If it's ever felt like everything in your body is breaking down at once, that might not be your imagination. A new Stanford Medicine study shows that many of our molecules and microorganisms dramatically rise or fall in number during our 40s and 60s. Researchers assessed many thousands of different molecules in people from age 25 to 75, as well as their microbiomes - the bacteria, viruses and fungi that live inside us and on our skin - and found that the abundance of most molecules and microbes ...