Lectins are proteins found in certain foods such as wholegrains, beans and some vegetables. They have recently come under fire for causing problems such as bloating, nausea, immune dysfunction, leaky gut and chronic disease. This could explain why some people, especially vegetarians, experience bloating and other health concerns even though they eat what is considered a ‘healthy diet’.
Let’s delve into the world of lectins to find out whether they are healthy for us or not.
Lectins explained
Lectins are a type of protein that is naturally present in 30% of our foods—especially grains and legumes. Once consumed they bind to glycoproteins which perform many functions in the body from regulating the immune system to maintaining protein levels in the blood. Lectins are resistant to human digestion as they enter the bloodstream unchanged.
It is believed that lectins are part of a plants natural defence system to protect against insects. They may also have evolved as a way for seeds to remain intact as the travel through the digestive system for later dispersal.
Foods high in lectins
Lectins are found throughout our entire food supply but are found in high concentrations in the following foods:
- Potatoes
- Eggplant
- Soybeans
- Lentils
- Capsicum
- Wheat germ
- Red kidney beans
- Peas
- Tomatoes
- Peanuts
If following a low lectin diet it is usually recommended to also avoid grain-fed meats, A1 milk, corn and grains. Instead the diet focuses on pasture-fed meats, A2 milk, olives and olive oil, sweet potato, leafy greens, cruciferous veggies and others.
The problem with lectins
Research has shown that lectins impact health in multiple ways, from digestion to chronic disease risk.
Inflammation
Chronic inflammation is linked to many serious medical conditions, including heart disease, cancer, and depression. Some scientists believe lectins are harmful and cause inflammation. Researchers have linked lectins to autoimmune diseases, including celiac disease, diabetes, and rheumatoid arthritis. Autoimmune diseases are a result of the immune system attacking healthy cells in the body resulting in fatigue, inflammation and chronic pain.
Leaky gut
Leaky gut syndrome is where the lining of the intestines is permeable and allows molecules to pass through to the bloodstream. This affects nutrient absorption, contributes to toxicity and can lead to irregularities in the immune and digestive system. Lectins are believed to contribute to leaky gut because they irritate the lining of the digestive tract.
Anti-nutrients
Lectins are classified as antinutrients since they block the absorption of some minerals and other nutrients. Nutrient deficiencies are very common and lectins might be a reason you are lacking in iron, magnesium or zinc, even when there should be adequate sources in the diet.
Immune response and toxicity
The presence of particular lectins can stimulate an immune system response by producing antibodies. This can be detected by performing food intolerance or allergy testing.
In certain circumstances if beans or lentils are served raw they can be especially dangerous.
There have been numerous cases of raw kidney beans causing food poisoning. This is because they contain a lectin called phytohemagglutinin which triggers extreme nausea, vomiting, diarrhoea and stomach cramps.
Digestive complaints
Adverse reactions to lectins that involve the digestive system are very common. Signs that you are sensitive to lectins in food include:
- Bloating
- Nausea
- Vomiting
- Diarrhoea/constipation
- Flatulence
- Stomach upset
Foods high in lectins are notoriously hard to digest. However, the good news is, proper preparation of foods containing lectins can help to reduce any unwanted side-effects.
Preparing foods that are high in lectins
Fortunately, there are many ways to reduce the lectin content of your food without going on a lectin-free diet or severely restricting your intake altogether.
Ways to decrease lectins in foods include
Soaking—before cooking soak beans and grains overnight and change the water often.
Pressure cooking & boiling—in legumes this can nearly eliminate all lectins. In other foods it can reduce the lectin content while also promoting easier removal from the body.
Sprouting—this helps to deactivate the lectins in seeds, grains or beans.
Fermentation—this allows beneficial bacteria to digest and convert many of the harmful substances. Think fermented soy products such as miso and tempeh and fermented vegetables like sauerkraut.
Peeling—lectins are found in higher concentrations in the skin of fruits and vegetables and peeling reduces its amount.
Deseeding—removing the seeds from pumpkin, zucchini, tomatoes and cucumber can help to reduce the lectin content.
The benefits of lectins
It’s not all bad news—lectins do offer health benefits and here’s a quick summary.
- Lectins have antimicrobial properties to protect against infection
- Certain lectins contain anti-cancer properties
- Regulate cell adhesion
- Help synthesize glycoproteins
- Involved in immune regulation
The thing is, lectins have been consumed as part of the diet without any major issues in many parts of the world. Especially in regions with low rates of chronic disease and where people live longer. Sometimes cutting out certain foods high in lectins can be beneficial for some people but may be unnecessary for others. Cutting out entire food groups can lead to nutrient deficiencies and reduces the amount of fibre in the diet.
The bottom line
Instead of focusing on cutting lectin foods out of your diet altogether focus on practicing proper preparation techniques to decrease lectin content. This ensures you’re not missing out on important nutrients which are often found in foods that contain lectins.
References
- https://www.medicalnewstoday.com/articles/319593.php
- https://gundrymd.com/reduce-lectins-diet/
- Hivrale AU, Ingale AG. Plant as a plenteous reserve of lectin. Plant Signal Behav. 2013 Dec; 8(12): e26595 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4091380/
- Vojdani A. Lectins, agglutinins, and their roles in autoimmune reactivities. Altern Ther Health Med. 2015;21 Suppl 1:46-51. https://www.ncbi.nlm.nih.gov/pubmed/25599185
- Cordain L, et al. Modulation of immune function by dietary lectins in rheumatoid arthritis. Br J Nutr. 2000 Mar;83(3):207-17. https://www.ncbi.nlm.nih.gov/pubmed/10884708
- Jiang QL, et al. Plant lectins, from ancient sugar-binding proteins to emerging anti-cancer drugs in apoptosis and autophagy. Cell Prolif. 2015 Feb;48(1):17-28 https://www.ncbi.nlm.nih.gov/pubmed/25488051/
- Chan YS, et al. Isolation of a glucosamine binding leguminous lectin with mitogenic activity towards splenocytes and anti-proliferative activity towards tumour cells. PLoS One. 2012;7(6):e38961 https://www.ncbi.nlm.nih.gov/pubmed/22720002
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