Fish oil and Alzheimer’s prevention: What happened when researchers tested high-dose DHA for two years and found no significant benefits for memory or brain health

Fish oils have been advertised as one possible method for enhancing memory and brain health through the ageing process. However, there is now new research that suggests that there is no evidence of an improvement in cognition from using a high dosage of omega-3 fatty acids during a two-year clinical trial of people who are at risk of developing Alzheimer’s disease, despite confirmation of entry into the brain. This study was carried out by researchers at Keck Medicine of USC and featured in eBioMedicine.

However, these findings dispute the idea that higher levels of a nutrient in the brain lead to better functioning.

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As stated in the report from ScienceDaily about this study, people who consumed DHA saw an increase in DHA levels in their cerebrospinal fluid; however, this increase did not bring about improved cognitive test performance or reduced atrophy in the area of the brain related to memory.

These results do not suggest that omega-3 fatty acids are worthless and consuming fish has no benefits. Rather, they cast doubt upon the use of fish oil supplements to reduce one’s risk of developing Alzheimer’s disease or cognitive impairment among older individuals.

Researchers tested whether high-dose DHA could protect an ageing brain

The trial consisted of 365 adult subjects aged between 55 and 80 who rarely consumed fish that is one of the principal sources of omega-3 fatty acid intake and were regarded as having a higher risk of contracting Alzheimer's disease.

Subjects were randomly distributed into two groups – one group received 2,000 mg per day of DHA supplementation while the other took a placebo. Participants and scientists did not know about the group division since it was a double-blind study.

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It was decided to use DHA because this compound is one of the key elements of brain cell membranes. It ensures maintenance of neurons and the formation of connections between them, which is vital for cognition.

As DHA has been shown to play an important part in the brain, scientists have tried to prove that an extra supply of it would protect elderly people from mental degradation.

The experiment ran for two years, giving scientists a chance to find differences in the mental skills and the brain structure of the subjects taking the supplement and those receiving the placebo. According to ScienceDaily, scientists created the experiment to find out whether the intake of DHA could protect people from Alzheimer's disease.

However, it was not just the absorption of the supplement which was important; scientists had to find out if DHA affected brain health in any way.

Brain DHA levels increased by 17%, but memory showed no improvement

One of the key findings from the experiment resulted after researchers analysed cerebrospinal fluid of participants, which is a fluid that surrounds the brain and spinal cord. The amount of DHA in cerebrospinal fluid helped researchers to determine whether the substance reached the central nervous system.

The level of DHA in cerebrospinal fluid increased by 17% after six months for participants who were taking the supplement.

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It proves the fact that the treatment influenced DHA concentration in the central nervous system. Nevertheless, improvements in memory and other cognitive functions have not been observed after two years.

Participants underwent cognitive tests both at the beginning of the experiment and during the follow-ups. Those participants who took DHA did not show any significant improvement compared to those taking placebo.

Neither did brain imaging studies show any protection from the supplements. There was no significant effect in terms of preventing any shrinkage of the hippocampus – a part of the brain that plays a vital role in the formation and organisation of memory.

This brings out the difference between the amount of a nutrient found in the brain and the actual performance of the brain despite the increased presence of the nutrient.

As per the ScienceDaily article, the authors of the study came to the conclusion that there was nothing in their findings that supported the use of fish oil supplements as a preventive measure against Alzheimer’s.

Why omega-3 supplements may not deliver the same benefits as food

This finding led to the need for further research on why increasing levels of DHA did not result in cognitive improvements. A theory being considered by researchers is that how the brain utilises omega-3s can be as important as consuming enough of them.

According to Hussein Naji Yassine, MD, lead investigator and director of the USC Center for Personalized Brain Health, his research group is exploring the impact of variables such as age, genetic risk, general health, and diet on the utilisation of nutrients by the brain.

Another variable being considered is whether the intake of these nutrients works in different ways when taken in a pattern versus in a concentrated form.

For instance, the Mediterranean diet involves taking fish together with vegetables, fruits, whole grains, legumes, nuts, and olive oil, which provide many nutrients and are linked to good health.

However, in the study on fish oil, there was no comparison between supplements and a Mediterranean diet, and hence one cannot conclude whether the diet is more beneficial than taking DHA supplements.

It is also important to note that the results should not be used by people to terminate the use of prescribed medicines and supplements, since the study only involved a particular amount of DHA supplements in a certain population of elderly people.

In any case, the researchers point out that brain health is linked to general health. Physical exercise, sufficient rest, a balanced diet, and proper risk management related to cardiovascular and other health conditions are important elements of healthy ageing.

There is one obvious message for consumers from the research results: although an ingredient is crucial for bodily processes, its extra intake in the form of supplements will not protect the individual from developing a disease.

Additional research will be required to find out whether DHA has different effects on certain individuals and to explore possible ways to improve brain metabolism of omega-3 acids.