Food as Medicine
In the past (and probably in the future) , the concepts "food" and "medicine" overlapped almost to the point of being interchangeable.
A person had a disease, whether an itch, an injury, hunger, weakness, etc, the solution was to consume the proper food in the proper way.
In our modern technological society there are two main classes of remedies. 1) Those that are patented, and therefore heavily marketed and profitable, and 2) those that aren't.
Consider the effects of two substances in modern society, one from each of those categories.
1) Vioxx (rofecoxib) was an arthritis drug heavily marketed by Merck. In 2003 sales of the drug were $2.3 billion. Merck withdrew it after being caught withholding information about rofecoxib's risks from doctors and patients for over five years, causing between 88,000 and 140,000 cases of serious heart disease. In other words, roughly a hundred thousand people got serious heart disease from a drug that they paid a lot of money to take. Of course a lot of those people died before Merck's game was exposed.
2) Potassium. No company markets potassium. You can get a lot of it from a banana or a potato so there isn't any real cash value in potassium. But one of the easiest ways to dramatically reduce heart attacks and stroke would be to increase the amount of potassium eaten by people. On the one hand there is no drug that could offer the widespread benefits of potassium to so many people. On the other hand Merck and similar Pharma companies don't make money on things like potassium. They make money on things like Vioxx.
Some general tips on diet as it relates to "mental health".
1) Eat some of the foods your ancestors ate. Find out which foods were common in the areas where your ancestors lived and try to eat some of those foods regularly. This applies mainly to fruits and seeds and vegetables.
2) Avoid seedless fruits, genetically modified foods and other frankenproducts. Foods produced by cutting edge science invariably (no exceptions) produce some kind of negative surprises. The chicken that has ten drumsticks and no wings may be very profitable for the company and the advertisements may be slick but let the people who make that food eat it. Stick with products that have existed for millions of years.
3) The more ingredients in a food or meal, the less natural. Ideally a meal will have no more than 5 total ingredients, not including salt and water. A very healthy purge is to eat single ingredient meals, several hours apart, for a few days. It's not necessary for a single food to contain ten or twenty different chemicals.
4) Eating meat generally gives a person quick strength, but it is extremely unhealthy for the mind in the long term. Most people who stop eating meat for at least a few days notice a dramatic increase in mental clarity and calmness. Eggs likewise give a lot of energy but it is a chaotic, unhealthy energy. Milk is not good for adults. Nothing complicated there. Milk encourages growth in children, but in adults it causes a pacified stagnation.
5) Salts are a food category of their own. A person should first become familiar with salts and how they balance, then with other minerals. Generally a salt or mineral balances with another. Sodium generally balances with Potassium, Calcium with Magnesium, etc. If you add one to your food you should also add the other.