trying to improve productivity with natural products (caffeine, guarana, kola nut & co.)

in an attempt to improve my efficiency and productivity, i’ve spent some time reading up on the most common natural products & substances that increase activity and energy.
 

here’s a short (non-exhaustive) list of things i’ve com across:

caffeine:

increases activity and concentration. stimulates the central nervous system, heart activity and blood pressure.
negative effects: adaption, addiction, nervousness and anxiety, irritability, anything up to cardiac arrhythmia.
overdose (according to wikipedia): 7 to 10 cups of coffee consumed within a short timespan.

guarana:

contains more caffeine than regular coffee. here, the caffeine is linked to tanning agents, which makes it longer-lasting (it’s released little by little).
same negative side-effects as with pure caffeine.
overdose: 20g guarana powder.

kola nut:

also contains more caffeine than coffee. caffeine is chemically bound, thus slightly different effects: enhanced alertness and physical energy, mood elevation, bronchodilatation.
effects last up to 6 hours.
also, the usual side-effects (anxiety, tachycardia) are limited.
kola nuts contain high amounts of N-nitroso compounds which are carcinogenic.

theobromine:

produced by cacao trees.
heart stimulant, vasodilator.
weaker effects than caffeine (less addicting!), but stronger heart stimulation.
may cause sleeplessness, tremors, restlessness, anxiety, cardiac arrhythmia, loss of appetite, nausea, and vomiting.
lethal dose: 10 kg of chocolate (who could eat 10 kg at once??)

omega-3 fatty acids:

positive effects on concentration and memory. amongst others, direct positive effects to the communication between nerve cells (in synapses).

available as fish oil pills/dragées.
no known negative effects, beside the eructations that occur if you don’t take the pills in an ideal moment. don’t take one at breakfast!

soy lecithin:

considered to be beneficial to concentration and productivity (by raising the level of acetylcholine, a neurotransmitter). improves energy budget during times of stress.
couldn’t find any reliable information on the web, lots of product advertisements though.

ginkgo essence

said to improve memory, but the effects could not be reproduced scientifically.
side-effects: higher risk of strokes and transient ischemic attack (mini-strokes)

ginseng

commonly used against tiredness and bad concentration. said to aid the immune system and cardiovascular system. effects not proven scientifically.
side-effects: sleeplessness, anxiety, diarrhoea, hypertonia. affects blood clotting.

in the end, i think that all the substances which are NOT just correcting deficiencies (such as omega-3 or soy lecithine), DO have adverse side-effects.
for more effect, it looks like i’ll have to resort to the usual: sports, plenty of sunlight and balanced nutrition.