Is healthy food healthy?

We're always hearing nutritional advice of one kind or another - eat three of this, no more than two glasses of that, and a handful of the other might be helpful. Only last week, a new style of egg box was launched with the aim of encouraging you to eat an egg for every day of the week.

But how healthy is that type of advice? With the help of top nutritionists, Dr Wendy Doyle from the British Dietetic Association and Brigid McKevith from the British Nutrition Foundation, we analyse the most popular claims.

Eggs

The advice Eat an egg a day.

Who says? The British Egg Information Service, which has just launched its campaign, along with the new seven-egg circular packages.

Pros: Eggs contain selenium, a powerful antioxidant that protects cell membranes, is thyroid protective, and may be especially good for preventing prostate problems in men.

Eggs offer good, cheap, quality protein; the yolk is particularly nutrient-rich.
Choline in eggs is said to be especially good for the foetus's brain.

Cons: Eggs contain some saturated fat and cholesterol, which are leading contributors to heart disease. However, the way they are cooked makes a difference: frying in oil is less healthy than poaching or boiling.

Although Lion-marked eggs come from hens that are vaccinated against salmonella, the FSA still advises against eating undercooked or raw eggs, especially for the young, elderly, unwell or pregnant.

Dr McKevith says: "Although eggs contain some cholesterol, they are quite low in saturated fat compared to cheese, for example, and their value as a cheap but excellent source of protein certainly outweighs this."

Health rating: 7/10

Dairy foods

The advice Eat three portions of low-fat milk, yoghurt or cheese a day.

Who says? The UK Dairy Council, which launched its campaign last year.

Pros: Dairy foods supply calcium and vitamin D, which strengthen teeth and bones, and help prevent osteoporosis - a health problem that is on the increase in Britain.

They also provide vitamin B12 (good for a healthy nervous system) and riboflavin, both of which are important for energy metabolism. They are especially valuable for pregnant and nursing mums.

Kids need calcium to build strong bones, but they also need some fat in their diet, particularly the under-twos. One glass of whole milk contains less fat than a packet of crisps, and more than half of a child's daily calcium requirement. Milk is also a "tooth-friendly" drink to have between meals.

Cons: You must choose carefully: many dairy foods are high in saturated fat and cholesterol, two leading causes of cardiovascular disease.

When eating cheese, the advice recommends consuming a "matchbox-sized" piece - a great deal less than many people have in a cheese sandwich.

Low-fat dairy foods contain hardly any vitamins A or D (essential for growth and for healthy eyes, skin, bones and teeth) as these are fat soluble vitamins, and are largely removed along with the fat.

People with milk allergy and lactose intolerance may not be able to digest dairy foods comfortably. And several cancers, such as ovarian cancer, have been linked to dairy-product consumption.

Dr Doyle says: "Anything that can reduce your osteoporosis risk is excellent, but you must choose low-fat dairy products to avoid cardiovascular problems." Low-fat dairy foods (skimmed milk, low-fat yoghurt and low-fat cheeses such as ricotta and cottage cheese).

Health rating: 7/10

High-fat dairy foods (full-fat milk, cream cheese, Stilton or Cheddar).

Health rating: 4/10

Fish

The advice Eat at least two portions of fish each week, one of which should be oily.

Who says? The Food Standards Agency (FSA).

Pros: Omega-3 fats in oily fish reduce the risk of heart attacks. They also make blood less "sticky", reducing the risk of thrombosis (blood clots). Improved mental function is associated with eating fish

Cons: Eating marlin, shark or swordfish increases potential exposure to mercury, as it accumulates in these fish to "relatively high" levels. A recent Which? report stated that it "can have toxic effects on the brain and nervous system, particularly in unborn babies and children".

Other oily fish, such as salmon, trout and mackerel, may contain levels of PCBs and dioxins that may cause cancer and have "gender-bending" effects.

Farmed trout and salmon may contain artificial colorants such as axanthin (carcinogenic if used in excess). Dr Doyle says: "Fish, particularly oily fish, is extremely healthy, but the limit of one portion of oily fish a week is important because of the potential for exposure to contaminants."

Health rating: 7/10

Coffee

The advice Four to six cups of coffee per day can confer health benefits.

Who says? The British Coffee Association.

Pros: Coffee can help you stay alert if you're tired, can counteract the "post-lunch dip" syndrome. Coffee may help prevent driving accidents caused by falling asleep at the wheel. And it may help relieve asthmatic symptoms in some sufferers. Caffeine also contains useful antioxidants.

Cons: The FSA warns that pregnant women drinking more than three cups a day have an increased risk of miscarriage and of having babies with lower birth weights.

Caffeine, a diuretic, is also found in chocolate, tea and many sodas and colas, so it's quite easy to reach (or exceed) the generally accepted maximum dose of 600mg daily.

Drinking coffee later in the day or evening can interfere with sleep, and may contribute to heartburn and indigestion.

If you're sensitive to caffeine and drink strong, brewed coffee (which can contain twice as much caffeine as instant coffee) you may start to suffer side-effects such as jitteriness, headaches and insomnia. Some people report nausea and palpitations as well.

Dr Doyle says: "If you need to keep awake, or it helps your asthma, then it has useful advantages, although antioxidant benefits also come from far healthier foodstuffs."

Health rating: 3/10

Fruit and vegetables

The advice Eat five portions of fruit and vegetables of varying colours (red, green, yellow) every day.

Who says? The World Health Organisation originally, but every health agency nowadays.

Pros: Fruit and vegetables contribute dietary fibre, which lowers the risk for many digestive problems, including constipation, bowel cancers and diverticular disease. They lower the risks of cardiovascular disease. Antioxidants and phytochemicals protect against many cancers. Vitamin C helps reduce the length and severity of colds, and boosts the immunity.

Fruit and vegetables contribute bulk with fewer calories, aiding weight loss. Dark green leafy vegetables are an important source of calcium for bone health.

Cons: Food Standards Agency surveillance shows that 30 per cent of our food contains pesticide residues. Washing and peeling fruit and vegetables helps, although systemic residues will remain inside food.

Dr McKevith says: "The pros totally outweigh the cons, especially as you can further avoid pesticides by choosing organic."

Health rating: 9/10