Cooking a dish as simple as macaroni or spaghetti can be detrimental to your health if salt is added at the wrong time. This is because disinfectants in tap water can create harmful products when combined with salt. Iodinated disinfection byproducts (DBPs) can cause cancer, liver damage, and decreased nervous system activity.
Scientists at the University of South Carolina discovered that when wheat flour is heated in tap water containing residual chlorine and seasoned with iodized salt, potentially harmful iodinated disinfection by-products can form.
To remove these toxins from the pasta, the researchers formulated two scientifically safe steps: boiling the water without a lid and straining all the pasta water. In addition, iodized salt should be added after cooking pasta, and non-iodized salt options should only be used if pasta is boiled in salted water. Boiling pasta without a lid allows vaporized chlorinated and iodized compounds to escape, and straining the noodles removes most of the contaminants.
The amount of iodinated trihalomethanes, potentially toxic compounds, in the cooked food and pasta water was measured in two different experiments. The researchers found that cooking conditions significantly affected the amount of contamination. The second experiment, in which scientifically safe steps were followed, reduced contamination and eliminated most of the iodinated disinfection by-products.