Testosterone is made from cholesterol. Oestrogen is made from cholesterol. Progesterone, the hormone that holds a pregnancy, is made from cholesterol. Cortisol, the hormone that gets you through a crisis, is made from cholesterol. Vitamin D is made from cholesterol, by sunlight, in your skin. The bile that digests your fat is made from cholesterol. Every cell in your body is wrapped in a membrane stiffened with cholesterol. Every nerve is insulated with myelin packed with cholesterol. Your brain is 2% of your body weight and holds about a quarter of your cholesterol. Breast milk is loaded with it, because a baby's brain can't be built without it. Most infant formula has almost none. Pregnancy raises it by up to half, because building a human takes a lot of it. Eat less of it and your liver simply makes more, because the body refuses to run without it. Then, in the late 1970s, we declared war on it. Around 8 million people in England now take a pill to lower it. That pill raises the risk of diabetes by about a tenth. Sperm counts have more than halved. Men's testosterone has been sliding about 1% a year, age for age. Antidepressant prescriptions in England have more than doubled since 2008. And in people over 70, the lowest cholesterol tracks with dying soonest. Reports from the front say the war is going well.