Tryptophan is an essential amino acid. It is used by the body to produce both serotonin and niacin. 5-HTP is another form of tryptophan, one which is better at crossing over the blood-brain barrier, and which is more quickly converted to serotonin. There is some evidence that these can act as empathogens and aphrodisiacs. There is no doubt that if a person has low tryptophan levels, they will have low levels of serotonin, one of the feel-good neurotransmitters. In that case, a tryptophan supplement may improve mood. Anxiety is reduced, and an overall feeling of well being is fostered. And this improvement can sometimes be dramatic, and spill over to bedroom activities. And that's not all ...

There are many reports that people taking Prozac (a serotonin enhancer) often experience enhanced sexuality when they start on the drug. Unfortunately, this usually fades out, and in the long term, Prozac and the SSRI antidepressants are more likely to interfere with sexuality.

The role of serotonin in sex is complex and not well understood. As recent as 2006, scientists were unsure if serotonin played a role in erections. A study at the Royal Hospital and Medical School in London found that serotonin was in fact involved in the balance between relaxation and contraction that determines if the penis is erect or not. Curiously, serotonin causes muscle contraction (which works against an erection).

But lab experiments do not always show the full dynamics of what is going on in the body. Even though serotonin may work against arousal when it is poured on cells in a test tube, the real organism is more complicated. My experience (which I don't consider universal) is that boosting serotonin can increase arousal.

I have noticed an increase in spotaneous erections when taking 5-HTP, especially on awakening. Part of this 'change' may be more apparent than real - spontanous erections while asleep usually occur in the REM phase (dreaming), and it could simply be that 5-HTP changed my sleep, and I woke up more when I was in a dream. But I do believe that it has had a prosexual effect on me.

I believe that when serotonin is low, it doesn't switch on and off in the neurons in a normal way. Low serotonin levels lead to diminished tone; at higher (normal) levels, the neurotransmitter seems to better move between the on and off states. Non-erections are more non-erect, while erections are fuller and more common.

Taking tryptophan also can increase the production of melatonin in the body. Melatonin is a sleep-inducing hormone. But tryptophan and 5-HTP do not make me sleepy all day. They help me sleep better at night, and I am fully awake in the day ... I switch better between the off-mode of sleep and the on-mode of being awake.

People with lactose intolerance or fructose intolerance seem to have difficulties in absorbing tryptophan from the gut. These sugars ferment and prevent tryptophan from crossing into the blood. Even complex carbs can ferment in transit and end up causing low tryptophan/serotonin levels. Frequent gas, bloating or diarrhea are all possible indicators of a problem with carbohydrate digestion (although other factors could also be at work, and a visit to the doctor may be in order if normality is not the norm).

That old belief that the tryptophan in turkey makes people sleepy on Thanksgiving day? Ignore it - its' probably wrong. The amount of tryptophan in turkey is not large compared to other protein-rich foods. I have taken relatively large doses of pure tryptophan on an empty stomach (to maximize the effect) and did not feel drowsy like I do when they bring out the pumpkin pie. I think the Thanksgiving Day Effect is from simply eating too much - the liver is overloaded, and the body wants to shut down to process the food.

In my personal experience, 5-HTP can also act as an empathogen and make a person more sociable. When I first started taking 5-HTP on a regular basis, I felt strong feelings of joy and connectedness to others... I went through my day smiling, talking to others, feeling like the sun was shining inside me. It was almost scary - and I figured my mood had improved enough to stop the 5-HTP. I have never taken Ecstasy (X or MDMA), but I believe the semi-euphoria I experienced is similar to what people have reported with X (though less intense).

Combining tryptophan or 5-HTP with anti-depressants is quite dangerous. An overdose of 5-HTP can easily lead to serotonin syndrome, which can be fatal. (Signs of serotonin syndrome include grinding the teeth or clenching the jaw, muscle spasms, euphoria, and elevated body temperature).

Other potential side effects are less understood. One researcher claims that 5-HTP (but not tryptophan) might cause damage to the heart valves like the prescription combination phen-fen. Although many people have taken 5-HTP for decades and the problem has not become apparent, this is remains a possibilty.

5-HTP seems to be more likely to disturb the bowels than tryptophan (the gut contains more serotonin than any other part of the body). I have never noticed a problem with this, although I know of some who do. People with IBS (irritable bowel syndrome) generally prefer tryptophan to 5-HTP. I usually take 5-HTP by opening the capsule and putting a little in my mouth at a time, allowing it be absorbed. This method may reduce the risk of bowel issues in people that are susceptible.

For the past few decades, tryptophan was difficult to obtain in the United States. That is starting to change, but it is still rather expensive. In the 1980s, a Japanese company that produced tryptophan changed their production method, and through negligence, they delivered a batch of tryptophan that was contaminated. There were several deaths and hundreds of people became ill. So the FDA banned most imports. If this prohibitionist attitude were carried over to other spheres of life, the government would permanently ban spinach after recent contamination incidents, and the Jack-in-the-Box E. coli incident a few years ago would have resulted in a ban on all hamburger. Ah, well, no sense in looking for rationality in government decisions.

Tryptophan needs to be taken on an empty stomach, and a glass of sugary beverage may help tryptophan cross into the brain. 5-HTP can be taken on an empty or full stomach - doesn't matter according to the research. Taking either an hour or two before a meal may reduce the appetite - with more serotonin, cravings for food seem to lessen, and food consumption is closer to the metabolic need.

Are these serotonin boosters aphrodisiacs or empathogens? I think they are - for some people. If anxiety or other conditions associated with low serotonin are limiting your life, a tryptophan supplement might help. A person with normal serotonin levels might not experience any improvement.