What is inflammation?

Inflammation is the body’s response to an illness, injury or something that doesn’t belong in it (like bacteria, viruses or toxic chemicals). Inflammation can harm us if it occurs in healthy tissues or occurs longitudinally.

In case an invader (like a virus) tries to enter our body, or we are injured, our immune system sends out its first responders. These comprise inflammatory cells and cytokines.¹

Importance of dietary impacts on inflammation

Diet is often considered a factor that contributes towards the development of many chronic conditions including obesity, cardiovascular disease (CVD), hypertension, stroke, type 2 diabetes (T2D), metabolic syndrome, some cancers, and neurological diseases.²

Dietary components, undoubtedly, influence immune response by modulating the metabolism of gut bacteria, impacting the risk of developing chronic diseases either directly in the gastrointestinal (GI) tract or in other organs that in turn, influence the general metabolism. Recent studies have investigated the long-term exposure to low doses of chemical extracts that can be a part of modern lifestyles, such as pesticides, food additives, or additives contained in food coating materials, proving that different disturbances appear from minor biochemical instabilities. These alterations are generally followed by oxidative stress induction and organ damage depending on the period of exposure. Recently, it has been shown that long-term exposure to stressors might also be positively associated with elevated vulnerability of the population to microbial and viral infections.³

Overview of the connection between diet and chronic diseases

Lifestyle factors such as poor diet, smoking, alcohol consumption, and lack of exercise contribute considerably to the incidence of chronic diseases. 

Foods that cause inflammation

Sugar and high-fructose corn syrup

Sources in the diet

• Candies
• Packaged sweets
• Soda
• Juice drinks
• Fast food
• Sauces and other condiments
• Ice cream and ice pops
• Breakfast foods
• Fruit preserves and jams
• Bread and crackers
• Pancake syrup and dessert syrup
• Applesauce

Effects of dietary sugars on low-grade chronic inflammation (LGCI)

High sugar intake leads to an increased incidence of numerous non-communicable diseases, including obesity, cardiovascular disease, metabolic syndrome, and T2D. Dietary sugars are mainly comprising hexoses, including glucose, fructose, sucrose and High Fructose Corn Syrup (HFCS); which are primarily absorbed in the gut as fructose and glucose.³

It has been demonstrated that the intake of dietary sugars in an excessive amount can result in metabolic disorders along with inducing the increase of inflammatory mediators and certain pro-inflammatory cytokines in various body tissues. This, in turn, leads to insulin resistance and LGCI.^4,5,6

Figure 1: Excessive consumption of dietary sugars is closely related to the occurrence and development of inflammation; adapted from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9471313/.

Health implications (e.g., obesity, diabetes)

Consuming high levels of dietary hexose can result in significant effects on rheumatoid arthritis (RA), multiple sclerosis (MS), psoriasis, inflammatory bowel disease (IBD) and low-grade chronic inflammation. Based on reported findings, Xiao et al. emphasise that dietary sugars and mixed processed foods may lead to the occurrence and aggravation of inflammation. Moreover, close attention should also be paid to the combination of high glucose-mediated immune imbalance and tumour development and strive to make substantial contributions to reverse tumour immune escape.³

Refined carbohydrates

Sources in the diet

• Breakfast cereals 
• Bagels
• Muffins 
• Waffles
• Pancakes
• Granola 
• Breakfast pastries 
• White bread
• White rice 
• Flour tortillas 
• Pizza dough 
• Crackers
• Chips 
• Cookies 
• Cakes 
• Candy 

Effects of refined carbohydrates on inflammation

Eating a lot of added sugar and refined carbohydrates (carbs) is linked to chronic inflammation in the body.

Gut and carbohydrates

The gut microbiota assists in a breadth of bodily functions, including:

• Harvesting energy from digested food
• Protecting against pathogens
• Regulating immune function
• Strengthening biochemical barriers of the gut and intestine

Gut microbiota also plays a role in the provision of essential capacities for the fermentation of non-digestible substrates (dietary fibres and endogenous intestinal mucus), thereby providing support to the growth of specialised species that produce short-chain fatty acids (SCFAs) and gases.⁷

Furthermore, dietary fibre can have a major impact on the composition, diversity, and richness of the microbiome.⁸ As such, consumption of high fibre in combination with specific species of microbes with the ability to ferment it, along with low consumption of refined carbohydrates, leads to a range of health benefits for the host.⁹

Processed meats

Sources in the diet

• Bacon
• Sausage
• Hot dogs
• Pepperoni
• Ham
• Corned beef
• Cold cuts like Bologna and Salami

Presence of AGEs and nitrites

Nitrite is often added to meat products during processing for the promotion of flavour and formation of colour and can reduce the activity of microorganisms. However, meat products cured with nitrites and/or nitrates can produce high levels of N-nitrosamines (NAs).¹⁰

Advanced glycosylation end products (AGEs) and NAs are common hazards produced due to the processing of meat products.

Associated health risks

According to the results of a study conducted by Srour et al., nitrites or nitrates do not play a protective role in cardiovascular health. They suggest a positive association between nitrites from food additives and hypertension risk, which needs confirmation by means of large‐scale studies.¹¹

Red meat

Difference between processed and unprocessed red meat

Growing evidence directs towards the effects of red meat consumption on coronary heart disease (CHD) and T2D having a variation depending on processing. The overall findings of meta-analyses suggest that neither processed or unprocessed red meat has a beneficial effect on cardiometabolic health and that clinical and public health guidance should specifically prioritise reducing the consumption of processed meat.¹²

Inflammatory compounds in red meat

Red meat is currently implicated to cause inflammation and compromise immune function. However, the consistency of the effects of red meat on these indices expects systematic assessment.

Trans fats

Sources in the diet

• Some spreads—such as margarine spreads or peanut butter
• Some snack foods—such as chips, crackers, and cookies
• Non-dairy creamer
• Pre-prepared cake frostings
• Vegetable shortening
• Tinned beans
• Commercially pre-prepared products, such as pie crusts, pizza dough, and cookie dough
• Some pastries, doughnuts, and pies

What is trans fat?

Trans fat is a type of unsaturated fat. Some trans fats may have a natural occurrence in animal products, while others are reported in industrially produced partially hydrogenated oils (PHOs).

Trans fats that are produced artificially, followed by the addition of prepackaged foods or commercially prepared deep-fried foods cause elevated levels of LDL (bad) cholesterol and reduced levels of HDL (good) cholesterol, increasing the risk of CVD.

There is also some evidence that artificial trans fats induce inflammation, which can contribute to CVD. Therefore, healthcare professionals emphasise limiting your intake of trans fats.

The Food and Drug Administration (FDA) determined in 2015 that PHOs cannot be classed among the ingredients that are “generally recognized as safe”.

Excessive alcohol

Definition of excessive consumption

Excessive drinking includes binge/heavy drinking. It is defined as consuming 4 or more drinks in the case of women and 5 or more drinks in the case of men, on a single occasion. Heavy drinking is defined as women consuming 8 or more drinks per week and men consuming 15 or more drinks per week.

Alcohol's impact on gut health and inflammation

In large amounts, alcohol along with its metabolites has the capability to overwhelm the GI and liver, resulting in damage both within the GI and other organs. Specifically, alcohol and its metabolites promote inflammation of the intestines through multiple pathways. This inflammatory response leads to the exacerbation of alcohol-induced organ damage, creating a vicious cycle and leading to additional deleterious local and systemic effects.¹³

Vegetable and seed oils

Linoleic acid, vegetable oils & inflammation

The primary basis of concern is that large amounts of Linoleic Acid (LA) will lead to excessive formation of arachidonic acid (AA) and subsequent synthesis of pro-inflammatory eicosanoids (e.g., prostaglandin E₂ (PGE), leukotriene B₄ (LTB₄) and thromboxane A₄ (TXA₂).^14,15

Balance between omega-6 and omega-3 fatty acids

Scientists have demonstrated that omega-6s are pro-inflammatory, while omega-3s are anti-inflammatory.

Omega-6

Omega-6 fatty acids can be found in vegetable oils, nuts and seeds. Omega-6 fatty acids can be helpful for heart health and seem to protect against heart disease.

The body requires fatty acids known as essential fatty acids. It can manufacture most of the fatty acids it needs. But the body can't manufacture LA, an essential fatty acid that includes omega-6 fatty acids.

Omega-3

What are examples of omega-3 fatty acids?

There are three main types of omega-3 fatty acids:

• EPA (eicosapentaenoic acid). EPA is a “marine omega-3” because it’s found in fish
• DHA (docosahexaenoic acid). DHA is also a marine omega-3 found in fish
• ALA (alpha-linolenic acid). ALA is the form of omega-3 found in plants

What are the benefits of omega-3 fatty acids?

Omega-3 fatty acids have many potential benefits for your cardiovascular health. One key benefit is that they play a significant role in lowering your triglyceride levels. Too many triglycerides in your blood (hypertriglyceridemia) result in an elevated risk of atherosclerosis, and through this, can increase your risk of heart disease and stroke. In addition, omega-3s may help you by raising your HDL (good) cholesterol and lowering your blood pressure.

What are the best food sources of omega-3 fatty acids?

Fish is the best source of omega-3s.

The chart below lists some types of fish that can increase the amount of omega-3 fatty acids in your diet. The serving size for each type of fish listed is 3 ounces (oz.), with nutrient data provided by the U.S. Department of Agriculture. While some types of fish contain a small amount of ALA, the chart contains the total DHA and EPA content for consistency. These totals reflect the DHA and EPA content in raw (uncooked) fish, except where noted.

Adapted from: https://my.clevelandclinic.org/health/articles/17290-omega-3-fatty-acids

Strategies to reduce inflammation

The easy ways to keep inflammation in check would involve the incorporation of lots of healthy habits including the elimination of inflammatory products and the involvement of dietary nutrients as well as fibre into your diet accompanied with daily exercise. This may help ward off chronic inflammation and keep you healthier!

Summary

Dietary components, undoubtedly, can influence the immune response. Lifestyle factors such as poor diet, smoking, alcohol consumption, and lack of exercise contribute greatly to the incidence of chronic disease.

Low fibre and high refined carbohydrate intake reduce the production of SCFAs and shift the GI microbiota metabolism towards the utilisation of less favourable nutrients, leading to the production of potentially detrimental metabolites. As such, high fibre consumption in combination with the specific species of microbes able to ferment it, along with low consumption of refined carbohydrates can lead to a range of health benefits for the host.

Additives in processed meat might have some relevance to human diseases, such as diabetes and cancer.

Regarding red meat, the overall findings suggest that clinical and public health guidance should especially focus on the reduction of processed meat consumption. Results from a meta-analysis of RCTs suggested that total and mixed, but not unprocessed, red meat intakes influenced blood CRP concentrations in the blood.

Alcohol and its metabolites promote intestinal inflammation through multiple pathways.

An omega-6 to omega-3 ratio that is too high may contribute to excess inflammation in the body, potentially raising the risk of various diseases.