GOOD A team at Reading University in Britain gave 50 primary-school children set breakfasts for a month and tested their IQs before, during and after the test period. They found orange juice and toast significantly improved IQs. Next best? Bacon sandwiches. BAD A 2007 study by American researchers found those who ate cured meat such as ham, hot dogs and bacon every other day were 78 per cent more likely to develop chronic obstructive pulmonary disease. C is for CHOCOLATE GOOD A couple of squares of the dark variety a day may ward off wrinkles and lower the risk of skin cancer. Researchers in London found volunteers who ate flavanol-rich chocolate - rich in anti-inflammatory and antioxidant agents - could tolerate more wrinkle-causing UV light on their skin. BAD The short high gained from eating chocolate could make depression worse. Researchers from the Black Dog Institute found comfort eating was more likely to prolong a negative mood than shorten it.

D is for DIETARY FIBRE GOOD Dietary fibre, or roughage, found in wholegrain breads and cereals, fruit and vegetables plays a big role in maintaining a healthy immune system and keeping asthma, type 1 diabetes and rheumatoid arthritis at bay. Researchers from the Garvan Institute of Medical Research found insoluble fibre is eventually converted by bacteria into short-chain fatty acids damping down inflammation in the gut. BAD Too much fibre and too little fat can lead to vitamin deficiencies. E is for EGGS GOOD Long blamed for causing cholesterol problems, it seems eggs are back in fashion. The Heart Foundation has lifted its recommended intake to six a week. Low in saturated fat and high in protein, eggs contain choline, good for the metabolism and for foetal brain development during pregnancy, and lutein, which lowers the risk for cataracts.

BAD Specialists at Harvard Medical School in Boston found eating an egg every day could increase the risk of Type 2 diabetes by about 60 per cent. F is for FOLIC ACID GOOD While it has long been known to decrease the incidence of neural tube defects in babies, University of California scientists found it can also improve sperm quality in men. Men with the highest levels had the lowest proportion of sperm harbouring genetic changes that can lead to Down syndrome and miscarriages. BAD A ground-breaking Australian study late last year found pregnant women who took too much of the supplement were 30 per cent more likely to have a child with asthma. G is for GERMS

GOOD Most bacteria within our bodies are helpful, constantly working to keep the numbers of disease-causing bacteria under control. Anti-bacterial or anti-microbial cleaning products kill both the good and the bad, sometimes disturbing the ratio and allowing bad bacteria to get the upper hand. BAD Hospitals can be havens for superbugs such as golden staph. A study published in the Medical Journal of Australia found only 39 per cent of doctors regularly wash their hands, despite knowing its importance in reducing infection rates. H is for HOLIDAYS GOOD Holidays offer the chance to relax and revive and can assist in achieving a healthy work-life balance. BAD Working too hard makes us stressed and our immune systems work at their peak. When we finally stretch out on a beach and relax, our body notes it is no longer under stress and begins to stand down from its state of heightened alert. This is unfortunate timing because our immune system becomes less vigilant at a time when we are being exposed to viruses and bacteria not encountered before.

I is for IRON GOOD Without iron our bodies can't transport oxygen in the blood. Good sources of iron include red meat, offal, spinach and broccoli. Drinking orange juice with your dinner helps iron absorption. Tannins from tea, coffee and wine reduce iron absorption. About one-third of the world's population is iron-deficient, many of them menstruating or pregnant women, babies and toddlers and teenage girls. BAD The body can't excrete excess iron and unnecessary supplements can interfere with the ability to absorb zinc and copper. J is for JUICE GOOD A study in the American Journal of Medicine showed that drinking juice more than three times a week reduced the risk of developing Alzheimer's disease by 76 per cent, compared with those who drank it less than once a week. It is the strong anti-oxidant properties of fruit and vegetable juices that have been shown to offer protection against the disease.

BAD But an Adelaide-based study found that some people can't process juice's natural sugar, resulting in bloating, flatulence and diarrhoea. K is for KISSING GOOD Swiss scientists have found you need to be in a close relationship to benefit. Indiscriminate kissing just won't do. University of Zurich researchers studied 51 German couples for a week and found those who reported more physical contact had lower levels of the stress hormone cortisol in their saliva. BAD Passionately kissing several partners can increase the risk of meningitis, a deadly infection of the lining surrounding the brain and spinal cord, researchers from the Children's Hospital at Westmead found. L is for LIPIDS

GOOD Having high cholesterol is never good but some lipid-lowering drugs have the potential to halve the risk of amputation in diabetic patients, according to a study of 1000 people with Type 2 diabetes. BAD The liver processes cholesterol and dietary fat. When we eat animal fats the liver transports the fat, with cholesterol, in the form of lipoproteins, into our bloodstream. Too much cholesterol leads to fatty deposits in the arteries, which can become blocked, leading to heart disease and stroke. M is for MILK GOOD A protein in milk can help fight drug-resistant bacteria that cause eye infections. It also speeds the healing of wounds to the cornea. When attached to contact lenses, it prevents bacteria growing on them, reducing the risk of eye disease. BAD Drinking milk can increase the risk of prostate cancer. A study of 82,483 men in the US found an increased chance of localised or non-aggressive tumours in those who drank low or non-fat milk. Drinking whole milk showed a decreased risk of developing prostate cancer.

N is for NUTS GOOD In a University of Wollongong study, 50 overweight adults with non-insulin-treated diabetes followed a well-balanced, low-fat diet. Those given 30 grams of walnuts a day had more good, unsaturated fats in their diets than those who followed a low-fat diet alone. BAD At least one in 200 children born in 1995 had a peanut allergy but, by last year, that had risen to one in 75. In a study that tracked patients in one of Canberra's two private allergy clinics, nine out of 10 children had their first reaction by age six. O is for ORGASM GOOD Orgasms are natural stress-relievers. Serotonin levels in the brain become elevated during sexual activity, promoting a sense of wellbeing that has a calming effect on cravings, such as those for junk food or cigarettes. An orgasm can also help boost the immune system and flush toxins from the skin.

BAD The inability to reach orgasm is known as anorgasmia. About 90 per cent of cases have a psychological base, such as stress, but drugs, alcohol, injury, multiple sclerosis or diabetes may play a part. P is for POTATOES GOOD The potato, like the banana, is one of the few foods which, if eaten in isolation, provides the essential elements for healthy survival. When boiled in its skin, a medium-size potato contains half the adult daily requirement of vitamin C and significant amounts of iron, zinc, folate, calcium, vitamin B and potassium. BAD The downside is weight gain but cutting them out can make you grumpy, as was revealed in a study by the CSIRO, the University of South Australia and Flinders University.

Q is for QUEUES GOOD Hospital waiting lists have blown out to the longest in four years but the State Government is unfazed, claiming waiting times are a better performance guide. BAD In 2007-08, the median waiting time for elective surgery in NSW increased to 39 days. In 2009 it was 40 days. Health Department statistics show 62,890 people were waiting for surgery in NSW public hospitals in the March quarter. The average waiting time was 2.66 months compared with 2.75 months for the same quarter last year when 58,839 people were waiting. R is for RUNNING GOOD Humans are designed to run. We have larger surface areas in hip, knee and ankle joints for shock absorption than our prehistoric ancestors as well as shoulders decoupled from the head and neck, allowing the body to rotate, bones in feet to create a stable arch for pushing off the ground and huge buttocks so we don't fall on our faces.

BAD CSIRO figures show more than 2000 people in Australia die each year from air pollution-related diseases. Those at risk include otherwise healthy people who exercise outdoors on high-pollution days. S is for SLEEP GOOD Sleep is important to every facet of our lives. Miss a few hours thanks to a crying baby or a long-haul flight and the day ahead looks grim indeed. Most scientists believe eight hours sleep a night is critical in immune function, metabolism, memory and learning. BAD For some people, getting a full night's sleep could be risky. Researchers from the University of California found those who slept between 6½ and 7½ hours had a lower mortality rate than people who slept for eight hours or more. T is for TEA

GOOD Research reveals that drinking just one cup of regular tea a day may help promote cardiovascular health. The research, conducted at the University of L'Aquila in Italy, is the first study to show that black tea can reduce both blood pressure and the stiffness of your arteries. BAD But wait at least four minutes before drinking your cuppa because researchers have found that drinking very hot tea can increase the risk of throat cancer. U is for UNDIES GOOD Wearing the loose cotton variety can make make life easier for women. Thrush, or fungal infection, thrives best in moist, airless and warm places such as the vagina or the anus. And be warned: persistent vaginal thrush could be a symptom of diabetes. BAD If you are trying to reproduce, wearing tight underwear can affect sperm production. Tight undies increase the heat of the testes, affecting the quality and quantity of sperm. The effects are temporary, but can last up to three weeks.

V is for VITAMINS GOOD People on restrictive diets, athletes, pregnant women, those with eating disorders and the elderly should take vitamin supplements, says a nutrition epidemiologist with the Cluster for Public Health Nutrition at the University of Sydney. BAD Nutritionist Rosemary Stanton says the body can become dependent on high doses of vitamins. When you stop taking them, it is no longer efficient at absorbing them from food and you can become nutrient-deficient, even though your diet may be good. W is for WATER GOOD Drinking plenty of water is directly related to your health. If you don't get enough water you will become dehydrated and experience other problems. Water helps regulate digestion and elimination, and improves skin quality.

BAD Drinking too much water causes cells to swell and upsets the body's electrolyte balance. This can cause an irregular heartbeat and cause fluid to enter the lungs. Swelling puts pressure on the brain and nerves, causing behaviour resembling alcohol intoxication. X is for X-RAYS GOOD X-rays are used to observe broken bones and swallowed objects and track blood flow in patients. They can also be used to diagnose cancer, kill bacteria in food, detect flaws in machinery and analyse the structure of crystals or distant stars. BAD Radiation experts warn of danger from overuse of medical X-rays, claiming they are responsible for many cancer and heart-disease deaths. They can cause the material through which they pass to become charged, or ionised. Ionisation can damage cells or DNA in living matter. Y is for YOGA

GOOD Yoga has been credited with improving flexibility and performance, reducing stress and providing inner peace. It has also been advocated as complementary treatment to help with conditions such as coronary heart disease, depression, anxiety, asthma, and extensive rehabilitation for disorders including musculoskeletal problems and traumatic brain injury. BAD Performing a pose wrongly for years may cause chronic injury so it is best to see accredited instructors and regularly check that your technique is correct. Z is for ZINC GOOD If you love oysters, you probably don't have a shortage of zinc. They contain more zinc a serving than any other food, but red meat and poultry usually provide us with most of our needs. Other good sources include beans, nuts, crab, lobster and whole grains. BAD If you've been experiencing hair loss, skin lesions, diarrhoea and cold sores you could have a deficiency. A lack of zinc also contributes to an increased incidence and severity of pneumonia and impairs cognitive and motor function in children.