Scientist in the Spotlight: Joshua D. Lambert, PhD
Creosote, Culture, and Catechins
Joshua Lambert, an Assistant Professor in the Department of Food Science at The Pennsylvania State University, has long drawn on cultural cues and plant behavior to motivate his research in cancer prevention. When Lambert was a student in toxicology and pharmacology, he focused his research on the creosote bush, an herb with a rich history of medical use by Native Americans. The creosote bush thrives in harsh, desert conditions and produces phytochemicals that not only suppress the growth of neighboring plants but also exhibit anti-cancer activity in humans.
Lambert continued his study of plants used for their medical benefits at Rutgers. There, he focused on the cancer preventive activities and metabolism of green tea polyphenols. Green tea is the second most commonly consumed beverage on the planet. “If we can find that green tea has a beneficial effect against cancer, that’s a pretty cheap, accessible way for people to do something to improve their own health and well-being," he said.
With the help of AICR, Lambert is seeing how green tea links to cancer prevention, obesity and metabolic syndrome, and why green tea supplements may not be such a good idea.
"There are things in the diet that have biological activity that can be either good or bad, depending on the dose. It’s that issue of if something’s good, more isn’t always better ".
Transforming Tea Compounds
Lambert’s current research focuses on a class of compounds found in green tea called catechins. One of these catechins, epigallocatechin 3-gallate (EGCG), is unique to green tea. Others, such as epicatechin, are relatively widespread in foods such as cocoa, apples and onions. The body’s metabolism of these catechins – referred to as biotransformation – plays a key role in the way green tea affects the body. Lambert’s laboratory studies have shown that catechins have both direct effects on cancer prevention, such as inhibiting tumor growth, and indirect effects, such as prevention of obesity and metabolic syndrome by changing the way the body metabolizes fat.
“Many people drink green tea because they are interested in its health benefits. But the body is not necessarily interested in having the compounds in green tea floating around,” says Lambert.
After the green tea is ingested, it is absorbed and travels to the liver where enzymes add water-soluble compounds to the catechins so they can be excreted. The biotransformed compounds have far less biological activity than the parent compound.
Research suggests that how much EGCG is biotransformed differs between individuals, due primarily to genetic variations. Whereas dietary levels of EGCG are considered safe, EGCG supplements can override the body’s ability to biotransform the compound. During one study by Lambert, mice given high-dose EGCG supplements experienced liver damage as well.
“Since EGCG and the other compounds in green tea are biologically active, there is the risk that at some dose, they will become toxic,” Lambert says.
With AICR support, Lambert is now extending his lab findings to human studies. He is looking at how piperine, a compound in black pepper, affects the bioavailability of EGCG and other green tea catechins.
But, as Lambert notes, people don’t drink EGCG; they drink green tea. “We can study the pure compounds as a means to understand how the whole food might work, but at the end of the day we really need to understand what is going on with the whole food,” he says.
And one point Lambert tries to drive home with his students is that “natural” does not always mean safe. “There are things in the diet that have biological activity that can be either good or bad, depending on the dose. It’s that issue of ‘if something’s good, more isn’t always better.’”
Excerpted from ScienceNow.
Published on August 27, 2012