Kippers and smoked mackerel fillets appear to be a convenient source of fish oils when the fresh varieties are hard to come by. But does the preserving process lead to any significant degradation of their Omega-3 fatty acid content?

Nothing fishy here

Kippers and smoked mackerel fillets appear to be a convenient source of fish oils when the fresh varieties are hard to come by. But does the preserving process lead to any significant degradation of their Omega-3 fatty acid content?

Omega-3 fatty acids seem to have no end of beneficial effects on the heart and cardiovascular system. Recent research at Harvard Medical School in America has shown that men with high levels of these fatty acids that are found in oily fish were much less likely to die suddenly that men with lower Omega-3 levels. Just eating fish also seems to keep you alive longer. Two to four portions of fish a week reduced the risk of coronary heart disease by more than 30 per cent among a group of 85,000 female nurses. Five portions of fish a week reduced the risk of dying from heart disease by 45 per cent. Omega-3 fatty acids are found in oily fish, particularly those with dark meat such as salmon and mackerel.

The theory is that the fatty acids reduce the chance of irregular heart rhythms, as well as lowering cholesterol and blood pressure. There does not seem to be any evidence that preserving fish by smoking reduces its Omega-3 fatty acid content. But there is some potential bad news associated with smoked fish. Research into colon cancer has found that people who regularly eat smoked and salted fish have high levels of N-nitrosodimethylamine. This may increase the risk of bowel cancer. Perhaps the answer is to eat your kippers coated in plenty of bran.

Red nose days

I am in my late fifties and since my teens I have had nose bleeds every three or four months. They started after an attack of whooping cough. What is the cause and what is the best way to deal with the bleeding? I have heard that it can be due to high blood pressure but my GP tells me this is an old wives' tale. Others say that it can be caused by weak arteries in the nose. How to stop it? Is it better to squeeze the nose tightly at the top of the nose, or to lie down with a cold towel on top of the nose? Is cauterisation of the veins effective? Is there any medication to stop the bleeding when it occurs?

It's traditional for doctors to check the blood pressure of patients with recurrent nose bleeds, but your doctor is right – most people with nose bleeds do not have high blood pressure, and most people with high blood pressure do not have nose bleeds. Your nose bleeds may have started after an attack of whooping cough, and strenuous coughing can certainly provoke nose bleeds. But I can't think of any reason why an attack of whooping cough 40 years ago should still be causing nose bleeds. That leaves us with the question of "weak" arteries. Most people who have nose bleeds do have fragile blood vessels inside the nose. Sometimes this is caused by chronic inflammation or allergy. Usually the cause is obscure. If there are one or two vessels that bleed, cauterisation is very effective. But if your nasal blood vessels are generally fragile, cauterisation will probably not help. The best way to stop a nose bleed is to squeeze the upper part of the nose firmly for about 10 minutes. Make sure you are squeezing the soft tissues and not the nasal bone, which is at the upper end of the nose. A cold towel may get you sympathy from your spouse, but it won't do much to stop the bleeding. If you take aspirin, this may make your bleeding tendency worse.

Trouble letting go

I have been having difficulty with my hands recently. The problem is that my grip seems be stiff. If I grab the steering wheel of the car, for example, particularly on a cold morning, I find if difficult to let go. Similarly, if I carry a suitcase or briefcase, it takes a few seconds to release it after I have been holding it for more than a few minutes. Both my father and one of my brothers has the same problem. I am 38 and in good health.

This unusual phenomenon is called myotonia – which is the word used to describe delayed relaxation of a muscular contraction. There are several conditions that can cause this. All of them are rare, but the most likely is something called myotonic dystrophy. This is a genetic condition that affects men and women equally. In its most severe form, it can be present from birth, but often it develops later in life and is relatively mild. It is important for you to see a neurologist who can make a firm diagnosis of the cause of your myotonia. If it is myotonic dystrophy you should ask for genetic advice, so that other members of your family can be checked. Other manifestations of myotonic dystrophy include early cataracts and baldness.

Have your say

Mrs MW disagrees with my advice about using an inhaler to treat a chronic cough:

What a pity that you have suggested the use of drugs for a problem which has a common-sense solution. Provided one drinks plenty of water and never gets dehydrated, it is possible, the moment one feels like coughing, to shut one's mouth firmly, swallow some spit and take a few deep breaths through one's nose. After a few breaths the urge to cough will disappear.

MM from Leeds gives some unsolicited advice on dealing with insect bites:

I have found that dabbing bites immediately with very hot, almost boiling, water stops the itch and makes them disappear. I assume it works because the heat breaks down the chemical structure of the poison. I started doing it after reading about an Australian who had neutralised a snakebite with a cattle-prod.

Please send your questions and answers to A Question of Health, 'The Independent', Independent House, 191 Marsh Wall, London E14 9RS; fax to 020-7005 2182 or e-mail to Dr Kavalier regrets that he is unable to respond personally to questions