4 things you've heard cause cancer versus the big 4 that really do.

It might seem “everything gives you cancer” as the singer Joe Jackson lamented.

News of upgraded warnings about red and processed meat and bowel cancer this week no doubt add to this feeling. But when it comes to cancer risk, it’s important to keep things in perspective.

Obesity and lack of exercise pose bigger cancer risks than red and processed meat, as some experts have pointed out this week. On the flipside, a lot of the things we hear cause cancer actually don’t.

Stories, rumours and fanciful claims about cancer are so widespread, Australia's peak independent cancer control organisation, Cancer Council Australia, has created a website to dispel them. It gives accurate, evidence-based answers to questions about everything from using a laptop on your lap to wearing a bra to bed (and if you're wondering, neither of these activities is believed to pose a cancer risk).

Here are four things you might have heard give you cancer but which - from all existing evidence - don't, and the big four you really should be worried about instead.

Don't worry about these:

1. Plastic water bottles.

The claim: heating, freezing or reusing plastic water bottles releases chemicals from the plastics that could cause cancer, including dioxins.

The facts: Water in plastic bottles should be no less safe than water in metal bottles or any other container. The plastic in water bottles contains no dioxins at all.

Source: Does drinking water from plastic drink bottles cause cancer?

2. Sugar.

The claim: Sugar feeds cancer cells so you should avoid it in your diet if you are having treatment for cancer.

The facts: All cells in the body use sugars as fuel. So do cancer cells. While cancer cells in the test-tube have been shown to grow well on glucose, this doesn't mean eating sugar will make cancer cells grow faster or even cause cancer. Even if it were possible to avoid all sugar and somehow stop sugars reaching any cancer cells from other foods like protein and fats, you would be starving your body's healthy cells along with any cancer cells. A healthy diet is the best way to give your body the fuel it needs and avoid weight gain, which does raise cancer risk.

Source: Does sugar feed cancer cells?

3. Deodorants

The claim: Aluminium in antiperspirants prevents us from getting rid of toxins in our sweat, which clog up lymph nodes and lead to breast cancer.

The facts: Yes, sweating does help your body get rid of toxins but breast cancer starts in the breast and spreads to the lymph nodes, not the other way around. There is no evidence that aluminium can lead to cancer. Some reports occasionally claim to have found aluminium, or other deodorant chemicals, in samples taken from breast tumours. But they usually involve a very small number of women, and they never compare levels of aluminium in the tumours to levels in other parts of the body, or to women who don't have breast cancer. On the other hand, one study looked at 1,600 women and found that those who use deodorant are no more likely to develop cancer than women who don't.

Source: Can deodorants and antiperspirants with aluminium cause cancer.

4. Radiation from microwaves

The claim: Food heated in a microwave oven becomes radioactive and when you eat or drink it, the radiation damages genes in cells in your body, causing cancer.

The facts: Microwaves are a form of radiation but they are not known to cause cancer. Microwaves are a type of low energy radiation called 'non-ionising' radiation, which is different from the high energy radiation in X-rays, which can damage DNA. Also while microwave ovens use microwave radiation to heat food, this does not mean they make food radioactive.

Source: Does radiation from microwaves cause cancer?

Do focus on these:

In the past, Professor Bernard Steward, Cancer Council Australia's chief scientific advisor has suggested focusing on the following four key cancer risk factors and avoiding getting 'distracted' by other factors.

(Note that list relates specifically to Australia. Infectious diseases are a cancer risk factor in many developing countries.)

1. Smoking

Smoking is the biggest of the big four and is thought to account for as much as a third of all cancers. It doesn't just cause lung cancer, but cancers at 13 other sites in the body.

For advice on stopping smoking, call the Quitline from anywhere in Australia on 131 848 .

2. Obesity

Obesity accounts for around 15 per cent of cancers, with breast and bowel cancer the ones you need to worry about the most. Monitor your weight and try to get yourself into the healthy weight range (for more information see Is your weight healthy?) If obesity is an issue for you, speak to your doctor about getting help to improve your diet and exercise habits.

3. Alcohol

Alcohol accounts for 4 per cent of cancers. It's identified as a cause of cancers of the mouth, larynx (voice box), pharynx (a section of the throat), oesophagus, bowel (in men) and breast.

"Initially we thought it was moderate to heavy drinking that caused breast cancer because that is easy to detect," Professor Stewart says. "But bigger surveys are now showing that daily intake of alcohol at any level, effectively one alcoholic drink a day, is enough to cause a very small incidence of breast cancer. In other words, avoiding daily alcohol is the way to go."

To reduce cancer risk, avoid daily alcohol and/or cut your alcohol intake.

4. Sun

Cancers caused by sun exposure are harder to quantify but are thought to be less than four per cent, says Professor Stewart. All are skin cancers.

Avoid deliberate sun exposure (that is sunbaking) and otherwise protect your skin (by covering up or using sunscreen) when you go in the sun.

This post originally appeared on ABC News.