The US Agricultural Research Service (ARS) is highlighting research that indicates resveratrol can both inhibit and promote the growth of prostate cancer cells – depending on the length of time cells are exposed to the compounds.
One in vitro and animal study published in the journal Carcinogenesis in 2008 found growth of human prostate cancer cells was inhibited when exposed to the antioxidant resveratrol.
But lead researcher Thomas Wang, who also works for the ARS Diet, Genomics and Immunology Laboratory at the Human Nutrition Research Center in Maryland, found lab animals fed 3 to 6mg of purified resveratrol daily showed increased blood vessels growing around the tumors after initial inhibition of cell growth.
The animals had sex-hormone-dependent tumor cells. Three to 6mg of resveratrol is equivalent to about five glasses of wine or grape juice.
How much is enough?
“Gauging the benefits of consuming these dietary compounds involves careful tracking of concentration, timing, and interactions with other compounds,” said Wang in a recent ARS missive.
“This showed that the concentration of the plant compound is important, but so is length of exposure,” he added. “More research needs to be done in this area. But focusing too much on getting inordinate amounts of a few single nutrients might increase cancer risk.”
The ARS highlighted the issue of overconsumption of particular nutrients with reference to folic acid – derived from the vitamin B form, folate.
“Some consumers might start the day getting 200 micrograms (mcg) of folic acid from a fortified breakfast cereal and another 400 mcg from a multivitamin,” ARS noted.
“For them, it would take just one fortified ‘energy drink’ with an additional 400mcg of folic acid to reach the upper level of 1000mcg per day. Any further enriched foods consumed, such as bread, rice, or pasta, would result in the consumer exceeding the amount thought to be well tolerated biologically. The recommended dietary allowance for folate is 400 mcg daily.”
Joel Mason, director of the ARS-funded Vitamin and Carcinogenesis Laboratory added: “Precancerous and cancerous cells divide rapidly, so they require a lot of building blocks for synthesis of new copies of DNA. It has been shown that under select circumstances, an overabundance of folic acid promotes tumor growth. Studies in laboratory animals substantiate this.”