On Nutrition: Questions about blood type diet and peanuts

A college student in Illinois writes, “I’ve always been interested in nutrition and one of the things I see popping up all the time is something called the 'Blood Type Diet.' I know that losing weight has nothing to do with your blood type and you can lose weight with any diet. But there’s another part of this diet regarding lectins that I’ve always wondered about.

"The author (of this book) claims if we eat foods that are wrong for our blood type, these lectins cause clumping of red blood cells. This supposedly leads to disease and illness later in life. Numerous foods are claimed to be healthy for people with certain blood types and bad for other blood types.

"Some of my favorite foods are supposedly bad for me because I am blood type A. I love tomatoes, cashews, avocados, mangos, coconut and yogurt. But according to the blood type diet, they are all bad for me, and can cause agglutination which leads to possible disease and illness.

"Maybe you can debunk this or point me in the right direction to somebody who can explain this." — Grant L.

I appreciate your confusion, Grant. This diet was popularized back in 1996 with a book called “Eat Right 4 Your Type” by neuropathic physician Peter D’Adamo. Dr. D’Adamo states that if you eat lectins that are not compatible with your blood type, you can experience serious health effects.

Trouble is, there have been no valid studies to prove this hypothesis. One study in 2013 searched all the available evidence and found no particular benefit of this type of diet. Another study in 2014 reported that any health effects seen with these diets was not related to blood type. In other words, eating healthier food is good for us no matter what our blood type.

Lectins are real, however. And some can be toxic such as those found in raw legumes such as beans, lentils, peas, soybeans and peanuts. But who wants to eat raw beans anyway? Boiling them in water deactivates these proteins.

Here’s another twist. Some lectins are actually being studied for their ability to kill off dangerous viruses and fight disease. My advice to you: Unless you have another reason to avoid the healthful foods you love, I wouldn’t base my choices on blood type.

John M. in Lynchburg, Virgina asks, “A recent column mentioned the benefits of many foods including nuts. My question concerns peanuts. I understand peanuts are not from a tree, but grow underground. We normally have them in our house. Do these provide any of the benefits of tree nuts? Or were they called peanuts to eliminate the rather backwoods sound of Goober Peas?”

You’re right, John. Despite their name, peanuts are legumes, not nuts. They are higher in protein than tree nuts and do provide similar health benefits. And according to the Peanut Institute, 98-100% of lectins are destroyed by boiling or roasting. I’ll save goober peas for another column.