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Table 7 Comparative composition of protein hair according to the data collected from 10 studies

From: Hair for brain trade-off, a metabolic bypass for encephalization

		Sulphuric compounds^a	Arginine %	Aromatic compounds^b
Caucasian, “brown hair”	Wolfram (2003).	18.2%	6%	3.6%
Asian	Wolfram (2003).	18.1%	6.1%	2.2%
African	Wolfram (2003).	16.8%	6.1%	4.2%
African	Lang and Lucas (1952).	18.7%	8.9%	4.6%
	Masukawa et al. (2004).	17.6%	6.2%	3.6%
	Sass et al. (2004).	17.4%	6.7%	1.7%
	Bradbury (1979).	17.1%	6.3%	3.8%
	Nagase et al. (2008).	16.8%	5.9%	1.8%
	Jones et al. (1996).	16.5%	6.2%	3. 8%
	Zahn and Gattner (1997).	16.6%	6.5%	3.7%
	Crewther et al. (1965).	15.9%	6.2%	5.7%
	Kim et al. (2013)^c.	14%	6.2%	5.7%
	McCullagh et al. (2005).	11.3%	9.3%	7.3%
	Yu et al. (1993).	8%	7.2%	4.5%
	Akhtar et al. (1997).	8%	7.2%	4.5%
Median values		17%	6.5%	3.8%

^aMethinine and cystein (methionine cannot derived from cysteine while cysteine might derived from methionine) and also cysteic acid which is a minor fraction derived from cysteine.
^bPhenylalanine and tyrosine (phenylalanine cannot derived from tyrosine while tyrosine might derived from phenylalanine).
^cAccording to the sulphur content of hair.

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