Precursor molecules of neurotransmitters, the biochemical messengers that regulate the functioning of your mind, are nutrients.
Depression and decay are associated with a deficit of serotonin, the synthesis of which requires vitamin B6 and tryptophan, a component of dietary proteins. Dopamine, the main responsible for your pleasure, cannot be made without iron and vitamin B9. And GABA, the neurotransmitter that prevents you from succumbing to anxiety, requires vitamin B6 and zinc.
A malnourished mind CANNOT be happy
And either does an inflamed mind
Deficiencies of certain essential nutrients (particularly zinc, B vitamins and omega-3 fatty acids), as well as inflammation, can lead to depression. In fact, chronic systemic inflammation (fueled by inflammatory diets and prolonged exposure to toxins and infections) has been shown to cause depressive symptomatology (even in the absence of an environmental trigger).
A healthy and nurtured mind can overcome any adversity. An inflamed and malnourished mind makes an adversity of its own existence. If you want to jump out of bed with the energy to conquer the world, reduce to a minimum the unflattering substances that reach your brain and make sure you provide it with all the nutrients it needs. And it will devote its time and energy to fixing your rose-coloured glasses and filling you up with vitality.
Anytime soon, diets deficient in essential nutrients and exposure to toxins (or a diminished ability to absorb the former and excrete the latter) will be part of the equation that will put an end to depression.