In a recent study published in the journal Nature Medicine, researchers review the adverse effects of Western diets on human health.

Review: Western diets and chronic diseases. Image Credit Shutterstock

The real cost of processed foods

Outside of nations like the United States and Western Europe, increased consumption of processed food products that are high in refined sugars, fats, and salts has been observed throughout the world. This shift in dietary habits, which is often referred to as the ‘Westernization of diets,’ has been largely attributed to the affordability and availability of these food products.

Despite the economic benefits associated with consuming a Western diet, the consistent consumption of these food products can increase an individual’s risk of both chronic and noncommunicable diseases. These diseases may include, but are not limited to, stroke, ischemic brain disease, myocardial infarction, ischemic heart disease, obesity, type 2 diabetes, metabolic dysfunction-related steatotic liver disease, inflammatory bowel disease (IBD), and colon cancer.

How does the Western diet affect gut health?

Several studies have documented the deleterious effects of the Western diet on the composition of the human gut microbiome. The reduced intake of dietary fiber and its replacement with food additives like emulsifiers and artificial sweeteners has led to microbial rarefaction, which refers to a reduction in the diversity and abundance of crucial microorganisms within the gut microbiome.

For example, the guts of individuals residing in urban settings often exhibit increased levels of Bacteroides and Prevotella species as compared to those living in rural areas. Higher concentrations of these bacteria can increase serum levels of lipopolysaccharides, which promotes chronic inflammation, as well as immune-mediated and metabolic diseases, such as obesity and type 2 diabetes.

Western diets and cardiovascular disease risk

Current estimates indicate that up to 66% of obesity-related deaths throughout the world are due to cardiovascular disease. Furthermore, both stroke and ischemic heart disease are leading causes of disability-adjusted life years.

Dietary cholesterol, which is often present in high concentrations in Western foods, can facilitate the accumulation of low-density lipoproteins (LDLs), thereby increasing the risk of atherosclerotic heart disease. Likewise, alcohol, saturated fats, and excess carbohydrates, all of which are also characteristic components of Western diets, can lead to high serum triglyceride levels.

Trimethylamine N-oxide (TMAO) is a hepatic metabolite of trimethylamine produced by the metabolism of choline and L-carnitine, both of which are present in red meat products. High plasma concentrations of TMAO are associated with an increased risk of cardiovascular disease, particularly ischemic heart disease.

Effects of Western diets on gut and liver health

Ultra-processed foods, trans fats, and inflammatory ingredients, all of which are present in high concentrations in the Western diet, increase the risk of developing IBD. Alternatively, adherence to a Mediterranean diet, which is associated with the consumption of fruits, vegetables, and whole grains, can reduce the risk of Crohn’s disease and even prevent the development of IBD.

The rising prevalence of several liver diseases, some of which include liver steatosis, cirrhosis, and hepatocellular carcinoma, has also been attributed to the Westernization of diets. The consumption of high levels of fat and fructose can lead to T-cell-mediated liver injury, which subsequently induces steatosis and inflammation. High cholesterol levels within food products can also lead to the oxidation of phospholipids, whereas trans fat consumption can induce cytotoxic T-cell infiltration and liver injury, all of which may induce or worsen both gastrointestinal and liver diseases.

Healthy diets and precision nutrition

Healthy dietary patterns, including the Mediterranean diet, often involve the consumption of plant-based foods such as vegetables, fruits, grains, dairy, and vegetable oils while restricting the consumption of processed foods, refined sugar, saturated fat, red meat, salt, food additives, alcohol, and canned foods. The combination of adherence to a Mediterranean diet and daily exercise can support weight loss in patients with metabolic dysfunction-associated liver disease, as well as overweight or obese individuals. In colorectal adenocarcinoma models, high-fiber diets can improve anti-tumor responses while decreasing tumor size.

Precision nutrition is a potential approach that can be used to improve human health by establishing direct diet-effect correlations. The implementation of precision nutrition may involve healthcare providers establishing patient phenotypes using clinical routine testing and emerging technologies, with artificial intelligence and machine learning aiding in the interpretation and classification of these results to determine optimal diets for their patients.
Understanding the variety of food effects necessitates large-scale prospective nutritional studies, long-term follow-ups, and detailed phenotyping. Thus, large-scale randomized controlled trials, extensive clinical and ‘omic’ profiling, digital patient tracking, and artificial intelligence are needed in the future, particularly when considering ethnic and regional variances in food culture.

Conclusions

Western diets, which are high in sugar and fat and low in fiber, increase chronic disease risk by increasing systemic inflammation and gut dysbiosis. Thus, there remains an urgent need for healthcare and public health professionals to increase awareness of the detrimental effects of a Western diet alongside global discussions on the affordability and sustainability of healthy diets. Stakeholders are also encouraged to promote healthy lifestyles using evidence-based educational programs, regulatory policies, and insurance incentives.