According to Dr John Bertram, carotenoids stop tumour growth by restoring communication between cells. And by keeping cells 'talking' to each other, they may also prevent cancer from developing in the first place.
The findings are further evidence of the potential value of carotenoids to the food industry, which so far has been slow to push the health benefits of the ingredient. Mostly used as a natural colouring, carotenoids have been 'under-utilised' by Europe's health food industry, according to a recent Frost & Sullivan report, and consumers are still unaware of their health benefits.
Speaking at BioScience2004 in Glasgow today, Dr John Bertram reported that dietary carotenoids increased the activity of a molecule called connexin 43. This molecule forms small channels between cells and, by doing so, connects virtually all cells in the body. Through these channels, cells exchange nutrients and many vital signals that ensure normal cellular growth.
Most tumour cells have lost this ability to communicate and, as a result, have isolated themselves from their normal neighbours. But when Bertram's team treated normal mouse cells with isolated carotenoids, they prevented the formation of cancer by cancer-causing chemicals and increased communication in these cells, he said.
Then they treated three different types of human tumours with carotenoids. Communication between cells was restored and the tumour cells behaved more normally, both in culture and when grown in laboratory animals.
"We've looked at five or six carotenoids and they all appear to have this ability to restore communication between cells," Dr Bertram told NutraIngredients.com.
"We're now working on the mechanism. A lot of work has been done on gap junctions but we were the first to discover that dietary compounds play a role here too."
Maintaining efficient communication between cells may also be how carotenoids and retenoids stop cancer forming in the first place. Studies have shown that up to 70 per cent of human cancer is preventable and 40 per cent of this can be attributed to diet. Dietary carotenoids have been associated with lower risk of cancer and heart and eye diseases.
The Hawaii scientists are also developing novel versions of water-dispersible carotenoids that they say are up to 100 times more potent in cell cultures, largely through their enhanced absorption.
Although carotenoids are available as dietary supplements, they typically do not dissolve well in water and are not readily absorbed by the body.
In collaboration with Hawaii Biotech, Dr Bertram has chemically modified the carotenoid molecule to make them water-dispersible. An ester linkage allows the ingredient to get in to cells and liberate the natural compound.
While the highly absorbable carotenoids are being targeted at clinical use - in prevention of cancer, chronic liver disease, eye disease, and damage to the heart due to short of blood supply- Bertram said they could also be used in food supplements.
"Most of vitamin E is synthetic and so is ascorbic acid. In any case, the ester allows the natural compound to be liberated," he said, adding that previously published research on animal models have found these new compounds to be very effective in protecting the heart after an artificial heart attack.
"If you look at the amount of lutein in dietary supplements, it probably isn't enough to do the job. We have developed a much more efficient delivery system that increases absorption and therefore could increase the protection," he added.
Bertram is currently developing water-dispersible lycopene to use in pre-clinical studies on human tissue to investigate prevention of prostate cancer and a new version of lutein, which has strong evidence of protection against age-related macular degeneration.