Myth Busters - I give 10 popular health claims a reality check.

Knowing what is good for you may seem daunting, with the endless and every-changing stream of health claims. It's hard to tell what will apparently give you cancer, protect you against it, damage your heart, cleanse your body, boost your immune system or help you lose weight.

Some of these health messages have become folklore but do they stack up? Some are just untrue, many are built on suspicions since disproved, and all lack conclusive scientific results. That said, anabsence of proof that somethin gis risky doesn't necessarily mean it's safe.

The Bulletin canvassed the experts on 10 common health claims.

1 Drink eight glasses of water a day.

There's no scientific backing for this oft-cited rule, which has seen the water bottle become a ubiquitous accessory. It's such a popular myth it was endorsed by Kidney Health Australia (KHA), until it reviewed the policy about five years ago and discovered a "distinct lack of evidence.

The origin of "8X8" - eight glasses of eight ounces (240mls) - is unclear, although a potential suspect is a 1974 book by American nutritionist, Dr Frederick J Stare.

KHA Medical Director, Dr Tim Mathew, says the best rule is drink when you're thirsty, and choose water. You can use the colour of your urine as a guide - pale amber is good, darker means you're dehydrated.

2 Foods like grapefruit, vinegar and chilli burn fat.

No foods can burn fat. Talk of a fat-burning enzyme in grapefruit, for example, isn't backed by evidence. Some foods, like chilli and caffeine, increase your metabolic rate briefly but no tenough to have any real effect, says Nutrition Australia.

Grapefruit is a healthy food, so include it in your diet (although it can interact with some medications) but any single-food regime, like the Grapefruit Diet reportedly favoured by celebrities such as Brooke Shields, is a bad idea.

3 Excessive mobile phone use will give you a brain tumour.

There's no increased risk in people who have used their mobile for less than 10 years, but the jury is still out on longer-term use.

Cancer Council CEO, Prof Ian Olver, says inconsistent findings for mobile phone use for over more than a decade mean that more investigation is needed - a Danish study found no link to incraesed cancer rates, but Swedish research suggested potential risk. Results generally aren't broken down for heavy versus infrequent mobile users, or for hands-free devices.

Proving such a link is difficult because it's likely most cancers are caused by a combination of factors. Olver says there's yet to be a convincing argument on how mobile phonen radiation could cause the DNA disruption necessary for cancer to develop.

4 Vitamin C stops you getting a cold.

Despite widespread use of the vitamin for this purpose, a Cochrane Review this year concluded that there's not much point.

The results of 30 trials showed that taking Vitamin C supplements (orally 0.2g+) makes almost no difference to whether you get a cold, unless you're doing extreme exercise and / or in very cold temperatures (marathon runners, skiers, soldiers on sub-arctic exercises).

Taking Vitamin C before the cold can cut its duration, but after you have symptoms it makes no significant difference. Severity isn't affected.

5 Artificial sweeteners are carcinogenic.

this concern arose when studies in rats found that high doses of saccharin, the oldest artificial sweetener, caused bladder stones, which can lead to bladder cancer.

But Dr David Thomas, an oncologist from the Peter MacCallum Cancer Centre, says that most of the associations made between sweeteners and cancer in humans have been technically flawed.

"There have been quite a number of reasonably powered association studies, and overall I don't think there is any evidence that any form of sweetener is associated with increased cancer risk, " he says.