Dr John Briffa: Going off the boil

The success of The Darkness and the return of Starsky & Hutch and the Chopper bike have made me quite nostalgic for the Seventies. Mind you, not everything about this era was good. These were the days, after all, when a glass of fruit juice or half a grapefruit might be found as starter options in restaurants, and the presence of the black forest gateau loomed large. Another portion of Seventies cuisine best forgotten was a general tendency for overcooked vegetables. Such culinary excesses not only resulted in a rather unappetising mulch, but would also rob vegetables of much of their rich stash of health-giving goodies. Many find the more recent vogue for al dente cooking to be more pleasing to the palate, and it may well help preserve a vegetable's nutritional bite, too.

Recognition of the fact that contracted cooking times mean extended benefits from food has led some to extol the rapid-fire food preparation offered by microwave ovens. Recently, this concept was subjected to a degree of scientific scrutiny. In a study published in the Journal of the Science of Food and Agriculture, researchers assessed the effects of a variety of cooking methods on nutrient levels in broccoli. While boiled broccoli was found to lose two-thirds of its original content of diseaseprotective nutrients, known as flavonoids, this actually compared quite favourably with the whopping 97 per cent loss induced by microwave cooking. Analysis of other nutrients revealed similarly dire depreciations.

Other research shows that how vegetables are boiled may also affect their nutrient status. One study found, for instance, that frozen vegetables such as spinach, peas and green beans retain appreciably more vitamin C when plunged into hot water direct from the freezer than when thawed prior to cooking. The amount of water in which vegetables are placed also seems to have an important bearing on their nutritional status. A study published last year discovered that the smaller the volume of water used to boil vegetables, the better their retention of important nutrients known as phenolics. The evidence suggests that the one way to preserve the nutritional value of boiled vegetables is to ensure that they don't end up in deep water.

There is some evidence that there are even more benefits to be had by steaming. In the study which identified hefty flavonoid losses from the microwaving and boiling of broccoli, steaming induced only an 11 per cent degradation in this type of nutrient. In another study, boiling was found to reduce the level of folate (believed to protect against both heart disease and cancer) in spinach and broccoli by more than half. In comparison, steaming had minimal effects on the level of this vitamin. For those looking to get maximum nutritional value from their cooked vegetables, I reckon it's full steam ahead.

Nutrition news

Dentists and health experts have made clear the potential for refined sugar to cause dental decay. However, this is not the only way in which our diet can affect the state of our teeth. For instance, it is known that acidic foodstuffs have the capacity to cause what is known as dental erosion, a wearing away of the hard enamel on the surface of the teeth that weakens them and increases the risk of chipping. In a recent study published in the British Dental Journal, the consumption of carbonated drinks (known to be acidic) in 12-year-old children was found to increase the risk of dental erosion from 59 to 252 per cent, depending on the amount and frequency of consumption. Because dental erosion is linked to the acidic nature (as distinct from the sugar content) of foodstuffs, it is thought that 'diet' drinks are as likely to erode teeth as their sugary versions. For the best dental health, the advice is to avoid the consumption of carbonated soft drinks, including those that have been artificially sweetened.

Dear John

I am considering taking ginkgo biloba to help my failing memory. I've read that this can thin the blood and increase a tendency to bleeding. Is this correct?
Clive Hislop

Ginkgo biloba is believed to be a circulatory stimulant, and some studies suggest that it might improve memory and mental function later in life. There have been some reports that individuals taking ginkgo might be prone to abnormal bleeding, especially when this herb is taken in combination with blood-thinning drugs such as aspirin or warfarin. In a recent study published in the journal Clinical and Laboratory Haematology, individuals were treated with 120mg (the usual recommended dose of the herb), 240mg or 480mg of ginkgo biloba each day for two weeks. None of these doses of ginkgo was found to have any effect on the clotting function of the blood. However, this study does not rule out the possibility that ginkgo may interact with drugs such as aspirin or warfarin. While it seems ginkgo is safe to take for the majority of people, those taking bloodthinning medication should consult their doctor before taking this herb.

· If you have any issues you would like Dr Briffa to address in his column, please email him on john.briffa@observer.co.uk. Please note that Dr Briffa cannot enter into any correspondence. You can also visit www.drbriffa.com. Before following any recommendations in this column, you should consult your own medical adviser about any medical problems or special health conditions.

Thanks to guardian.co.uk who have provided this article. View the original here.