According to statistics, the number of people living with dementia around the world has reached 46.8 million in recent years. Their medical condition is mostly due to Alzheimer's disease, according to a new report by Alzheimer's Disease International. The same report estimates that by 2050, there will be 131.5 million people living with cognitive decline.

For many aging people, the simple idea that you could lose your intelligence and memory is terrifying. For this reason, it's no surprise that many turn to anything that offers hopes for a possible way to prevent the progressive loss of mental faculties.

Certain supplements such as omega-3 fatty acids, mostly found in fish oil are often presented as ways to prevent cognitive decline. Previous research has shown that people who have diets that are (naturally) high in omega-3s are less likely to lose their cognitive function.

For this reason, certain health sites and news articles claim that fish oil could help protect your mind. For instance, a post on Dr. Oz's website presents a "5-step Alzheimer's prevention plan". The first step is taking omega-3s as a "brain booster".

However, a major new analysis  has demonstrated that these claims are wrong, or at least there is no evidence to support the fact that nutritional supplements such as omega-3s can help protect your brain.

The new study has been published in the Journal of the American Medical Association.The new evidence is one of the largest randomized controlled trials ever made in order to assess the effects of supplements on cognitive function. A number of 4,000 patients have participated in the study. They were followed over a period of five years by researchers from the National Eye Institute.

The average age of the participants was 72 years. Around 58% were women and all of them had early or intermediate Alzheimer's. The participants in the study were assigned randomly into groups that took omega-3s, a placebo, nutrients from leafy greens, or a combination of those nutrients and omega-3s. Cognitive functions such as memory, attention and mental quickness were tested at the beginning of the study, two years later and after four years in.

The results of the study suggested that none of the supplements made a difference.  According to Dr. Emily Chew of the NIH, as she explained in a press release that contrary to popular belief, the research team could not find and benefit of omega-3 supplements for preventing or stopping the cognitive decline. This also comes to confirm the findings of previous studies, which have also shown that taking omega-3 supplements doesn't seem to slow cognitive decline.