Foods That Heal, Foods That Kill—Blood Types and Lectins

Are those back to the stone age, paleolithic, zone, and other variant diets all they're cracked up to be?

by Heidi Stevenson

30 June 2009

It's utterly mindboggling the claims and counterclaims about nutrition and diet. How can you know what is and isn't true? What will help you heal? What will harm you? There are so many diet plans out there—plans to lose weight, plans to be fit, plans for your particular type, plans that say carbohydrates are good and others that say they're bad, ones that say meat is bad and others that are based on it. How can you possibly know what to eat?

The answers aren't simple, but it is possible to find your way through the maze—and that's the goal of Gaia Health, to sort out fact from fiction. To understand some of the nutrition basics, we're going to start with an unusual term: lectins. These are central to unraveling some of the greatest confusion.

Lectins

Lectins are complex protein molecules, made by both plants and animals, which bind to carbohydrates. There are many lectins, a virtually infinite number. Each one can be thought of as carrying a code for a specific carbohydrate molecule. In relation to its particular carb, each lectin is "sticky". That is, it virtually glues itself to its carbohydrate. That's why they're also called agglutinins.

Lectins in Animals

A lectin molecule acts as a messenger to make a cell do something, such as manufacture glycoproteins or remove itself from the bloodstream. Lectins can act as part of the immune system by identifying intruders.

Let's step aside for a bit to discuss blood types—not to worry, the reason will soon become clear.

• An antigen is a molecule that recognizes foreign substances and initiates the production of antibodies to attack them.
• The surface of each red blood cell is covered with antigens. There are four types: O, A, B, and AB.
• Each blood type has antigens of a different type, or none:

  Blood Type	Antigens on Surface	Blood Plasma.
  O	None	A and B Antibodies
  A	Type A	B Antibodies
  B	Type B	A Antibodies
  AB	Both A and B	No Antibodies

• These are the major blood types. There are other subgroupings, such as Rh positive and negative. However, in the discussion of nutrition, both appear to be relatively minor factors and there has been little study.

There is no stronger imperative in the blood system than to attack anything that matches the antibodies circulating in plasma. So, if blood from a type A person enters the blood stream of a type B person, that blood is rapidly glued together, effectively coagulated. This can be a deadly response if a transfusion of the wrong blood type is administered.

Some microbes, such as bacteria, use lectins to fool this system. Some can mimic the receptors on cell surfaces, thus tricking the immune system into thinking they're normal. In fact, this is often necessary for us. Probacteria are critical to the digestive function. Such friendly bacteria need to be recognized by the body. It does, of course, become problematic in the case of harmful bacteria.

Lectins in Plants

The functions of lectins in plants seem to be different. They appear to be a factor in germination, and are often found in seeds as protective devices. Plant lectins can be very dangerous poisons. The castor bean is well known for its lectin poison, ricin. A tiny amount of it can kill by causing red blood cells to clump (agglutinate)—coagulating the blood so it can't flow.

Many plants contain lectins that make them, or their seeds, inedible to animals. Though the lectin ricin is an extreme example, there are many others, including some from animals, that can cause negative effects when eaten. Naturally, systems are in place to protect from them. The catch is that responses by different people are not the same. What's harmful to one person is healthy for another.

The Good and Bad of Lectins

Our bodies contain many lectins. Their ability to latch onto microbes identified as harmful is an integral part of our immune systems. They line the liver's bile ducts, grabbing and gluing harmful microbes. We need them to survive. Yet, some lectins can be poisonous when eaten.

Food-borne lectins can cause problems in different ways. For example, the gluten in wheat contains a protein that can bind to the cells lining the digestive tract. This results in a constant, though usually low-grade, inflammatory process, one that can damage the ability of the digestive tract to absorb nutrient, or even produce holes, resulting in leaky gut syndrome.

Lectins are generally not well digested, passing intact into the blood system. Milk contains a lectin similiar to type B blood. When this lectin passes into type A's blood system, it agglutinates the blood.

Because these aren't wholesale invasions, as with blood transfusions, the damage isn't necessarily noted by us as injurious for a long time, perhaps even years. This, though, is how eating foods with the wrong types of lectins can cause chronic diseases, and why people of different blood types can require different foods for optimal health. Literally, what's healthy for one person can kill another, just as Lucretius noted.

How This Applies to You

At this point, the discussion has covered what lectins are, how they affect the body, and how one's blood type can determine whether a particular food may be harmful. The next article gets into the history of blood types—and that explains why particular foods are okay, while others are harmful for different people, and why there is no one-size-fits-all diet: Foods That Heal, Foods That Kill—Optimal Diet.