The Health risks of ultra-processed foods

In this Article (Index)

• Ultra-processed foods (UPFs) are unhealthy
• They cause Weight Gain
• They are addictive
• They cause low-grade inflammation
• They may cause cancer
• They are linked to diabetes and heart disease

Ultra processed food is convenient but unhealthy

Food processing began with the first humans: gathering tubers and fruit, cutting them, drying them; sun-drying meat, salting or smoking it, cooking to tenderize tough meat or roots. It was a survival tool. Later, with the discovery of agriculture, processing food for safe long-term storage ensured a steady supply of food to cover the lack of fresh produce during the winter season; pickles, fermented vegetables, cheese, vinegar, milling cereal to obtain whole grain flour, olive oil are some examples of these early fodd processing products.

During the industrial revolution, food became a mass produced article that produced affordable and safe products; they didn't spoil, and were safe to eat. Chemical products were developed to preserve food, enhance its flavors, colors and textures, meat and plant-origin foods were broken apart into their building blocks like protein, fat, sugar, fiber, starches, these were modified and reassembled into more heavily processed and ultra processed foods.

Ultra processed foods or UPFs have higher content of sodium, chemicals, added fats and sugars that are associated to health risks, such as weight gain, diabetes, stroke and heart disease.

In the following sections we will look at the health risks of ultra-processed foods:

Weight Gain

Most ultra-processed foods (UPFs) have an unhealthy nutrient and energy content. They are cheap, convenient, tasty and sold in large portions. They also have a reduced satiety potential, meaning that they don't provoke satiety, that good feeling of fullness. Instead, they lead to additional ingestion of an excessive amount of calories (1).

A study involving 20 adult participants that were allowed to eat all they wanted on an ultra-processed or an unprocessed food diet found that those who ate ultra-processed foods consumed 500 additional calories per day. They ate their meals faster too: 50 calories per minute versus 30 calories per minute for those eating unprocessed foods. This lead to a weight gain of almost 2 lb. (0.9 kg) in those following the ultra-processed diet compared to a loss of almost 2 lb. (0.9 kg) during the unprocessed diet (2).

Addicting power of ultra-processed foods

Ultra processed foods contain added sugars and fats, these are calorie dense ingredients that are addicting.

Refined carbohydrates (sugars and starches) and also fats "evoke similar levels of extracellular dopamine in the brain ... to those seen with addictive substances such as nicotine and alcohol... foods that deliver high levels of refined carbohydrates or added fats are a strong candidate for an addictive substance" (3).

The release of "feel-good" dopamine leads to food craving and addiction.

Processing also makes these foods easier to digest as they lack natural fiber and complex carbohydrates. The body uses less energy to digest this type of food in comparison to less processed or unprocessed foods.

Less energy expended to digest, and more energy intake means a net gain of energy and in consequence, weight gain.

Extra energy input is stored as adipose tissue leading to weight gain and obesity; and being overweight or obese is associated with a wide range of health conditions (more at our The dangers of belly fat page).

UPFs cause Low-grade Inflammation

There is strong evidence to support the relationship between low-grade inflammation, a promoter of chronic disease, and excessive intake of ultra-processed foods (4).

Below we list some of the possible mechanisms by which ultra-processed foods produce inflammation:

• "Excessive sugar intake is closely associated with the development of low-grade chronic inflammation and autoimmune diseases" (9).
• "High salt intake is associated with enhanced inflammation" (8).
• Hydrogenated oils or trans fatty acids also promote low-grade inflammation (5).
• Ultra processed foods contain a high proportion of vegetable fats that are rich in omega-6 fatty acids; this disrupts the balance omega-6 and omega-3 fatty acids.
• Replacement of unprocessed foods like fruits and vegetables that have anti-inflammatory properties due to their phytochemicals, leads to a surge in inflammation.
  They should have a ratio of 1 to 1 (omega-3 fatty acids are found in unprocessed healthy foods like fatty fish, nuts, and seeds), but modern diets alter this balance to values of up to 17 to 1 (6)(7).

Human beings evolved on a diet with a ratio of omega-6 to omega-3 essential fatty acids (EFA) of approximately 1 whereas in Western diets the ratio is 15 ⁄ 1 to 16.7 ⁄ 1. A high omega-6 ⁄ omega-3 ratio, as is found in today's Western diets, promotes the pathogenesis of many diseases, including cardiovascular disease, cancer, osteoporosis, and inflammatory and autoimmune diseases, whereas increased levels of omega-3 polyunsaturated fatty acids (PUFA) (a lower omega-6/omega-3 ratio), exert suppressive effects. Simopoulos AP, (2006) (7)

Therefore the combined effects of high sugar, salt and unhealthy fats, the replacement of healthy unprocessed foods and nutrients (like omega-3 fatty acids) lead to chronic low-grade inflammation.

This type of inflammation leads to immune alterations and promotes chronic metabolic inflammation leading to diabetes, cardiovascular disease and cancer (4).

UPFs are Linked to Cancer

A study (10) that analyzed data obtained from 450,111 subjects that were followed for approximately 14 years found that Ultra-processed foods have been linked to a higer risk of mouth, throat and oesophagus cancers, and it doesn't seem to be linked only by the increased body fat caused by eating junk food.

Eating 10% more ultra-processed foods is associated with a 23% higher risk of head and neck cancer, and a 24% higher risk of oesophageal adenocarcinoma.

There are several mechanisms that can explain the link between ultra-processed foods and cancer; chronic inflammation may favor cancer by promoting cell proliferation and metastasis, slowing down cell death, and increasing formation of blood vessels to nourish tumors (4).

Ultra-processed foods also disrupt the gut microbiota which has an impact on the immune system. Other factors that could play a role in increasing cancer risk are the carcinogenic compounds present in ultra-processed foods, such as additives like artificial sweeteners, the manufacturing processes used and contaminants transferred from packaging materials (10).

This conclusion makes sense as there are over ten thousand chemical compounds that are added to processed foods and that are regarded as safe but have not undergone testing in humans (11).

Heart Disease and Diabetes

An observational study involving 104,707 participants found that "a higher proportion of ultraprocessed foods in the diet was associated with a higher risk of T2D [Type 2 diabetes]" and that a 10% increase in the ultra-processed foods content in the diet was linked to a 15% increase in the risk for suffering from type 2 diabetes.
It also suggested that a 10% increase in the unprocessed or minimally processed foods in the diet had the opposite effect: a 9% reduction in the type 2 diabetes risk. (12).

Another study analyzing data from 325,403 subjects found that a 10% increase in ultra-processed food consumption was associated to a 6% increase in heart disease risk, while those whose ultra-processed foods intake represented less than 15% of their daily diet had the lowest risk of cardiovascular disease (13).

Moderate intake of UPF was associated with a lower risk of cardiovascular events, with the lowest risk at <15%/day of UPF consumption out of total calorie intake. Heavy UPF consumption was significantly and positively associated with increased risk of cardiovascular events. Y Qu, W Hu, C Xing, L Yuan, J Huang, (2023) (13)