The choice of protein is crucial, as these are fundamental elements for the structure and functionality of our body. When we talk about high quality proteins we refer to bioavailability, digestibility and composition in amino acids. In particular, digestibility consists in the amount of protein that the body is able to absorb compared to the amount consumed. This depends on several factors, such as the structure of protein, its processing, and the presence of ANF anti-nutritional factors. Anti-nutritional factors are the natural compounds that, being present in various ways in vegetable foods, such as legumes, nuts, seeds and fruits, act against the correct and optimal absorption of nutrients, reducing the nutritional value of the food consumed.
First of all, what are the anti-nutritional factors in plant proteins?
According to the study “Plant food anti-nutritional factors and their reduction strategies: an overview“, anti-nutritional factors present in plant proteins include fiber, phytates, saponins, tannins and enzyme inhibitors.
Especially fiber is contained in most plant foods. As an anti-nutrient, fiber reduces the assimilation of minerals, and can sometimes even lead to intestinal problems. However, it also has several proven positive effects, such as increasing satiety, intestinal regularity, or stabilizing blood sugar and reducing cholesterol, for example.
Phytates, or phytic acid, is found in seeds of plants, mainly in legumes, peanuts, cereals and oily seeds, and reduces the absorption of minerals, in particular calcium, magnesium and zinc, during digestion, therefore decreasing their assimilation by the human organism.
Saponins, on the other hand, terpene glycosides of plant source, are anti-nutritional factors found in most plant-based foods. These have an impact on the absorption of vitamin A and E, as well as lipids. It should be noted that when taken at low levels, saponins do not have harmful effects on health.
Tannins, also contained in coffee, wine, tea and cocoa, are aromatic substances of phenolic nature which together with proteins create indigestible compounds, and therefore they also affect the assimilation of essential amino acids. They also bind to digestive enzymes, reducing the absorption of all nutrients.
Finally, enzyme inhibitors can vary in type, such as trypsin or amylase inhibitors, and have different effects on protein or carbohydrate digestion. For example, trypsin inhibitors are contained in legumes, such as soybeans, and can result in depressant effects on the normal and proper functioning of protein digestion.
The question is, how do we reduce or remove these anti-nutritional factors?
In addition to reducing the absorption of various minerals and nutrients, anti-nutritional factors can cause toxicity when taken in high amounts in the diet. There are several strategies for reducing these anti-nutritional components in plant foods, and these include technological processing procedures such as soaking, milling, cooking, sprouting, and fermentation.
For example, milling is the most traditional method of separating the anti-nutritional factors present in cereal bran, such as phytic acid. However, removing anti-nutritional factors may also result in removing important nutrients, such as minerals. Fermentation can also be a useful strategy to reduce anti-nutritional factors in plant foods, as well as a way to improve mineral absorption. Soaking, used on both legumes and seeds as well as grains, is also an interesting approach to lower the content of anti-nutritional factors, as well as improving enzyme release, digestibility and overall nutritional value. As well as soaking, other traditional techniques such as cooking and boiling promote increased nutritional value and lower anti-nutritional factors.
Although the term “anti-nutritional” is strongly related to a negative image, it is necessary to highlight that these compounds can also bring benefits to human health. According to the study “Food processing for the improvement of plant proteins digestibility ” fibers are very important for the proper functioning of our body, playing a key role in satiety and intestinal regularity. In addition, several studies claim that tannins have the great potential to reduce the risk of some cancers and strengthen the immune system, while phytates have beneficial antioxidant activities, anticarcinogenic, and may help reduce the formation of kidney stones.