Carnitine is used by the body to convert fat to energy in the mitochondria. It is only derived in sufficient quantities from meat. The amounts in veggies are negligible. Many people can synthesize their own from the ten essential aminos. 1 in 40,000 are so poor at protein synthesis that they can die from carnitine deficiency. Others only show trouble in times of metabolic stress. It is well documented that pregnant women often become carnitine deficient. Since ethnic groups from non agricultural areas rarely need to master carnitine synthesis it would be wise to consider supplementing. It is very cheap. 8$ for a bottle containing 35 grams. When I go all veg I go from 500g a day to a full gram. I am rather excited about this as it took 20 years of tinkering to figure it out. I get terribly ill without it. I get exhausted in a few days. I crave sugar and exhibit many of the symptoms of low blood sugar. Though when tested my blood sugar is always fine. I ahve not experimented with carnosine yet, but that may be beneficial as well. I hope that the science progresses to the point that with a few supplements a veggie diet really is healthier than an omnivorous one.
In Canada it is currently prescription only due to the fact that certain brands sold in health food stores were of questionable purity and deficient persons were getting very ill. Health Canada will now allow carnitine to be sold only if they guarantee pharmaceutical purity. None have come forward to pay for testing last time I checked.