Safety evaluation of certain food additives - ipcs inchem

PHYTOSTEROLS, PHYTOSTANOLS AND THEIR ESTERS 121
Free phytosterols and phytostanols are absorbed from the gastrointestinal
tract to a much lower extent than cholesterol, which is taken up by 55–60% (Patel
& Thompson, 2006). Published data reviewed by the Scientific Committee on Food
(2002) indicated that in humans, about 5% of -sitosterol, 15% of campesterol and
less than 1% of phytostanols are absorbed in the gastrointestinal tract. In humans,
esterified and free phytosterols and phytostanols are mainly transported by lowdensity
lipoprotein (LDL). In healthy adults, less than 1% of total plasma sterol
consists of phytosterols (Moghadasian, 2000).
(a) Rats
Lymphatic recovery was studied after application of emulsions of cholesterol
and phytosterols into the stomach of thoracic duct–cannulated male rats. Recovery
from the thoracic duct was 59%, 2%, 15%, 0.5%, 3% and 0.3% for cholesterol, sitosterol,
campesterol, stigmasterol, brassicasterol and -sitostanol, respectively
(Hamada et al., 2006).
In a study with several 14 C- and 3 H-labelled phytosterols and phytostanols in
male and female rats, the following absorption rates were calculated, based on
recovery of radioactivity from urine, air trap, tissues and carcass. Absorption of
cholesterol in female rats was 27%. Absorption was 13% for campesterol, 4%
for -sitosterol and stigmasterol, and 1–2% for -sitostanol and campestanol.
Absorption was lower in male rats than in female rats (Sanders et al., 2000). The
Committee noted that as biliary excretion was not determined in this study, real
absorption presumably was higher than reported values.
A lower bioavailability of -sitosterol and campesterol in rats was found when
administered as water-soluble emulsified micelles compared with administration as
free phytosterols dissolved in soya bean oil (Delaney et al., 2004).
In animal studies, -sitosterol was distributed to various organs, with the
highest concentrations in the adrenal cortex, ovary and testis, and liver
(Moghadasian, 2000; Sanders et al., 2000). Rats receiving a diet containing 0.5%
phytostanols (-sitostanol/campestanol) for 4 weeks showed a 4-fold increase in
plasma levels of phytostanols and 2- to 3-fold increases in phytostanol levels in
skeletal and heart muscle (Connor et al., 2005). In rats, phytosterols are mainly
transported in blood by high-density lipoproteins (HDL) (Moghadasian, 2000).
Excretion of absorbed phytosterols and phytostanols predominantly takes
place via the bile in the faeces (Sanders et al., 2000).
(b) Humans
The systemic absorption of -sitosterol, campesterol, campestanol and sitostanol
was investigated in 10 healthy humans (7 females, 3 males). Phytosterols
and phytostanols derived from soya beans were deuterium-labelled and administered
consecutively in two tests 2 weeks apart. Phytosterols and phytostanols
were emulsified with lecithin and administered in single-meal absorption tests.
Systemic absorption from uptake of 600 mg phytosterol or phytostanol was 1.89 ±
0.0041% for campesterol, 0.512 ± 0.038% for -sitosterol, 0.155 ± 0.0017% for