The thymus is a gland in the chest that plays an important role in the development of the immune system in early childhood. As we get older, the thymus gradually shrinks and becomes fatty, so for many years, scientists assumed it does nothing in adults.

    Because the thymus lies directly behind the sternum, it is in the way during open-heart surgery. Because it was presumed to be useless, some surgeons removed it. In a previous email, I described a study in patients who had undergone open-heart surgery, comparing outcomes in those who had their thymus removed to those whose thymus was left intact. Cancer and all-cause mortality were higher when the thymus had been removed.

    In a study published in Nature in March 2026, a “deep learning model“ (aka artificial intelligence) was used to create a radiographic measure of thymic functionality, “thymic health” by analyzing CT imaging data. The researchers found that “thymic health” was associated with a variety of better health outcomes.

    In another article in the same issue of Nature, the investigators reported that “thymic health” was associated with good response to immunotherapy in cancer patients.

    The next logical question would be, “How can we get the thymus to be healthier?” While we wait for the medical literature to enlighten us, I would suggest taking thymus glandulars, or eating “sweetbreads.” See my article on glandulars for more information.