Excitotoxins are mostly amino acids such as glutamate, aspartate, and metabolites of L-cysteine and homocysteine. Glutamate is a common food additive, and aspartate is a component of the artificial sweetener aspartame.

A considerable number of studies have shown that glutamate is a major stimulant for the growth and invasion of several types of cancer, including colorectal cancers. The gut, including the colon, is lined with many glutamate receptors.

Processed foods contain glutamate additives, and many foods naturally have high levels of glutamate. These foods include:

• Meats

• Tomatoes

• Black beans

• Green peas

• Mushrooms

• Nuts

Food additives high in glutamate include:

• Hydrolyzed vegetable and plant proteins

• Soy protein isolate and concentrates

• Natural flavoring

• Caseinate

• Autolyzed yeast extract

• Carrageenan

You should look for all of these additives on food labels.

Of particular concern is the discovery that glutamate and aspartate make colorectal cancers much more invasive, and therefore more likely to metastasize. This may help explain why meats, with their high heme iron content, are so carcinogenic. It also explains why high-protein diets are associated with high rates of colorectal cancer.

One study found mice that were made diabetic by MSG were highly susceptible to colorectal cancers later in life.

It has also been shown that people with colorectal cancers have significantly higher plasma glutamate levels than healthy individuals.

Blocking glutamate receptors can reduce cancer growth and spread, and significantly improve chemotherapy effectiveness.