Experts promised mackerel and salmon made for healthy eating. Now the food watchdog says otherwise. Conflicting evidence on foodstuffs and medicines leaves the consumer baffled. Maxine Frith reports

Oily fish can harm unborn children

The first guidelines on the maximum amount of oily fish it is safe to eat were issued by the Food Standards Agency (FSA) yesterday.

After a year-long expert review of the evidence, the FSA has recommended that girls and women of child-bearing age should not eat more than two portions a week of oily fish such as salmon, trout, mackerel and sardines.

Boys, men and women who are not planning to have children can eat up to four portions a week.

The new guidelines are the first to set maximum levels of oily fish consumption and come after years of confusion and controversy about the health benefits and risks of the food. Experts have been concerned that oily fish can contain cancer-causing chemicals such as dioxins and PCBs (polychlorinated biphenyls), both industrial pollutants. There have also been fears that PCBs in the environment could have so-called "gender-bending" effects because they mimic the female sex hormone oestrogen.

However, oily fish also contains essential omega-3 fatty acids which have been proved to reduce heart disease and promote development of the brain and central nervous system in babies. Previous FSA advice had been that everyone should eat at least two portions of fish a week, one of which should be oily.

Partly because of the conflicting health messages, most people in Britain are not eating enough fish. Seven out of 10 adults do not eat any oily fish, and average consumption is a third of a portion a week.

Alan Jackson, professor of human nutrition at Southampton University, who carried out the review, said: "It was a challenge to weigh up both risks and benefits. We tried to focus in on exactly what were the benefits and risks, not just for the population as a whole, but for any particular groups."

The FSA chairman, Sir John Krebs, said: "This extensive review of the scientific evidence has reduced the uncertainty about how many oily fish people can safely eat without the benefits being outweighed by the risks." In 1999, the Government issued guidance advising people not to eat more than one portion of oily fish a week after a study showed higher-than-average levels of dioxins and PCBs in samples. Three years later, the same fish were found to prevent the development of asthma in the unborn child.

Last year, American doctors said that eating oily fish could help to prevent heart attacks.

Mixed message for a one-time wonder-drug

Since being patented in 1899 by the German chemist Felix Hoffman, aspirin has been widely administered to relieve the pain of headaches and arthritis, and for the reduction of fever symptoms.

It was not until the 1970s that the British pharmacologist John Vane showed that the drug slowed the production of prostaglandins, preventing clotting and decreasing the risk of heart attacks. Numerous studies have since produced conflicting reports about the potential effects.

In 1980s researchers found evidence of a link between aspirin and Reye's syndrome, a liver degeneration condition in children under 16.

Hysteria about the threat of deep vein thrombosis at the end of the 1990s led many doctors to recommend aspirin to air passengers. But this month scientists warned against the practice, saying the side-effects far outweighed the benefits.

The drug has increasingly been linked with the fight against cancer, with doctors announcing in 2000 that women taking regular doses of aspirin had a 28 per cent lower chance of developing a tumour. However, work by American scientists this year found the drug may be associated to an increase in pancreatic cancer in women.

For men who stop at second glass, red is on prescription

THIS WAS one piece of health advice that made Middle England drinkers rejoice: red wine is good for you.

After years of received wisdom that alcohol was bad for the health, researchers began to look at why the wine-guzzling French had much lower rates of heart disease than people in Britain and America. Studies suggested that the explanation could be found in the chemicals in red wine, which could have a protective effect against cardiovascular disease.

In 1992, scientists concluded that two to three glasses of red wine a day could reduce the risk of heart disease by up to 17 per cent. Another study in 1999 found some of the compounds in red wine can cut the risk of mouth and throat cancers.

By then, the health benefits of red wine were a hot topic for research. Herpes, asthma, lung diseases, strokes could be prevented or reduced with a glass of rioja, it seemed. It is believed that red wine is "better" than white because the production process involves the skin and seeds of the grape, which contain cancer-busting chemicals.

But the health benefits of red wine are probably outweighed by the risks posed by Britain's culture of over-drinking.

Alcohol experts are concerned that with the majority of people drinking more than the recommended safe levels, they are more likely to increase the risk of heart disease, cancer and liver disease than they are to benefit from the health advantages of the occasional tipple.

And the news is not all good - especially for women. A study last year found that just one glass of wine a day can raise the risk of breast cancer.

Cheese on the comeback trail after years in the cooler

The British Cheese Board's announcement earlier this year that, far from causing nightmares, cheese reduces stress and aids sleep, has capped a comprehensive overhaul of the food's image.

Fuelled by the Atkins diet, which allows followers to eat as much as they want, cheese has gone from an outlawed lump of fat to a nutritious snack that tames the waistline.

For much of the past century, cheese and other calcium and nutrient-rich dairy products were considered part of a healthy balanced diet. But researchers in the 1970s linked raised levels of saturated fat to raised blood cholesterol levels.

There were cancer scares in the 1980s and 1990s - and even now, pregnant women are warned off eating some soft cheeses. But this year the British Cheese Board has pointed out the nutritional benefits of cheese, and published some guidelines for consumption. They say 11- to 18 year-olds should be eating 800 to 1000mg of calcium each day. A matchbox-sized piece of cheddar (30g) provides 219mg of calcium. The BCB also says cheese benefits teeth, contains vitamin A which keeps skin healthy and is rich in protein.

White or brown? Who did you ask? What do you spread?

From as early as the 1930s, people were told that bread was carbohydrate-heavy and unhealthy. But in 1962, research found that the "crude", starchy diets of people in rural Africa were linked to a lower incidence of colon cancer. High-fibre breads have also been shown to protect against diabetes, obesity, irritable bowel syndrome and rectal cancer.

White bread, however, remains the bête noire of the dietary world. A 2003 study found that the refined grains found in white bread were more likely to remain in the gut than whole grains, and that people with a more distended gut are at increased risk of heart disease.

The reputation of bread has also suffered at the hands of the low-carbohydrate Atkins diet, with sales falling over the past three years. Last week the Federation of Bakers hit back with a Vitality eating plan extolling the virtues of foods, including bread, which are rich in complex carbohydrates and warning people off "fad" diets.

The Food Standards Agency also issued new guidance this year saying bread and cereals should make up a third of the diet. But it said that wholegrain, brown and wholemeal bread should be eaten in preference to the white variety.

Dietitians have also pointed out that it is not bread that it is necessarily unhealthy, but the butter, jam, and other fillings we pile on to it.

Renaissance for red meat as fatty food wins approval

Once, lovers of T-bone steaks and lamb chops were told they risked everything from obesity to CJD.

Now red meats have undergone a health renaissance of sorts.

For years, red meat was seen as unhealthy because it was high in saturated fats which increase blood cholesterol levels and raise the risk of strokes and heart disease.

A study published in the British Medical Journal in 1998 found that deaths from heart disease were 30 per cent lower among vegetarians, compared with meat eaters. Other research linked red meat to an increased incidence of cancer of the colon.

Beef - and even lamb - became food to be feared in the 1990s as the first cases of vCJD, the human form of mad cow disease, began to appear.

However, sales of red meat have soared recently as a result of the huge popularity of the Atkins diet.

Recent research has also found that eating fatty foods such as red meat may actually reduce, rather than increase, the risk of stroke.

Scientists from Harvard Medical School found that for every 3 per cent increase in total fat consumption, there was a 15 per cent decrease in the risk of stroke - so long as a person is not obese.

Additional reporting by Stuart Maclean and Vicki Kellaway