Oils and arthritis – can they help?
Reproduced from Issue 109 of Arthritis Today
Dr Gail Darlington, consultant rheumatologist at Epsom General Hospital, examines the effectiveness of oils on arthritis.
As with much that is written about nutrition and arthritis, the use of oils contains both sense and nonsense, scientific fact and considerable uncertainty. It is, however, important, since many arthritis patients take some form of oil, albeit frequently in doses probably too small to be of definite benefit, and always on the assumption that oils are beneficial and without risk. They need to know whether the money they spend on oils is well spent or a waste of time and whether these oils are safe.
Oils are polyunsaturated fatty acids (PUFAs) and fall into three major classes: n-3, n-6 and n-9 groups, also known as Omega 3, 6 and 9.
What are fatty acids?
Fatty acids are named according to their length i.e. short-chain medium chain and long chain and also by their degree of chemical saturation. PUFAs (polyunsaturated fatty acids) are further described according to the position of the first-double bond e.g. n-3 fatty acids, in fish oils, have their first double bond between the third and fourth carbon atoms in the chain while n-6 fatty acids, found in vegetable oils, have the first double bond between carbon atoms six and seven.
Both plants and animals can make the parent fatty acid of the 9 series, i.e. oleic acid.
Only plants can make the n-3 and n-6 parent fatty acids (α-linolenic
and linoleic acid respectively), so in animals these 'essential
fatty acids' must be obtained from the diet.
(α-linolenic acid is found in dark green vegetables, rape seed oil,
soya bean oil and certain nuts) and is converted in humans to produce
eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These
are also obtained from the oils of the fish that eat phytoplankton
and are stored in cod livers or the flesh of herring or mackerel.
ANTI-INFLAMMATORY ACTIVITY OF OILS
FISH OILS
Diets rich in n-3 PUFAs produce suppression of the immune system, and populations which have high dietary intakes of fish, such as Greenland Eskimos, have a low incidence of inflammatory and auto-immune disorders, such as arthritis. As a result, there has been an increasing interest in the use of n-3 PUFAs to treat rheumatoid arthritis, psoriasis and other inflammatory conditions.
Different dietary fats have different effects on inflammation. In humans, n-6 PUFA, found in margarines and cooking oils, tend to increase inflammation whereas n-3 PUFA and monounsaturated fatty acids tend to reduce inflammation.
Changing the fat we eat can also alter the fatty acid composition of many cells in the body including those essential in immune responses.
Rheumatoid arthritis (RA)
Little is known about the efficacy of fish oils when taken by patients who treat themselves with the low doses bought from the chemist. In research studies in which high doses of fish oil are used, however, fish oil supplements have produced modest but useful improvement in symptoms of rheumatoid arthritis, although usually when used in doses much larger than those frequently bought over the counter by patients. An increased intake of fish oils, therefore, may be a useful additional treatment in RA by suppressing immune responses and by allowing the number of non-steroidal anti-inflammatories (NSAIDs) to be reduced.
Osteoarthritis (OA)
Fish oil has been reported to be of some benefit in OA but further work is required to determine its role, if any, in this condition.
Systemic Lupus Erythematosus (SLE)
Some benefit has been claimed in patients with lupus who were given a low fat diet with additional fish oils. However, clinical trials in humans have yielded a range of responses and more work is required to clarify the situation.
Fish oil safety
Fish oil supplements are generally considered to be safe, although side effects can arise.
Side effects of fish oils include:
- Nausea and flatulence.
- May exacerbate asthma in aspirin-sensitive people.
- May increase blood glucose in non-insulin dependent diabetics.
- Nosebleeds – use carefully in patients taking anticoagulants or aspirin, and in haemophiliacs.
- Avoid in early pregnancy: fish oils contain vitamin A which may produce birth defects.
- Fish oil metabolism uses vitamin E – a powerful antioxidant, so increased vitamin E intake is required if fish oil is being taken to avoid the lowering of vitamin E levels.
- Long-term, the full effects of large doses of fish oils are unknown, but they could lead to problems in the blood and in the immune system. Until more is known about the long-term effects, the lowest effective doses should be take, ie 500–750mg a day of EPA.
Beneficial effects
Fish oil may lower blood fats, blood viscosity (thickness) and blood pressure, with beneficial affects on coronary heart disease. The Department of Health recommends that everyone should eat a portion of fish (preferably oily) at least once weekly to reduce the risk of heart disease.
Fish oil supplements produce modest but useful improvement in symptoms of rheumatoid arthritis, as already mentioned above.
OTHER MARINE OILS
Mussel oil from New Zealand green-lipped mussel (Seatone and Lyprinol)
Seatone is an oily extract of the New Zealand green-lipped mussel,
Perna canaliculus, which has been shown to have anti-inflammatory
activity in rats, but results in humans have largely been unimpressive.
Lyprinol is a much more concentrated version of the same mussel
oil and is reported to have anti-inflammatory activity similar to
that of (NSAIDs) without abrasive effects in the stomach or seafood
allergy, but further work is required to investigate the role of
this oil.
Evening Primrose Oil (EPO)
EPO is rich in gamma linolenic acid (GLA), a parent substance of prostaglandin E1 (PGE1) and of 15 hydroxy-dihomo-gamma linolenic acid (DGLA) – both of which have anti-inflammatory activity.
Use of EPO in RA has produced various responses and further research is required to assess its role but, when taken with fish oil, GLA and EPA together have useful anti-inflammatory effects.
EPO may also be of benefit in Raynaud's phenomenon with systemic sclerosis.
Other oils
Olive oil has been shown to have some beneficial effect in RA, as have borage oil (starflower oil) and blackcurrant seed oil. More work is required to clarify the role of these oils.
SUMMARY
Oils, particularly fish oil, have a mild but useful anti-inflammatory effect which may enable dosage and side effects of other drugs to be reduced.
More research is needed, however, to clarify the role of oils in the treatment of arthritis since, although generally beneficial, they have some side effects. We await the results of further studies with interest.
