Mannose - nutritional supplement, could slow some cancers

By Dr. Ananya Mandal, MDNov 21 2018

Mannose is a sugary nutritional supplement that has shown promise in slowing down the growth of certain cancers in laboratory mice. The results of the five year-long study from Glasgow were published in the latest issue of the journal Nature.

The team of researchers gave mannose to mice with simulated pancreatic, lung or skin cancers. There were no side effects while the cancer growth slowed significantly. Mannose is also found naturally in cranberries and other fruits, the authors explain. Researchers warn however that it is too early to know the direct connection and people should not start supplementing with mannose because it carries risk of side effects.

Cranberries, a natural source of mannose. Image Credit: Tim UR / Shutterstock

The team of researchers gave mannose supplements to mice with the cancers that were also being treated with anticancer drugs such as cisplatin and doxorubicin. On administration of mannose the chemotherapy effects were enhanced, they add. The tumours shrunk in size and the mice lived longer. The team then exposed other cancer cells from bone cancer (osteosarcoma), leukaemia, bowel cancer and ovarian cancer and found that some of the cells responded while others did not respond to mannose in the laboratory set up. They noted that cells that contained high levels of the enzyme phosphomannose isomerase (PMI) were less likely to respond to mannose.

According to lead author Prof Kevin Ryan, from the Cancer Research UK Beatson Institute, the principle behind mannose and its benefits in tumours was the fact that it could block the uptake of glucose by the tumour and thus effectively starve it and slow its growth. Mannose did not affect the surrounding healthy cells which led to the side-effect free profile. He said, “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.”

The team hopes that they can start testing the supplement on human cancer patients soon and would know if it actually worked in humans as well. The team needs to understand why some cancers respond to mannose while others do not, Prof Ryan said.

Martin Ledwick, Cancer Research UK's head nurse warned that these results have not yet been extrapolated in humans and people with cancer should not start supplementing their diet with mannose. Dr Helen Rippon, chief executive of Worldwide Cancer Research too lauded this study saying, “This is a brand-new discovery and only the first step in working out whether mannose might help treat cancer.”

This study received support from the Cancer Research UK and Worldwide Cancer Research.

Source: https://www.nature.com/articles/s41586-018-0729-3