It has long been known that cancers are caused by a combination of our genes, diet and lifestyle. However, as we come to understand more about epigenetics - the way our genes are switched on and off by factors in our environment - we will discover what we can do to help turn on genes linked with cancer protection and switch off those linked with causing the disease. Indeed, though research is still in its early days, epigenetics may one day be able to identify the exact lifestyle and dietary factors that could prevent cancer.
Until then, however, here is what is already known and proven to lower your risk.
1: Eat yogurt
Our gut bacteria, or microbiome, has recently been linked to everything from mood to obesity, and a growing number of studies are linking it to a lowered cancer risk.
The latest, published last month in the journal PLOS One, gave one group of mice beneficial bacteria through probiotic supplements and the other non-beneficial bacteria. The mice receiving the good bacteria produced metabolites known to prevent cancer in their gut and were also better able to metabolise fats, which could help lower the risk of cancer, according to researchers.
"The results are positive and that is probably because the microbes help break down some of the toxins in the gut that might normally cause cancer, but also because they keep the immune system in great shape generally so it beats off cancer cells," says Tim Spector, professor of genetic epidemiology at King's College London, founder of the British Gut Project and author of The Diet Myth.
To keep your gut bacteria healthy, eat a mix of probiotic foods, such as live yogurt, kefir (fermented milk drink) and sauerkraut, as well as prebiotic foods, such as fruit, vegetables and high-fibre whole grains and legumes, to feed bacteria and help it grow, says Prof Spector.
2: Take an aspirin
While research shows that a low-dose aspirin a day may help prevent the risk of heart attack, the latest evidence suggests it could also help prevent colorectal or bowel cancer, which strikes more than 40,000 people in Britain each year.
In April, the United States Preventive Service Task Force updated its guidelines to recommend all adults aged 50-59 should take a low-dose aspirin for 10 years. Though the UK is yet to follow, many medical experts are convinced of aspirin's benefit.
"The evidence is strong that taking aspirin for five years or more reduces the risk of developing bowel cancer," says Peter Johnson, professor of medical oncology at the University of Southampton and chief clinician for Cancer Research UK.
"It's also been found that people who do get cancer are at less risk of having it spread if they take aspirin."
If there is an inherited tendency toward bowel cancer, taking a low-dose aspirin is a good idea. "Aspirin may work by reprogramming the way the immune system works, affecting the inflammation pathways in the lining of the gut, thus helping it to recognise early cancers and remove them," Prof Johnson says. But it comes with risks such as bleeding from ulcers in the stomach, so always consult a GP first.
3: Marinate your meat
In the Nineties, the biggest study into nutrition and cancer began tracking the diets of 500,000 healthy people aged 45-79 across 10 countries in Europe, including Britain, to see who would get cancer.
Among key findings from the European Study on Diet and Cancer (Epic) were that processed and red meat are associated with a higher risk of developing bowel and stomach cancers. Current recommendations suggest sticking to 70g a day (about two rashers of bacon) and, according to Cancer Research UK, this one change alone could prevent a staggering 8,800 cases of bowel cancer each year.
Research also suggests charred or well-done meats may be associated with increased risk because of cancer-causing heterocyclic amines (HCAs), which form when meat is cooked at high temperatures.
But meat-lovers shouldn't despair - fascinating research from Kansas State University has found that marinating meat in spices, such as rosemary, thyme, oregano, basil, sage and marjoram, before cooking can lower the HCA components (so could taking the skin off chicken).
4: Go for fibre
Simply increasing your fibre, and your fruit and vegetable intake, to five portions a day could help prevent 14 different types of cancers, the Epic study found. Increasing intake of fibrous whole grains, such as oats, brown rice and wholemeal bread, was particularly associated with a lowered risk of bowel cancer, and some research has suggested it may help prevent breast and prostate cancers, too. It's not certain how it happens, but some speculate that this might be linked to gut bacteria.
"Studies such as Epic show consistently that people who eat lots of fibre, fruit and vegetables have low levels of cancer, and the reason could be that these people consequently have a healthy gut microbiome that helps the immune system fight off cancers," says Prof Spector.
5: Know the new sun rules
While we know that wearing sunscreen helps prevent malignant melanomas, a survey last year showed one in five UK adults was unaware that the SPF rating did not mean protection against all sun damage - only that from UVB rays, which cause sunburn. Ultraviolet A rays (UVA) penetrate the skin more deeply, so look for the level of UVA protection (denoted by a UVA star rating or the letters UVA inside a circle).
Cancer Research UK recommends applying two tablespoons of sunscreen every two hours in the UK. But the colour of your clothing can provide protection, too. Spanish research found that blue and red fabrics offered better sun protection than white or yellow.
However, it is also important to protect areas the sun hits since these are where most cancers develop. Think bald heads and torsos in men and exposed calves in women.
Be mindful to protect children "as those who have been exposed to sunburn are more likely to develop skin cancer as adults", says Linda Bauld, professor of health policy at the University of Stirling, in Scotland.
6: Lose 5 kilos
About 60 per cent of Britons are overweight, and being the fat man of Europe causes 52,000 cases of cancer each year (obesity is second only to smoking, which causes 64,000 cases annually). "The heavier you are, the greater your risk of these particular cancers," says Prof Bauld.
Last month, the World Cancer Research Fund released evidence linking obesity with stomach cancer, now the third-biggest cancer killer in the world.
7: Spread your alcohol load
Earlier this year, the chief medical officer, Dame Sally Davies, changed weekly recommendations to 14 units for men and women. The key reason was the link between even low alcohol consumption and seven types of cancers, including those of the mouth and throat.
"The risk of cancer starts at even low levels of alcohol, so it's best to stick to just one glass a night," says Prof Bauld.
How about saving up your units for a special occasion? "Alcohol is ethanol, which is metabolised into a substance called acetaldehyde which the body finds difficult to process," she says. "High levels cause dehydration, which makes cells more vulnerable to multiplying, and this effect is greater the more alcohol you drink on one occasion."
8: Move more
Being more active could prevent about 3,400 cases of breast, bowel and womb cancer in Britain. "It improves hormone levels, which can help reduce a woman's risk of developing breast and womb cancer," says Prof Johnson. "It also helps transit times in the intestine, helping food move through faster, so there is less chance of inflammatory reaction in the bowel, which is how it lowers bowel cancer risk."