People with type 2 diabetes "should not be encouraged to take omega-3 fish oil supplements," according to researchers at the University of East Anglia ,
There was concern that omega-3 could be harmful to people with this condition.
However, a BMJ review of more than 80 studies found no evidence of this.
Diabetes UK said it was better to maintain omega-3s by eating oily fish as part of a healthy diet.
Most people with diabetes ̵
Being overweight or obese or being a close relative increases the risk.
The researchers found that omega-3 from fish oils had little or no influence on the likelihood of diabetes diagnosis for glucose metabolism, regardless of how long humans were being studied.
Dr. Lee Hooper, who led the research, told the BBC that there were concerns that omega-3 supplements could damage people with type 2. by making the glucose control more difficult.
But those who suffer or are in danger of developing this disease may also have high levels of triglycerides – a type of blood fat – that has been shown to be reduced by omega-3.
She said, "We found no harm or benefit."
"This is really expensive stuff. When someone is threatened with diabetes, there are much better things to spend money on, such as physical activity – or greasy fish. "
Douglas Twenefour, Deputy Head of Diabetes Care UK, said," A healthy, varied diet is incredibly important, and we know that certain foods – including fruits, vegetables, whole grains, yogurt and cheese – can help to reduce the risk of type 2 diabetes.
"While omega-3 fatty acids are vital to our overall health, it's generally better for people with type 2 diabetes to eat at least two servings of oily fish a week than through the intake of nutritional supplements. "
Dr. Carrie Ruxton from the industry-funded Health and Food Supplements Information Service (HSIS) said: "I would prefer people to follow the government's advice and eat more fish, but that's not the reality and a daily omega-3 affair Supplementation – whether from fish oil or algae – can close the gap. "