Highlights
Different studies and meta-analyses found that a high intake of ultra-processed foods such as processed meats (examples- bacon and ham), salt preserved meats and fishes, fried crisps, sweetened beverages and pickled foods/vegetables may lead to an increased risk of different cancer types such as breast, colorectal, esophageal, gastric and naso-pharyngeal cancers. However, minimally processed foods and some of the processed foods, though altered, may not be detrimental to our health.
Over the last few decades, the consumption of processed foods has tremendously increased. As compared to the raw foods such as fruits and vegetables, whole grains and other ingredients that we pick up for cooking, ultra-processed foods are more tastier and convenient, and often take over 70% of our shopping baskets. Moreover, our cravings for a chocolate bar, a packet of crisps, foods like sausages, hotdogs, salamis and a bottle of sweetened beverages have further urged us to ignore the isles filled with healthy foods in the supermarket. But do we really understand how damaging the regular intake of ultra-processed foods could be?
According to a study published in the BMJ Open in 2016, ultra-processed foods comprised 57.9% of calories eaten in the United States, and contributed 89.7% of the energy intake from added sugars (Eurídice Martínez Steele et al, BMJ Open., 2016). The increased usage of ultra-processed foods aligns with the rising prevalence of obesity and related diseases in the US and different countries across the world. Before we discuss further on the impact of ultra-processed foods on the risk of developing life-threatening diseases such as cancer, let us understand what processed foods are.
What are Processed and Ultra-Processed foods?
Any food that has been altered from its natural state in some way or the other during preparation is termed as ‘Processed Food’.
Food processing can include any procedure that alters the food from its natural state including:
- Freezing
- Canning
- Baking
- Drying
- Refining
- Milling
- Heating
- Pasteurizing
- Roasting
- Boiling
- Smoking
- Blanching
- Dehydrating
- Mixing
- Packaging
Additionally, processing may also include the addition of other ingredients to the food to improve its flavor and shelf-life such as:
- Preservatives
- Flavors
- Other Food Additives
- Salt
- Sugar
- Fats
- Nutrients
This means that most of the foods that we usually eat are taken through some degree of processing. But does this also mean that all processed foods are bad for our body? Let us find out!
According to NOVA, a food classification system which categorises foods based on the extent and purpose of food processing, the foods are broadly classified into four categories.
- Unprocessed or minimally processed foods
- Processed culinary ingredients
- Processed foods
- Ultra-processed foods
Unprocessed or Minimally Processed Foods
Unprocessed foods are those foods that are taken in its raw or natural form. Minimally processed foods may be slightly modified, mostly for preservation, but the nutritional content of the foods are not altered. Some of the processes include cleaning and removing unwanted parts, refrigeration, pasteurization, fermentation, freezing, and vacuum-packaging.
Some examples of un-processed or minimally processed foods are :
- Fresh fruits and vegetables
- Whole grains
- Milk
- Eggs
- Fishes and Meats
- Nuts
Processed Culinary Ingredients
These are often not eaten on their own but are ingredients that we generally use for cooking, derived from minimal processing including refining, grinding, milling or pressing.
Some examples of foods which fall under this category are :
- Sugar
- Salt
- Oils from plants, seeds and nuts
- Butter
- Lard
- Vinegar
- Whole grain flour
Processed Foods
These are simple food products made by adding sugar, oil, fats, salt, or other processed culinary ingredients to unprocessed or minimally processed foods. This is mainly done for increasing the shelf-life or improving the taste of the food products.
The processes include different preservation or cooking methods and non-alcoholic fermentation as in the case of breads and cheese.
Some examples of processed foods are:
- Canned or bottled vegetables, fruits and legumes
- Salted nuts and seeds
- Canned tuna
- Cheeses
- Freshly made,unpacked breads
Ultra-Processed Foods
As the term suggests, these are highly processed foods, typically with five or more ingredients. Many of these are usually ready-to-eat or need only minimal extra preparation. Ultra-processed foods are taken through multiple processing steps using multiple ingredients. In addition to the ingredients found in the processed foods such as sugar, oils, fats, salt, anti-oxidants, stabilisers, and preservatives, these foods may also include other substances such as emulsifiers, sweeteners, artificial colours, stabilisers and flavours.
Some examples of ultra-processed foods are:
- Reconstituted/processed meat products (examples : Sausages, ham, bacon, hot dogs)
- Sugary, carbonated drinks
- Icecream, chocolate, candies
- Some frozen ready-to-eat meals
- Powdered and packaged instant soups, noodles and desserts
- Cookies, some crackers
- Breakfast cereals, cereal and energy bars
- Sweet or savoury packaged snacks such as crisps, sausage rolls, pies and pasties
- Margarines and spreads
- Fast foods such as french fries, burgers
Many of these ultra-processed foods such as bacon and sausages are part of the Western diet. These foods should be avoided to stay healthy. However, minimally processed foods and some of the processed foods, though altered, are not detrimental to our health. In fact, some of the minimally processed foods cannot be avoided from a healthy diet such as low-fat milk; freshly made whole grain breads; washed, bagged and freshly-cut vegetables, fruits and greens; and canned tuna.
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Why should we avoid Ultra-Processed Foods?
Inflammation is the body’s natural way of resisting against diseases or stimulating the healing process when injured. However, long term, chronic inflammation in the absence of a foreign body may damage the body’s healthy tissues, weaken the immune system and lead to life-threatening diseases such as cancer.
Ultra-processed foods often result in chronic inflammation and associated diseases including cancer.
When we eat ultra-processed foods with added sugars, the levels of glucose, which is the primary source of energy, increases in the blood. When the glucose levels are high, insulin helps to store the excess in the fat cells. This can ultimately lead to weight gain, obesity and insulin resistance which is associated with other diseases such as cancer, diabetes, fatty liver disease, chronic kidney diseases and so on. Fructose, present in sugar, may also cause inflammation of the endothelial cells which line the blood vessels, leading to cardiovascular diseases.
Ultra-processed foods may contain trans-fats that are formed through hydrogenation, a process done for improving the texture, stability and shelf life. Many of the foods such as french fries, cookies, pastries, popcorns and crackers may contain trans-fats.
Trans fats may increase the bad cholesterol (LDL) levels and lower the good cholesterol (HDL) levels, thereby increasing the risk of heart diseases, stroke, cancer and diabetes.
Processed meats also contain high levels of saturated fats that may increase the bad cholesterol (LDL) levels, thereby increasing the risk of heart diseases, stroke, cancer and diabetes. Examples of processed meats include sausages, hot dogs, salami, ham, cured bacon and beef jerky.
Impact of taking foods made of refined carbohydrates is similar to those which have added sugars. The refined carbohydrates also break down to glucose after ingestion. When the levels of glucose are high, the excess is stored in the fat cells ultimately leading to weight gain, obesity and insulin resistance. This results in associated diseases such as cancer, diabetes, cardiovascular diseases and so on.
Many of the ultra-processed foods have very high salt content which can increase the levels of sodium in blood and may result in high blood pressure and cardiovascular diseases.
Ultra-Processed Foods may be addictive, lack fiber and nutritional value
Some of these food products are designed with the intent of increasing the cravings in people, so that they will purchase the product more. Today, both kids and adults are equally addicted to ultra-processed foods such as carbonated beverages, french fries, confectioneries, sausages and other processed meats (example foods : ham, hot dogs, bacon) and so on. Many of these foods may also lack required nutrients and fiber.
Association between Ultra-Processed Foods and Cancer
Researchers across the world have done various observational studies and meta-analyses to evaluate the association of ultra-processed foods with the risk of different types of cancer.
Consumption of Ultra-Processed Foods and Breast Cancer Risk
NutriNet-Santé prospective cohort Study
In a study published in 2018, the researchers from France and Brazil used data from a population based study called the NutriNet-Santé cohort Study which included 1,04980 participants aged at least 18 years and a mean age of 42.8 years to evaluate the association between the consumption of ultra-processed food and risk of cancer. (Thibault Fiolet et al, BMJ., 2018)
The following foods were considered as ultra-processed foods during the evaluation – 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 (examples: processed meats such as sausages, ham, hot dogs, bacon) transformed with addition of preservatives other than salt; 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.
The study found that every 10% increase in consumption of ultra-processed foods was associated with a 12% increased risk for overall cancer and 11% increased risk for breast cancer.
Intake of Energy-Dense foods, Fast foods, Sugary Drinks, and Breast Cancer Risk
Researchers from the Robert Wood Johnson Medical School, New Jersey in the United States evaluated a study with 1692 African American (AA) women including 803 cases and 889 healthy controls; and 1456 European American (EA) women including 755 cases and 701 healthy controls, and found that frequent consumption of energy-dense and fast foods with poor nutritional value may increase the risk of breast cancer in both AA and EA women. Among postmenopausal EA women, breast cancer risk was also associated with frequent consumption of sugary drinks. (Urmila Chandran et al, Nutr Cancer., 2014)
Consumption of Ultra-Processed Foods and Colorectal Cancer Risk
Processed Meat Consumption and Risk of Colorectal Cancer
In a recent analysis published in January 2020, the researchers analyzed data from 48,704 women aged between 35 to 74 years who were participants of the US and Puerto Rico-based nationwide prospective cohort Sister Study and found that higher daily intake of processed meats (examples: sausages, hot dogs, salami, ham, cured bacon and beef jerky) and barbecued/grilled red meat products including steaks and hamburgers were associated with an increased risk of colorectal cancer in women. (Suril S Mehta et al, Cancer Epidemiol Biomarkers Prev., 2020)
Fast Foods, Sweets, Beverage Consumption and Risk of Colorectal Cancer
Researchers from the University of Jordan evaluated data from 220 colorectal cancer cases and 281 controls from the Jodanian population and found that the intake of fast foods such as falafel, daily intake or ≥5 servings/week of potato and corn chips, 1-2 or >5 servings per week of fried potatoes or 2-3 servings per week of chicken in sandwiches may increase the risk of colorectal cancer. (Reema F Tayyem et al, Asian Pac J Cancer Prev., 2018)
The researchers concluded that the consumption of fried fast foods may be significantly associated with an increased risk of colorectal cancer risk in Jordan.
Consumption of Ultra-Processed Foods and Esophageal Cancer
In a systematic meta-analysis done by the researchers from the Fourth Military Medical University, Shanxi Province in China, they evaluated the association between esophageal cancer risk and intake of processed and pickled foods/vegetables. The data for the study was obtained through literature search in PubMed and Web of Science databases for studies published from 1964 to April 2018. (Binyuan Yan et al, Bull Cancer., 2018)
The analysis found that groups with a very high intake of processed food were associated with a 78% increased risk of esophageal cancer compared with the lowest intake groups. Study also found a significant increased risk of esophageal cancer risk with increased intake of pickled foods (may include pickled vegetables).
In another similar study, it was found that preserved vegetable consumption may be associated with an increased risk of esophageal cancer. However, unlike the previous study, the results of this study didn’t show a significant association between esophageal cancer risk and pickled vegetables. (Qingkun Song et al, Cancer Sci., 2012)
However, based on these studies, we can conclude that some processed foods or preserved foods may be associated with an increased risk of esophageal cancer.
Salt-Preserved foods and Risk of Gastric Cancer
Researchers from the Kaunas University of Medicine in Lithuania carried out a hospital based study including 379 gastric cancer cases from 4 hospitals in Lithuania and 1,137 healthy controls and found that a high intake of salted meat, smoked meat and smoked fish was significantly associated with an increased risk of gastric cancer. They also found that the intake of salted mushrooms may also increase the risk of gastric cancer, however, this increase may not be significant. (Loreta Strumylaite et al, Medicina (Kaunas)., 2006)
The study concluded that salt-preserved meat as well as fish may be significantly associated with an increased risk of gastric cancer.
Cantonese Style Salted Fish and Nasopharyngeal Cancer
A large-scale hospital based study done by the researchers of State Key Laboratory of Oncology in Southern China, which included 1387 cases and 1459 matched controls, found that the intake of cantonese style salted fish, preserved vegetables and preserved/cured meat was significantly associated with an increased risk of nasopharyngeal cancer risk. (Wei-Hua Jia et al, BMC Cancer., 2010)
Consumption of Ultra-Processed Foods and Obesity
Obesity is one of the major risk factors of cancer.
In a study done by few researchers from Brazil, United States and United Kingdom based on data from the 2008-2009 Brazilian Dietary Survey, which included 30,243 individuals aged ≥10 years, they found that ultra-processed foods such as candies, cookies, sugar-sweetened beverages, and ready-to-eat dishes represented 30% of the total energy intake and a high consumption of ultra-processed foods had significantly higher body-mass-index and risk of being obese. (Maria Laura da Costa Louzada et al, Prev Med., 2015)
In a study named the PETALE study which evaluated how diet influences the health of 241 childhood acute lymphoblastic leukemia survivors with a mean age of 21.7 years, it was found that ultra-processed foods accounted for 51% of total energy intake. (Sophie Bérard et al, Nutrients., 2020)
Foods such as Red and processed meats (examples: sausages, ham, bacon) also significantly increases the risk of obesity.
Conclusion
Findings from different studies and meta-analyses indicate that a high intake of ultra-processed foods such as processed meats (examples : sausages, hot dogs, salami, ham, cured bacon and beef jerky), salt preserved meats and fishes, sweetened beverages and pickled foods/vegetables may lead to an increased risk of different types of cancers such as breast, colorectal, esophageal, gastric and nasopharyngeal cancers. Cook more meals at home and avoid the intake of ultra-processed foods such as sausages and bacon as it leads to chronic inflammation and associated diseases including cancer.
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