When it comes to cancer prevention, Omega-3 fatty acids from fish pack a stronger punch than flaxseed and other oils, new research has found.

Marine-based omega-3s are eight times more effective at inhibiting tumour development and growth than plant-based sources, said the study published in the Journal of Nutritional Biochemistry. "This study is the first to compare the cancer-fighting potency of plant-versus marine-derived Omega-3s on breast tumour development," said David Ma, Professor at University of Guelph in Ontario. "There is evidence that both Omega-3s from plants and marine sources are protective against cancer and we wanted to determine which form is more effective," Ma said.

There are three types of Omega-3 fatty acids: a-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). ALA is plant-based and found in such edible seeds as flaxseed and in oils, such as soy, canola and hemp oil. EPA and DHA are found in marine life, such as fish, algae and phytoplankton.

The study involved feeding the different types of Omega-3s to mice with a highly aggressive form of human breast cancer called HER-2. Ma exposed the mice to either the plant-based or the marine-based Omega-3s.

"The mice were exposed to the different omega-3s even before tumours developed, which allowed us to compare how effective the fatty acids are at prevention," said Ma. Overall exposure to marine-based omega-3s reduced the size of the tumours by 60 to 70 per cent and the number of tumours by 30 per cent.

However, higher doses of the plant-based fatty acid were required to deliver the same impact as the marine-based Omega-3s, the study said. Omega-3s prevent and fight cancer by turning on genes associated with the immune system and blocking tumour growth pathways, said Ma. Based on the doses given in the study, humans should consume two to three servings of fish a week to have the same effect, he said.