PUMP A LITTLE IRON\nWell-trained muscles produce an enzyme that purges the body of kynurenine, a substance formed during stress that can lead to depression, a new study finds. Researchers at Karolinska Institutet in Sweden exposed two groups of mice to stressors such as loud noises and flashing lights. After five weeks, the group of normal mice developed depressive behaviour, whereas the group bred with the characteristics of well-trained muscles showed no depressive symptoms. \n\nSTRESS HAS A GENDER BIAS\nYoung women with coronary heart disease are much more vulnerable to emotional stress than their male counterparts, according to research presented at a meeting of the American Heart Association late last year. The study put 534 heart patients through a mental stress test and found that women aged 55 or younger suffered a reduction in blood flow to the heart that was three times greater than that of men the same age. The gender difference was smaller for those aged 56 to 64, and there was no difference between men and women over the age of 65. The results may partially explain why female cardiac patients are more likely to suffer fatal heart attacks than male patients.