Advice on eating legumes

What are legumes?

Legumes are a type of food that come from a specific type of plant.

Examples of legumes include green beans, lentils, peas, kidney beans, French beans, sugar snap peas, etc. They are considered a source of good quality protein and soluble fibre and are low in fat and calories. Legumes contain naturally-occurring compounds called lectins.

What are lectins?

Lectins are proteins found in many plants, especially in legumes. Lectins are thought to play a role in the natural defence mechanism of plants against harmful bacteria and predators. 

Lectins are also found in many other plants (such as tomatoes, potatoes and whole grains), but legumes contain the highest concentrations. 

Are lectins harmful to consumers?

Yes, consumption of lectins from insufficiently prepared legumes can cause illness in some consumers. For example, eating uncooked fresh green beans (e.g., French beans) or insufficiently prepared dried beans (e.g., dry kidney beans) may cause illness due to the presence of lectins.

Symptoms can include nausea, vomiting and diarrhoea within 1-3 hours after eating the uncooked or insufficiently prepared legumes. The severity of illness depends on the type of lectin consumed, the amount consumed, and an individual’s sensitivity to that type of lectin. If you think that you may be ill as a result of having eaten uncooked or insufficiently prepared legumes, you should seek medical advice. This applies in all cases if you believe that any food you have eaten has made you ill.

How can I reduce the risk of getting sick?

The FSAI recommends that consumers take the following precautions to reduce or eliminate the harmful properties of lectins, making legumes safe to eat:

Dried Beans: The product manufacturer’s instructions should be followed for the preparation of these beans. In the absence of cooking instructions, dried beans should be first soaked for at least 12 hours. It is important to discard the water used for soaking, and to use fresh water for the cooking step to ensure the removal of lectins present in the water that was used for soaking. The beans should then be boiled for at least 30 minutes before eating them.

Fresh Beans: These beans should be thoroughly rinsed in fresh water and cooked/boiled for 10 minutes before eating them.

Canned Beans or Beans in Jars: These types of beans are already fully cooked, which ensures that lectins are destroyed. It is important to follow the manufacturer’s instructions for the preparation and consumption of these beans.

Do I need to avoid lectin-containing foods? 

No. Properly prepared legumes pose no risk and are a low-cost source of nutrients which are important in maintaining good health.