Researchers have linked an amino acid found in a variety of foods including asparagus to the spread of breast cancer, work that has been labelled as a "really important study" by Cancer Society New Zealand.
A team of international cancer researchers have shown in mice that limiting the consumption of the amino acid asparagine stopped the spread of triple-negative breast cancer.
Published in medical journal Nature, experts say the study adds to a growing body of evidence that suggests diet can influence the course of the disease.
Speaking on TVNZ 1's Breakfast programme this morning, Cancer Society New Zealand's chief medical director Chris Jackson says "this is a really important study."
"Many people who have cancer worry about whether or not what they eat will fuel the growth of their cancer, and so naturally people are very interested in this," he said.
"What the study did is it look at a particular amino acid which is a building block of protein and looked at whether asparagine concentrations could lead to cancer spread and cancer growth.
"Researches deprived mice of asparagine through a few strict diet or used a drug to stop asparagine metabolism and found quite surprisingly that the breast cancer cells didn't spread.
"This is a rare sub type of breast cancer called triple-negative breast cancer so it does not apply to all breast cancers and of course it is a mouse model so we can't really say the same is true for humans."
Amino acids are used by cells to make proteins. Foods rich in asparagine include dairy, whey, beef, poultry, eggs, fish, seafood, asparagus, potatoes, legumes, nuts, seeds, soy and whole grains.
Most fruits and vegetable are low in asparagine.
"Extreme dieting is certainly going to be very bad for you if you have cancer, but what it does show is that this is a really important potential mechanism and there is actually a drug out there already which we use for leukemia called L asparaginase which actually blocks the metabolism and so this means... this old drug could be used in a new way and could prevent against the spread of cancer," Dr Jackson said.
"I think if people are worried about their risk of cancer, there are many things that we know that we already need to do. We need to not smoke, if we are smokers we need to quit, we probably all need to think before we have that second drink and we need to make sure we maintain our weight in a healthy range.
"Cancer is the number one cause of death in New Zealand, it's the most important cause of death and the rates of cancer are actually going up or the number of people affected by cancer but also the rate of cure from cancer is going up and the cure rates are higher than they have ever been but there is still a lot of work we need to do for cancer in terms of prevention, detection and treatment in order to reduce the impact on thousands of New Zealanders every year."