Pectin is a water-soluble carbohydrate found in ripe fruits such as apples, grapefruits, and plums. It has always been associated with human consumption since it is found in all terrestrial plants and is most concentrated in citrus fruits. Commercial uses include manufacturing foods, drugs, and cosmetics. It is probably best known as the gelling agent used in producing marmalades and jellies.

In modified citrus pectin (MCP), the pH and polysaccharides have been altered to form groups of the simple sugar galactose. In making MCP, the carbohydrate chains are split into smaller pieces. MCP's source is the peel and membrane of citrus fruits. MCP is purportedly useful for anti-metastatic purposes, but not for treatment of primary tumors.

MCP is available in powder or capsule form. For the powder, 5-6gm is mixed with water or juice and taken 2-3 times per day with meals.

Certain cancer cell types, such as prostate cancer, breast cancer, colon cancer, lymphoma, melanoma, glioblastoma, and laryngeal epidermoid carcinoma, all have specific protein molecules on their cell surface, called galectins.Metastatic cells express significantly more galectin-3 than the original primary tumor cells from which they were derived. Galectins are known for their carbohydrate-binding abilities. These proteins on the cancer cell surface are involved in binding between cells. They play an important role in cellular interactions during the metastatic process, binding to galactose on neighboring cancer cells and oligosaccharides on the surface of normal cells.

Human studies of colon, stomach and thyroid cancers showed that the amounts of galectin produced increased proportionally as the cancers progressed from their early to advanced stages. Higher galectin levels permit greater adhesion of cancer cells and increases the ability of these cells to bind to non-cancerous cells at a distant site where metastasis occurs. It is felt that MCP works by blocking tumor cell surface galectins, so that tumor cells cannot adhere to other cells. This galectin blockage inhibits the aggregation (colony forming) of cancer cells and inhibits adhesion of cancer cells to host cell surfaces.