Phytosterols and phytostanols, new assessments on their beneficial effects

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The fortification of foods with phytosterols and phytostanols is of considerable interest for food companies wishing to extend their products to consumers who already have slightly or moderately high cholesterol levels or who want to prevent this problem.

Phytosterols and phytostanols are lipid molecules naturally present in the plant kingdom. The main source from which they are extracted is lumber: as a matter of fact these substances represent an important by-product of wood processing to get cellulose; they can be also extracted from some vegetable oils. They have cholesterol-lowering power, i.e. they are able to inhibit the absorption of cholesterol (due to structural analogy with the same), resulting, with regular intake of appropriate amounts in a slight but significant reduction of cholesterol blood levels. Several scientific studies have shown that with daily intake of at least 1-3 g of these substances (excess seems to not make further effectiveness and is therefore not recommended) you get 10-12% decrease in cholesterol blood levels. This decrease, seemingly small, is enough in theory to obtain a reduction of ¼ cardiovascular risks already within a few years. Excessive levels of cholesterol in the blood are associated with a higher incidence of cardiovascular diseases such as atherosclerosis, coronary diseases, thrombosis, ischemia, etc. For this reason the fortification of foods with these substances is of considerable interest for food companies wishing to extend their products to middle-aged consumers (especially men), which already have slightly or moderately high cholesterol levels or who want to prevent this problem without undergoing particularly restrictive diets. Concerning the characteristics of these groups of substances, phytosterols, phytostanols and their esters are steroid substances whose function is to contribute to the fluidity and permeability of vegetal cell membranes. The main structural difference between the two groups lies in the fact that phytosterols have more unsaturation (that is, a double carbon-carbon bond) than phytostanols (Figure 1). Concerning efficacy and safety, at this time there are no definitive conclusions about which group of substances is better than the other. The molecules in each group are numerous, but the most abundant in nature are ß-sitosterol, campesterol and stigmasterol for the first ones and sitostanol and campestanol for the latter. Thanks to their structural similarity with cholesterol, which is very similar although it is only of animal source (Figure 1), phytosterols and phytostanols are able to prevent intestinal absorption. Lipids in blood and human tissues are chiefly cholesterol, cholesterol esters, triglycerides, and phospholipids. Since lipids are insoluble in blood, they need to be transported in a special way to the cells, by means of carrier molecules: lipoproteins, of which there are several subtypes, including LDL (low density lipoproteins) and HDL (high density lipoproteins). Excess of lipids in blood (hypercholesterolemia or hypertriglyceridemia), or abnormalities in their metabolism, or in the ratio between LDL and HDL (in particular excess of LDL or deficiency of HDL), lead to pathological conditions that are collectively referred to as “Dyslipidemia”, which are certainly due to cardiovascular disease. The number of patients with Dyslipidemia has tripled over the last 15 years in the United States, according to the Institute of Health of the United States, and the situation is not much better in Europe.

 

 

 

Figure 1. Structure of cholesterol and some phytosterols. Phytostanols are devoid of the double bond between C5-C6. By G. Garcìa-Llatas and M.T. Rodrìguez-Estrada. 2011

For these reasons, phytosterols and phytostanols have been added successfully to various foods for about 15 years, in an always growing market due to consumers’ awareness towards health and nutrition. Among the foods fortified with phytosterols or phytostanols launched successfully on the market since the end of the ’90s there are mainly dairy products such as margarine (often simultaneously characterized by reduced fat content) milk, yogurt and fermented milks, cheeses, but also products like mayonnaise, salad dressings, chocolate-coated cereal bars, breakfast cereals, fruit juices and other beverages, meat products and bakery products (for example croissants and muffins). It seems that to get better phytosterols and phytostanols bio-availability, it is important for them to be in soluble form; therefore their integration in liquid or semi-liquid foods seems the most efficient…  modality. The amount of fat in the food doesn’t seem to be discriminating. Concerning the safe use of these substances, given the considerable quantities (several grams per day) necessary to achieve the beneficial effect, there are numerous studies that confirm the harmlessness of phytosterols and phytostanols, although it should be noted that currently there are no long-term studies. Some negative effects could be malabsorption of beneficial lipids, such as carotenes as well as phytosterols and phytostanols oxidation products, potentially toxic. The United States FDA (Food and Drug Administration) has classified them in the lowest risk category that is GRAS (Generally Recognized as Safe). Even in Europe, their use has been approved and also allowed to associate their addition to foods with health claims (according to EC regulations 1924/2006 and 432/2012) relating to the reduction of cholesterol levels, which is very important for the companies interested in launching this type of product on the market. In the recent opinion adopted on April 26th, 2012 by EFSA (European Food Safety Authority) the effectiveness of these substances is confirmed again.

References

“Response to comments on the Scientific Opinion on the substantiation of a health claim related to 3 g/day plant stanols as plant stanol esters and lowering blood LDL-cholesterol and reduced risk of (coronary) heart disease pursuant to Article 14 of Regulation (EC) No 1924/2006”. Technical Report of EFSA, Supporting Pubblications 2012:333

T. Bacchetti, S. Masciangelo, V. Bicchiega, E. Bertoli, G. Ferretti. 2011. Phytosterols, phytostanols and their esters: from natural to functional foods – Review. Mediterranean Journal of Nutrition and Metabolism, 4(3):165-172

G. Garcìa-Llatas, M.T. Rodrìguez-Estrada. 2011. Current and new insights on phytosterol oxides in plant sterol-enriched food – Review. Chemistry and Physics of Lipids, 164:607:624

M. Majeed, L. Prakash. 2011. “Getting to the heart of the matter – Phytonutrients and nutritional interventions to support cardiovascular health and wellness”. Sabinsa Corporation white paper

K. Weiner. 2010. Configuring users of cholesterol lowering foods: A review of biomedical discourse. Social Science and Medicine, 71(9):1541-1547

N. de Jong, M.M. Ros, M.C. Ockè, H. Verhagen. 2008. A general postlaunch monitoring framework for functional foods tested with the phytosterol/-stanol case. Trends in Food Science and Technology, 19:535-545

 

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