Fatty acids and Alzheimer’s disease
Wendy Jones, 24th October 2008
Several newspapers and TV programmes, including The Guardian and the Daily Telegraph, have reported this week on a recent research study which is said to have suggested that arachidonic acid might be damaging to brain cells and that therefore dietary omega-6 fatty acids might raise the risk of developing Alzheimer’s disease. It was suggested in the press that this research provides a route for treatment of the disease; while it suggests a route for future drug development, this is still quite speculative.
WHAT ARE THE FACTS?
Arachidonic acid is a very long-chain omega-6 fatty acid, which is produced in the human body naturally from omega-6 fatty acids found in many commonly used vegetable oils, nuts and seeds, as well as animal fat and dairy produce. It is, however, rarely found in vegetable oils; the major dietary sources are eggs, meat and fish. It has important roles in immune and neurological development and function.
Importance of arachidonic acid in brain and immune development and function: Along with the very long-chain omega-3 fatty acids, arachidonic acid forms a major component of the phospholipids found in the brain and nervous system. It is also important because it is the precursor (or starting material) for production of eicosanoids, molecules involved in the body’s inflammatory response (reaction to infection or injury), so a sufficient supply of omega-6 fatty acids is essential to ensure that we have the capability to fight infection and injury.
Importance for babies: Arachidonic acid is known to be present in small amounts in human breast milk, and in recent years has begun to be added in to infant formulae by the major babymilk manufacturers. Indeed, infant formula containing added arachidonic acid, as well as the omega-3 fatty acids DHA and EPA, are associated with improved growth and development as well as improved development of the immune system.
WHAT DID THE RESEARCH SHOW?
The research which was the subject of these press reports was carried out in a lab in San Francisco using mice which had been specially bred to develop a condition like Alzheimer’s disease, and reported in the medical journal NATURE. What the research showed was that high levels of arachidonic acid in the brains of these mice seemed to be linked with other chemical changes that are found in the brains of Alzheimer’s patients.
This recent study did not investigate the effects of dietary omega-6 fatty acids on the production of arachidonic acid or the other chemical changes in the brain. To understand how relevant the research is to Alzheimer’s disease will require more studies, first in human tissues in the lab and then in living humans. Any therapeutic developments are a long way off.
WHAT DID THE PRESS REPORTS SAY?
The Guardian report was inaccurate in a number of aspects.
- It suggests that arachidonic acid is found in foods such as vegetables and nuts – this is not the case. It is found in small amounts in fish, eggs and meat.
- Arachidonic acid is generally considered as vital to to a healthy diet. It is not an essential fatty acid, as it can be made in the body provided there is a sufficient supply of linoleic acid, the ‘parent’ compound
Both the Daily Telegraph and the Daily Mail suggested that the research would lead to a cure for Alzheimer’s disease. At best, it suggested a route to follow in developing new drugs.
The suggestion that an excess of omega-6 fatty acids may have adverse consequences on brain development and function is not new – for example a study reported in 2007 by a French group suggested that a diet rich in fish, omega-3 oils, fruits and vegetables may lower the risk of dementia and Alzheimer’s disease, whereas consuming omega-6 rich oils could increase chances of developing memory problems. This research team looked at over 8,000 men and women over 65 years of age and followed them for 4 years. They showed that people who regularly consumed omega-3 rich oils, which they described as canola oil, flaxseed oil and walnut oil (and this would include hempseed oil), reduced their risk of dementia by 60 percent compared to people who did not regularly consume such oils. People who ate fruits and vegetables daily also reduced their risk of dementia by 30 percent compared to those who didn’t regularly eat fruits and vegetables.
High omega-6;omega-3 ratios in the human diet have also been associated with other aspects of brain dysfunction, such as higher incidences of depression and ADHD.
What are the implications for GOOD OIL?
This research looked at particular chemical pathways involving fatty acids in the brains of experimental mice bred for the purpose. While interesting, it does not directly lead to the conclusion that eating omega-6 fatty acids will increase the risk of developing Alzheimer’s disease. Other research such as the French study shows that there are benefits from ‘balanced’ oils such as GOOD OIL which contain omega 6 and omega 3, compared with the traditional oils containing a predominance of omega-6.
Both omega-6 and omega-3 fatty acids, as found in GOOD OIL, are essential components of a balanced diet, allowing the body to build the components of the brain and immune system which enable it to function effectively. Dietary intakes of omega-6 compared with omega-3 have increased dramatically over the last hundred years (from 2-3: 1 to around 15-17:1) and it seems possible that this ‘inbalance’ may contribute to a number of physical and mental disorders in the modern world. The bulk of evidence from dietary and developmental studies suggests that a good balance of both omega-6 and omega-3 is optimum for development and maintenance of good health, always of course as part of a well-balanced and healthy diet.
- The recent research reported in the Guardian etc: Sanchez-Mejia RO et al (2008) Phospholipase A2 reduction ameliorates cognitive deficits in a mouse model of Alzheimer’s disease. Nature Neuroscience 11: 1311-1318.
- The French study from 2007: Barberger-Gateau P et al (2007) Dietary patterns and risk of dementia; the Three-City cohort study. Neurology 69: 1921-1930
- Calder PC (2007) Dietary arachidonic acid: harmful, harmless or helpful? British Journal of Nutrition 98: 451-3
- Rapoport SI (2008) Brain arachidonic and docosahexaenoic acid cascades are selectively altered by drugs, diet and disease. Prostaglandins, Leukotrienes and Essential Fatty Acids, e-published last month ahead of print.