Much of the health advice that we follow isn't validated by scientific research. Here, we've debunked some of the more commonly held health myths by separating fact from fiction.
1 Eating more than three eggs a week raises cholesterol levels
There is no link between eggs and high cholesterol. According to Dr Bruce Griffin, a researcher from the University of Surrey, "The link between egg consumption and raised cholesterol levels, which ultimately could lead to cardiovascular disease, was based on out-of-date information. The egg is a nutrient-dense food, a valuable source of high-quality protein and essential nutrients that is not high in saturated fat."
In fact, more recent research has shown that people who ate two eggs per day, while on a calorie-restricted diet, reduced their blood cholesterol levels.
2 Cracking your knuckles leads to arthritis in later life.
Lisa Mehigan of Arthritis Ireland (arthritisire land.ie) says: "The 'crack' you hear is actually a small bubble of gas popping. There is no evidence that cracking knuckles causes any damage such as arthritis in the joints. However, a couple of reports associate knuckle cracking with injury of the ligaments surrounding the joint or dislocation of the tendons. A study found that after many years, habitual knuckle-crackers may have reduced grip strength compared with people who don't crack their knuckles."
3 You need to drink eight glasses of water a day
This is one of the most peddled health myths, but it was recently dispelled by Glasgow GP Dr Margaret McCartney, in the British Medical Journal.
She revealed that there is no scientific evidence to suggest that we need so much water and said that most people meet their daily hydration needs by letting thirst be their guide. McCartney went on to speculate that the myth has been propagated by bottled-water companies.
"There are many organisations with vested interests who would like to tell doctors and patients what to do. We should just say no." What's more, water intake can also come from tea, coffee, soft drinks and soup. In fact, you will take in an additional 400ml of water by eating your five a day.
4 Eating late leads to weight gain
Fitness trainer John O'Connell (sffitness camps.com) says: "Many people claim that not eating after a certain time will help you lose weight. I disagree. Most people tend to eat the most calories during the evening and so, if they make a rule not to eat after a specific time, then they are just eating less calories and will, of course, lose weight. There is no magical time that eating a minute after will make us fat.
"I recommend eating every three to four hours so if this means you eat your last meal at 9pm, then that's fine. My only recommendation is not to eat too close to bed; try to leave around an hours' gap between eating and sleeping."
5 Chocolate causes acne
There is no conclusive evidence linking chocolate to acne. According to dermatologist Diana McShane: "Studies that specifically address the association of diet and acne are difficult to design with enough power to determine true cause and effect.
"This makes it difficult to determine not only what foods might be bad for your skin, but also what foods promote skin health.
"I suggest a balanced diet with a full complement of the recommended vitamins and minerals as the best way to promote skin health."
6 Antibiotics make the birth control pill less effective
In 2009, the World Health Organisation changed its recommendation to state that most broad spectrum antibiotics do not affect the effectiveness of combined oral contraceptives.
US doctors speculate that this myth emerged in the 1970s when women taking oral contraceptives reported high rates of irregular bleeding and unwanted pregnancies while being treated with a specific antibiotic called rifampicin. Women taking rifampicin or antibiotics that induce liver enzymes still require additional contraception, as is the case if antibiotics cause vomiting or diarrhoea. In these situations, patients are advised to follow the 'seven-day rule': use other methods of contraception, eg condoms, or abstain from sexual intercourse for the duration of antibiotic treatment and the following seven days.
7 You should feed a cold and starve a fever
Listen to your body when you are ill. If you are hungry, eat; if you're not hungry, don't. This adage probably came about because fevers generally cause people to lose their appetite while colds do not. Though there is some evidence to suggest that the loss of appetite can trigger the immune system to fight bacterial infections (associated with fevers) and eating food can stimulate a localised immune response suited to fighting viral infections (colds are generally viral), most doctors concur that the most important thing to do whether you have a fever or cold is to drink plenty of fluids as the amount you need increases due to sweating or mucus production. And remember, the immune system requires energy to function properly.
8 Shaving makes more hair grow back
Technician Lisa Hurley at Therapie Clinic (www.therapieclinic.com) says "When you shave, the hair that grows back looks more coarse because the top of the hair has been cut off, creating a blunt edge, whereas when you wax the hair that grows back is softer because it is a new hair.
"However, while shaved hair might feel more coarse, it won't actually increase the amount of hair follicles that you have. You are born with a certain amount of hair follicles -- you can't develop more."
9 Excessive hair washing leads to premature baldness
Carol Johnson, a hair-loss consultant at Universal Hair & Scalp Clinic, says: "This is a very commonly held belief, but no, it is not the case. In fact, when the scalp is washed it is stimulated and it needs to be stimulated. What's more, you are removing deleterious matter, sebum and styling products, all of which can block the pores.
"So by washing the hair you are unclogging the pores and, therefore, making it easier for hair to grow. You're also drawing a lot of nutrient-rich blood into the pivotal crown by stimulating it."
10 Sex addiction doesn't exist
“Some people think sex addiction doesn’t exist, that it is just an excuse for rich, powerful men to get off the hook. This is not the case.
“There are tens of thousands of people who have issues of sexual compulsivity.
Their lives are ruined - and they aren’t rich or powerful. Their lives are dominated by a need for sex or thinking about sex continuously as a way to avoid their pain.
“I have a huge amount of clients who are getting themselves into dangerous situations, waking up on Sunday mornings not knowing where they are or what the person beside them is called.
“Addiction happens when the brain is constructed in a way that doesn’t allow the person to retain control over their behaviour, until such time that they start a treatment programme and reshape their brain,” says David Kavanagh of Avalon Counselling.