More Americans have peanut allergies today than at any point in history. Why? In 2000, the American Academy of Pediatrics issued a strict recommendation that parents avoid giving their children peanut products until they're three years old. Getting the science perfectly backward, triggering intolerance with lack of early exposure, the US now leads the world in peanut allergies-and this misinformation is still rearing its head today.

How could the experts have gotten it so wrong? Could it be that many modern-day health crises have been caused by the hubris of the medical establishment? Experts said for decades that opioids were not addictive, igniting the opioid crisis. They demonized natural fat in foods, driving Americans to processed carbohydrates as obesity rates soared.

These failures of medical groupthink have been seen throughout history. Philosophers of the 16th century who claimed that blood circulated throughout the body (instead of resting in a layer below the epidermis) faced capital punishment. James Lind, who discovered that Vitamin C prevented scurvy, was ignored for 40 years. Ignaz Semmelweis was rejected by the medical community for suggesting that doctors should perhaps wash their hands before operating on patients.

Today’s guest is Marty Makary, author of “Blind Spots: When Medicine Gets It Wrong, and What it Means for Our Health.” We see how when modern medicine issues recommendations based on good scientific studies, it shines. Conversely, when medicine is interpreted through the harsh lens of opinion and edict, it can mold beliefs that harm patients and stunt research for decades.