Phytosterols

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Structural formula of stigmasterine.
Structural formula of β-sitosterol.
Structural formula of campesterine.

Phytosterols , also phytosterols , are a group of chemical compounds from the class of sterols that occur in plants . Together with the mycosterols of the mushrooms , they differ from the animal zoosterols by C 1 or C 2 substituents on C-24 and in some cases by a double bond on C-22. The hydrogenated forms (5 α -hydrogenation) of the respective phytosterols are called phytostanols . The phytosterols occur freely in plants, in ester or in glycoside form and in the unsaponifiable portion of vegetable fats and oils . The most common plant sterols are stigmasterol , β-sitosterol , campesterol and brassicasterol. Phytosterols function as a structural component in the cell membrane of plants, analogous to the cholesterol in the cell membrane of animals, which is not itself a phytosterol because it does not occur in plants. The presence of cholesterol can therefore also be used to demonstrate the adulteration of vegetable fats with animal fats.

In the European Pharmacopoeia, on the other hand, a substance is monographed under "Phytosterol" according to content (at least 70% β-sitosterol) and origin (only Hypoxis, Pinus and Picea plant genera).

Analytics

The reliable qualitative and quantitative determination of phytosterols succeeds after adequate sample preparation z. B. from the unsaponifiable portion of fats and oils through the coupling of chromatographic processes with mass spectrometry

Occurrence

Phytosterols are mainly found in high-fat parts of plants. They are particularly rich in sunflower seeds, wheat germ, sesame and soybeans and pumpkin seeds. By processing, e.g. B. refining of oils, these lose a large part of their content. The untreated native oils, fats and seeds are therefore particularly valuable .

Phytosterols are obtained commercially from soybeans or from conifers as a by-product of paper manufacture (Finland). A particularly rich source of phytosterols are the unsaponifiable components of vegetable fats and oils, as well as the by-products that arise during the refining of vegetable fats / oils.

At around 65%, β-sitosterol is the phytosterol most frequently found in normal food. Further sterols are stigmasterine and campesterine . An important representative of the phytostanols is stigmastanol .

Absorption and metabolism

With a normal, Western European diet, 160-360 mg of phytosterols are consumed daily. Vegetarians get about twice that amount. This is also reflected in the higher sitosterol concentration in the serum of vegetarians. 5–10% of the amount consumed is absorbed (taken up in the intestine), the rest is excreted with the stool. The absorbed portion is excreted in the bile.

The phytosterol concentrations in the serum are accordingly far below those of cholesterol and fluctuate between 0.3 and 1.7 mg / dl with a normal diet.

Phytosterols and stanols
Modification of the basic structure Modification of the side chain Absorption
Sterols cholesterol > 40%
Campesterine 9.6%
Stigmaster 4.8%
Sitosterol 4.2%
Stanol Campestanol 12.5%
Stigmastanol
Sitostanol 0-3%

Phytosterols as active ingredients

Phytosterols are used therapeutically to lower cholesterol and for the symptomatic treatment of benign prostatic hyperplasia . They are also used to treat skin irritation and itching.

Mechanism of action

The mechanism of action is assumed to be competitive inhibition of cholesterol uptake in the intestine , i.e. H. the presence of phytosterols reduces the absorption of cholesterol. Since about 90% of the cholesterol is produced by the body independently of food, an increased endogenous (endogenous) synthesis occurs as a result of phytosterol intake. Nevertheless, overall there is a slight reduction in total and LDL cholesterol (partial compensation).

In addition to the reduced absorption, other mechanisms - accelerated excretion of the absorbed sterols and others - seem to play a role. Phytosterols lower total and LDL cholesterol regardless of whether the individual has normal or elevated blood lipid levels. Phytosterols have the same effect in men and women and are independent of age.

Triglycerides and HDL cholesterol remain unchanged. As far as tested, all clinical parameters except serum cholesterol (GPT, GOT, hemoglobin , glucose, serum proteins, serum bilirubin) remain unaffected.

Due to their strong similarity to cholesterol, phytosterols themselves have atherogenic potential ( causing arteriosclerosis ). The concentration at which this atherogenic potential becomes effective is currently controversial.

dosage

The minimum effective amount is 2 g per day. This amount can be increased by consuming 100 ml of yoghurt drink (enriched with 1.6 g of phytosterols) or 20–30 g of spreadable fat / margarine with added phytosterols (usually approx. 10%) in addition to the 0.2–0 that was consumed with a normal mixed diet , 4 g per day can be achieved.

Side effects, interactions, toxicity

In practically all studies, apart from lowering total cholesterol and LDL cholesterol, no influence on other metabolic parameters was found. Phytosterols show an additive effect with statins and other cholesterol lowering drugs in terms of lowering blood lipids. Experience has shown that doubling the statin dose can achieve an additional 6–8% lowering of LDL cholesterol. A combination therapy (statin + e.g. phytosterol-enriched yogurt) can lower the LDL cholesterol level by 10%.

So far there has been no study that clearly proves that foods fortified with phytosterols, such as Becel , have a harmful effect on people without phytosterinaemia. According to the latest findings, however, plant sterols can also have negative effects on vascular health and therefore not have the cardio-protective effect with which they are advertised. Genetic polymorphisms, which have an influence on phytosterol absorption, play an important role. Their sponsorship is linked on the one hand to increased phytosterol levels in the blood and at the same time to an increased cardiovascular risk.

Influence on other fat-soluble nutrients

There is evidence that phytosterols impair the absorption of fat-soluble vitamins. Decreased carotene , vitamin E (α-tocopherol) and lycopene levels were found.

The absorption of vitamin D is not impaired.

Effect of commercially available phytosterol products

Functional food products (margarine, milk, yoghurt products) are of the greatest importance in the market . Individual dietary supplements are on the market. Medicines are (currently) not available in Germany. In the area of ​​benign prostatic hyperplasia, mainly drugs and individual food supplements are on the market.

The cholesterol-lowering effect of plant sterols was first described in 1951 and subsequently confirmed by numerous clinical studies. According to this, a dose-dependent LDL cholesterol reduction of 5–15% of the initial values ​​can be achieved by taking 1–4 g phytosterols per day. Foods enriched with phytosterols (yoghurt drink, margarine) are now available on the market.

Several randomized, placebo-controlled studies confirm the improvement in the lipid profile after 6 weeks of consumption of a yogurt drink fortified with phytosterols (1.6 g per serving). Within 3 weeks, the LDL cholesterol in the phytosterol group decreased by up to 12.2% compared to placebo, and within 6 weeks by up to 10.6%. HDL cholesterol and triglycerides did not show any significant changes.

20 g of fat spread with 2-3 g of sterols can lower the cholesterol level by an average of 6-10%.

Evidence of effectiveness on relevant clinical endpoints (such as reduction in mortality , heart attacks and strokes ) is lacking.

The preparations in the area of ​​benign prostatic hyperplasia contain significantly lower daily doses of around 100 mg. They are discussed under the topic of β-sitosterol .

Contraindication

In order to avoid potential hypovitaminoses (A and E), children under 5 years of age, pregnant and breastfeeding women should not consume products fortified with phytosterols.

Phytosterinemia

Is a very rare recessive inherited disorder of phytosterol absorption. If phytosterinaemia is present, significantly more sterols are absorbed (50–60% of nutritional sterols). Those affected should limit their intake of phytosterols as much as possible.

Criticisms

Keyword-like summary of the criticisms and concerns of the EFSA (European Food Safety Authority):

  • The maximum amount of sterols should not exceed 3 g per day.
  • Possible risk of carotene deficiency
  • Particular hazard
    • People with phytosterolemia
    • Patients on cholesterol-lowering medication
    • nursing mothers
    • pregnancy
  • possible risk from continuous consumption or cumulative consumption in different foods
  • Effect on the absorption of fat-soluble vitamins and carotenoids
  • the exact composition and stability of the phytosterone mixture
  • possible ingestion by people who do not have high cholesterol levels
  • the difficulties of adequate labeling

Other uses

Derivatives of phytosterols (P. ethoxylates and polyoxyethylene) are used as emulsifiers in cosmetics .

literature

  • Opinion of the Scientific Panel on Dietetic Products, Nutrition and Allergies on a request from the Commission related to a Novel Food Application from Forbes Medi-Tech for approval on plant sterol-containing milk-based beverages. In: The EFSA Journal. 15, Parma 2003, pp. 1-12. (Request No. EFSA-Q-2003-075)
  • B. Watzl, G. Rechkemmer: Phytosterols. Characteristics, occurrence, absorption, metabolism, effect. ( Memento of March 14, 2012 in the Internet Archive ) (PDF; 40 kB). In: Nutrition review. (48), 2001, pp. 161-164.
  • I. Kiefer, Ch. Haberzettl, Ch. Panuschka, A. Rieder: Phytosterols and their importance in prevention . In: Journal of Cardiology. Gablitz, Vol. 9. No. 3, 2002, pp. 96-101. (PDF; 968 kB)
  • E. Mutschler: drug effects. Textbook of pharmacology and toxicology. 5th edition. Scientific publishing bookstore, Stuttgart 1986, ISBN 3-8047-0839-0 .
  • Alice H. Lichtenstein et al .: Stanol / Sterol-Containing Foods and Blood Cholesterol Levels. In: Circulation . Philadelphia 2001, pp. 1177-1179. ( Abstract )
  • M. Law: Plant sterol and stanol margarines and health. In: British Medical Journal . (BMJ). London 320.2000, pp. 861-864. PMID 10731187 .
  • JH O'Keefe Jr, L. Cordain, WH Harris, RM Moe, R. Vogel: Optimal low-density lipoprotein is 50 to 70 mg / dl: lower is better and physiologically normal. In: Journal of the American College of Cardiology . New York 43.2006, pp. 2142-2146. PMID 15172426 .
  • Manoj D. Patel, Paul D. Thompson: Phytosterols and vascular disease. In: Atherosclerosis. Amsterdam 186.2006, pp. 12-19, doi: 10.1016 / j.atherosclerosis.2005.10.026 .
  • L. Van Horn, M. McCoin, PM Kris-Etherton, F. Burke, JA Carson, CM Champagne, W. Karmally, G. Sikand: The evidence for dietary prevention and treatment of cardiovascular disease. In: Journal of the American Dietetic Association. Chicago 108.2008, pp. 287-331. PMID 18237578 .
  • N. Plana, C. Nicolle, R. Ferre, J. Camps, R. Cos, J. Villoria, L. Masana: Plant sterol-enriched fermented milk enhances the attainment of LDL-cholesterol goal in hypercholesterolemic subjects. In: European Journal of Clinical Nutrition. Basingstoke 47.2008, pp. 32-39. PMID 18193377 .
  • B. Hansel, C. Nicolle, F. Lalanne, F. Tondu, T. Lassel, Y. Donazzolo, J.Ferrières, M. Krempf, JL Schlienger, B. Verges, MJ Chapman, E. Bruckert: Effect of low- fat, fermented milk enriched with plant sterols on serum lipid profile and oxidative stress in moderate hypercholesterolemia. In: The American journal of clinical nutrition. Bethesda 86.2007, pp. 790-796. PMID 17823447 .
  • O. Weingärtner et al .: Controversial role of plant sterol esters in the management of hypercholesterolaemia. In: European Heart Journal . Oxford 30.2009, pp. 404-409. PMID 19158117 .
  • O. Weingärtner, M. Böhm, U. Laufs: Plant sterols as food additives for the prevention of cardiovascular diseases. In: Dtsch. Med. Wochenschr. 133, 22 May 2008, pp. 1201-1204. doi: 10.1055 / s-2008-1077238 PMID 18491276

Individual evidence

  1. Entry on phytosterols. In: Römpp Online . Georg Thieme Verlag, accessed December 10, 2014.
  2. CL Flakelar, PD Prenzler, DJ Luckett, JA Howitt, G. Doran: A rapid method for the simultaneous quantification of the major tocopherols, carotenoids, free and esterified sterols in canola (Brassica napus) oil using normal phase liquid chromatography. In: Food Chem. 214, Jan 1, 2017, pp. 147–155. PMID 27507459
  3. B. Xu, P. Li, F. Ma, X. Wang, B. Matthäus, R. Chen, Q. Yang, W. Zhang, Q. Zhang: Detection of virgin coconut oil adulteration with animal fats using quantitative cholesterol by GC × GC-TOF / MS analysis. In: Food Chem. 178, Jul 1, 2015, pp. 128-135. PMID 25704693
  4. D. Kim, JB Park, WK Choi, SJ Lee, I. Lim, SK Bae: Simultaneous determination of β-sitosterol, campesterol, and stigmasterol in rat plasma by using LC-APCI-MS / MS: Application in a pharmacokinetic study of a titrated extract of the unsaponifiable fraction of Zea mays L. In: J Sep Sci. Sep 2, 2016. PMID 27591043 .
  5. CL Flakelar, PD Prenzler, DJ Luckett, JA Howitt, G. Doran: A rapid method for the simultaneous quantification of the major tocopherols, carotenoids, free and esterified sterols in canola (Brassica napus) oil using normal phase liquid chromatography. In: Food Chem. 214, Jan 1, 2017, pp. 147–155. PMID 27507459
  6. Process for the production of sterols and tocopherols. Document DE10038457B4.
  7. Sabine Junglas: The influence of a vegetarian diet on the unsaponifiable lipid components of human serum. Dissertation . TU Berlin, 1988, DNB 890684782 .
  8. B. Watzl, G. Rechkemmer: Phytosterine. Characteristics, occurrence, absorption, metabolism, effect. ( Memento of March 14, 2012 in the Internet Archive ) (PDF; 40 kB). In: Nutrition review. 48, 2001, pp. 161-164.
  9. ^ W. Ling, PJ Jones: Dietary Phytosterols, A Review of Metabolism, Benefits and Side Effects. In: Life Sciences . 57 (3), 1995, pp. 195-206 ( PMID 7596226 ).
  10. O. Weingärtner et al .: Controversial role of plant sterol esters in the management of hypercholesterolaemia. In: Eur Heart J. 30, 2009, pp. 404-409. PMID 19158117 .
  11. O. Weingärtner et al .: The Relationships of Markers of Cholesterol Homeostasis with Carotid Intima-Media Thickness. In: PLoS ONE . 5 (10), p. E13467. doi: 10.1371 / journal.pone.0013467
  12. O. Weingärtner et al .: Differential Effects on Inhibition of Cholesterol Absorption by Plant Stanol and Plant Sterol Esters in ApoE - / - Mice. In: Cardiovasc Res . 2011. doi: 10.1093 / cvr / cvr020
  13. Do plant sterols damage the heart? In: aerztezeitung.de. June 6, 2008, accessed April 30, 2015 .
  14. D. Teubser et al .: Genetic regulation of serum phytosterol levels and risk of coronary artery disease. In: Circ Cardiovasc Genet. 3 (4), Aug 2010, pp. 331-339. PMID 20529992 .
  15. BO Ajagbe, RA Othman, SB Myrie: Plant Sterols, Stanols, and Sitosterolemia. In: J AOAC Int. 98 (3), May-Jun 2015, pp. 716-723. PMID 25941971 .
  16. Moghis U. Ahmad: Lipids in Nanotechnology. Elsevier, 2015, ISBN 978-0-12-804345-5 , p. 36.
  17. ^ Krister Holmberg: Novel Surfactants. CRC Press, 2003, ISBN 0-203-91173-3 , p. 231.

See also