The jury is out on the efficacy of probiotic supplements. Photo / NZME
The jury is out on the efficacy of probiotic supplements. Photo / NZME
COMMENT:
Gut health is a hot nutrition topic. Most of us are pretty familiar now with some forms of probiotics, prebiotics and fermented foods, all designed to help us improve the mysterious population of bacteria that lives inside us (we carry around a couple of kilos of bacteria each; aslightly icky but fascinating thought).
There's a huge industry now around probiotics; in particular supplements. There's lots of research on probiotics, but it's fair to say that even though scientists are learning a lot, there's still a huge amount that's unknown. This hasn't stopped the natural health industry taking the probiotic ball and running with it, though. The trouble is, we really don't know if the probiotics we might be taking are doing anything, or worse: whether they might be doing harm.
This has been highlighted in some new research on probiotics and cancer treatment, reported on recently at a meeting of the American Association for Cancer Research.
It's known that patients who are undergoing cancer treatment can get better results from some therapies if they have a diverse gut microbiome; in other words if they have a wide range of healthy bacteria in their guts. It's a promising idea that makes sense: gut bacteria play a big role in moderating the immune system; so changing it might be able to help patients undergoing immunotherapy. But taking a bunch of probiotics might not be the best way to achieve that, and in fact, it might have the opposite effect.
The researchers reported that eating whole grains, fruits and vegetables, and a high-fibre diet was positively associated with bacteria previously shown to confer response to particular cancer treatments. (Patients who consumed a high-fibre diet were about five times as likely to respond to treatment compared to patients who consumed a low-fibre diet). Diets high in added sugars and processed meat were negatively associated with these bacteria.
The surprise finding was that patients who also took probiotic supplements had lower gut microbiome diversity, and poorer response to cancer therapy.
Gut health is a hot nutrition topic. Photo / 123RF
This point was brought home in a personal way to cancer researcher Dr Lorenzo Cohen, who has written about his diagnosis of advanced melanoma, and his confidence that he could improve his chances by boosting his gut bacteria. He pulled out all the stops: probiotics, prebiotics and fewer grains. But as he wrote in the Wall Street Journal:
"After about six months of this modified diet, I expected my gut microbiome to be in great health. Instead, to my shock, its diversity was less than before I started the diet. I had actually made the health of my microbiome worse".
Cohen changed his approach and started to add more whole grains like oats, buckwheat and barley and seeds such as hemp, flax and chia, which reversed the negative effects of his previous diet.
We know from University of Otago research that fibre and whole grains are associated with reduced risk for many diseases. It seems they're also what we need if we're living with cancer; perhaps far more than pricey supplements.
• Niki Bezzant is editor-at-large for Healthy Food Guide; www.healthyfood.com
