original article (opens in new window):
by Jacob Schor, ND, FABNO
Ultra-Processed Foods and Cancer
Starting in 2009, a new food classification system emerged in public health research that is so strikingly novel that it has been named the NOVA food classification system. In the past, attention has focused on nutritional content of foods and how the vitamins and their combination with macronutrients such as fats, carbohydrates, proteins, fiber, etc. affect individual health status. Currently, much of our food advertising seems to focus on not what is in foods but what is not as in fat, gluten, cholesterol, GMOs, etc. The NOVA system ignores all those details and focuses only on the degree a food has been processed.
Findings published so far looking at public health as it relates to this NOVA system are troubling, even if not unexpected. We have vastly underestimated the significance of harm that industrial food processing is having on global health.
A significant percentage of the world’s population has shifted away from traditional diets to branded, ready-to-eat fast and convenient food and drink products. The food supplies in the US, Canada, the UK, Australia, and a long list of other developed countries are now dominated by packaged, ready-to-eat products.
The NOVA classification divides foods into four groups based on the extent and purpose of processing that the foods have undergone between when separated from nature and when they are eaten.
Group 1 foods are the least processed foods. Group 1 foods are edible parts of plants or animals and also fungi, algae, and water after separation from nature. These include seeds, fruits, leaves, stems, roots, animal muscle and other parts, eggs and milk. They may have inedible or unwanted parts removed, they may be crushed, ground, fractionated, filtered, roasted, boiled, pasteurized, refrigerated, frozen or vacuum packed. They contain no added substances such as salt, sugar, oil or fats. The purpose of processing of group 1 foods is to extend shelf life, allowing longer storage. Fermentation of milk to make yogurt, roasting coffee beans, etc. are considered group 1 processes. Antioxidants may sometimes be added to preserve freshness.
Group 2 foods are the processed culinary ingredients. These are foods that come directly from group 1 foods or directly from nature by processes such as pressing, refining, grinding, milling or drying. The purpose of this processing is to make things used in the home or in restaurant kitchens. These group 2 foods almost always accompany group 1 foods. Examples are salt derived from seawater, sugar and molasses derived from sugar cane or beets, honey extracted from honeycomb, butter and lard, or combinations of several of these ingredients for example vinegar. Some additives may be added; for example, oils may contain antioxidants, or salt may be added to prevent microorganism growth.
Group 3 foods are the relatively simple food products that are made by adding sugar, oil salt and other group 2 substances to group 1 foods. Most processed foods in this group have two or three ingredients. Processing includes preservation or cooking and in the case of bread and cheese, fermentation. The purpose of this processing is to increase durability of group 1 foods and to modify or enhance sensory qualities. Examples are canned or bottled vegetables, fruits and beans, salted or sugared nuts, seeds, cured meats, fruit in syrup, cheeses, and breads.
Group 4 foods are what the researchers are calling ultra-processed foods and drinks. These are the industrial formulations that typically contain five or more ingredients. These ingredients may include sugar, oils, fats, salt, antioxidants, stabilizers, and preservatives. Some ingredients are only found in this category and include additives to imitate sensory qualities of group 1 foods or to disguise undesirable sensory qualities. Group 1 foods make up a small proportion of these foods or may be totally absent. Substances that are extracted from real foods, such as casein, lactose, whey, gluten, or modified food extracts such as hydrogenated oil, hydrolyzed protein, soy isolates, etc may be included along with dyes, colors, flavors, non-sugar sweeteners, carbonation, firming, bulking agents, etc. The main purpose of ultra-processing is to create ready-to-eat products that replace less processed foods.
Group 4 foods are often hyper-palatable; they come in sophisticated packaging and have aggressive marketing. They may rely on health claims to help market them; and perhaps most strikingly, they are highly profitable. Transnational corporations usually own the manufacturers of such food.1
This seemingly simple NOVA classification system is rapidly proving to be a better predictor of health impact than any other system of food classification to date. A recently published study is a good example.
In a February 2018 issue of the British Medical Journal, Fiolet et al reported a positive association between consumption of ultra-processed foods and cancer risk.2
They had performed a population-based cohort study that included 104,980 French adults whose median age was just under 43 years old during the period between 2009 and 2017. Food consumption data were collected using repeated 24-hour dietary records, designed to reveal the usual consumption for 3300 different food items. These foods were categorized according to their degree of processing by using the NOVA classification system.
Associations were calculated between group 4 ultra-processed food intake and the overall risk of cancer and then specifically for risk of breast, prostate, and colorectal cancer using multivariable Cox proportional hazard models adjusted for known risk factors.
Ultra-processed food intake was associated with higher overall cancer risk (n=2228 cases). For every 10% increase in the proportion of calories obtained from ultra-processed foods in the diet, cancer risk increased 12% [HR 1.12 (95% confidence interval 1.06 to 1.18) P <0.001]. For the women in the study risk for breast cancer increased by 11% [n=739 cases; HR 1.11 (1.02 to 1.22); P =0.02]. These results remained statistically significant after adjustment for several markers of the nutritional quality of the diet (lipid, sodium, and carbohydrate intakes and/or a Western pattern derived by principal component analysis). In other words, it appears that food processing may have a more substantial impact than the specific initial ingredients themselves. This should be getting our attention.
The American Institute for Cancer Research claims that about a third of the most common cancers in the world could be avoided by changing lifestyle and dietary habits in developed countries.3 Within our naturopathic profession, we have seen some claim that as much as 95% of cancers are preventable by diet and lifestyle—while this writer assumes that the lower estimates may be too conservative and the later are uninformed exaggerations.4 As there is such a wide range of disparate beliefs being proclaimed, this reader has become particularly attentive to any evidence that might better inform this question. It certainly does not help our professional reputation to make unsupported claims as if they were proven facts.
Those of us of a certain age have borne witness to how much the diets of many countries have shifted dramatically toward higher amounts of ultra-processed foods.5 Surveys conducted in Europe, the US, Canada, New Zealand, and Brazil have all suggested that ultra-processed foods now contribute between 25 to 50% of total daily energy intake in these countries.6-9 While it may be hard for us to imagine this level of consumption, we have to remind ourselves that we, and our patients, are not representative of the average global consumer.
There are a number of reasons why ultra-processed foods might increase risk of cancer. We might think it obvious, but in reality, we do not know exactly. These foods certainly have a higher total fat and saturated fat content. Fat consumption may, or may not, be associated with risk for some types of cancer (prostate yes, and breast no). The low vitamin density and high sugar and salt content of these foods may also play a role. Yet it is still unclear whether vitamin deprivation in itself is responsible for cancer. The low fiber content affects gut biome and thus may change cancer risk.10 Processing may lead to formation of carcinogenic chemicals such as acrylamides, heterocyclic amines, and polycyclic hydrocarbons. Food packaging may contain carcinogens that leach into the food during storage or during preparation such as bisphenol A. Some food additives, such as sodium nitrite, though legal to add to processed meat, may still be carcinogenic. While all of these possible causes may be to blame, we just don’t know exactly.
The very concept of studying the effects of food processing on disease risk is still in its infancy. It wasn’t until this NOVA classification system was created in the last few years that these effects could be even quantified.11
While these data only seem to confirm a message we have been trying to teach our patients for decades, the degree of impact surprises this reader. If every 10% increase in calories derived from ultra-processed foods is associated with an 11% increase in overall cancer, we certainly have a serious problem brewing. Many segments of the population consume far more than 10% of their energy from ultra-processed foods. In some countries, the increases may be five-fold.
Note: The definition according to the NOVA Classification system of ultra-processed foods includes the following:
- mass produced packaged breads and buns;
- sweet or savory packaged snacks;
- industrialized confectionery and desserts;
- sodas and sweetened drinks;
- meat balls, poultry and fish nuggets, and other reconstituted meat products transformed with addition of preservatives other than salt (for example, nitrites);
- instant noodles and soups;
- frozen or shelf stable ready meals; and
- other food products made mostly or entirely from sugar, oils and fats, and other substances not commonly used in culinary preparations such as hydrogenated oils, modified starches, and protein isolates.
Industrial processes notably include hydrogenation, hydrolysis, extruding, moulding, reshaping, and pre-processing by frying. Flavoring agents, colors, emulsifiers, humectants, non-sugar sweeteners, and other cosmetic additives are often added to these products to imitate sensorial properties of unprocessed or minimally processed foods and their culinary preparations or to disguise undesirable qualities of the final product.1
Many of us along with our patients believe that foods labeled as natural, organic, GMO free, low fat, cholesterol, or gluten free are healthy choices. None of these labeled categories measure degree of processing, and little data associates these categories with significant inverse cancer risk. In other words, these claims may not be relevant predictors of long-term health. Processing takes its toll whether the food is sold in a chain grocery store or in Whole Foods.
For patients who want to lower cancer risk, reducing, or better eliminating, consumption of ultra-processed foods now appears to be a decent evidence-based choice in food selection.
1. Monteiro CA, et al. NOVA. The star shines bright. [Food classification.Public health]. World Nutrition. January-March2016;7,1-3: 28-38. back to text
2. Fiolet T, et al. Consumption of ultra-processed foods and cancer risk: results from NutriNet-Santé prospective cohort. BMJ. 2018 Feb 14;360:k322. back to text
3. World Cancer Research Fund International/American Institute for Cancer Research. Cancer preventability estimates for diet, nutrition, body fatness, and physical activity. 2017. wcrf.org/cancer-preventability-estimates. back to text
5. Monteiro CA, et al. Ultra-processed products are becoming dominant in the global food system. Obes Rev. 2013;14(Suppl 2):21-8. back to text
6. Luiten CM, et al. Ultra-processed foods have the worst nutrient profile, yet they are the most available packaged products in a sample of New Zealand supermarkets–CORRIGENDUM. Public Health Nutr. 2016;19:539. back to text
7. Adams J, White M. Characterisation of UK diets according to degree of food processing and associations with socio-demographics and obesity: cross-sectional analysis of UK National Diet and Nutrition Survey (2008-12). Int J Behav Nutr Phys Act. 2015;12:160. back to text
8. Costa Louzada ML, et al. Ultra-processed foods and the nutritional dietary profile in Brazil. Rev Saude Publica. 2015;49:38. back to text
9. Martínez Steele E, et al. Ultra-processed foods and added sugars in the US diet: evidence from a nationally representative cross-sectional study. BMJ Open. 2016;6:e009892.back to text
10. Bultman SJ. The microbiome and its potential as a cancer preventive intervention. Semin Oncol. 2016 Feb;43(1):97-106.back to text
11. Monteiro CA, et al. The UN Decade of Nutrition, the NOVA food classification and the trouble with ultra-processing. Public Health Nutr. 2018;21:5-17. back to text>