“Thinking it is good for you, you added it to a salad”… Beans and mushrooms that can cause illness when eaten raw - 경향신문

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It is easy to assume that the fresher vegetables are, the better, and that eating them without applying heat lets you take in more nutrients. However, this principle does not apply to all vegetables and ingredients. Some foods, such as bean sprouts, are prone to the proliferation of foodborne bacteria because of their growing conditions, and some beans contain natural toxic proteins that can cause vomiting and diarrhea when not cooked thoroughly. Raw shiitake mushrooms can also trigger dermatitis in some people.

That does not mean you must avoid all raw vegetables. Some foods must be cooked; for others, hygienic controls to prevent contamination are crucial; and with some, you should watch intake because of particular components. It is necessary to distinguish the sources of risk and the countermeasures by ingredient.

Bean sprouts and sprouts such as radish sprouts and alfalfa sprouts can carry a higher risk of food poisoning when eaten raw or only lightly cooked. The warm, humid conditions used during cultivation also favor foodborne bacteria.

The U.S. Food and Drug Administration (FDA) warns that sprouts can be contaminated with Salmonella, Listeria, and E. coli. Even if only a small number of bacteria adhere to seeds, they can multiply rapidly during germination, and it is difficult to eliminate the risk completely even when growing them hygienically at home. According to the FDA, from 1996~2020 there were 52 reported outbreaks of food poisoning linked to contaminated sprouts, with more than 2700 cases.

The key point is not that bean sprouts themselves are poisonous, but that bacteria introduced during growing and distribution can survive when the product is eaten raw. Adequate heating reduces the risk from harmful bacteria. In particular, pregnant people, children, older adults, and those with weakened immunity should avoid raw or undercooked sprouts.

Not all beans are the same. Red kidney beans in particular contain a lectin protein called phytohemagglutinin. This compound, which occurs naturally in plants, can cause nausea, severe vomiting, and diarrhea when raw or undercooked beans are consumed.

The FDA advises soaking dried kidney beans in water for at least 5 hours, discarding the soaking water, and then boiling the beans in fresh water for at least 30 minutes. Thoroughly cooked kidney beans and properly processed canned kidney beans can be eaten safely. However, this risk should not be applied uniformly to all beans. Warnings about raw or undercooked kidney beans do not apply wholesale to tofu, fully cooked beans, or store-bought frozen green soybeans. Because some frozen green soybeans are pre-blanched while others require additional heating, check the cooking instructions on the package.

The way mushrooms are eaten differs by type. In particular, shiitake mushrooms can, on rare occasions, cause ‘shiitake dermatitis’ when eaten raw or insufficiently cooked. It is characterized by whip-like red linear rashes on the torso and arms, accompanied by intense itching. Symptoms may not appear until several days after consumption.

Researchers at the University of Nebraska Medical Center and Rutgers New Jersey Medical School summarized the link between consuming raw or undercooked shiitake mushrooms and this dermatitis, suggesting that a polysaccharide called lentinan in shiitake mushrooms may be the cause. Lentinan is a compound whose activity diminishes with heat. Although this dermatitis was first described in Japan, it has since been reported in Asia, North America, South America, and Europe.

That does not mean all mushrooms are toxic when eaten raw. Some, such as the button mushrooms sold in stores, are commonly eaten raw. Because edibility differs by mushroom type, shiitake mushrooms should be cooked thoroughly to the center.

Ginkgo nuts are a seasonal delicacy in autumn, but you should watch how much you eat. They contain a toxic compound called methylpyridoxine. This compound interferes with the action of vitamin B6 and can cause neurological symptoms such as vomiting and convulsions.

In a literature review published in 2019 in the Journal of the Pharmaceutical Society of Japan, Daisuke Kobayashi and colleagues at Hokkaido University School of Pharmacy summarized poisoning cases and toxic mechanisms associated with excessive ginkgo consumption. Children require particular caution. In Japan, a case involving a two-year-old child who, after eating many ginkgo nuts, developed vomiting and diarrhea followed by convulsions was reported in the international journal ‘Pediatrics’.

The toxic risk cannot be considered completely eliminated even when ginkgo nuts are cooked. Therefore, do not eat them raw, and avoid eating large amounts of cooked ginkgo nuts at once. Extra care is needed for children. Rather than applying a one-size-fits-all rule like ‘adults are safe up to a certain number’, it is better to limit intake and avoid overeating.

Spinach: is it wrong to eat it raw?

Spinach should be distinguished from the ingredients above. Spinach contains oxalic acid, which can bind to calcium to form calcium oxalate. Calcium oxalate is among the main types of kidney stones. However, this does not mean that a healthy person is at risk from eating raw spinach.

The U.S. National Institutes of Health (NIH) advises people who have kidney stones or are at high risk of stones to moderate their intake of high-oxalate foods such as spinach. Oxalate content can also vary with cooking method. A 2005 study published in the international journal ‘Journal of Agricultural and Food Chemistry’ found that boiling vegetables in water reduced water-soluble oxalate more than steaming.

Therefore, there is no reason to categorically rule out eating spinach raw. However, those with a history of kidney stones or who have been advised by clinicians to limit oxalate intake should adjust their diet and may consider cooking methods such as blanching and discarding the cooking water.