Not so long ago the humble egg was viewed as a cheap, nutritious and versatile food. For many of us, the 60s advertising slogan 'Go to work on an egg' is hard to forget. However, since then the egg has experienced a spectacular fall from grace. Eggs, we are told, are full of cholesterol and saturated fat. As a result, many doctors and dieticians have warned us against eating them lest they clog our arteries and hasten our demise. Yet despite the fact that eggs have made their way on to the nutritional blacklist, there is little evidence that they do us much harm at all. Scientific studies suggest that eggs might be the wholesome food advertisers have always cracked them up to be.

Eggs are composed of two main parts, the yolk and the white. While the white is mainly protein, the yolk contains significant quantities of both saturated fat and cholesterol. Doctors have spent the past 20 years warning us of the danger of these fats upping the risk of heart disease, and when individuals with raised cholesterol levels seek dietetic advice, they are often advised to give eggs a wide berth.

However, the idea that eggs increase the risk of heart disease, is based, like a lot of dietetic dogma, on assumptions that may turn out to have little basis in reality. It is, for instance, taken for granted that because eggs contain saturated fat and cholesterol, eating them will raise the level of cholesterol in the bloodstream. However, scientific studies have generally failed to bear this out. One study found that feeding men and women two extra eggs each day for six weeks did not increase their cholesterol levels. In another study, men consuming four eggs a day for two months saw no change in their cholesterol scores.

Most doctors and dieticians see saturated fat as the major spectre in our diet. As eggs are rich in it, conventional wisdom dictates that eating fewer of them can only enhance our heart health and promote longevity. But in looking at the effects of lowering fat intake on the risk of heart disease and the overall risk of death, at least three major studies show that this does not appear to reduce either. Counter-intuitive though this may be, the bulk of the evidence does not support the notion that avoiding saturated fat, from eggs or other sources, is the key to a longer life.

Further evidence for the relatively benign effect of eggs came from two very large studies that examined specifically the link between egg consumption (up to one egg per day) and heart disease. The results of these studies show that non-diabetic men and women eating the most eggs were not at increased risk of heart disease or stroke compared to those eating the least. So perhaps it might not be such a bad idea to go to work on an egg after all.

Nutrition news

Stroke is the term used to describe what happens when part of the brain is starved of blood and dies. About 100,000 people in England and Wales suffer their first stroke each year, and the incidence is rising. A recent study published in the medical journal Neurology found that risk of stroke may be linked to levels of potassium in the diet. One of potassium's effects is to lower blood pressure, raised levels of which are a major risk factor for stroke. Individuals consuming the most potassium had about two-thirds the risk of suffering a stroke over the next four to eight years compared to those with the lowest intake of this mineral. The evidence suggests that plenty of potassium-rich fruits and vegetables such as bananas, tomatoes and oranges may help reduce risk of stroke in the long term.

Dear John

I am 36 and started taking regular exercise three years ago. I run about 30 miles a week. Over the past few months I've been prone to cramp, and am aware of my heart 'jumping' from time to time. I've had a heart trace, which was normal. Do you have any advice?
Terry Wilkinson, Surbiton, Surrey

Exercise can deplete the body of certain nutrients, such as magnesium. This mineral takes part in hundreds of reactions within the body, particularly those involved in energy production. It also plays a vital role in the healthy function of muscle, including the heart muscle. Magnesium deficiency seems to be a very common cause of cramp, and is often a feature in those suffering from heart-rhythm irregularities.

I advise you to eat more magnesium-rich foods including beans, pulses, nuts, seeds, green leafy vegetables and wholegrain starches such as brown rice. Also, for at least two or three months, take a 350-500mg magnesium supplement per day. After this, taking a good-quality multivitamin and mineral supplement in the long term can help you to avoid problems with nutrient deficiencies.