(March 2013) A new US study suggests that flaxseed, which is rich in omega 3 fatty acids and lignans, can stop prostate cancer tumours from growing. The study was presented at the 43rd annual meeting of the American Society of Clinical Oncology (ASCO) in Chicago on Saturday by researchers from Duke University Medical Center, Durham, North Carolina. The researchers think that flaxseed, which has similar properties to sesame seed, probably interrupts the chain of events that eventually makes cells multiply out of control and become a tumour.

Dr Wendy Demark-Wahnefried, a researcher in Duke's School of Nursing and lead investigator on the study said that: "Our previous studies in animals and in humans had shown a correlation between flaxseed supplementation and slowed tumor growth, but the participants in those studies had taken flaxseed in conjunction with a low-fat diet." However, she explained that: "For this study, we demonstrated that it is flaxseed that primarily offers the protective benefit."

The study was funded by the National Institutes of Health, and researchers at the University of Michigan and the University of North Carolina at Chapel Hill also took part. Demark-Wahnefried and colleagues recruited 161 men who were due to have surgery for prostate cancer (prostatectomy: where all or part of the prostate gland is removed). The patients were randomly assigned to one of four groups. One group took 30 grams of flaxseed a day for an average of 30 days before they had the operation (the flaxseed only group). Another group did the same but also followed a low-fat diet (20 per cent or less of their calories from fat). A third group did not take the flaxseed and only followed a low-fat diet, while the fourth group, a control, had none of the interventions.

After the surgery, the researchers examined the tumour cells under a microscope to assess how quickly they had multiplied. They then compared the men who had only flaxseed, with or without following a low-fat diet, with the men in the other two groups: no intervention and low-fat diet only. They found that the slowest rate of tumour growth occurred in the two flaxseed supplemented groups. Demark-Wahnefried said: "The results showed that the men who took just flaxseed as well as those who took flaxseed combined with a low-fat diet did the best, indicating that it is the flaxseed which is making the difference." The flaxseed supplement was given in ground form because in the whole form the seed coat is hard and undigestible. The patients took the flaxseed either in drinks, sprinkled on food, or with yogurt.

Flaxseed is thought to stop the growth and spread of cancer cells. This could be because the omega-3 fatty acids it contains interferes with the ability of cancer cells to cling onto other body cells, said Demark-Wahnefried. The lignans it contains may also have antiangiogenic properties, the ability to stop the blood supply to the tumour. Demark-Wahnefried said that they were "excited that this study showed that flaxseed is safe and associated with a protective effect on prostate cancer". In next phase of their research the team hopes to study the preventative properties of flaxseed, and its effect on patients with recurrent prostate tumours. As well as being antiangiogenic, the lignans in flaxseed, one of the richest sources of these fibre-related compounds, are thought to interfere with or prevent cell division and affect hormones. They are antimitotic, affect androgen metabolism and have estrogenic effects, said Demark-Wahnefried.