Dr Atkins talks about it in his book 'Vita-nutrient solution'. It is an amino acid which is manufactured by the body in quite large amounts anyway.

He says it helps with short term bursts of energy and is useful for weight lifters, sprinters etc.

He also says that in order for it to make any difference you have to take such a large dose (about 20 grams) it's going to work out expensive!

I don't think it would hurt the diet but I think there may be other things you'd be better off spending your money on.