Gluten in the human diet

Excessive weight has become a challenge for modern humanity. Reduced physical activity, sedentary lifestyle, stress eating, the culture of fast food, and overeating are just some of the main causes of increased weight, metabolic disorders, and obesity. Lately, there have been numerous discussions about the detrimental role of gluten on digestion, its impact on the digestive system, and disruption of metabolic processes in general. Is the intake of gluten into the human body really so unsafe? In 2022, the "Nutrition Bulletin" published the results of a study titled "Do gluten peptides stimulate weight in humans?" (Fred Bronus et al., 2022). The article's authors speculated that the level of excess weight observed in different countries is not related to the consumption of gluten, which is sourced from grains and wheat products.

Let's delve into human history: throughout the development of agriculture, the traditional grain crops have been wheat, corn, and rice. Currently, approximately 40% of all grain production is allocated to human food, while 35% is used for animal feed (Poutanen et al., 2021). About 95% of wheat grown worldwide belongs to the so-called "bread wheat" varieties (Triticum aestivum var. Aestivum), which are used for bread and bakery products. Only 5% is made up of durum wheat (Triticum turgidum var. durum), which is used for pasta production. Differences in the protein content of cereals are a result of genetic variations among species and varieties, the amount of nitrogen fertilizers used, and growing conditions in the environment (Godfrey et al., 2010; Kasarda, 2013). Grains are an essential source of protein and carbohydrates in human consumption.

Let's analyze the nutritional composition of wheat:

Protein: up to 16%.
Starch: up to 75%.

So, what is it in grains' composition that is considered dangerous and leads to the abandonment of this excellent nutritional product? Indeed, certain protein fractions can cause gastrointestinal diseases such as celiac disease, which is a disruption of the absorption process in the small intestine, typically with a genetic nature.

Wheat protein consists of:

Gluten: up to 75%.
Non-gluten protein: up to 25%.

Gluten is composed of:

Gliadin: up to 50%.
Glutenin: up to 50%.

The non-gluten fraction includes:

Albumins: up to 70%.
Globulins: up to 30%.

These two fractions are known as amylase trypsin inhibitors (ATIs). It is these two protein (gliadin and glutenin) and two non-protein fractions (ATIs) that can cause digestive disorders in some individuals.

All wheat varieties contain gluten, which makes up:

70-80% of all proteins in soft wheat varieties.
77% in durum wheat varieties.

Barley and rye contain proteins closely related to gluten, so they are included in the list of gluten-containing grains (Gellrich & Schieberle, 2003; Schalk et al., 2017). These proteins have specific names:

Hordein in barley, accounting for 50% of all proteins.
Secalin in rye, accounting for 50% of all proteins.

The protein in oats is called avenin. It is less closely related to gluten, so oats are not classified as gluten-containing. However, during production, transportation, and processing, oats can become contaminated with gluten-containing grains or flour.

In 2019, the World Health Organization and the United Nations published a joint document titled "Sustainable healthy diets: guiding principles." The research presented in this document describes the current situation of low consumption of plant-based foods and high consumption of animal products, along with the significant consumption of ultra-processed foods, which adversely affect health. The document recommends shifting the dietary focus towards plant-based rather than animal-based foods, emphasizing the importance of increasing the consumption of diverse plant-based foods, including whole grains. Similar recommendations can be found in most documents on balanced nutrition and food consumption (Martini et al., 2021).

However, on the other hand, there is growing public concern about the gluten content in cereal crops, which is a protein causing digestive disorders, various chronic gastrointestinal diseases, and weight gain.

If gluten is indeed the cause of increased weight, what are the biochemical mechanisms behind this process? What do modern studies on the effects of gluten on the human body say? Is there a connection between the amount of gluten-containing products consumed and body weight? You will find the answers to these questions in our article "Does Gluten Contribute to Weight Gain?"