Enhanced Energy and Focus
I’ve had a few concussions in my time, generally thanks to being rubbish at MMA and other combat sports and martial arts.  After the last one, I had a bad head and felt ‘out of it’ for quite a few weeks.
I did some reading up, and all the studies that I read tended to suggest that after 3 concussions, whenever they have been incurred during your life, there is always a long term detrimental effect on cognition, that remains for the rest of your days.

Ah hell. Not to worry though; everyone from professors to ex NFL players have started bringing out neuro-protective supplements, and cognitive enhancing supplements that supposedly offset the effects of any damage.

Taking L carntine, especially with a choline supplement, makes a huge different to my attention span, energy levels and enhances my mood.  Which is lucky, as I’m turning into a miserable old get.

Apparently acetyl l-carnitine is the form to opt for if focus and concentration is your goal, as it passes the blood brain barrier more efficiently.

Male Fertility
Good news for some, perhaps something to be aware of for others – l carnitine makes your swimmers, swim, faster.  Or at least more efficiently. The little buggers.

Here’s some more info from a fella with beautiful hair: http://www.drbriffa.com/2010/08/19/l-carnitine-found-to-boost-sperm-quality-and-fertility/

In fact, I got the wife up the duff whilst taking acetyl l-carnitine on a daily basis.

http://www.swansonvitamins.com/blog/vitamins-supplements-faqs/what-is-the-difference-between-l-carnitine-and-acetyl-l-carnitine-v1

Endurance
Take 200mg of caffeine, and 500mg of acetyl l carnitine before a workout, and bloody hell, you’ll go like the clappers.
If you don’t believe me though, look at this study

Heart Health
There appears to be some confusion around this at the moment.
Whilst the Mayo clinic concluded that L carnitine was actually beneficial for heart health, there has been one study suggesting that carnitine alters gut bacteria somehow, and this in turn can impact on heart health over time.
For this reason I would smash the probiotic foods like kefir to offset any effects, or just cycle your carnitine usage.

Side affects of L-Carnitine

Taken on an empty stomach, acetyl or standard l carnitine gives me a bad stomach.  I keep doses at 200mg or below ans take after food.

Some people theorise that acetyl l-carnitine or l-carnitine might actually be bad for heart health, via a molecule called TMAO. This potential side effect is said to be offset by the consumption of garlic.