The impact of apo E phenotypes on applicability of relative cholesterol synthesis (lathosterol:cholesterol) and absorption (ratios of cholestanol, campesterol and sitosterol to cholesterol) during diets of various cholesterol and fat content is unclear. We examined and compared with each other both relative and absolute synthesis and absorption among twenty-nine men, of whom eight, nine and twelve had apo E phenotypes 2 (2/2, 2/3, 2/4), 3 (3/3) and 4 (3/4, 4/4), respectively. Serum lipids,

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... roteins, sterols and cholesterol metabolism were examined on four subsequent diets: high-cholesterol high-fat (home diet; HD), low-cholesterol low-fat (LCLF), high-cholesterol low-fat (HCLF) and low-cholesterol high-fat (LCHF). LDL-cholesterol (LDL-C) level was about 40 % lower (P,0·05) in apo E2 than apo E3 and E4 groups irrespective of dietary fat and cholesterol. Serum proportions of phytosterols were determined apo E-dependently on LCLF and HCLF, and those of lathosterol, cholestanol and campesterol were increased in apo E2 and E3 groups (P,0·05 for each v. HD). Serum proportion of sitosterol reflected almost consistently apo E phenotype (r range þ 0·308 to þ 0·383; P range 0·214 -0·011). Relative cholesterol synthesis and absorption reflected respective absolute values during each diet in the apo E4 group (r rangeþ0·713 to þ 0·893; P, 0·05 for each), but only during HD (r þ 0·594; P¼ 0·015) in the apo E2 þ E3 group. The consumption of a high amount of fat did not interfere with cholesterol metabolism or serum levels of LDL-C differently in apo E phenotypes. Surrogate sterol markers of cholesterol metabolism reflected absolute ones (especially in the apo E4 group) and apo E phenotypes despite variable amounts of dietary cholesterol and fat. Apolipoprotein E: Cholesterol: Non-cholesterol sterol metabolism: Phytosterols