Myths and controversies about what causes cancer

Our health information team explore what other organisations are saying about the rumours, fiction, media reports and urban legends about whether everyday products increase cancer risk.

> On the blog: 5 diet and cancer myths debunked

Vegan diets

Following a vegan diet means only eating plant-based foods and avoiding all animal products including meat, dairy and eggs.

There is no direct evidence that following a vegan diet reduces the risk of developing cancer. However, there are many characteristics of a healthy vegan diet that align with our Cancer Prevention Recommendations – such as eating lots of wholegrains, pulses, fruit and vegetables, and avoiding red and processed meat.

This is not only because plant-based foods contain fibre, which protects against bowel cancer, but including more plant-based food in the diet can also help people to maintain a healthy weight – and being overweight or obese increases the risk of 13 types of cancer.

We also know that eating red and processed meat increases the risk of bowel cancer. There is no evidence to suggest consuming white meat or fish increases the risk of cancer.

In 2022, our researcher Associate Prof Aurora Pérez-Cornago published research showing that, compared with regular meat-eaters, being a low meat-eater, fish-eater, or vegetarian were all associated with a lower risk of all cancer.

Plastic bottles and cling film

There are claims that chemicals in plastic drinks bottles, cling film and food containers can cause cancer by seeping into the contents. While some studies have shown that a very small amount of chemicals in plastic packaging can get into drinks or food when heated, these amounts have been well within safe limits – which are very strictly regulated in the UK.

There is no reliable evidence that using plastic bottles to drink from, or cling film to store or freeze food, increases your risk of cancer. However, if you are using plastic utensils while cooking, the best thing to do is to follow the directions and only use plastics that are specifically meant for cooking. Inert containers, such as heat-resistant glass, ceramics and stainless steel, are preferable for cooking.

The risk of using plastics for cooking is very small. Not smoking, followed by maintaining a healthy weight through eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk.

Psychological stress

Some people have suggested a link between psychological stress (which is what people experience when under mental, physical or emotional pressure) and an increased risk of cancer. However, there is no strong evidence for this. Most studies have not found that such stress increases the risk of cancer.

However, people under stress can sometimes behave in unhealthy ways, such as smoking, overeating or drinking heavily, which do increase their risk of many cancers. If you’re under stress, it’s important to try to find other ways of coping, such as doing physical activity.

> On the International blog: stress and cancer risk (Feb 22)

Cosmetics and toiletries

Most studies have found no link between cancer and the chemicals used in cosmetic and toiletry products such as moisturisers, shampoos, deodorants, and toothpastes. The majority of countries have strict regulations to ensure these products are safe.

Some studies have found a link between talcum powder (talc) and ovarian cancer, but there is not enough evidence to be certain of this. Even if there were an increased risk, scientists estimate it would be small. Not smoking, followed by maintaining a healthy weight through eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk.

Breast implants

There have been many studies into whether silicone leakage from breast implants increases the risk of breast cancer. None of them so far have found any evidence that this is the case. Not smoking, followed by maintaining a healthy weight through eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk.

Underwire bras

The majority of research has found no link between the use of underwire bras and breast cancer. Not smoking, followed by maintaining a healthy weight through eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk.

Organic food

Organic farming makes use of crop rotation, environmental management and good animal husbandry to control pests and diseases. This means that there are limited additives used in organic food production. Processed organic foods use ingredients that are produced organically, and for a food to be certified organic, at least 95% of the food must be made up of organic ingredients.

There are many different reasons why consumers choose to buy organic food, such as concern for the environment and animal welfare. Consumers may also choose to buy organic food because they believe it is safer and more nutritious than other food and that artificial fertilisers and pesticides may increase the risk of some diseases, including cancer.

Two large studies have looked at organic food consumption and cancer risk. The Million Women Study, a large study of UK women, showed in 2014 little or no decrease in the incidence of cancer associated with consumption of organic food.

A study published in 2018 in a large group of French adults showed that people who had more organic foods, more often, in their diets had a lower risk of several types of cancer.

However, this is a single study and due to its design, it is not possible to be sure that the organic food was causing the lower risk of cancer. There may be other factors, such as income, which influence the results.

There is currently limited evidence to suggest that organic foods may offer added protection against cancer compared to conventionally grown produce.

Research shows that eating a healthy diet, along with not smoking and keeping active, are very important in cancer prevention, but choosing fresh, frozen, canned, conventional or organic produce does not affect your cancer risk.

Pesticides

Both organic and conventional food have to meet the same legal food safety requirements. Before pesticides are approved they are rigorously assessed to ensure they do not pose an unacceptable risk to human health or the environment, and that any pesticide residues left in food will not be harmful to consumers.

Pesticide residues in the food chain are also monitored to check they are within legal and safe limits. Additives are also subject to rigorous, pre-market safety assessments before they can be used in foods. Their use is controlled by legal limits, which ensures consumption does not exceed safe levels.

Hormones in cattle

Legislation about hormones in cattle varies from country to country. For example, growth hormones are used in dairy farming in the US, whereas the use of hormonal growth promoters for livestock is banned in the UK. Antibiotic growth-promoting feed additives have also been phased out due to concerns about the potential spread of antibiotic resistance.

Bovine somatotropin (or BST) is a hormone used to increase milk or meat production in cattle and is banned in the UK and Europe but is licensed in the US. BST was banned on animal welfare grounds, not because there is any proven effect on human health. An EU Scientific Committee report has stated that there is no scientific evidence that this hormone is a health risk.

Milk is rigorously tested for traces of antibiotics by law to ensure that food is safe for consumption. Cows receiving antibiotics are milked separately from the rest of the herd to ensure that the milk is discarded and does not enter the food supply.

In the UK, the Food Standards Agency regulates the content of milk and other dairy products to ensure these products are safe to consume.

Not smoking, followed by maintaining a healthy weight through eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk. Research shows that eating too much red meat, and any amount of processed meat, increases the risk of bowel cancer. For cancer prevention, it is best to eat no more than about three portions a week of red meat (350 to 500 grams in total cooked weight), such as beef, pork and lamb, and to eat little, if any, processed meat, such as ham and bacon.

Food additives

Food additives are ingredients added to foods for various reasons – to add colour, enhance flavours or to make them last longer. All additives are assessed for safety before they are used in foods. An E number is a reference number given to food additives that have passed safety tests and have been approved for use in the UK and throughout the European Union.

The only additives for which evidence has shown a link with cancer are nitrites and nitrates, which are used as preservatives in processed meat. Eating processed meat is strongly associated with an increased risk of bowel cancer.

There is currently no other strong evidence linking food additives to an increased cancer risk.

Coffee

There is no strong evidence that coffee increases cancer risk, but there is strong evidence that coffee can actually reduce the risk of womb (endometrial) and liver cancer. However, we cannot make any specific recommendations because there are too many unanswered questions – for example, are the benefits a result of drinking coffee regularly, or in large amounts? There is also no evidence on the effects of adding milk and/or sugar, or on drinking caffeinated, decaffeinated, instant or filter coffee.

For general health, research from the European Food Safety Authority (EFSA) shows it is safe for healthy adults, including pregnant women, to drink single doses of up to 200mg of caffeine. Drinking up to 400mg of caffeine through the day does not raise safety concerns in the general population, which is equal to around four cups of filter coffee a day.

Burnt or browned foods (acrylamide)

The UK’s Food Standards Agency has recommended that foods with a high starch content, such as bread, chips and potatoes, should be cooked to a golden yellow colour, rather than brown, to reduce intake of a chemical that has been associated with causing cancer in mice.

Acrylamide is present in many different types of food and is a natural by-product of the cooking process. The highest levels of the substance are found in foods with high-starch content which have been cooked above 120C, such as crisps, bread, breakfast cereals, biscuits, crackers, cakes and coffee (as a result of the roasted beans).

It can also be produced during home cooking, when high-starch foods – such as potatoes, chips, bread and parsnips – are baked, roasted, grilled or fried at high temperatures. When bread is grilled to make toast, for example, this causes more acrylamide to be produced. The darker the colour of the toast, the more acrylamide is present.

However, the research linking acrylamide to cancer has only been carried out using animals. The World Cancer Research Fund has carried out a review of studies in people, and found no link between acrylamide in food and cancer. More research is needed but, in the meantime, maintaining a healthy weight and eating a healthy diet – together with not smoking and keeping active, are the most effective ways to reduce your cancer risk.

Tap water

WCRF research has found that drinking water contaminated with arsenic increases the risk of skin, lung and bladder cancer. Water contaminated with arsenic is not a public health issue in the UK, although it does affect some other countries that have high natural concentrations of arsenic in soil.

In some parts of the UK, fluoride is added to the water supply to help prevent tooth decay. Public Health England monitors the effects of water fluoridation on health. To date, there is no evidence of a difference in the rate for all types of cancer between fluoridated and non-fluoridated areas.

Water is a healthier choice than many other drinks, particularly compared with those high in sugar and calories, which can contribute to weight gain. Not smoking, followed by maintaining a healthy weight through eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk.