There has been a flurry of new studies on the topic of omega-3s and fish oil in the prevention of heart attacks, prevention of cognitive decline and Alzheimer's disease, and the prevention and treatment of arthritis. Here I take a closer look at some of these.
In the past studies of brain health in relation to omega-3 have largely focused on two groups, the aging population and baby in utero, or the very young child, where the brain is still very active growing. I shall consider three different scientific papers. The first of these was published by Muldoon and colleagues,1 based in Pittsburgh who tested the potential associations between the blood levels of omega-3 fatty acids and cognitive functioning in 280 middle aged volunteers drawn not from patients attending doctors or hospitals but from the open community. The age range was 35 to 54 years and all subject were free of any major neurological or psychiatric disorders, and not taking fish oil supplements. The only sources of omega-3s were thus through food. They measured the levels of three omega-3s, the marine sourced docosahexaenoic acid, or DHA, eicosapentaenoic acid, or EPA and the vegetable sourced alpha-linolenic acid, or ALA. Five major dimensions of cognitive functioning were assessed with a 75-minute battery of neuropsychological tests. People with higher blood levels of DHA did better on 4 different tests, as follows:
1. Nonverbal reasoning.
2. Mental flexibility
3. Working memory
Criticism of the study:
This is what scientists call an observational study, which is not as predictive as an interventional study – one in which the invigilators change the dietary intake of a specific ingredients in one of two closely matching groups. In such observational studies, it is regarded as more significant if the association between a variable, such as blood DHA levels, and cognitive functioning shows a linear rise of cognitive functioning in parallel with rising levels of the variable, DHA, in the blood. This was the case here, where “generally" linear associations between DHA and nonverbal reasoning and working memory persisted with additional adjustment for participant education and vocabulary scores. Neither EPA (an omega-3 associated with heart attack prevention) or the vegetable-sourced ALA levels were associated with cognitive performance on any of the five tests. This study confirmed the findings of an intervention study conducted in Italy by Fontani and his colleagues,2 which I reported in The Brain Food Diet, and which showed that supplementing the diet of young healthy individuals improved attention and complex mood profiles, with improved vigor and less anxiety and depression.
Muldoon and colleagues concluded that DHA is important for brain health throughout the lifespan and may be worth studying in the treatment of neuropsychiatric disorders.
The second study I would like to report on is by Farzaneh-Far and colleagues from a number of centres in the United States.3 You could regard chromosomes as constituting very long strings of DNA, which are divided into sections we call genes. At the extreme ends of chromosomes there are strengthened areas, rather like the aiglets, or plastic-covered, bits that protect the ends of laces. These are called “telomeres”. An important part of the ageing process appears to involve the fraying and loss of the telomeres. So anything that strengthens of lessens the fraying and loss of telomeres would be expected to improve life expectancy and health into old age.
Farzaneh’sFar and colleagues measured telomere lengths on the chromosomes of 608 ambulatory coronary artery patients attending outpatient departments in California, being recruited from the ongoing Heart and Soul study. They also compared rates of damage to the telomeres among groups based on the DHA and EPA blood levels at the start of the study to show that, the lower the levels of DHA and EPA in the blood, the greater the level of deterioration of the telomeres over time.
This suggested that increasing omega-3s in our diet offered some protection against the effects of ageing on the chromosomes – or to put it bluntly, omega-3s appeared to offer a healthier and longer life.
The third study, reported by Kim and colleagues from Sweden,4 looked at fish consumption in roughly 10,000 schoolchildren aged 15, comparing subsequent academic grades in relation to levels of fish intake in the diet. The study concluded that grades were better in those who ate fish once a week than those who didn't, and even better still in those who ate fish more often than this. The study also examined the effects of parental education and concluded that the results still applied regardless of differences in education among the parents, suggesting a linear dose-effect relationship between fish intake and academic grades.
All of these studies, like many already performed in this and related fields, give additional support to the importance of the marine-associated omega-3s in brain development and brain (and perhaps mental) health throughout life. They also support earlier studies that suggested that omega-3s also help to prolong a healthy life. Ideally, these results should be extended to interventional studies. However, in the past it was difficult to perform double blind intervention studies, because controls could easily tell if they were eating fish, or taking fish oil products, but with the arrival of the manufacture of pure DHA and EPA from algal and other sources, major intervention studies, similar to conventional pharmacological studies, are now possible in key areas, such as prevention of cognitive decline and the prevention, and possibly also the treatment, of Alzheimer’s disease– and are indeed under way. We look forward to the results in due course.
It is to be hoped that in formulating the methodology of such studies that the organizers take care in some vitally important aspects:
All subjects should be screened for omega-3 blood levels to start with and groups separated to differentiate those with low initial levels from those with normal levels. It is far more likely that people with low levels will respond than those with normal or high levels to start with.
In Alzheimer’s disease it will be important to try omega-3s as early in the disease process as possible. It is possible to diagnose the disease much earlier than is presently the case – the big new trials will no doubt attempt to spot it early.
Patients with the genetic forms of Alzheimer’s, which may be commoner than we previously thought, will need to be examined separately from people not thought to have genetic predisposition since they might respond differently.
While it may be wise to trial DHA alone in neurological prevention and treatment, it might also be wise to include a cohort treated with DHA plus EPA – because EPA, while it has little structural function in the brain, has important anti-inflammatory properties.
1. Muldoon, MF, Ryan CM, et al, 2010. Serum phospholipid docosahesaenoic acid is associated with coginitive functioning during middle adulthood. The J of Nutrition February 24, doi: 10.3945/jn.109.119578.
2. Fontani G, Corradeschi A, et al (2005). Cognitive and physiological effects of omega-3 polyunsaturated fatty acid supplementation in healthy subjects. Eur J Clin Invest 35: 691-9.
3. Farzaneh-Far R, Lin J, et al (2010). Association of marine omega-3 fatty acid levels with telomeric aging in patients with coronary heart disease. JAMA 303(3): 250-7.
4. Kim J-L, Winkvist A, et al (2009). Fish consumption and school grades in Swedish adolescents: a study of the large general population. Acta Paediatrica 99: 72-7.