Carotene absorbtion: some necessary fats?

[Guest guest]

Reducing fat seems like the cautious thing to do considering the

results of the studies recently posted by myself. But the question

remains which fats should be reduced and which kept at sufficient levels?

It may be that dietary fat functions as a facilitator in certain

processes associated with food digestion and absorbtion. In other

words, are you getting all you think you are getting out of a high

plant food diet if you cut back on fats?

A search using the key words carotene and bioavailabilty will yield

many results. There is much evidence that carotene absorbtion (and

conversion to vitamin A)is much improved if certain kinds of fats are

included with a meal.

In one study titled:Carotenoid Absorption from Salad and Salsa by

Humans Is Enhanced by the Addition of Avocado or Avocado Oil,

The authors set out tenuously with the following:

" Dietary lipids are hypothesized to be an important factor for

carotenoid bioavailability. However, most carotenoid-rich fruits and

vegetables are low in lipids. "

But they conclude that " adding avocado fruit can significantly enhance

carotenoid absorption from salad and salsa, which is attributed

primarily to the lipids present in avocado. "

http://www.nutrition.org/cgi/content/abstract/135/3/431

Another study concludes: " High-sensitivity HPLC with coulometric array

detection enabled us to quantify the intestinal absorption of

carotenoids ingested from a single vegetable salad. Essentially no

absorption of carotenoids was observed when salads with fat-free salad

dressing were consumed. A substantially greater absorption of

carotenoids was observed when salads were consumed with full-fat than

with reduced-fat salad dressing. "

http://www.ajcn.org/cgi/content/abstract/80/2/396

Carotenoid absorbtion seems very variable from one individual to

another.But which fats works best for the most efficient intestinal

absorbtion? How to tell? The following study provides some answers.

Intestinal absorption of ß-carotene ingested with a meal rich in

sunflower oil or beef tallow: postprandial appearance in

triacylglycerol-rich lipoproteins in women.

" Background: Evidence indicates that different types of fat have

different effects on the postprandial plasma triacylglycerol response.

Therefore, the type of fat may influence the appearance of ß-carotene

in postprandial triacylglycerol-rich lipoproteins, which is used as an

indicator of intestinal ß-carotene absorption.

Objective: We compared in female subjects the appearance of ß-carotene

in plasma triacylglycerol-rich lipoproteins after ß-carotene was

ingested with a meal containing sunflower oil or beef tallow. "

In the intro it is said from firmly established evidence that:

" Dietary fat is a major determinant of the intestinal absorption of

ß-carotene, partly because the intestine is unable to secrete

significant amounts of triacylglycerol-rich lipoproteins in the

absence of dietary fat. "

you'll find the cited support for this bold premise here:

http://www.ajcn.org/cgi/content/abstract/57/2/175?ijkey=7e8a2340ae8306db210c6e5e\

f3d542003e9d7bee & keytype2=tf_ipsecsha

But, " although it is known that dietary fat is needed for intestinal

absorption of ß-carotene, there has been little systematic study of

the effects of the amount or nature of dietary fat on the appearance

of ß-carotene in plasma triacylglycerol-rich lipoproteins, which is

used as an indicator of intestinal absorption "

And: " The effects of meals with different fatty acid compositions on

the postprandial lipemic response suggest potential effects on the

intestinal absorption of fat-soluble dietary components such as

ß-carotene. "

Thus:In 1978, Hollander and Ruble (12) reported distinct effects of

long-chain fatty acids of different saturation on the absorption of

ß-carotene from an intestinal perfusate in rats. If analogous effects

could be shown in humans by using ingested fats with different fatty

acid compositions, new insight would be provided regarding mechanisms

of intestinal ß-carotene absorption. Such insight could be applied to

optimize the provitamin A and other effects of dietary ß-carotene

through modification of dietary fat. The objective of the present

study was to compare, in healthy young women, the appearance of

ß-carotene in plasma triacylglycerol-rich lipoproteins after ingestion

with a polyunsaturated fat, sunflower oil, and a more saturated fat,

beef tallow.

After much discussion of the results, the authors feel confident

enough to conclude that " ingestion of ß-carotene with a

sunflower-oil–rich meal high in polyunsaturated fatty acids, as

compared with a beef-tallow–rich meal, results in a greater

triacylglycerol response and lower apparent absorption of ß-carotene,

as measured by its appearance in plasma triacylglycerol-rich

lipoproteins. "

http://www.ajcn.org/cgi/content/full/71/5/1170

also of interest:

http://www.nutrition.org/cgi/content/abstract/128/8/1361

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve & db=PubMed & list_uids=1\

2885395 & dopt=Citation

> >

> > Wow, nice! Perhaps DR helps to protect us from the little but

> certain

> > methylmercury that we may ingest eating fish...

> >

> > " The results suggest that even mild calorie restriction is enough to

> > attenuate oxidative stress and age-related morphological changes in

> > skeletal muscle. Additionally, DR was effective in protecting

> against

> > methylmercury-induced pathological changes. "

> >

> > Acta Neuropathol (Berl). 2004 Jul;108(1):1-9. Epub 2004 Apr 17.

>

> >

> > Beneficial effects of mild lifelong dietary restriction on skeletal

> > muscle: prevention of age-related mitochondrial damage,

> morphological

> > changes, and vulnerability to a chemical toxin.

> >

> > Usuki F, Yasutake A, Umehara F, Higuchi I.

> >

> > Department of Clinical Medicine, National Institute for Minamata

> > Disease, 4058-18 Hama, 867-0008, Minamata, Japan. usuki@n...

> >

> > The effect of mild lifelong dietary restriction (DR) on

> > age-related changes was investigated in rats. Histopathological

> > findings were compared between 25-month-old male rats fed ad libitum

> > and 25-month-old male rats that were calorie restricted (80% of ad

> > libitum calories; protein 15%) from 9 weeks of age. DR-fed rats

> > retained motor activity even in old age compared with ad libitum-fed

> > rats. Histopathological studies on soleus muscles clarified

> myopathic

> > changes in the ad libitum-fed rats, including variations in fiber

> size

> > and an increase in the number of central nuclei. Increased

> > non-grouping atrophic angulated fibers were also observed. The

> > specimens revealed a confused arrangement of the mitochondria and

> > decreased mitochondrial electron transduction enzyme activities,

> > indicating mitochondrial insults in the ad libitum-fed rats. In

> > contrast, no myopathic changes, little mitochondrial insult, and

> fewer

> > angulated fibers were recognized in the DR-fed rats. The

> accumulations

> > of heme oxygenase-1, alphabeta crystallin, 8-hydroxydeoxyguanosine,

> > and heat shock protein 27 were recognized in ad libitum-fed rats,

> > indicating the attack of oxidative stress. In contrast, the

> > expressions of these proteins were suppressed in DR-fed rats. The

> > results suggest that even mild calorie restriction is enough to

> > attenuate oxidative stress and age-related morphological changes in

> > skeletal muscle. Additionally, DR was effective in protecting

> against

> > methylmercury-induced pathological changes. Small fiber size and

> > suppression of mitochondrial electron transduction enzyme activities

> > in skeletal muscle and degenerative changes in peripheral nerves

> were

> > milder in methylmercury-exposed DR-fed rats. The results indicate

> that

> > mild lifelong DR also protects skeletal muscle and peripheral nerves

> > against a chemically-induced form of oxidative stress.

> >

> > PMID: 15095099

> >

>