Phenylalanine comes in several forms as a supplement:
L-phenylalanine is an essential amino acid. It's also found in protein in the foods we eat.
DL-phenylalanine, which contains both the D- and L-forms
The human body cannot digest pectin in its natural form. But an altered form of pectin, known as modified citrus pectin (MCP), has properties that allow it to be digested.
Why do people take MCP?
People take MCP for a variety of reasons. Some research suggests that pectin, like other soluble fibers such as those found in oatmeal and in psyllium husks, can help lower LDL "bad" cholesterol. But the effect is a small one. If you have high cholesterol, soluble fibers such as pectin may help to lower it, but they usually can't do the job on their own.
Pectin has also been used to control diarrhea, and some evidence points to its effectiveness for treating very young children. The FDA, though, decided in 2003 that the available evidence does not support such a use. The following year it banned the use of pectin in over-the-counter diarrheamedications.
Pectin may have a potential role in cancer care. Studies done on animals showed that pectin can slow or stop the spread of prostate, breast, and skin cancer, particularly to the lungs. However, MCP had no effect on the cancer where it started.
In a small study of men with prostate cancer for whom standard treatment had failed, MCP appeared to slow the growth of their cancer.
Larger, better designed studies are needed before any conclusions are drawn about MCP's potential as an anticancer agent.
Pectin has also been used to try to treat heavy metal toxicity, which can result from exposure to lead, mercury, arsenic, and other elements. Some people believe that MCP can help the body excrete such poisonous substances. But little unbiased research exists to support such claims.
Optimal doses for MCP have not been established for any condition, though 6-30 grams divided throughout the day have been used. Also, as with supplements generally, the quality of the active ingredients in products that contain MCP varies from maker to maker.