GMOs and Other Hot Topics
Do genetically modified organisms link to cancer? What about artificial sweeteners, cell phones and plastic wrap? Here's what the research says.
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 keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.
Burned or browned foods
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 248 degrees Fahrenheit, such as chips, bread, breakfast cereals, cookies, 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, fries, bread and parsnips - are baked, roasted, grilled or fried at high temperatures. When bread is toasted, for example, this causes more acrylamide to be produced. The darker the color of the toast, the more acrylamide is present.
However, the research linking acrylamide to cancer has only been carried out using animals. AICR/WCRF 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 – which includes eating fewer high-calorie foods such as chips, fries and cookies – together with not smoking and keeping active, are the most effective ways to reduce your cancer risk.
There is no strong evidence that coffee increases cancer risk, but there is strong evidence that coffee can actually reduce the risk of 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 of 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 200 milligrams 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.
Not smoking, followed by maintaining a healthy weight, eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk.
Learn more on coffee and cancer risk in AICR's Foods That Fight Cancer.
Computer screens and monitors do emit electromagnetic radiation, but only at low levels that are considerably below the safe levels laid down by international recommendations. Studies have found no links between computer screens and risks to health.
Cosmetics and toiletries
Most studies have found no link between cancer and the chemicals used in cosmetic and toiletry products such as moisturizers, 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. Research is ongoing. Not smoking, followed by maintaining a healthy weight, keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.
Visit the Food and Drug Administration for individual lists of approved color additives in food, drugs and cosmetics.
AICR/WCRF latest comprehensive report on breast cancer did NOT find strong evidence that dairy foods have an effect on breast cancer risk. It is a review of ALL the relevant literature in the field, using highest quality evidence. For pre- and post-menopausal breast cancer, evidence was limited-suggestive that diets high in calcium decrease risk. For pre-menopausal breast cancer, evidence was also limited-suggestive that dairy products decrease risk. That means it is not strong enough to say there is a link, but the studies point in that direction.
For post menopausal breast cancer, evidence was even weaker for dairy products – is was judged to be limited-no conclusion. So there were no links showing that dairy foods increase risk for breast cancer.
However for colorectal cancer, evidence shows that dairy products decrease risk for that cancer.
Food additives are ingredients added to foods for various reasons – for example, to add color, enhance flavors or to make them last longer. All additives, including artificial sweeteners, are assessed for safety before they are used in foods.
In the US, the Food and Drug Administration (FDA) assesses all additives before they can be used.
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 colorectal cancer.
There is currently no other strong evidence linking food additives to an increased cancer risk. 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.
Genetically modified (GM) foods
Genetically modified foods are produced from organisms that have had specific changes introduced into their DNA using genetic engineering. There is currently insufficient evidence to conclude that genetically modified foods affect cancer risk.
There is no clear research showing that grilling links to cancer risk. But cooking meats at high temperatures, such as grilling, can lead to two main types of potential carcinogens. Polycyclic aromatic hydrocarbons (PAHs), found in smoke, can adhere to the meat on an open fire. Heterocyclic amines (HCAs) form in meat when the meat proteins react to intense heat, such as on a grill.
Laboratory experiments have shown that HCAs and PAHs can cause changes in DNA that may increase the risk of cancer.
Hormonal contraception (such as the pill)
Research to date suggests all types of hormonal contraception, including the combination (estrogen and progesterone containing) pill, the progesterone-only pill (known as the mini-pill), and the contraceptive patch (which contains estrogen and progesterone), increase the risk of breast cancer compared with women who do not use these forms of contraception. But more research is needed to confirm this, especially the link between the progesterone-only pill and breast cancer, where the evidence is less clear.
There is also some research suggesting a link between long-term use of combined (estrogen and progestogen) contraception, such as the combination pill and patch, and a small increased risk of developing cervical cancer.
With the combination pill -- the evidence is less clear for the progesterone-only ‘mini’ pill -- the risk slightly increases when taking the pill, but slowly returns to normal after you stop. For both breast and cervical cancer, evidence shows that 10 years after you stop taking the combination pill, your risk will be the same as if it had never been taken. This has also been shown for breast cancer risk on women who took the progesterone-only pill.
Evidence shows the pill offers some protection against some cancers by reducing the risk of developing ovarian (risk continues to decrease the longer the pill is taken), endometrial (for at least 15 years after you stop taking the pill), liver and colorectal cancers. This may also be the case for the contraceptive patch. More research is needed to confirm these links.
The increase in cancer risk from using any form of hormonal contraception is very small and, for many women, the benefits may outweigh the risk. However, if you are concerned, it is best to discuss your options with your doctor. Not smoking, followed by maintaining a healthy weight, keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.
Visit IARC for more information.
Hormone Replacement Therapy (HRT)
HRT is taken by women going through menopause to help reduce symptoms, such as hot flashes, night sweats and mood changes. It works by increasing the amount of estrogen, which naturally drops during menopause, in the body.
There is strong evidence that taking HRT increases the risk of breast, endometrial and ovarian cancers. However, this increase is only slight. A woman’s exact risk is dependent on the type of HRT being taken, how long it is taken for and how strong the dose is.
HRT does have benefits for women. It can improve quality of life by relieving many of the symptoms of menopause. There is also evidence that it can reduce a woman’s risk of developing colorectal cancer and osteoporosis (thin or weak bones).
It is best to discuss whether to start or stop using HRT with your doctor, who will be able to tell you what options are available to you. For some women, the benefits may outweigh the risks. However, to minimize the risk of breast cancer, it is preferable to use the lowest dose of HRT necessary to relieve your symptoms for the shortest possible time.
Not smoking, followed by maintaining a healthy weight, keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.
HRT does affect different cancers in different ways, though the overall increased risk is small.
- Breast cancer - Studies have shown that taking combined HRT (which contains the hormones estrogen and progesterone) increases the risk of breast cancer. The evidence about estrogen-only HRT is less clear – it may also increase risk, but to a lesser extent than with combined HRT.
With combined HRT, the risk of developing breast cancer increases slightly the longer you take HRT, but decreases gradually once you stop. Five years after stopping HRT, the risk of developing breast cancer will be the same as if it had never been taken. The evidence is less clear for estrogen-only HRT.
Naturally occurring estrogen and progesterone are thought to affect the growth of some breast cancers – having higher levels of these hormones from taking HRT might explain why it increases the risk of breast cancer, but we don’t yet know for sure.
- Endometrial cancer - There is strong evidence that estrogen-only HRT increases the risk of endometrial cancer. The evidence relating to combined HRT is less clear: the increase in endometrial cancer risk seems to be smaller in women using combined HRT than estrogen-only HRT. It is also possible that, with the correct dose of progesterone within combined HRT, there is no effect on risk, but this is still to be shown in the evidence.
- Ovarian cancer - Evidence has shown an increase in risk of ovarian cancer from taking both combined and estrogen-only HRT. The size of the increase in risk is small, but it is seen quite quickly (in women who have been taking HRT for less than five years). However, once HRT stops being taken, the risk does start to reduce.
- Colorectal cancer - There is some evidence that HRT may reduce the risk of colorectal cancer, but as yet there is insufficient evidence to confirm which type of HRT is most beneficial, the size of the reduction in risk or how long the benefit lasts. More research is needed to confirm these.
Visit the National Cancer Institute for more information on hormones.
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. A EU Scientific Committee report has stated that there is no scientific evidence that this hormone is a health risk.
In the US, the Food and Drug Administration regulates the content of milk and other dairy products to ensure these products are safe to consume.
Visit the FDA's Milk Guidance Documents & Regulatory Information for more information.
Indoor air pollution
The main sources of indoor air pollution are tobacco smoke and radon gas. Exposure to tobacco smoke in your home, including passive smoking through exposure to other people’s smoke, increases your risk of cancer.
Radon is a naturally occurring radioactive gas which is associated with a slightly increased risk of lung cancer. In areas where the gas occurs naturally in high concentrations, it can build up to high levels.
The US Environmental Protection Agency provides guidance on how you can reduce the amount of radon you are exposed to in the home to a safe level: https://www.epa.gov/radon
However, exposure to radon is associated with a very small amount of lung cancer cases in comparison with the number caused by smoking. Most of these are actually caused jointly by radon gas and smoking – smokers living in areas with high levels of radon gas are more than 20 times more likely to develop the disease. Not smoking, followed by maintaining a healthy weight, keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.
Inherited genes/family history
Only about five to ten per cent of all cancer cases result from specific inherited genes. Scientists have identified some inherited gene mutations that are linked to cancer, such as BRCA1 and BRCA2 which increase the risk of breast and ovarian cancers in particular. However, these gene mutations are relatively rare.
People who inherit gene mutations such as these have a higher than average risk of developing some types of cancer, although it doesn’t mean they will definitely get cancer. If you have a history of cancer in your family, or are concerned you may have inherited genes that increase your cancer risk, it is always best to speak to your doctor. Everyone can lower their risk of developing many types of cancer by not smoking, followed by maintaining a healthy weight, eating a healthy diet and keeping active.
Visit the National Institute for Health for more on cancer and genetics.
Microwave ovens do produce electromagnetic radiation, but most countries have manufacturing standards that specify maximum leakage levels for new ovens. This reduces leakage outside the ovens to almost non-detectable levels, and leakage also drops as you move further away from the oven.
Although some studies have suggested an association between microwave ovens and cancer, most research has found no link. A modern oven in good condition is safe to use if you follow the instructions correctly.
Cooking food in microwave ovens does not cause cancer either. However, it’s important to remember that any type of cooking can affect the nutritional value of some foods, such as fruit and vegetables. In general, the best way to keep as many nutrients as possible in fruit and vegetables is to use a little water and avoid overcooking them.
Mobile phones are an example of where there is not yet enough data to draw strong scientific conclusions. Some smaller studies have found a possible link between use of mobile phones and cancer, but these studies were not considered of good enough quality to be certain of a true effect. The largest study carried out so far has found no link. However, mobile phones have only been in use in relatively recent years, so there has not yet been enough research into their long-term effects.
The radiofrequency electromagnetic radiation that mobile phones give off is very weak and cannot directly cause cancer. In 2012 an independent report concluded that there is no convincing evidence that health risks could be caused by exposure to radiofrequency fields, including those from mobile phones, cell phone towers and base stations, at levels within international guidelines.
Studies in this field are continuing but, in the meantime, most governments recommend avoiding heavy mobile phone use by, for example, using a hands-free set and keeping calls short. And as there has not been enough research into the effects of mobile phone use on children’s health, it is advised that children under the age of 16 should only use mobile phones for essential calls.
Night shift work
Some studies in the past have suggested that working on night shifts or being exposed to artificial light at night could increase the risk of cancer, in particular breast cancer. However, many of these studies looked at breast cancer in animals, and so did not prove that shift work increases the risk of breast cancer in humans.
In 2007, the International Agency for Research into Cancer (IARC) concluded that working night shifts “probably” does increase the risk of cancer, based on the available evidence at the time. But more recently, a review of ten different studies in humans showed that night shift work is unlikely to increase your risk of breast cancer. This research also found that women working night shifts are more likely to be overweight or obese than women who don’t work night shifts – and overweight and obesity are associated with a higher risk of many cancers, including breast cancer. This may be because the working pattern of night shift workers makes it more difficult to shop for and cook healthy food, or take part in regular physical activity.
Based on all the research to date, there is not enough reliable evidence to suggest that night shift work causes breast cancer. IARC is now planning to review the evidence on shift work. In the meantime, it’s important to remember that maintaining a healthy weight, keeping active and eating a healthy diet, together with not smoking, are the most effective ways to reduce your cancer risk.
CDC National Institute on Occupational Safety and Health and the NIH have more information on occupation risks and occupational exposures.
Exposure to radiation, asbestos, pesticides or other cancer-causing chemical substances through your occupation can be associated with a higher risk of developing cancer. It’s important to remember that this usually affects only a small number of people in very specific jobs, and that the main risk comes from heavy exposure over several years. However, most countries now have strict regulations for hazardous substances in the workplace, which means that exposure to them, and the associated health risks, have been significantly reduced in recent years.
Regulation of these substances is generally more effective than individual actions. In addition, smoking often increases the risk related to occupational cancer-causing substances. Non-smoking asbestos workers are five times more likely to develop lung cancer than non-smokers not exposed to asbestos; if they also smoke, the risk factor jumps to 50 or higher. Environmental exposures also can increase the risk of lung cancer death.
It is best to follow your employer’s safety guidelines to limit your exposure and reduce your risk, while also avoiding other risk factors, particularly smoking or being overweight or obese.
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 fertilizers 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 frequently, 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.
Outdoor air pollution and diesel exposure
Air pollution is linked to a slightly increased risk of cancer. Sources of air pollution range from those caused by human activity, such as vehicle fumes and smoke from burning fuels, to natural pollutants such as desert dust and radon gas.
In particular, a specific type of air pollutant called particulate matter, which is present in diesel and gasoline exhaust fumes (and tobacco smoke), has been shown to increase the risk of cancer, especially lung cancer. Levels of particulate matter and other air pollutants are relatively low in most of the US, though levels are higher in some cities, and they can vary according to factors such as traffic density and weather conditions.
However, it’s important to remember that smoking – including breathing second-hand smoke – increases your cancer risk much more than air pollution does. Not smoking, followed by maintaining a healthy weight, eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk.
Both organic and conventional foods 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.
Visit the US Environmental Protection Agency for more information.
Plastic bottles and plastic food wrap
There are claims that chemicals in plastic drinks bottles, plastic food wrap 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.
There is no reliable evidence that using plastic bottles or plastic food wrap to drink from, store or freeze food and liquids increases your risk of cancer. However, if you are cooking with plastics or 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 to use for cooking.
Having said this, the risk involved in using plastics for cooking is very small. Not smoking, followed by maintaining a healthy weight, eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk.
The type of radiation given off by power lines is low-frequency electromagnetic radiation which does not have sufficient energy to damage cells and thereby cause cancer. However, some studies have suggested a link between exposure to magnetic fields and a small increase in the risk of childhood leukaemia. The evidence for this is limited but a risk cannot be ruled out. No link has been found with health risks in adults.
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. Not smoking, followed by maintaining a healthy weight, eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk.
Visit the National Cancer Institute's section on coping with cancer for more information.
Some types of radiation can cause us harm, including raising the risk of cancer, if we are exposed to too much of it. Ionizing radiation has enough energy to damage DNA and increase the risk of cancer. Non-ionizing radiation has lower energy and, in most cases, has not been found to increase the risk of cancer, unless exposed at much higher levels than experienced in daily life. However, some technologies are relatively new, or the ways in which they are used have changed, and in these cases there is not yet enough data for scientists to be certain about the level of cancer risk.
Radiation at the levels experienced by most people in most situations carries only a very small health risk, if any. Not smoking, followed by maintaining a healthy weight, keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.
- Naturally occurring radiation - This is ionizing radiation given off by natural sources (see radon), but the vast majority of people are rarely exposed to amounts high enough to cause us damage.
- Medical radiation - Our main exposure to ionizing radiation is through diagnostic medical X-rays and other types of body imaging such as radiography. It is estimated that about six in 1000 cancers are associated with diagnostic radiation but it’s important to remember that, while it’s worth avoiding unnecessary X-rays or scans, medical X-rays are generally used where they are the best solution and the need for the investigation outweighs the small potential risk. Where possible, doctors will recommend other types of imaging that don’t use radiation (such as ultrasound or an MRI scan). Talk to your doctor if you are concerned about having an X-ray, and tell them about any previous ones you may have had.
- Airport scanners - Most airports now use body scanners as part of their security measures. These scanners use either radio waves or ionizing radiation, but in both cases at such small doses that they do not raise your cancer risk.
Non-ionizing radiation is given off by, for example, mobile phones, power lines and microwave ovens:
Sugar and artificial sweeteners
There is no strong evidence to directly link sugar to cancer risk. However, foods that are high in added sugar tend be high in calories without being nutritious or filling. Eating high-calorie foods or drinking sugary drinks too often or in large quantities can lead to weight gain, and there is strong evidence that being overweight or obese increases the risk of eleven cancers. Maintaining a healthy weight through eating a healthy diet and keeping active, coupled with not smoking, are the most effective ways to reduce your cancer risk.
Studies on artificial sweeteners, including saccharin and aspartame, have shown no convincing evidence of an association with cancer. Earlier cancer scares linked with certain sweeteners have been discredited.
Research has found that drinking water contaminated with arsenic increases the risk of skin, lung and bladder cancer. In the US, the Environmental Protection Agency is responsible for checking the quality of water. The Clean Water Act and regulation of drinking water contaminants fall under the EPA’s authority; state and municipal water systems must comply with the standards set by the EPA to make sure that levels of chemicals and contaminants meet safe standards.
The EPA 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 to those high in sugar and calories, which can contribute to weight gain. Not smoking, followed by maintaining a healthy weight, eating a healthy diet and keeping active, are the most effective ways to reduce your cancer risk.
Visit the Environmental Protection Agency for more information.
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, keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.