Peter R. Cheeke, Ph.D.


Professor of Comparative Nutrition


My research interests include the effects of various phytochemicals, particularly pyrrolizidine alkaloids and saponins, on domestic animals and humans. Pyrrolizidine alkaloids (PA) occur in a number of poisonous plants (e.g., tansy ragwort) as well as in various herbs (e.g., comfrey, borage).

The PA cause irreversible liver damage and some are carcinogenic. PA-induced liver damage alters various aspects of vitamin A, vitamin E, iron, and copper metabolism. By impairing the synthesis of proteins in the liver, including retinol-binding protein that transports vitamin A (retinol) in the blood, PA results in dramatic reductions in tissue and blood vitamin A levels. Vitamin E is similarly affected. It is possible that human consumption of PA in herbal products such as comfrey could cause subnormal tissue levels of vitamins A and E, with the potential for adverse effects on health.

Another area of research interest concerns the dietary effects of saponins, which are detergent-like substances found in many plants, including yucca and ginseng. Yucca saponins have cholesterol-lowering properties in humans and animals. As feed additives, they may be of value in producing eggs and meat with reduced cholesterol content. These and other issues are discussed in the second edition of my book Natural Toxicants in Feeds, Forages and Poisonous Plants.

Last updated November, 1996 

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