Research reveals devastating impact of Western diet on human health

In a recent study published in the journal Nutrients, researchers discuss the impact of the Western diet on various aspects of human health including metabolism, the gut microbiome, inflammation, cardiovascular health, mitochondrial fitness, cancer, and mental health.

Study: Global Impacts of Western Diet and Its Effects on Metabolism and Health: A Narrative Review. Image Credit: Ekaterina Markelova / Shutterstock.com

The evolution of the human diet

The industrial revolution and subsequent advancements in animal husbandry and agriculture have changed our diets and the nutritional content of our foods. Improvements food processing technologies have also allowed humans to combine food types and nutrients in novel ways.

Preagricultural diets of humans were completely devoid of foods such as dairy products, alcohol, refined oils and sugars, and cereals, that are now the major component of Western diets. Additionally, modern Western diets often include large amounts of processed foods such as baked goods rich in sugar, snacks, and breakfast cereals.

The shift in dietary patterns throughout history has been accompanied by a rise in epidemiological problems such as obesity, cardiovascular disease (CVD), and diabetes, all of which have significantly increased the public health burden. Likewise, unhealthy diets increase the risk of osteoporosis among postmenopausal women and cancer-related mortality.

Understanding the impact of unhealthy dietary patterns on the various aspects of human health is essential for encouraging changes at both the individual and federal levels.

What constitutes the Western diet?

The Western diet primarily consists of processed foods, soft drinks, and fast food products that are nutrient-poor and energy dense. This diet also comprises large amounts of red and processed meat, which have been linked to an increased risk of CVD and colorectal cancer.

Another key feature of the Western diet is the high sugar content of many food products, the consumption of which has been directly related to an increased risk of obesity, type 2 diabetes, and CVD. Likewise, the Western diet often includes food products that are high in saturated and trans fats, which also increase the risk of CVD.  

The composition of the Western diet differs significantly from that of the Mediterranean diet, which has been widely studied for its beneficial effects on cardiovascular health. As compared to the highly processed foods that are often found in Western diets, the Mediterranean diet comprises fruits, vegetables, whole grains, legumes, and healthy fats like olive oil and nuts.

The proportion of vegetables, fruits, nuts, and whole grains is very low or even absent in the Western diet. These foods are essential sources of vitamins, antioxidants, and other nutrients and, as a result, the low intake of these foods in Western diets has been linked to the prevalence of chronic diseases such as type 2 diabetes, obesity, CVD, cancer, and various inflammatory and metabolic problems.

Key mechanisms that increase disease susceptibility

The Western diet has been shown to alter epigenetics and gene expression due to changes in nutrient availability, hormonal levels, supply of cofactors for gene expression, transcription factors, cellular signaling pathways, deoxyribonucleic acid (DNA) methylation, as well as inter- and transgenerational effects. The Western diet also modifies the gut microbiome, which induces changes in microbiome gene expression, subsequently affecting immune and inflammatory responses.

In addition to the lack of antioxidants present within Western dietary food products, this diet is often high in pro-oxidant compounds that increase the production of free radicals and, as a result, increase oxidative stress throughout the body. The widespread circulation of free radicals like reactive oxygen species (ROS) and reactive nitrogen species (RNS) can directly damage DNA, proteins, and lipids, subsequently leading to cell dysfunction and death.

The frequent consumption of saturated fats, processed foods, and refined sugars, all of which are major components of the Western diet, has been associated with persistent low-grade inflammation. To this end, the Western diet has been shown to increase inflammatory biomarker levels, some of which include C-reactive protein, interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α). In addition to the direct damage elicited by increased oxidative stress, the aforementioned imbalance between free radicals and antioxidants also facilitates the release of pro-inflammatory cytokines.

High-fat diets such as the Western diet result in unfavorable lipid profiles with an increase in the low-density-lipoprotein (LDL) levels and a decrease in high-density lipoprotein (HDL) levels, thereby leading to endothelial dysfunction. Altered endothelial function can subsequently promote inflammatory processes, as well as increase the risk of various pathological processes, including emboli development, calcifications, stenosis, and hemorrhage.

Challenges to improving Western diets

By replacing the high-fat and sugar products often found within the Western diet with fruits, vegetables, legumes, nuts, and whole grains may reduce low-grade inflammation and, as a result, prevent the development of CVD. Despite the seemingly straightforward resolution to this issue, there are many socioeconomic factors that prevent many individuals from consuming a healthier diet.

Income and education levels can be directly correlated to Western diet adherence, with those of a lower income more likely to have poor dietary habits and, as a result, be at an increased risk of chronic diseases like obesity, type 2 diabetes, and CVD.

The surrounding food environment is also crucial in determining dietary choices, as individuals residing in food deserts with limited access to fruits and vegetables are also at an increased risk of poor health outcomes as compared to those living in areas with more access to healthy food options.