[the_economist]

Not just anecdotally -- plenty of studies confirm this. Some people -- 30% of the people by some estimates -- simply suffer from fructose malabsorption. This means that when they eat foods with excess fructose (even fruit), they fail to properly absorb nutrients.

In particular, individuals who suffer from fructose malabsorption fail to absorb tryptophan: http://en.wikipedia.org/wiki/Fructose_malabsorption

Tryptophan deficiency is extremely common in depressed individuals: http://www.ncbi.nlm.nih.gov/pubmed/2148339

Tryptophan is a serotonin precursor, so to anyone who has ever taken an SSRI, it intuitively makes some sense that it could be related to happiness.

Sadly, no one wants to be told that their diet is a problem, or that they have to do all the hard work of changing their diet. They just go for a pill. Which wouldn't even be so bad, if the pills we made were truly effective and side-effect free. But they aren't.

[neutronicus]

Or, you know, they just believe that non-doctor people telling them it will get all better if they just eat X are out of their minds.

[hcarvalhoalves]

Nutrition is everything.

My dad last year suffered from a mix of dizziness, nausea, depression and if he got too nervous, muscular contractions.

Went to a bunch of doctors, each one gave a different pill, and his situation wasn't improving. I had to research the internet looking for symptoms and possible causes.

Then, in the end, talking with a generalist doctor, it ended up being a thyroid disfunction (he was taking pills for that) and magnesium deficiency. After a year taking kelated magnesium and cutting the thyroid medicine (the doctor told to), he's 100% again.

[mej10]

Any time I have mentioned that someone should change their diet to help them deal with any number of problems (weight, mild depression, seasonal affective disorder, overall energy levels), I am universally met with disbelief and dismissal.

The fad diet industry has ruined people's ability to think clearly about the topic of diet. The part that gets to me the most is that I have had profound changes in my life due to diet and exercise changes, and they know that. They still won't even try.

[mcguire]

Possibly because there are many people out there with any number of problems (weight, depression, asthma, acne, diarrhea, rising of the lights,...) who, when mentioning those problems, are universally met with suggestions to change their diet. From someone who has no idea what diet the sufferer has.

But I'm with you, there, buddy. It's like these people don't even know rutabagas exist and supply all of the particulas vitae necessary for human existence.