Eating a modest amount of walnuts can help protect against prostate cancer, say researchers.
Researchers at the School of Medicine at the University of Texas Health Science Center San Antonio injected immune-deficient mice with human prostate cancer cells.
Within three to four weeks, tumors typically start to grow in a large number of these mice.
The study asked whether a walnut-enriched diet versus a non-walnut diet would be associated with reduced cancer formation. A previous study found this to be true for breast cancer.
Three of 16 mice (18 percent) eating the walnut-enriched diet developed prostate tumors, compared with 14 of 32 mice (44 percent) on the non-walnut control diet.
Also of note, the final average tumor size in the walnut-fed animals was roughly one-fourth the average size of the prostate tumors that developed in the mice eating the control diet.
"We found the results to be stunning because there were so few tumors in animals consuming the walnuts and these tumors grew much more slowly than in the other animals," study senior author Russel Reiter, Ph.D., professor of cellular and structural biology at the Health Science Center, said.
"We were absolutely surprised by how highly effective the walnut diet was in terms of inhibition of human prostate cancer," he added.
The study is published in the journal Cancer Investigation.