Cancer Myths Quick Check Guide - Carcinogenicity

Table of contents

1 Introduction

2 Cancer-causing rumors

3 Cancer prevention rumors

4 Conclusion

Preface

The International Agency for Research on Cancer (IARC) under the World Health Organization classifies carcinogens into five categories:

Class 1 carcinogens: Carcinogens that are determined to be man-made.

Class 2A carcinogens: are likely to cause cancer in humans. There is limited evidence of the carcinogenicity of this type of carcinogen in humans, but sufficient evidence of its carcinogenicity in experimental animals.

Class 2B carcinogens: may cause cancer in humans. The evidence of carcinogenicity of this type of carcinogens in humans is limited, and the evidence of carcinogenicity in experimental animals is insufficient; or the evidence of carcinogenicity in humans is insufficient, but the evidence of carcinogenicity in experimental animals is sufficient.

Category 3 carcinogens: Suspected carcinogenicity to humans, with no adequate human or animal data.

Category 4 carcinogens: probably not carcinogenic to humans.

This classification is based on the degree of certainty of the evidence of carcinogenicity and is not necessarily related to the intensity of the carcinogenicity or the actual threat to humans. The actual probability of a carcinogen causing cancer is related to the exposure/contact dose and time, etc.

This handbook summarizes common cancer-causing and cancer prevention rumors in recent years for your convenience.

Cancer rumor

Diet

× Soy milk and milk cause cancer

Soy milk and milk are not carcinogenic and can be consumed normally.

× Thousands of boiled water and overnight water can cause cancer

Drinking boiled water or overnight water will not cause cancer, but you should pay attention to water hygiene.

× Beer contains carbendazim which causes cancer

So far, studies have not found that carbendazim causes cancer. But it should be noted that drinking alcohol increases the risk of cancer, so it is better to drink less.

× Coffee causes cancer

Acrylamide (a Class 2A carcinogen) is produced during the coffee roasting process, but drinking a few cups of coffee a day is far from reaching the carcinogenic dose, so there is no need to worry about cancer.

× Bottled water left in the car causes cancer

Bottled water left in the car will not cause cancer, but it is still recommended to avoid storing it in a high temperature environment for a long time. It is best to drink it immediately after purchase. If the bottle has been opened, drink it up in time.

× Toona sinensis causes cancer

Toona sinensis contains a small amount of nitrite, but in fact nitrates and nitrites are widely present in water and soil in nature, so there is no need to worry about cancer if consumed daily.

× Baby cabbage causes cancer

It is said online that baby cabbages soaked in formaldehyde look better and can be stored longer. However, formaldehyde is not a food additive, and if added to baby cabbages, it will be harmful to the human body. Baby cabbages purchased through regular channels that do not contain illegal additives will not cause cancer.

× Bracken causes cancer

The "protoptanoic acid" contained in bracken is a Class 3 carcinogen. It is recommended to consume it in moderation after processing and not to consume it in large quantities or frequently.

× Zucchini causes cancer

When zucchini is stir-fried at high temperature, a small amount of acrylamide will be produced, which is a Class 2A carcinogen. However, normal and moderate consumption will not cause cancer. It is recommended to avoid cooking methods such as stir-frying and roasting as much as possible.

× Houttuynia cordata (Houttuynia cordata) causes cancer

Improper consumption of Houttuynia cordata may damage the kidneys, but there is no clear scientific evidence to prove that it is carcinogenic.

× Crab roe causes cancer

A water pollution occurred in New York, which caused the concentration of chemical substances in crab roe and excessive heavy metals. However, most crabs in China are artificially cultivated, and the water quality and ecological environment are safe and controllable, so there is no need to worry about normal consumption.

× Sunflower seeds cause cancer

It is said online that sunflowers absorb heavy metals, which can cause excessive heavy metal content in sunflower seeds. This is actually a problem with the soil quality of the planting area, not the sunflower seeds themselves. It is recommended to avoid eating substandard and moldy sunflower seeds (containing aflatoxin).

× Iodized salt causes cancer

There is a lack of evidence to support the claim that “thyroid cancer is related to iodized salt”. There is no need to worry about it and you can make your own choice.

× MSG, chicken nuggets and cancer

There is no evidence that MSG and chicken essence can cause cancer and they can be consumed normally.

× Eating too much soy sauce can cause cancer

There is no scientific basis for the claim that soy sauce causes cancer, so you can consume it safely.

× Ramen ash causes cancer

The main ingredient of ramen noodles is fluffy ash, which contains arsenic, but the content is not excessive and will not harm health.

× Stir-frying garlic can cause cancer

Acrylamide is produced during the garlic-frying process, which is a Class 2A carcinogen, but the amount is small and not enough to cause cancer. In fact, many vegetables such as onions and zucchini also produce acrylamide during the cooking process such as frying and roasting. Although it is not carcinogenic, it is recommended to minimize this cooking method.

× The black film on cooked egg yolk is carcinogenic

There is a layer of green "black film" on the surface of the cooked egg yolk, which is not carcinogenic and can be eaten with confidence.

× Boiled eggs with brown sugar can cause cancer

Brown sugar boiled eggs are "boiled in water and cooked at low temperature" so there is no need to worry about cancer.

× Citric acid causes cancer

There is no definitive research proving that citric acid causes cancer.

× Chewing gum causes cancer

Food additives added to chewing gum within the limit standards are safe and there is no need to worry.

× Artificial sweeteners cause cancer

There is no need to worry about cancer with normal intake.

× Glyphosate in cereal causes cancer

There is currently insufficient evidence to show that glyphosate causes cancer, and the glyphosate content in cereal is very low, so there is no need to worry about normal consumption.

× Steaming food with a lid on tap water can cause cancer

This worry mainly comes from the chlorine content in tap water. Chlorine is classified as "Class 3" among carcinogens, and the residual chlorine in tap water is very small, so there is no need to worry about cancer.

× Duck neck causes lymphoma

The "ball of flesh" on the duck's neck is not lymph, but thymus. Even if there is a small amount of residue, it will not harm your health after eating, and there is no need to worry about causing lymphoma.

× Long-term use of vitamin D and calcium tablets can cause cancer

This rumor stems from a misinterpretation of a US study. There is no need to worry about the so-called cancer-causing effects of taking vitamin D and calcium tablets. However, you should follow your doctor's advice on whether you need calcium supplements.

× Sugary foods provide nutrition for cancer cells

Sugary foods can provide energy for all cells in the body, so there is no problem of them being "enjoyed" exclusively by cancer cells. However, obesity may increase the risk of cancer, so from a health perspective, excessive intake of sugary foods should be limited.

× Fried foods cause cancer

Foods processed at high temperatures, such as frying, deep-frying, and baking, will produce acrylamide, a Class 2A carcinogen. It will not cause cancer if consumed normally, but it is recommended to eat less.

× Leftovers cause cancer

Leftovers do not cause cancer, but you should also pay attention to storing food properly, avoid contamination, and do not eat expired or spoiled food.

× Eating bread for breakfast often causes cancer

It will not cause cancer, but you should pay attention to dietary diversity, balanced nutrition, and avoid picky eating.

× Pickles cause cancer

Traditional Asian pickles are classified as Class 2B carcinogens. If consumed in moderation, you don't usually have to worry too much about causing cancer, but it is still recommended to eat less or not eat them.

× Acidic body constitution causes cancer

There is no such thing as "acid-base body type" in medicine. This concept is actually a commercial scam.

Cancer rumor

Life

× Microwaved food causes cancer

Cooking at a high temperature of over 200°C may produce some carcinogens in some foods. This is not a problem only in microwave heating, so the key is to avoid overheating. Microwave cooking mainly uses water molecules as a heat transfer medium, and the heating temperature is basically unlikely to exceed 200°C, so there is no need to worry about the production of carcinogens.

× Fluorescent agents in laundry detergents and sanitary napkins are carcinogenic

There is currently no clear research evidence to support that fluorescent whitening agents in laundry detergents and sanitary napkins are carcinogenic, but you should purchase regular and qualified products.

× Radiation from electric blankets can cause cancer

There is no research evidence to prove that the radiation from electric blankets is related to the occurrence of cancer. When an electrical appliance is plugged in, it will emit electromagnetic radiation, which is extremely low-frequency non-ionizing radiation and there is no need to worry about cancer.

× Placing toilet cleaners in the toilet can cause cancer

The main ingredients of toilet cleaning blocks are common chemicals, which are non-toxic or slightly toxic, so there is no need to worry about carcinogenicity.

× Contact with shopping receipts can cause cancer

Shopping receipts may contain bisphenol A, but there is no need to worry about cancer from daily contact.

× 5G signals cause cancer

× Masks have 5G antennas that can control people and cause cancer

× WiFi signals cause cancer

× Cell phone radiation causes brain cancer

× Electronic products cause cancer

× Wireless headphones cause cancer

Antennas, WIFI, mobile phones, electronic products, wireless headphones, etc. have radiation, but they are all non-ionizing radiation. There is currently no clear and effective evidence to support that these non-ionizing radiations in life can cause cancer.

× Energy-saving lamps cause cancer

The dose of ultraviolet rays emitted by energy-saving lamps that reaches human skin is very low and can be ignored, so there is no need to worry about cancer.

× Medical examination causes cancer

Medical examinations cover a wide range, including CT, X-ray, PET and other examinations that involve ionizing radiation and pose a risk of cancer. There is no need to worry about cancer during normal diagnosis and treatment.

× Dental X-rays can cause cancer

The radiation from dental X-rays is very small, so there is no need to worry about cancer.

× Long-term manicure can cause cancer

Nail polish may contain toxic and harmful substances, and even some inferior nail polish may contain excessive amounts of heavy metals such as lead and arsenic. Long-term manicures may cause some harm to your health, but whether they cause cancer is still unclear.

× Hair dye causes cancer

Hair dye products are classified as Class 3 carcinogens. Frequent and long-term exposure to hair dye products by hairdressers or barbers may increase the risk of cancer. It is safe for individuals to use hair dye products normally, but it is still recommended to minimize the frequency of hair dyeing and pay attention to choosing regular and qualified hair dye products.

To be continued…

Guiding expert: Pan Zhanhe, oncologist, associate chief physician of Zhongshan Hospital affiliated to Xiamen University, and member of the Standing Committee of the Health Communication Working Committee of the Chinese Medical Doctor Association.

Popular Science in China: Talks from Masters at the Frontier of Science and Technology

China Internet Joint Rumor Refutation Platform

Xinhuanet Science Department

Co-production