Tumours use more glucose than normal, healthy tissues. However, it is very hard to control the amount of glucose in your body through diet alone. In this study, the researchers found that mannose can interfere with glucose to reduce how much sugar cancer cells can use.
“Tumours need a lot of glucose to grow, so limiting the amount they can use should slow cancer progression. The problem is that normal tissues need glucose as well, so we can’t completely remove it from the body. In our study, we found a dosage of mannose that could block enough glucose to slow tumour growth in mice, but not so much that normal tissues were affected. This is early research, but it is hoped that finding this perfect balance means that, in the future, mannose could be given to cancer patients to enhance chemotherapy without damaging their overall health.”
Professor Kevin Ryan, lead author from the Cancer Research UK Beatson Institute said.
It significantly slowed the growth of their tumours, with no obvious side-effects, researchers found.
However, patients are being told not to start supplementing with mannose because of the risk of side-effects.
Scientists hope to test the supplement in people soon.
Mannose, which can be bought in health food shops and is sometimes used to treat urinary tract infections, is thought to interfere with the ability of tumours to use glucose to grow.
They found it enhanced the effects of chemotherapy, slowing the growth of tumours and reducing their size. It also increased the lifespan of some mice.
Some cells responded well, while others did not. How well the cells responded appeared to depend on the levels they had of an enzyme that breaks down mannose.
Lead author Prof Kevin Ryan, from the Cancer Research UK Beatson Institute, said his team had found a dosage of mannose that “could block enough glucose to slow tumour growth in mice but not so much that normal tissues were affected.”
Bodies require glucose for energy but cancerous tumours also use it to fuel their growth.
“This is early research but it is hoped that finding this perfect balance means that, in the future, mannose could be given to cancer patients to enhance chemotherapy without damaging their overall health,” he said.
One advantage of mannose is that it is cheaper than drugs produced by pharmaceutical companies.
And Prof Ryan said he hoped tests in people could begin soon.
However, he and other experts warn that the findings do not mean people with cancer should start supplementing with mannose.
Martin Ledwick, Cancer Research UK’s head nurse, said, “Although these results are very promising for the future of some cancer treatments, this is very early research and has not yet been tested in humans.”
“Patients should not self-prescribe mannose, as there is a real risk of negative side-effects that haven’t been tested for yet.”
“It’s important to consult with a doctor before drastically changing your diet or taking new supplements.”
Prof Ryan said his team would next seek to investigate why mannose worked in some cancer cells and not others, so they could work out which patients might benefit the most.
While it will be interesting to see how humans respond to the mannose treatment, scientists have warned patients to avoid self-prescription of mannose as there might be potential health risks for humans.
The research is published in the journal Nature.