The Minster Practice, Lichfield
|
|
|
Oily fishNew oily fish advice issued was issued by the Food Standards Agency in June 2004 recommending for the first time maximum levels at which the health benefits clearly outweigh the possible risks from dioxins.
Cod liver oilTwo of the fatty acids in cod liver oil are of interest, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In addition, high levels of vitamins A and D bring additional benefits. Its high vitamin D content giving protection against rickets led to its sound reputation with "helping the bones" extending its use. From the 1950s evidence has emerged of its various properties. Effects include raising good cholesterol, reducing triglycerides, reducing blood pressure, reducing risk of blood clots, reducing inflammation and role in cell membrane development. (High vitamin A levels mean that cod liver oil must not be taken by pregnant women: see diet and pregnancy; interaction with prescribed medication can be a major problem: see general information about complementary medicine). DHA and EPA are types of omega-3 fatty acids which are important structural components of cell membranes and seem to be active anti-inflammatories (e.g. reducing joint pain and stiffness in patients with rheumatoid arthritis). Oily fish and the livers of some non-oily fish in addition to cod are high in omega-3s but the origin are microscopic oceanic plants (phytoplankton) which synthesise the omega-3 before being eaten by the fish. Tinned salmon and pilchards contain similar levels of omega-3 to fresh fish but tinned tuna contains little omega-3 as it is lost in the canning process.
Role of omega-3 fatty acidsThe introduction of a report for the US National Institute for Health summarised the position of omega-3. "Over the past 40 years, an increasing number of physiological functions have been attributed to omega-3 fatty acids, including movement of calcium and other substances into and out of cells, relaxation and contraction of muscles, inhibition and promotion of clotting, regulation of secretion of substances that include digestive enzymes and hormones, control of fertility, cell division, and growth. In addition, omega-3 fatty acids may play an important role in brain development and function. Some evidence has suggested that omega-3 fatty acids in the diet may protect against heart attack and stroke, as well as certain inflammatory diseases like arthritis, lupus, and asthma. The major dietary sources of omega-3 fatty acids in the U.S. population are fish, fish oil, vegetable oils (principally canola and soybean), walnuts, wheat germ, and some dietary supplements."
Fortified hens eggsBy feeding hens fish-based special feed, the eggs become rich in omega-3 polyunsaturated fatty acids. These eggs are commercially available from supermarkets and are big business in the US though much more expensive than ordinary eggs. Omega-3s seem to benefit heart and brain health but oily fish has other benefits besides omega-3 so the fortified eggs should not be seen as a replacement for fish. The eggs do NOT taste of fish! Other fortified foods are available around the world: Australia has bread, Canada has milk from herring fed cows, Finland has blackcurrant juice, Spain has soups and milkshakes and Sweden has omega-3 rich low fat liver pate.
Fish oil supplementsAs is usually the case with dietary matters, supplements are only part of the story with the natural food having additional benefits. However, you would have to eat salmon, mackerel or herring several times a week to take in the levels of omega-3 suggested nowadays so cod liver oil becomes an economic way of boosting intake. Non-repeating varieties are available for the 20% of the population suffering from this problem. Those in favour of supplements also point out that pollutants such as flame retardant chemicals (PDBEs) polychlorinated biphenyls (PCBs) and dioxins can be screened out from products on sale. However, the Food Standards Agency (FSA) has had to advise that some brands should be withdrawn because of higher than acceptable contaminants. For vegetarians who eat fish but not meat, there are gelatine free capsules. A different type of omega-3 (ALA alpha linolenic acid) is available that is sourced from nut and seed oils.
Heart diseaseA study of the Intuit in Greenland in the 1970s showed a very low incidence of heart disease compared to Danish neighbours and the high omega-3 intake from fish was suggested as the reason. A trial of 2033 Welsh men who had suffered a heart attack was published in the Journal of the American Medical Association and showed that deaths were 29% lower in the group that ate oily fish regularly.
OsteoarthritisCod liver oil seems to slow the destruction of joint cartilage that occurs in this condition and a reduction in the levels of destructive enzymes has been shown n those taking cod liver oil daily.
Brain, intelligence, memory, learning, mental healthLow levels of omega-3 have been linked to impaired memory, depression, schizophrenia, Alzheimer's disease, and attention deficit hyperactivity disorder (ADHD). Omega-3 supplementation has been suggested to improve learning, memory, problems with co-ordination and autistic type problems. However, evidence is not yet clear.
Diabetes, blood lipids and omega-3Among 18 studies of type II diabetes or the metabolic syndrome, omega-3 fatty acids had a favourable effect on triglyceride levels relative to placebo but had no effect on total cholesterol, HDL cholesterol, LDL cholesterol, fasting blood sugar, or glycosylated haemoglobin, by meta-analysis. Omega-3 fatty acids had no effect on plasma insulin or insulin resistance in type II diabetics or patients with the metabolic syndrome, by qualitative analysis of four studies.
Inflammatory bowel disease and omega-3Among 13 studies reporting outcomes in patients with inflammatory bowel disease, variable effects of omega-3 fatty acids on clinical score, histological score, induced remission, and relapse were reported. In ulcerative colitis, omega-3 fatty acids had no effect on the relative risk of relapse in a meta-analysis of three studies. There was a statistically non-significant reduction in requirement for corticosteroids for omega-3 fatty acids relative to placebo in two studies. No studies evaluated the effect of omega-3 fatty acids on requirement for other immunosuppressive agents.
Rheumatoid Arthritis and omega-3Among nine studies reporting outcomes in patients with rheumatoid arthritis, omega-3 fatty acids had no effect on patient report of pain, swollen joint count, Erythrocyte Sedimentation Rate (ESR), and patient's global assessment by meta-analysis. A previously performed meta-analysis2 reached the same conclusions for swollen joint count, ESR, and patient's global assessment. That meta-analysis found a statistically significant improvement in tender joint count compared to placebo. The one study that assessed the effect on joint damage found no effect. In a qualitative analysis of seven studies that assessed the effect of omega-3 fatty acids on anti-inflammatory drug or corticosteroid requirement, six demonstrated reduced requirement for these drugs. No studies assessed the effect on requirements for disease modifying anti-rheumatic drugs. None of the studies used a composite score that incorporates both subjective and objective measures of disease activity, such as the American College of Rheumatology response criteria.
|
Send mail to webmaster @minster.org.uk with questions or comments about our website. N.B. Website is for practice patients ONLY.
|
