This is very simplified information about lectin intolerance – there are more resources available at the end of the page for further reading for those who are interested in knowing more.

What are lectins?

Lectins are also sometimes called hemagglutinins, they are carbohydrate binding proteins found in many plants. They act as a first line of defence in plants as a way to make themselves less likely to be eaten.

What causes a lectin intolerance?

Other food intolerances are usually the result of a lack of metabolic enzymes. You can read more about them on the Food Intolerance Page. You could say that lectin intolerance is caused by poor food preparation.

Eating foods high in lectins without cooking them can cause them to not be digested as quickly as other foods. The proteins then either start to become digested lower down in the digestive tract which can cause pain and discomfort or the lectin proteins can bind to the cell walls of the gut and pass into the bloodstream. This second route can cause an immune response to lectins in the bloodstream, causing symptoms which can look like food poisoning.

Can you be allergic to lectins?

The simple answer is no, lectins are a large group of proteins which differ in shape. Allergic reactions are usually determined by shape of proteins. You can be allergic to some of the proteins which are functioning like IgE allergens like hevein, chitinases and wheat agglutinins which can also be problematic for those with coeliac disease.

Which are the symptoms of a lectin intolerance?

As these proteins are difficult to digest most of the symptoms are related to gastrointestinal discomfort suffered. Symptoms may include:

Nausea

Vomiting

Diarrhoea

Bloating and inflammation

Flatulence

Stomach cramps

Abdominal pain

Which foods contain lectins?

The Fabaceae family of plants are the most strongly associated with lectins, these are generally legumes and beans. They include:

Black Eyed Peas

Black Turtle Beans

Borlotti Beans

Butter Beans

Cannellini Beans

Chickpeas

Edamame Beans

Fenugreek

Flageolot Beans

Garbanzo Beans

Green Beans

Haricot Beans

Kidney Beans

Lima Beans

Mung Beans

Peanuts

Pinto Beans

Soya Beans

Tamarind

White Beans

You can read more about Legumes on the dedicated page.


Another family of plants which contain moderate amounts of lectins are the Nightshades, also called the Solanaceae family of plants. These include:

Aubergine (Eggplant)

Bell Pepper

Chilli

Goji Berry

Gooseberry

Potato

Tomato

You can read more about Nightshade foods on the dedicated page.

Other foods containing moderate or high amounts of lectins include:

Ackee Fruit

Agave

Almonds

Bamboo Shoots

Barley

Buckwheat (Common and Tartarian)

Canola

Cashew

Cherry

Cacao

Corn

Courgette (Zucchini)

Cow’s Milk

Cucumber

Grape

Hazelnut

Jackfruit

Oats

Okra

Pumpkin Seeds

Quinoa

Rapeseed

Rice

Sunflower Seeds

Wheat

Many of these foods are highly processed before we eat them, for example, sunflower, canola and rapeseed oils, so they may not have as much an effect on a person with a lectin intolerance than other foods. You can read more about any of these foods from the dedicated Food Allergy Index or you can download a Lectin Factsheet from the Allergy Resources Ko-fi Shop for just $0.50 (£0.40 or €0.45).

What about animal lectins?

Casein, a component of cow’s milk is high in lectins. Lectins are found in the meat of other animals like cows and chickens, but these foods are generally cooked before being eaten, so are not as much of a concern as plant-based lectins.

Are lectins bad, do I need to avoid them?

No, foods containing lectins are excellent sources of fibre and protein, they just need cooking properly to minimise the risk. Lectin free diets are discounting a whole lot of important foods containing much needed vitamins and minerals. If you have an additional health condition like leaky gut, Chron’s Disease, colitis or Irritable Bowel Syndrome you may want to reduce foods containing them in your diet or consult your doctor.

How do we inactive lectins in the food we eat?

Soaking legumes or cooking for a long time at high heats will inactivate the proteins. Problems are more likely when raw legumes are not soaked before being cooked or are cooked at too low a temperature for too short a time.

Further Reading

Harvard - Antinutrients - Lectins
Healthline - Lectins
IBD Relief
Science Direct - Lectins

Articles and Journals

Antinutrients: Lectins, goitrogens, phytates and oxalates, friends or foe? 2022
Are Dietary Lectins Relevant Allergens in Plant Food Allergy? 2020
Dietary Lectins: Gastrointestinal and Immune Effects, 2020
Nutrition and gut health: the impact of specific dietary components – it's not just five-a-day, 2020
Effect of corn lectins on the intestinal transport of trace elements, 2019
Dietary Lectin exclusion: The next big food trend? 2019
Lectins, colitis and colon cancer, 2000