Recent research shows that taken in high doses, capsaicin - the compound responsible for chilli's heat - can kill prostate cancer cells while leaving healthy cells unharmed. A new study by the Indian Institute of Technology Madras reveals clues about the substance's mechanisms, opening the door for the development of an effective drug in the form of an injection or pill. Previous research shows that the capsaicin molecule binds to a cell's surface and affects the membrane that surrounds and protects the cell. The Indian scientists were able to detect how the compound interacts with cell membranes by monitoring its natural fluorescence. Their new study showed that capsaicin lodges in the membranes near the surface. Add enough of it, and the capsaicin essentially causes the membranes to come apart. Struggles with sleep raises risk of heart disease Sleeping seven good quality hours a day seems to be the sweet spot. Sleeping less or more may put you at higher risk for early signs of heart disease, according to a study published in the journal Arteriosclerosis, Thrombosis and Vascular Biology . Researchers at Sungkyunkwan University School of Medicine in Seoul studied more than 47,000 young and middle-aged adults who completed a sleep questionnaire and had advanced tests to detect early coronary artery lesions and measure arterial stiffness. Early coronary lesions were detected as the presence of calcium in the coronary arteries. Adults who sleep five or fewer hours a day were found to have 50 per cent more calcium in their coronary arteries than those who sleep seven hours a day. Those who sleep nine or more hours a day have more than 70 per cent more coronary calcium compared to those who sleep seven hours. Adults who reported poor sleep quality had more than 20 per cent more coronary calcium than those who reported good sleep quality. A similar pattern was observed with arterial stiffness. Humans wired for laziness People who spend hours at the gym with the aim of burning as many calories as possible may be disappointed to learn their nervous systems are subconsciously working against them. Researchers reporting in Current Biology have found that our nervous systems are adept in changing the way we move so as to expend the least amount of energy possible. Subjects were asked to walk on a treadmill while wearing a robotic exoskeleton which made it more tiring to walk normally than to walk some other way. Researchers analysed the subjects' walking styles and calculated their energy costs. "We found that people readily change the way they walk to save quite small amounts of energy," says Max Donelan of Simon Fraser University in Canada. "This is consistent with the sense that most of us have that we prefer to do things in the least effortful way, like when we choose the shortest walking path, or choose to sit rather than stand."