18 phytosterols Flashcards
Phytosterols are structually similar to?
cholesterol
What are phytosterols
plant derived sterols
- similar to cholesterol
- not synthesized by humans
Phytosterols can be subdivided into?
sterols
- double bond at position 5
stanols
- reduced double bond
- less in food
- product of intestinal degradation of sterols
Atherogenic
tending to promote the formation of fatty plaques in arteries
- Phytosterols and Cholesterol
Difference between phytosterols and cholesterol
Phytosterols
- plant
- 1-15% absorbed (helps its function)
- blood levels 200times less
Highest food sources of phytosterols
nuts seeds legumes vegetable oils - processing influences content - hydrogenation DOESNT influence content
Cholesterol lowering effects of phytosterols apparent in what amount?
low gram amounts
Phytosterols 3 areas of focus on health
- CVD**(most attention)
- Cancer
- Immune Health
supplement form
Phytosterols and CVD
lowers blood lipids (2gram sterol/stanols per day)
- total and LDL
- no effect HDL cholesterol of TG
*note - no direct link to heart disease yet
Phytosterols mechanism for reducing total and LDL-cholesterol?
- compete with cholesterol for limited space on mixed micelles in the intestine
- more hydrophobic - therefore greater affinity
- decreases cholesterol absorption 30-50%
- dietary and endogenous chol.
Types of cholesterol phytosterols compete with?
dietary chol. (20%)
endogenous chol. (80%)
- biliary chol, secreted in bile
where does unabsorbed cholesterol go?
feces
Does form of phytosterols influence efficacy?
ALL EFFECTIVE
plant sterol/stanol esters
free sterol/stanol
Study on CVD; phytosterols vs drugs
American Journal of Cardiology 2002
- cervistatin and sterol-ester margarine together
- possible synergistic effect
- result additive effect
sterols added further benefit to drug (lower cholesterol in different ways)
why phytosterols hard to incorporate in foods?
how to overcome this?
low fat solubility
- esterfied with fatty acid to increase solubility
- esterfied gram amounts higher than sterol itself (overestimated)
1g sterol/stanol
.6g FAs
USA recommendation of phytosterols for CHD
2 servings of foods
- 2-3grams
Typical foods phytosterols are incorpertated in?
Fatty foods
- margarine, salad dressing, yoghurt, cream cheese
- Benecol Softgels (supplement)
- Take Control (supplement)
Why are phytosterol functional foods NOT in canada?
Benecol (softgels)
- caused many problems when labelling regulations were limited
Phytosterols and cancer
prostate cancer
- inhibited cancer cell growth in vitro
- improved symptoms associated with benign prostate hyperplasia in humans
colon cancer
- inhibit colon cell proliferation
- inhibit proliferation of cancer cells (in vitro)
Potential mechanisms of action of phytosterols on cancer
membrane - structure - fluidity - integrity - bound enzymes signal transduction apoptosis effects on neutral and acidic sterols in the colon
What is a glucoside
a glycoside derived from glucose
- a molecule which sugar is bound to another functional group
What phytosterols are shown to be immune modulators?
Beta-sitosterol (BSS)
and its glucoside (BSSG)
Phytosterols relation to immunity
BSS and BSSG
In VItro:
- increase proliferation of lymphocytes
- anti-inflammatory
In humans:
- recovery tuberculosis
- improvement HIV
- rheumatoid arthritis
Phytosterol safety issues?
Decreased absorption of fat soluble nutrients (acute)
- timing
- consumed with phytosterols
Fat soluble nutrients affected / not affected when consumed with phytosterols
decreased plasma carotenoids
- beta carotenoids 25%
- alpha carotenoids 10%
decrease lycopene
Vitamin A, D, E and K NOT affected
-carotenoids carried by LDL but Vit A is not
> 1 serving of veggies will maintain satisfactory levels
Phytosterolemia
- error in phytosterol metabolism
- intestinal inability to distinguish between phytosterol and cholesterol
- no sterol excretion in bile
Result:
- premature atherosclerosis
- Extremely high conc. of phytosterols
VERY RARE (40 worldwide)
Cholesterol 7alpha-hydroxylase
rate limiting step in bile acid synthesis
- inhibited by sitosterol during phytosterolemia
Max free phytosterol amount allowed in food per serving?
1g per serving
- effects believed to plateau >3g
Meaning of “specific composition criteria”
ex. phytosterols
- must be in product with low saturated fat
- can’t claim lowers cholesterol when contains other substances that will raise cholesterol
