On Fri, 5 May 2000, Bruce Sherrod wrote:
> >Then again sesame turns out as a real wonder seed - high in calcium
> >iron many vitamins - and tryptophan.
> >100g sesame providing 150mg tryptophan together with nice carbos look fine.
>
> And yet, sesame seeds have an extremely poor lipid profile, containing
> 21.375g of linoleic acid (omega 6) and only 0.376g of linolenic acid
> (omega 3). This gives an o6/o3 ratio of 57 to 1!
An interesting thing about sesame seeds is that they also contain
a lignan called sesamin, which is a specific inhibitor of delta-5
desaturase. This enzyme is, among other things, responsible for
the conversion of DGLA to what Sears calls the "bad" eicosanoids.
If Sears is correct, then this inhibitor may override the poor
lipid profile, since the reason why the high w6:w3 ratio is
considered poor is because it facilitates the production of those
eicosanoids.
Todd Moody
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(Sorry about the HTML codes)
Institute of Environmental Science for Human Life , Ochanomizu
University, Tokyo, Japan.
Sesamin is a specific inhibitor of delta 5 desaturation, the
conversion from dihomo-gamma-linolenic acid (20:3,
n-6) to arachidonic acid (AA, 20:4,
n-6). Previously, we reported that sesamin inhibited
delta 5 desaturation of n-6 fatty acids in rat hepatocytes but
not that of n-3 fatty acids, from 20:4 (n-3) to
eicosapentaenoic acid (EPA, 20:5, n-3). In
this study, we investigated the interaction of sesamin and EPA on
delta 5 desaturation of both series and the n-6/n-3 fatty
acids ratio by measuring actural fatty acid contents in
vivo. Rats were fed three types of dietary oils;
1) linoleic acid (LA, 18:2, n-6):
linolenic acid (LLA, 18:3, n-3) = 3:1,
n-6/n-3 ratio of 3:1 (LA group), 2)
LA:LLA = 1:3, n-6/n-3 ratio of 1:3
(LLA group), 3) LA:LLA:EPA =
1:0.5:3, n-6/n-3 ratio of 1:3.5
(EPA group) with or without sesamin
(0.5% w/w) for 4 weeks. In all
groups, sesamin administration increased the content of
dihomo-gamma-linolenic acid (20:3, n-6) in the
liver and decreased the delta 5 desaturation index of n-6 fatty
acid, the ratio of 20:4/20:3 (n-6).
On the contrary, the delta 5 desaturation index of n-3 fatty
acid, the ratio of 20:5 + 22:5 +
22:6/20:4 (n-3), was increased by the
administration of sesamin. These results suggest that
sesamin inhibits the delta 5 desaturation of n-6 fatty acid, but
not that of n-3 fatty acid in rat livers. Sesamin
administration decreased incorporation of EPA (n-3) and
simultaneously increased the AA (n-6) content in the
liver. The n-6/n-3 ratio in the liver was increased by
administering sesamin under n-3 rich conditions, i.e.,
the LLA and EPA groups.
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