Lectins are natural substances found in plants, fungi and animals. They protect plants against diseases and pests. Lectins are therefore also found in foods such as pulses, wholemeal cereals and vegetables. If they are ingested in large quantities, e.g. if you eat undercooked beans, they can lead to symptoms of poisoning such as nausea, stomach pain, vomiting and diarrhoea.

Lectins are found in foods such as pulses, whole grains and vegetables. They are widespread and have been found in various plant families. Pulses such as beans, kidney beans, soya beans, peas, chickpeas and lentils have the highest lectin content. The lectin content is greatly reduced by soaking and sufficient cooking.

Eating foods with a high lectin content can lead to poisoning. It is therefore important to prepare these foods correctly in order to reduce the lectin content. The first symptoms of poisoning become noticeable after around two to three hours and range from mild stomach upset and abdominal pain to intestinal inflammation. In the worst case, excessive consumption can lead to death. Tolerance varies from person to person. Children are particularly at risk due to their low body weight. Medical advice should always be sought in the event of symptoms of poisoning.

There are currently no legal maximum levels or health guidelines for lectins.

Lectins are glycoproteins that can impair the absorption and utilisation of nutrients in the body. They are used by plants to protect them from herbivores, diseases and pests and have been found in various plant families, such as:

• Adoxaceae (e.g. elderberry...)
• Amaranthaceae (e.g. quinoa, black cumin seeds...)
• Cannabaceae (e.g. hemp seeds)
• Fabaceae (e.g. adzuki beans, chickpeas, lentils...)
• Gramineae (e.g. barley, rice, wheat...)
• Lamiaceae (e.g. chia seeds)
• Linaceae (e.g. linseed)
• Pedaliaceae (e.g. sesame seeds)
• Solanaceae (e.g. peppers, potatoes, tomatoes, aubergines...)

Different types of lectins have different binding abilities, so their effects vary. Lectins can be very resistant to both the acidic pH in the stomach and the digestive enzymes in the intestine. As a result, they cannot be completely broken down in the gastrointestinal tract and intestinal transit is therefore delayed. They bind to the cells of the intestinal mucosa, causing damage to the microvilli located on the intestinal villi. The microvilli increase the surface area of the intestine and optimise nutrient absorption. If they are damaged, nutrient absorption is impaired. Studies show that lectins impair the absorption of calcium, iron, phosphorus and zinc. Lectins are therefore classed as anti-nutritive agents. On the other hand, lectins also have positive properties such as an antioxidant effect, and they also ensure a longer feeling of satiety, a slower rise in blood sugar and a stable insulin level. Lectins are found in foods such as pulses, wholemeal cereals and vegetables. These are also rich in B vitamins, proteins, fibre and minerals. Eating these foods has beneficial properties for the body despite the presence of lectins.

The highest lectin activity has been measured in fabaceae, i.e. pulses such as beans, kidney beans, soya beans, peas, chickpeas and lentils. The best-known lectin is phasin, which is mainly found in raw beans.

Lectins are measured in haemagglutination units (HAU). Measurements have shown that red kidney beans in their raw form contain 20,000 - 70,000 HAU and after a thorough cooking process the lectin content drops to 200 - 400 HAU. In one study, lectin activity was measured in various foods in their raw and processed state (soaked, cooked). Chickpeas had around 13,312 HAU/g in the raw state. After soaking for 12 hours and cooking for 30 minutes, the lectin activity was reduced to 6,656 HAU/g. Soaking and cooking have a major influence on the lectin concentration in the food.

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