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Summaries of the latest research:

Your brain needs DHA

Professor of Nutrition in Medicine at Cornell University, Dr Barbara Levine, believes that postpartum depression, attention deficit hyperactivity disorder (ADHD) and low IQs are all linked to the dismally low DHA intake common in the United States. Dr Levine also points out that low DHA levels have been linked to low brain serotonin levels which again are connected to an increased tendency to depression, suicide and violence.

Dr Levine is concerned about the totally inadequate intake of DHA by most Americans. DHA is the building block of human brain tissue and is particularly abundant in the grey matter of the brain and the retina. Low levels of DHA have been associated with depression, memory loss, dementia and visual problems. DHA is particularly important for fetuses and infants; the DHA contents of the infant’s brain triples during the first three months of life. Optimal levels of DHA are therefore crucial for pregnant and lactating mothers. Unfortunately, the average DHA content of breast milk in the United States is the lowest in the world, most likely because Americans eat comparatively little fish. Making matters worse is the fact that the United States is the only country in the world where infant formulas are not fortified with DHA. This despite a 1995 recommendation by the World Health Organization that all baby formulas should provide 40mg of DHA per kilogram of infant body weight.

DHA is abundant in marine phytoplankton and cold-water fish and nutritionists now recommend that people consume two to three servings of fish every week to maintain DHA levels. If this is not possible, Dr Levine suggests supplementing with 100mg per day of DHA.

Levine, Barbara S. Most frequently asked questions about DHA. Nutrition Today, Vol.32, November/December 1997 pp.248-49

Fish consumption and depression

Dr Joseph Hibbeln, a researcher at the National Institute on Alcohol Abuse and Alcoholism reports in a letter to The Lancet that he has found a convincing correlation between fish consumption and the incidence of major depression. Dr Hibbeln correlated the annual incidence of major depression per 100 people in nine countries with the consumption of fish. He found a high incidence of depression in countries with low fish consumption. New Zealand with an annual fish consumption of only 40 lbs had an annual incidence rate of depression of 5.8 per cent while Korea with a fish consumption of more than 100 lbs/year had an annual incidence rate of only 2.3 per cent. Japan with a fish consumption of almost 150 lbs/year had the lowest incidence of major depression (0.12 per cent). Dr Hibbeln cautions that various economic, social, cultural and other factors could have influenced his results, but points out that high blood plasma concentrations of DHA (docosahexaenoic acid), an essential fatty acid found in fish, has been linked to increased serotonin turnover and lower incidences of depression and suicide.

Hibbeln, Joseph R. Fish consumption and major depression. The Lancet, Vol.351, April 18, 1998, p.1213 (correspondence)

Fish consumption slows mental decline

A study in the Netherlands involved almost 1000 men born between 1900 and 1920. The men’s diet was assessed and cognitive function was evaluated in 1990 and 1993 using the Mini-Mental State scale. This includes questions on orientation to time and place, registration, attention and calculation, recall, language, and visual construction.

The researchers found that men with the highest intake of linoleic acid (mainly from margarine, butter, baking fats, sauces, and cheeses) had a 76% higher degree of cognitive impairment than men with the lowest intake. This association held true even after adjusting for age, level of education, cigarette smoking, alcohol consumption and calorie intake.

The intake of omega-3 fatty acids, on the other hand, was not associated with any degree of impairment. Men with a high fish intake were less likely to be cognitively impaired than men with a low intake and their rate of decline over the period 1990-93 was half that of men with a low intake and their rate of decline over the period 1990-93 was half that of men rarely consuming fish.

Kalmijn, S., et al. Polyunsaturated fatty acids, antioxidants, and cognitive function in very old men. American Journal of Epidemiology, Vol.145, January 1, 1997, pp.33-41

Docosahexaenoic acid (DHA) fights depression

Researchers at the National Institute of Alcohol Abuse and Alcoholism believe that the increasing rates of depression seen in North America over the last 100 years are due to a significant shift in the ratio of omega-6 (arachidonic acid, linoleic acid) to omega-3 (DHA, linolenic acid) fatty acids in the diet.

The human race evolved on a diet with a ratio of about 1:1 of these acids. It is now estimated to be between 10:1 and 25:1.

Docosahexaenoic acid (DHA) is a main component of the synaptic membranes and a lack of it has been linked to depression.

Fish oils are a rich source of DHA and it can also be biosynthesized in the body from linolenic acid (e.g.flaxseed oil).

The researchers speculate that the depressions which often accompany alcoholism, multiple sclerosis, and childbirth (postpartum depression) are all due to a lack of DHA and can be corrected by increasing the dietary intake of DHA or linolenic acid (flax seed oil). They also point out that depression and coronary heart disease are strongly associated and that a low intake of omega-3 fatty acids has been linked to both.

Hibbeln, Joseph R and Salem, Norman. Dietary polyunsaturated fatty acids and depression: when cholesterol does not satisfy. American Journal of Clinical Nutrition, Vol.62, July 1995, pp.1-9

Fish consumption reduces suicide risk

Researchers at the University of Kuopio report that regular fish consumption reduces the risk of depression and suicide. Their study involved 1767 Finnish men and women who were evaluated for depression and suicidal tendencies using the 21-item Beck Depression Inventory. They were also asked about their fish consumption. The researchers conclude that people who consume fish twice a week or more have a 37 per cent lower risk of being depressed and a 43 per cent lower risk of having thoughts of harming themselves (suicidal tendencies).

The results are consistent with those of a large Japanese study involving 265,000 subjects who were followed up for 17 years. This study found a decreased risk of suicide among people who consumed fish daily. Dr Andrew Stoll, MD of the Harvard Medical School points out that Icelanders who consume a lot of seafood have far lower rates of seasonal affective disorder (SAD) than do inhabitants of other countries situated at similar latitudes. Both Dr Stoll and the Finnish researchers urge large-scale trials to conclusively determine whether it is appropriate to recommend increased fish intake or fish oil supplementation to depressed people or indeed to the population as a whole.

Tanskanen, Antti, et al. Fish consumption, depression, and suicidality in a general population. Archives of General Psychiatry, Vol.58, May 2001, pp.512-13.

EPA helps schizophrenia

Researchers at the Imperial College School of Medicine in London report that schizophrenia symptoms can be eliminated or at least vastly diminished by oral supplementation with EPA, the major component of fish oils. Their experiment involved a 30-year-old man who had suffered from schizophrenia for over 10 years. He had frequent (at least daily) hallucinations and also suffered from persecutory delusions and thought disorder. The patient was put on 2 grams/day of EPA and was evaluated for schizophrenia symptoms and blood plasma and red blood cell membrane levels of fatty acids at monthly intervals for 6 months. The results were spectacular. After 6 months the overall score for schizophrenia symptoms had dropped by a factor of 6 (an 85% reduction in severity). Episodes of delusions were completely eliminated and there was an 88% reduction in the number of hallucinatory episodes.

Clinical improvement in symptoms in this case was associated with substantial increases in the levels of EPA, DHA and AA in red blood cell membranes and with significant increases in EPA and DHA levels in blood plasma. The researchers conclude that EPA supplementation is able to reverse the abnormal fatty acid profiles found in schizophrenics and that this reversal is associated with, and is likely to be the cause of, the clinical improvement.

Richardson, A. J., et al. Red cell and plasma fatty acid changes accompanying symptom remission in a patient with schizophrenia treated with eicosapentaenoic acid. European Neurophyschopharmacology, Vol. 10, 2000, pp. 189-93.

Fish Oil supplementation helps schizophrenia patients

The Cochrane Library, Oxford, UK, a prestigious medical think-tank dedicated to the development of evidence-based medicine, has released a review of the evidence concerning the use of polyunsaturated fatty acids (fish oils and evening primrose oil) in the treatment of schizophrenia. A wide-ranging literature survey revealed 4 studies that met the Library’s stringent quality measures. The most recent study (Shah 2000) included 30 newly diagnosed schizophrenia patients who were not on antipsychotic drugs at the beginning of the trial. The patients were randomized to receive either a placebo or a daily dose of eicosapentaenoate (quantity not specified). At the end of the 12 weeks all the patients in the placebo group needed to be placed on antipsychotic drugs. Only 9 of the 15 patients in the active treatment group needed these drugs after the 12 weeks.

Another study (Peet 1997) compared evening primrose oil supplementation with placebo in 43 schizophrenics. The patients’ mental state was not improved in either the placebo or the treatment group after 12 weeks. A third study involving 29 schizophrenics compared supplementation with fish oil to evening primrose oil and found fish oil superior.

The researchers conclude that fish oils may be useful in the treatment of schizophrenia and that medical doctors should not discourage their patients from taking fish oil supplements. They add that fish oils seem to be well tolerated and free of adverse effects.

Joy, CB, et al. Polyunsaturated fatty acid (fish or evening primrose oil) for schizophrenia. The Cochrane Library, Issue 4, 2000.

Dementia associated with low DHA levels

Dementia now affects about 47% of the population over 80 years of age in Western countries. The incidence of Alzheimer’s disease, a leading cause of dementia, is growing especially rapidly. There is no cure for Alzheimer’s disease (AD) and it is not at all clear what causes it. Researchers at the University of Guelph now report that they have found low levels of long-chain polyunsaturated fatty acids, notably DHA , in people suffering from Alzheimers Disease and dementia.

The study involved 84 people (aged 80 years or older) who were given a thorough clinical evaluation. Nineteen of the people were diagnosed as having Alzheimers, 10 as having non-Alzheimers dementia, 36 were characterised as non-demented but cognitively impaired, and 19 had normal cognitive functioning. Blood samples were obtained from all participants and analysed for fatty acids. The researchers observed significantly lower levels of EPA (by about 42%), DHA (by 17-33%) and total omega-3 fatty acids (by 23-28%) in the blood of patients with Alzheimers Disease, other dementia and cognitive impairment (non-demented) than in normal controls. DHA is highly concentrated in the cerebral cortex and a deficiency in blood plasma is likely to translate into a deficiency in the brain.

Other research has confirmed the association between low DHA and EPA levels and impaired cognitive function. Other studies have found that fish oil supplementation improves mood, cooperation, appetite, sleep, and short-term memory in Alzheimer patients. The Guelph researchers conclude that an effort should be made to increase the intake of fish or fish oils in the population at large and the elderly in particular.

Conquer, Julie A., et al. Fatty acid analysis of blood plasma of patients with Alzheimer’s disease, other types of dementia, and cognitive impairment. Lipids, Vol.35, Deember 2000, pp.1305-12

Omega-3 fatty acids: the missing link?

Dr Emanuel Severus of the Berlin University finds that major depression is characterised by a deficiency of omega-3 fatty acids and that these acids possess powerful anti-arrhythmic properties. He suggests that the missing link in the recently established association between major depression and sudden cardiac death may be the omega-3 fatty acid deficiency which characterises both conditions.

Severus, W. Emanuel, et al. Omega-3 fatty acids: the missing link? Archives of General Psychiatry, Vol.56, April 1999, pp. 380-81 (letter to the editor)

Low docosahexaenoic acid (DHA) levels and Alzheimer’s disease

DHA, a major component of fish oils, is the most important fatty acid in the brain and retina and makes up more than 30% of the structural lipid (fat) in neurons. There is ample evidence that a deficiency of DHA is associated with depression, attention deficit hyperactivity disorder, and dementia. Clinical studies have shown that an increased intake of DHA may benefit patients with dyslexia and Alzheimer’s disease.

Researchers at Boston University and Tufts University School of Medicine now report that they have found a clear association between low blood levels of DHA and the risk of developing Alzheimer’s disease. Their study involved 1188 Americans (mean age of 75 years) who had blood samples drawn and analysed for DHA in 1985. Sixteen of the participants had clinically diagnosed Alzheimer’s at the time of blood sampling. The researchers noted that 11 of the 16 (69%) had DHA levels in the lower half of the DNA distribution. The remaining 1172 participants were followed for 10 years. Again the researchers noted that participants with DHA levels in the lower half of the distribution had a 67% greater risk of developing Alzheimer’s disease. The researchers suggest that maintaining adequate levels of DHA through the consumption of fish or dietary supplements rich in DHA may be particularly important for the elderly.

Kyle, D. J., et al. Low serum docosahexaenoic acid is a significant risk factor for Alzheimer’s dementia. Lipids, Vol.34 (suppl), 1999, p.S245.

Fish oils and manic-depressive illness

Manic-depressive illness (bipolar disorder) is a common, severe mental illness involving repeated episodes of depression, mania (rapid mood changes, hyperactivity, and excessive cheerfulness) or both. It is usually treated with drugs such as lithium carbonate or valproate. Unfortunately, these drugs are not very effective and recurrence rates are high. It is generally believed that bipolar disorder involves an overactivity in the neuronal signal pathways. Omega-3 fatty acids are known to dampen this overactivity and medical researchers at the Harvard Medical School have confirmed that omega-3 oils may be useful in the treatment of bipolar disorder.

The double-blind, placebo-controlled study involved 30 patients (men and women 18 to 65 years of age) who had all been diagnosed with bipolar disorder. Half the patients were given seven fish oil capsules twice a day while the placebo group were given seven olive oil capsules twice a day. Each fish oil capsule contained 440mg of eicosapentaenoic acid and 240mg of docosahexaenoic acid. All of the participants except four in the fish oil group and four in the placebo group also continued to receive a standard mood-stabilizing drug prescribed previously. The mental state of the participants was measured using four scales (Clinical Global Impression Scale, Global Assessment Scale, Young Mania Rating scale, and the Hamilton Rating Scale for Depression) at the start of the study and after two, four, six, eight, twelve and sixteen weeks. Twelve of the 14 participants in the fish oil group completed the four-month study without major episodes of mania or depression as compared to only six out of 16 participants in the placebo group. Also, while nine of the placebo group members experienced worsening depression none of the fish oil group members did. The four patients in the fish oil group who had not been prescribed mood-stabilizing drugs all completed the study without major episodes, but only one member in the placebo group not on mood-stabilizing drugs did. The average decline in depression rating on the Hamilton Scale was almost 50 per cent in the fish oil group as compared to an increase of 25% in the control group. The Harvard researchers urge further trials of fish oils in the treatment of depression and manic-depressive illness.

Stoll, Andrew L. et al. Omega 3 fatty acids in bipolar disorder. Archives of General Psychiatry, Vol.56, May 1999, pp.407-12 and pp.415-16 (commentary)

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