It may be increasingly unPC to jump on a plane and jet off to sunny destinations for your summer break, but tens of thousands of us are still due to do so this holiday season. If you are one of them, or if you fly often for business, you will find plenty of advice in in-flight magazines and audiovisual systems telling you how to exercise in your seat to reduce the risk of deep-vein thrombosis (DVT).

There is, however, little advice on eating to avoid DVT, especially relevant for those at high risk – meaning anyone who is over 40, obese, uses contraceptive pills that contain oestrogen, takes hormone-replacement therapy, is pregnant, has recently had a baby or surgery or has a family history of DVT.

The sheer immobility of sitting in a plane (or coach, train or car) for more than four hours slows down the blood flow, and flying in a pressurised cabin causes a potential further problem because some of the fluid component of your blood moves into surrounding tissues (the process which causes our ankles and feet to swell when we fly). This makes our blood thicker and more prone to clotting.

If you add a meal rich in saturated fat into the mix, the problem may intensify, since saturated fats raise the levels of blood fats after eating which activates a substance called Factor 7, a central component of the blood-clotting mechanism.

“While no specific clinical research has been done to find out if one-off fatty meals in-flight will push you over the edge and trigger DVT,” says the nutrition scientist Sa-rah Stanner of the British Nutrition Foundation, “in theory eating fatty meals could make a difference.”

Many airlines have responded by offering lighter food options – indicated by their Well Being symbol – which include dishes lower in fat, salt and sugar and higher in fibre (BA does this). It is also a good idea to contact the airline before you fly and order a special meal. Virgin airlines offer a “low fat/low cholesterol” option, for example, which is well worth looking for.

If this is not possible, and you find yourself confronted with a standard in-flight main meal, then try to cut down on one of the following: the relatively harmless-looking cheese and biscuits, the extra butter that goes with your bread roll, the synthetic puddings and treats like ice cream that many airlines offer between meals.

Should you indulge in all of the above, you will add 51g of total fat (men should have a maximum of 90g a day and women 70g) – but, more importantly, 32g of saturated fat, which is just above a man’s daily maximum and is 10g more than a woman’s.

They also add 688 calories, which are likely to make you feel drowsy and less like moving around the cabin or doing your seat-based exercises.

The good news is that there are things you can eat that have quite the opposite effect. Oily fish is rich in beneficial oils that help to reduce the tendency for blood to clot. Salmon is a good option: if it comes with a creamy sauce, try to leave this on the side. It may even be worth taking fish-oil capsules for a week before and after you fly and making a conscious effort to eat more foods fortified with omega3, such as certain brands of eggs, milk and yoghurt. If you have room in your hand luggage, and are particularly well-organised, you can take some John West Tuna Light Lunches with you (they do not need refrigerating and can survive a long-haul flight), or a pot of reduced-fat hoummos with some pitta bread which, if you eat it within a few hours of boarding, will still be safe. Hoummos is rich in sesame seeds and chickpeas, the former being a source of good oils and the latter rich in soluble fibres which help to lower blood cholesterol.

At breakfast time avoid the pastries on offer such as cr-oissants, Danish pastries and muffins which have a good 10g of saturated fat each. Opt instead for fruit and yoghurt, which is available on most airlines and is virtually free of saturated fat. Alternatively, you can take your own breakfast cereal in the form of a small plastic bag of mues-li or bran flakes. Yes, you will look like a health nut, but given that they contain soluble fibre and can lower blood fats, do you care? Drink plenty of water, which in turn will mean that you have to get up regularly to go to the loo: this means you will keep moving, be well hydrated and have thinner blood. Plane-friendly fruit such as grapes, and crudités such as carrot and celery sticks, also give you extra water.

Alcohol, on the other hand, may make you less active and, like coffee and tea, could dehydrate you.

Extra willpower is needed in business and first class, where one tends to be offered alcohol more frequently, usually starting with a pretakeoff glass of champagne and a string of good wines and liqueurs during and after your meal.

Add to this the general “fine dining” experience, with richer food being served more frequently and in greater amounts (foie gras, for example, or a cheese platter rather than a slice), and this means that you should be more careful in your food choice.

In other respects, however, such as the luxury of having more leg space in business or first class, specialists agree that there is no evidence to suggest that those in economy are more prone to developing DVT than others.

In 2003, the results of the world's largest medical research study into the links between long-distance air travel and DVT, published in the South African Journal of Medicine, July 5, 2003, concluded that DVT occurred just as often in economy, business and first class. amandaursell.com

DO

— Avoid big meals and snacks before taking off when in the departure lounge – it is harder to digest food when flying

— Carry herbal teas. Camomile helps to relieve stress and anxiety and also helps you to relax. Ginger is good for circulation and peppermint can help trapped wind, which can be a problem because air expands in your stomach and digestive tract up to 30 per cent when at altitude.

— Drink fruit juices which have high levels of polyphenols. According to Jeya Henry, professor of nutrition at Oxford Brookes University, “these supernutrients found in cranberry, pomegranate and cloudy apples juice help reduce risk of blood clots while the fluid in them improves hydration.”

DON’T

— Eat foods that produce intestinal gases before flying as they will expand in your stomach and cause bloating. Onions, cauliflower, cabbage and pulses like baked beans are the main offenders.

— Drink carbonated drinks, which also cause bloating.

— Drink alcohol. According to Aviation Health, a nonprofit company that provides information on safe flying, it has been demonstrated that one alcoholic drink in the air has the effect of two on the ground and while initially it can promote sleep, within several hours of consumption it can cause insomnia and dehydration.

— Eat a diet high in fat in general day-to-day life and if overweight, try to correct the problem, especially if you are a frequent flyer

Do you have a nutritional topic that you would like Amanda to cover on this page?
E-mail amanda.ursell@thetimes.co.uk
Write to: times2, 1 Pennington Street, London E98 1TT.
Amanda cannot enter into personal correspondence.

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