21st February 2018

Don’t believe All You Read – Asparagus Has Not Been Shown to Cause Cancer!

 

Quite strangely, Asparagine, a building block of protein, has hit the news. This followed publication of a study in mice that showed this compound, first identified in asparagus but present in many other foods, may promote the metastases (the spread) of breast cancer to other parts of the body. This caused a flurry of headlines suggesting asparagus may promote breast cancer, but this is not what the study showed.

The More Accurate Story on Asparagine

The more accurate story was that when scientists limited Asparagine in laboratory mice with aggressive breast cancer (triple-negative, which is hard to treat and has a high mortality rate), they found that the number of secondary tumours in other tissues fell significantly. This is interesting because it is the spread of cancer typically to bones, lungs and brain which is the main cause of death among breast cancer patients.

Research suggests that high Asparagine levels might impact on the ability of cancer cells to spread. So in this study, the scientists tested the effects of changing Asparagine levels in the lab in a number of ways. They "turned off" the gene encoding the enzyme (Asparagine Synthetase) that helps make Asparagine in the body, gave the mice a compound that breaks down Asparagine (L-Asparaginase), or fed the mice a diet that was low in Asparagine (a specific mouse chow with 0% Asparagine). In all three cases, the breast cancer was less likely to spread. When the mice were given food rich in Asparagine (4% Asparagine chow), the cancer cells spread more rapidly.

Potential for Asparagine to Slow Spread of Cancer (But in Mice)

The implications of the research are potentially substantial. It is possible that along with chemotherapy, reducing Asparagine could be used as a way to slow the spread of the disease and improve patient outcomes. However at this stage, it's important to remember that the research was only conducted in mice, and even in the mice, Asparagine wasn't found to cause cancer and didn’t affect the growth of the primary tumour in the breast.

Although the study suggests Asparagine restriction, either with drugs or dietary restriction, would help prevent cancer cells from spreading, drug treatments are likely to be more promising. Humans, in any case, produce Asparagine naturally in the body and Asparagine is found in a large number of foods we commonly eat including beef, poultry, eggs, fish, asparagus, potatoes, nuts, legumes and soy.

No Current Evidence to Restrict Certain Foods for Cancer Patients

Human trials have not yet been conducted, so if you or your service users do have cancer, you shouldn't restrict their diet. At the moment, there is no evidence that restricting certain foods can help fight cancer. Giving up Asparagus is not a DIY fix to prevent cancer.

*All information is correct at the time of publishing

Ayela Spiro

Nutrition Science Manager, British Nutrition Foundation

Ayela is a nutrition scientist at the British Nutrition Foundation, where her role involves providing expert advice on nutrition and health issues to a number of key audiences including consumers, health professionals, charities, the media and the food industry. At the heart of her work is the communication of nutrition science that promotes understanding of nutrition and health and contributes to the improved wellbeing of all.

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