MadSci Network: Biochemistry

Re: What is the amount of lecithin in 100g egg yolk?

Date: Fri Mar 11 18:25:30 2005
Posted By: Peter Bosani, Independent
Area of science: Biochemistry
ID: 1110195784.Bc

Hello, Grace.

Here are the statistics on an egg yolk derived from a chicken. The yolk is about 50% water, 34% lipids and 16% protein. Lecithin makes up part of the lipid portion. Depending on the size of the egg, 100 grams of egg yolk, (equivalent to 5.9 egg yolks), will yield approximately 5 to 8 grams of lecithin.

The bigger question is, why is this important? Claims for lecithin abound, from its presumed cholesterol lowering effects, to its memory enhancing abilities.

As to the latter, I can't remember if this is true, even though I've just finished eating my omelette. Seriously though, the theory goes that lecithin contains choline, which is a precursor and constituent of acetylcholine. Acetylcholine is a neurotransmitter that is involved in neuron brain cell firing and memory. Unfortunately, there is no evidence that taking lecithin is any more effective in improving memory, than eating bull's testicles is to improve men's vigor.

The claim that lecithin can lower cholesterol has been around a long time, but this too is false. Studies on lecithin that were carefully designed, using controls, did not find lecithin to be effective in lowering cholesterol. (See my answer on 'diet & cholesterol', on this website) .

Finally, remember that each gram of lecithin delivers 9 calories a gram, and about 90% of those calories come from fatty acids, a concern for the weight-conscious.

Lecithin makes a great emulsifier though, but I prefer to contemplate the wonders of the egg in a more esoteric light. Such as, which came first, the chicken or the egg? Or, how can a standard egg withstand the pressure of 50 pounds a square inch across its longest axis? And also, why do ground laying birds lay round eggs, but birds that live on cliffs only pointy ones?

Then again, maybe I 'll stop 'yolking' and simply resort to the pleasures of eating them!

Hope that helps,

Peter Bosani.


             Nutrition Concepts & Controversies - Hamilton & Whitney
             On Food & Cooking - Harold McGee
             Food Values - Jean Pennington & Helen Church
             50 Outrageous Animal Facts - Animal Planet

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