Choline is an important nutrient in humans and may be essential. Choline is classed as part of the B complex of vitamins. Choline is present in the diet in its free form (not attached to anything), and this is absorbed from the gut where it then accumulates in the blood. Here it acts as a reservoir to raise brain levels of choline, which in turn is synthesised into acetylcholine, an important neurotransmitter involved in movement and memory. Choline is also required to metabolise fats in the liver. Lecithin is a source of choline present in the diet which can be found in some foods such as eggs. Lecithin is actually choline containing phospholipid (choline joined to two fatty acids and a phosphate molecule) and is often synthesised into granulated supplements, the source of which is usually soybeans.
High intakes of free choline in the diet only result in transient increases in blood levels of choline and so a frequent intake is required to maintain blood levels. In addition, some of the free choline ingested is degraded by gut bacteria and so is never absorbed. The product of this bacteria degradation is trimethylamine, which can produce a fishy odour for the individual consuming it. However, because lecithin is not degraded by bacteria in the gut it is a good way to avoid this problem. In addition, lecithin raises blood levels of choline to a greater degree than free choline and these elevations can last for up to 8 hours (compared to 3 for free choline). Lecithin is therefore a superior dietary form of choline compared to its free form.