Tomorrow sees the coming into force of the Food Supplements Directive - a piece of eurocratic legislation which is likely to see the banning of dozens of nutrients from use in supplements, and also threatens to impose strict limits on the permitted dosages of the nutrients that remain. This is said to be an effort to protect consumers from the potentially adverse effects of vitamin and mineral supplements. However, some have questioned this legislation on the basis of evidence which suggests that vitamin and mineral pills are not only generally safe, but may have supplementary benefits, too.

Some believe that the directive has been driven by a pharmaceutical industry keen to protect its patch. What is not in doubt is the fact that the directive will restrict people's abilities to do something potentially positive for their own health. Others say that we get all we need nutritionally from a 'healthy' diet. Yet many of us have diets that are far from healthy, for reasons including affordability, convenience and taste.

Even those who have nutritious diets may not get optimal levels of nutrients. The nutrient content of fruits and vegetables appears to be in perpetual decline. A recent study published in the Journal of the American College of Nutrition discovered significant reductions in levels of calcium, iron and vitamin C over the past 50 years in American fruit and veg. A study published in the British Food Journal unearthed marked reductions in several minerals in British fruits and vegetables, too. One explanation is the emphasis on high-yielding crops, which fall short nutritionally.

Another factor that may influence our need for nutrients concerns the widespread use of pesticides and other chemicals in our food supply and environment. Such alien-to-nature compounds have the potential for toxic effects in the body and may increase the risk of chronic health issues such as cancer (rates of which are on the rise). Many nutrients have disease-preventing properties, and in view of our polluted planet, our need for replete nutritional status in the body is perhaps greater than ever.

When one considers the evidence of a declining nutrient content in our diet and an increased need for disease prevention from these nutrients, there does seem quite a strong argument for supplementation. The new directive is likely to do little else than increase the disease burden in the UK. Some cynical commentators have suggested that this side-effect of the legislation will be another boon for the industry some believe cooked up this piece of legislation in the first place.

For more details, go to www.healthchoice.org.uk

Dear John

Do you know of any foods that might help alleviate psoriasis?
Sara Kane

Psoriasis is believed to be caused by more rapid than normal proliferation of skin cells, or keratinocytes. Sufferers have raised levels of an inflammatory fat known as arachidonic acid and some scientists believe that it may be an important factor in psoriasis. This acid can be formed from omega-6 fatty acids, such as those found in many margarines, vegetable oils, processed foods and fast foods. These are worth limiting in the diet, as are foods that contain arachidonic acid naturally, such as dairy products and red meat. While this acid may worsen psoriasis, omega-3 fats (which have anti-inflammatory effects) have the reverse effect.

Eat oily fish (such as salmon, trout, mackerel, herring and sardine) two or three times a week. Also, supplement with 1tsp a day of cod-liver oil. This offers significant amounts of vitamin D, which also seems to benefit psoriasis sufferers. Another natural agent that may help is mahonia aquifolium, a herb that reduces keratinocyte proliferation, and thus may help to heal your psoriasis.

· 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

Nutrition news

Heart attacks and strokes are usually caused by a blocking off of one or more arteries supplying blood to the heart and brain, respectively. Arteries are not rigid structures and can expand (dilate) and contract in response to changes in blood flow and blood pressure. Relatively elastic arteries are thought to be a sign of healthy functioning in the circulatory system and are something that is believed to be associated with a reduced risk of heart attack and stroke.

In a recent study published in the American Journal of Hypertension, scientists fed subjects with dark chocolate to see the effect on arterial elasticity. Dark-chocolate consumption led to a significant increase in the dilation of blood vessels in response to an increase in blood flow, and also reduced stiffness in the aorta (the body's main artery). Quite how chocolate has these beneficial effects on the blood vessels is not known, though it has been theorised that chocolate may increase the levels of blood- vessel-dilating substances, such as nitric oxide and prostacyclins.

The results of this study suggest that the regular consumption of dark chocolate may well have benefits for our arteries and may help reduce the risk of heart disease and stroke in the long term.