Two new University of Illinois studies say that lunasin, a soy peptide often discarded in the waste streams of soy-processing plants, could be beneficial for fighting leukaemia and blocking the inflammation due to chronic health conditions such as diabetes, heart disease, and stroke.
In the cancer study, researchers identified a key sequence of amino acids-arginine, glycine, and aspartic acid, (the RGD motif)-that triggered the death of leukaemia cells by activating a protein called caspase-3.
"We confirmed lunasin's bioavailability in the human body by doing a third study in which men consumed 50 grams of soy protein-one soy milk shake and a serving of soy chili daily-for five days. Significant levels of the peptide in the participants' blood give us confidence that lunasin-rich soy foods can be important in providing these health benefits," said Elvira de Mejia, a U of I professor of food science and human nutrition.
"Other scientists have noted the cancer-preventive effects of the RGD sequence of amino acids so it's important to find proteins that have this sequence," she added.
The scientists also verified lunasin's ability to inhibit topoisomerase 2, an enzyme that marks the development of cancer.
The researchers could also quantify the number of leukaemia cells that were killed after treatment with lunasin in laboratory experiments.
In another study, the first to report lunasin's potential anti-inflammatory activity, they showed that lunasin blocked or reduced the activation of an important marker called NF-kappa-B, a link in the chain of biochemical events that cause inflammation.
They also found statistically significant reductions in interleukin-1 and interleukin-6, both important players in the inflammatory process. The reduction in interleukin-6 was particularly strong, she said.
Although inflammation is linked in the public mind with chronic health problems such as heart disease, diabetes, and rheumatoid arthritis, de Mejia said it also plays a role in the development of cancer.
"We know that chronic inflammation is associated with an increased risk of malignancies, that it's a critical factor in tumor progression," she said.
"And we can see that daily consumption of lunasin-rich soy protein may help to reduce chronic inflammation. Future studies should help us to make dietary recommendations," she added.