The Economist [no paywall]: “…With mental-health disorders rising, a growing number of scientists are investigating how food or nutritional supplements affect the mind. Brains, being the most complex and energy-demanding of the body’s organs, almost certainly have their own specialised, nutritional needs. Welcome, then, to the emerging field of nutritional psychiatry. An adult human brain, which accounts for about 2% of a body’s mass, uses 20% of its metabolic energy. A host of vitamins and minerals are necessary to keep it going. Even in one small section of the brain’s metabolic pathways, many essential nutrients are needed. The conversion of tryptophan to serotonin alone requires vitamin B6, iron, phosphorus and calcium. Disentangling the brain’s nutritional needs from those of the rest of the body is tricky. Recommended daily allowances (rdas) are little help. They were formulated during the second world war on the basis of the nutrients needed for the physical health of troops. No such rdas exist for the brain. Not yet, at least. Compared with other fields, nutritional science is understudied. That is partly because it is hard to do well. Randomised controlled trials (rcts), used to test drugs, are tricky. Few people want to stick to an experimental diet for years. Instead, most nutritional science is based on observational studies that try to establish associations between particular foods or nutrients and diseases. They cannot be used to definitively prove a causal connection between a disease and a particular contributing factor in a diet. But as with smoking and lung cancer, put together enough of these kinds of trials and causal narratives begin to emerge…”