A common belief is that our metabolism steadily slows as we age. In fact, metabolic efficiency holds constant between ages 20 and 60. What we eat matters. A growing body of research links ultraprocessed foods, whose effects on the brain can mimic those of nicotine and ethanol, to a long list of health problems. Our bodies need sufficient amounts of about 30 vitamins and minerals to function, although doctors have overdiagnosed vitamin D deficiency. The science says that rather than striving for eight glasses of water a day, relying on your body’s thirst cues is adequate to stay hydrated.