Apparently picky eating is common among children, but I suspect there was something wrong with me. My parents suspected something as well and later flew me out for an endocrinology inspection (I grew up in a remote area), but they said I was normal but just small. They did not, however, do any sort of gastrointestinal examination. The endocrinologists were apparently unaware of the long literature which show that zinc supplementation can safely increase growth (see a 2002 meta-analysis which references a 1998 meta-analysis). If they had been aware of this literature, I would probably be a few inches taller.
When I was around 19-20, I became even more sickly. I suffered from constant constipation at first, and when I say constipation I don't mean hard stool so much as I mean incomplete evacuation, the most frustrating and terrible form of constipation. I also developed hemorrhoids, which oddly I was able to cure using some Chinese herb that I bought off the internet (can't remember the name). Embarrassed, I would sneak into the most remote bathroom on the college campus. I visited the nurse and she said I just had a "spastic colon", suggesting it was normal and untreatable. However, she also said it could be a dietary issue, but I could hardly try an elimination diet when I had to eat cafeteria food. I suspected celiac disease on some vague level, but she didn't mention it specifically (even though this like 2006) and I didn't want to go through the endoscopy.
When I went home for the summer, the constipation became diarrhea and I started getting intense stomach pains which made me double over. I went to the doctor and told him I suspected celiac disease; he started with a blood test suggestion but instead I went ahead with a gluten-free diet on my own, and my issues instantly went away. For the average MD, the blood test is almost meaningless - whether it is positive or negative, it is unreliable enough that it likely should be followed up by an expensive endoscopy, which in my area would have meant a flight out of town or a several month wait. So I'm an undiagnosed celiac - doctors technically require the biopsy from the damaged colon, so they might be reluctant to so I have celiac disease at all. Nevertheless, I can tell when I accidentally eat gluten and there is no way I would eat a loaf of bread for a week simply to damage my colon enough to be "diagnosed".
I no longer have gastrointestinal issues at all, really. I spend less than 5 minutes on the toilet on average, usually substantially less than that. Ever since I had the constipation issues in college I have squatted on the toilet which probably has a minor beneficial effect overall, but it does little good when there are underlying diet issues. These days I don't even bother with squatting most of the time because it's so easy sitting. Gastrointestinal issues in the United States are common, and there's the impression that it's normal for it to take a fair amount of time - thus you have people reading magazine on the toilet. I guess I'm biased, but I don't think it is normal.
All this long story to say that I suspect, based on certain factors, that I may be zinc deficient. I've had continuing appetite issues as I try to bulk up and put on muscle, and I've been aware for a while of the scientific literature showing that zinc is related to appetite (and anorexia), but I was reading a scientific article in the Journal of Nutrition and this caught my eye:
After a few days, rats fed a severely zinc-deficient diet fail to gain, and essentially all of the food consumed is used for maintenance. '''Forced-feeding fails to stimulate growth and actually causes zinc-deficient rats to become ill and die sooner than otherwise''' (Chesters and Quarterman 1970, Flanagan, 1984). These observations have stimulated considerable research into the mechanism by which appetite is impaired by zinc deficiency.Now, these are rats, but sometimes meself-control can only take you so far and underlying biological chemistry has to be addressed. For the past few months, I've been trying to force-feed myself and it hasn't been working - it's made me feel sick. I began supplementing zinc a couple weeks ago for different reasons, and I'm hoping that one side effect could be a stimulated appetite. There seem to be few other appetite stimulants which are as promising as zinc (although antipsychotics are one candidate!). Unfortunately, it's hard to tell one's zinc status since plasma zinc stays in a tight homeostatic range regardless of muscle and bone levels, although plasma levels on the low side of this range could be indicative of deficiency - see the above noted meta-analysis which notes that those with low serum levels are reasonably predictive of beneficial supplementation. However, the National Academies Food and Nutrition Board's 2001 book on the topic says "plasma zinc concentration is preferable because of the lack of contamination of zinc from the erythrocyte" (page 451).