Considering that food is full of foreign proteins, it makes sense that the intestine is the immune system’s version of Grand Central station. It’s the largest organ to regularly sweep up and annihilate molecules that don’t belong. And because food comes from outside, it’s no surprise that some people have allergies to it. The bigger mystery is why most don’t. Somehow during evolution, the immune system and food components developed a secret handshake that allows munchables to pass without a fuss. Most of the time, that is. Once relatively rare, serious allergies to peanuts, milk,... (p. 20)

The hip bone is connected to the backbone. The backbone is connected to the neck bone. And lately, scientists have begun to think that all dem bones may be connected to the intestine — at least by biochemical signals. If the current evidence holds up, it means that a chemical better known for influencing the brain may also corrode the internal structure of the skeleton. Such is the state of research into bone biology: “The more we understand, the more complex it gets,” says Clifford Rosen of the Maine Medical Center Research Institute in Scarborough. Rosen is one of a growing number... (p. 16)

The patient, known as only “MBM,” was just 7 years old the first time doctors saw her. She had always been prone to night sweats, but now excessive perspiration was forcing her to change clothes several times a day. She was endlessly thirsty, fatigued and losing weight despite a voracious appetite. A dozen years later, at age 19, doctors checked her into a hospital, thinking she had some kind of unusual metabolic condition. After aggressive treatment with drugs, her symptoms improved, but only for a short time, and the next year surgeons removed most of her thyroid. When she was 35 — gau... (p. 20)

First, let’s clear the air: Nicotine invites addiction, and it employs a delivery device that’s been killing people for centuries. But let’s also be honest: Nicotine has some attractive qualities. Smokers use it to calm jitters or perk themselves up. It’s a common (if ill-advised) tool for weight control. Nicotine lowers the risk and eases the symptoms of Parkinson’s disease. Patients with mental illness have high rates of tobacco use, partly because nicotine helps quiet the mind. Because of these talents—along with nicotine’s intense grip on the brain—scientists have... (p. 28)

A common gene variation in men is linked to marital crises and less bonding in a study of more than 500 long-term couples.