By Allen Bryan
Human beings are omnivores, so we eat both plant and animal products. Most people know that uncooked meat or eggs and unpasteurized milk products can have harmful bacteria, so we usually cook them. Fresh vegetables are, on the other hand, frequently not cooked. Raw vegetables are good for us and a part of our regular diet. We serve them in salads, with dip, and as additions to sandwiches. Should we be more concerned about how our vegetables are prepared?
It is true that fresh vegetables can make you sick. Between 1998 and 2008, 22% of reported foodborne illness was from fresh leafy vegetables. While food packers now spray lettuce with chlorine to kill bacteria, it only seems to be partially working. In 2018, romaine lettuce was found to carry a dangerous form of the bacteria E. coli, which caused illnesses in at least 19 states. The CDC also warned of Salmonella contaminated bean sprouts in three states in 2018. If eating fresh vegetables is can be dangerous, why don’t we just cook everything?
Studies show that nutrients can be lost during cooking. Up to half of the water soluble vitamins, such as the C and B vitamins, can be lost. In one German study, it was shown that people who ate fresh vegetables had higher levels of beta carotene. Canned vegetables show far worse results for maintaining nutrient levels, with up to 95% loss of their natural vitamin C. One interesting note is that fresh frozen vegetables (uncooked) retain higher levels of vitamin C, because the fresh unfrozen veggies lose a lot of this nutrient during the shipping process.
Cooking your vegetables is not all bad news. Levels of some nutrients become more bioavailable when the is cooked. One study showed that, while vitamin C decrease in cooked tomatoes, there was an increase in the levels of antioxidants available to the body. It has also been noted that, while raw spinach has more fiber, cooked spinach provides up to 3 times as much beta carotene. Also, if vegetables are cooked as soup, the water soluble vitamins can be retained in the liquid.
So there seems to be a trade-off. Well-cooked vegetables are generally safer from disease and may give better access to some nutrients, while fresh, uncooked vegetables, provide more of some vitamins and are at greater risk of carrying dangerous bacteria. If you choose salads or uncooked veggies, just make sure they are well washed just before serving to reduce the bacterial load.