10 Most Radioactive Foods

You ate radioactive food today! Technically, all food is slightly radioactive because it contains the elements carbon, hydrogen, and potassium. The natural abundance of each of these elements includes radioactive isotopes. However, some foods are more radioactive than others. Here’s a list of 10 radioactive foods and how much exposure to radiation you get from them.

10 Common Radioactive Foods

Brazil nuts are the most radioactive everyday food. However, large quantities of Brazil nuts, lima beans, and bananas all can set off radiation detectors when they pass through shipping. The radiation dose from eating one banana is calculated at 10⁻⁷ Sievert or 0.1 microSieverts. To put the number in perspective, a chest x-ray delivers around 5.8 mSv or 5800 microSieverts. Some drinking water is slightly radioactive, depending on its source.

Common radioactive foods contain potassium-40, radium, or radon (the immediate daughter isotope of radium). Potassium-40 undergoes both types of beta decay, while radium and radon emit alpha and gamma radiation.

Potassium accounts for about 0.2% of human body mass. A 70-kg person contains about 170 grams of potassium, of which 0.0164 grams is potassium-40. Potassium-40 produces about 4300 disintegrations per second throughout a person’s life. Most ingested radium (80%) exits the body through the feces, but about 20% accumulates in bones.

Other Radioactive Foods

Normal radioactive food is no big deal, but some food gets its radioactivity from proximity to a nuclear test or nuclear accident site. For example, several foods contained radiation beyond the Japanese legal limits following the Fukushima accident. Particularly problematic foods include fish and other seafood from the Pacific ocean, seaweed (nori), bamboo shoots, mushrooms, tea, and dairy products. The Yokohama Citizen’s Radioactivity Monitoring Station measures radioactivity to help people living in or visiting Japan determine whether food is safe to eat. Similarly, the radiation levels in crops and livestock within and surrounding Chernobyl exclusion zone continue to be monitored.

Why Some Food Is Radioactive

Common radioactive foods usually get their radioisotopes from the soil, although it’s also possible to absorb isotopes with water. All soils and fertilizers contain small amounts of radioactive potassium. Brazil nuts and other produce containing radium or radon absorb the elements through their root system from soil and water.

Food radioactivity due to accidents is a bigger problem because radioisotopes are absorbed into the plants and animals and may also form a dust on their surfaces.

Is Radioactive Food Dangerous?

All foods naturally high in potassium contain some potassium-40 isotope. It’s just a fact of life and not a cause for concern. People, plants, and animals are all very slightly radioactive from the potassium in their cells. Cells contain repair mechanisms to counteract ordinary exposure to radiation.

Foods that are radioactive from radium or radon could pose more of a risk because ingesting these isotopes exposes the mouth, esophagus, stomach, and intestines to alpha particles. But, these radioisotopes only occur naturally in trace amounts in food. Again, they aren’t cause for concern.

Food and water made radioactive due to man-made contamination may be unsafe to eat or drink. Examples include crops, livestock, and water exposed to fall-out from a nuclear test or reactor accident. Some radioisotopes persist for years. For example, the half-lives of tritium, cesium-137, and strontium-90 are 12.3 years, 30 years, and 29 years, respectively. The half-life of uranium-238 is 4.5 billion years.

Is Irradiated Food Radioactive?

Irradiated food is not radioactive. Irradiation works by applying ionizing radiation, using x-rays, an electron beam, or gamma rays from cobalt-60 or cesium-137. The ionizing radiation breaks chemical bonds, killing pests and pathogens and delaying ripening or sprouting. Unlike radioactive foods, irradiated food doesn’t contain or come into direct contact with radioactive isotopes. Basically, irradiated food is not radioactive in exactly the same way a person isn’t radioactive after getting a dental x-ray or flying in an aircraft. Ionizing radiation does interact with the cells in food, but doesn’t appreciably alter its flavor, texture, appearances, or nutritional value. Consumer concerned about changes due to irradiation can recognize irradiated whole foods by the radura symbol. However, processed food made using irradiated ingredients won’t bear the special labeling.

References

• Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). “The NUBASE2016 evaluation of nuclear properties”. Chinese Physics C. 41 (3): 030001. doi:10.1088/1674-1137/41/3/030001
• Bin Samat, S.; Green, S.; Beddoe, A. H. (1997). “The 40K activity of one gram of potassium”. Physics in Medicine and Biology. 42 (2): 407–13. doi:10.1088/0031-9155/42/2/012
• U.S. Environmental Protection Agency. Natural Radioactivity in Food.
• U.S. Food and Drug Administration. Food Irradiation: What You Need to Know.