Hypolipidemic Dietary Components

Abstract

Several prospective epidemiological studies over the past 20 years concluded that ingestion of certain food or dietary components improves serum lipid profile and are effective in management of hyperlipidemia. The objective of this paper is to identify and quantify selective lipid lowering dietary components. This review focuses on identifying, quantifying and understanding the possible mechanism of action of soy, flaxseeds, oats and psyllium in improving lipid profile and reducing atherosclerotic cardiovascular disease (ASCVD) risk factor. A systematic search of database was performed to retrieve studies of published human studies and trials from 1995-2012, concentrating on recent systematic reviews, meta-analysis and intervention trials done to further elucidate the role of selective food (soy, oats, flaxseeds and psyllium) and their bioactive components (soy protein, soy isoflavones, flaxseed lignan, flaxseed omega 3 fatty acid, b-glucan, insoluble fiber) involved in improving lipid profile and reducing the cardiovascular disease risks. The findings quantify the amounts showing beneficial effects on serum lipid profile. Overall, the review of these clinical evidences suggested that inclusion of these food items can moderately but significantly reduce the risk of dyslipidemia, when consumed regularly as a part of a healthy diet and thus may help reduce any untoward cardiovascular event Key word: Soy, Flaxseeds, Psyllium, Oats, and lipid profile. dyslipidemic conditions and eventually CHD risk begin with the adoption of a healthy lifestyle. Thus, as a part of a comprehensive strategy to reduce complications of hypercholesterolemia, NCEP (National Cholesterol Education Programme) endorsed the use of several lipid lowering dietary agents3. This review emphasize on the quantity of soy, flaxseeds, oats and psyllium that have shown to improve the lipid profile, the mechanisms of each bioactive component responsible in reducing the risk of ASCVD and several human clinical trials data regarding their safety and efficacy. Bioactive components Dietary Fiber (DF) are the edible parts of plants or analogous carbohydrate that are resistant to digestion & absorption in the human intestine with complete or partial fermentation in the large intestine and which promote beneficial 60 MADAN & NARSARIA, Curr Res Nutr Food Sci. Jour., Vol. 1(1), 59-70 (2013) physiological effects including laxation and/or blood glucose attenuation and /or blood cholesterol attenuation. Total dietary fiber (TDF) occurs in 2 major forms i.e. soluble dietary fiber (SDF) and insoluble dietary fiber (IDF). (4.) DF content of various foods are mentioned in Table1 Mechanism of Action Soluble fiber lowers total and LDL-c cholesterol which can be attributed to enhanced gastric emptying, intestinal binding of bile acids thus reducing entero-hepatic bile recirculation, lowered dietary cholesterol absorption, affects VLDL composition which then contains more amount of phospholipids and less of cholesterol, also improves satiety. It also undergoes fermentation to short chain fatty acids (SCFA) in the colon thus reducing endogenous synthesis of cholesterol. It also decreases dietary glucose absorption thereby down regulating cholesterol synthesizing anabolic hormone insulin release7-13. Omega-3 fatty acid from a plant source They are essential fatty acids for competitive synthesis of eicosonoids which are antiinflammatory, anti aggregatory and anti-thrombotic in action14-15. Additional physiologic functions of omega 3 fatty acids which may prevent ASCVD include several mechanisms such as; maintain fluidity of the cell membrane thus facilitating removal of cholesterol, down regulating phosphotidic acid phosphatase (PAP) and diacylglycerol acyl tranferase (DGAT) thus reducing fatty acid synthesis, also activates PPAR involved in B-oxidation of fatty acids, upregualting lipoprotein lipase (LPL) activity thus increasing fats hydrolysis. N-3 fatty acids also modulate sterol regulating element binding protein (SREBP) and increases degradation of apoprotein B which eventually decreases LDL-c secretion and transport16-18. Table 2 illustrates nutrient composition of flaxseed Phytoestrogens Are a diverse group of naturally occurring non steroidal plant compounds that, because of their structural similarity with estradiol (17-βestradiol), have the ability to cause estrogenic or/ and antiestrogenic effects20. Phytoestrogen content of selective foods are discussed in Table 3. There are 2 major classes of phytoestrogens including: Isoflavones contains major bioactive components i.e. daidzein and genistein. They are primarily present in soy as much as 3 mg/g dry weight of soy. Lignans and their major bioactive components secoisolariciresinol and matairesinol are primarily found in flaxseeds21. Mechanism of Action Clinical evidence suggest that phytoestrogens is effective in lowering serum cholesterol via a series of mechanism which include; up regulation of LDL-c receptor activity thus increasing its clearance, it also depresses the activity of platelet activating factor receptor antagonists eventually reducing oxidation of the lipid , the primary step in process of hypercholesterolemic atherosclerosis. Phytoestrogens also enhances the activity of cholesterol-7 hydoxylase which in turn decreases endogenous cholesterol synthesis. There is also down regulation of the enzyme tyrosine kinase thus reducing thrombin production and ultimately myocardial infarction risk (MI) risk22-27. Soy protein Recently soybeans are considered by many agencies as a source of a complete protein. Hence variety of foods such as salad dressings, beverage powders, cheese, infant formulas and others contains soy proteins. The nutritional value of soy protein is equivalent to that of animal protein of high BV. For instance, isolated soy protein has a PDCAAS (Protein Digestibility Corrected Amino Acid Score) of 1.0, which is the same as that of casein and egg protein. 100g of Whole soybeans contains 43.2 g of protein28-30. Biological value of various soy products like whole soybean, soy milk, soy protein isolates are 96.0, 91.0, and 74.0 respectively31. Mechanism of Action Various studies have shown that soy proteins effectively lowers cholesterol through series of mechanisms such as; it binds bile acids thus reducing enterohepatic recirculation of bile, it also up regulates the apo B and apo E receptor activity thus reduces serum LDL-c levels. Soy proteins have also shown to reduce HMG-CoA 61 MADAN & NARSARIA, Curr Res Nutr Food Sci. Jour., Vol. 1(1), 59-70 (2013) Table 2: Various Flaxseed Products Composition Form of Weight Energy ALA Total dietary Soluble SDG content flaxseeds (g) (kcal) (g) fiber(g) fiber (g)* (mg)* Whole seed 11 50 2.5 3.0 0.75 8.8 Ground seeds 8 36 1.8 2.2 0.55 6.4 Flaxseed oil 14 124 8 0.0 0.0 0.0 ALA=Á Linolenic Acid, SDG: Secoisolariciresinol Diglucoside Table 1: Dietary fiber content of selected foods5,6 TDF (g)/100g IDF (g)/100g SDF (g)/100g Wheat 12.5 9.6 2.9 Oat Bran 5.0 -5.0 Oats, Whole (1/2 Cup Cooked) 1.6 1.1 0.5 Soybean 23 17.9 5.1 Black Gram , Whole 20.3 15.4 4.9 Bengal Gram ,Whole 28.3 25.2 3.1 Flax Seeds 27.3 22.0 5.3 Gingelly Seeds 16.8 13.6 3.2 Psyllium Husk (10 g) 8 0.9 7.1 Apple 3.2 2.3 .9 Guava 8.5 7.1 1.4 Sapota 10.9 9.1 1.8 Carrot 4.4 3 1.4 Peas, Green 8.6 7.2 1.4 (TDF: Total Dietary Fiber; IDF: Insoluble dietary fiber; SDF: soluble dietary fiber) Table 3: Phytoestrogens content of foods21 Phytoestrogens content (μg/100g) Flax seed 379380 Soy beans 103920 Tofu 27150.1 Soy yogurt 10275 Sesame seed 8008.1 Flax bread 7540 Soy milk 2957.2 Dried dates 329.5 reductase activity, the rate limiting enzyme in cholesterol synthesis and increase cholesterol-7 hydroxylase activity which eventually lowers cholesterol synthesis31-33. Human studies To identify the majority of human studies on cardiovascular effects of these food items we performed a systematic search of the following databases: PubMed, Medscape, MDconsult etc from 1995-2009. We used the headings “soluble fiber, botanical n-3 fatty acids, Phytoestrogens and soy proteins.” and searched the terms “soy, flaxseeds, oats and psyllium.” using this strategy we identified 75 relevant articles and book chapters. The description below highlights the information on potential CV application of this food items. Epidemiological data Epidemiological data concerning intake of fiber, n-3fatty acids, phytoestrogens and soy 62 MADAN & NARSARIA, Curr Res Nutr Food Sci. Jour., Vol. 1(1), 59-70 (2013) Table 4: Interventional trial data on lipid lowering effects of soy (RCT-randomized control trial, TCTotal cholesterol, LDL-Clow density lipoprotein, HDLhigh density lipoprotein, TG-triglycerides; ↓: Reduced; SPI: Soy protein isolate; P<0.05: Statistically significant) 63 MADAN & NARSARIA, Curr Res Nutr Food Sci. Jour., Vol. 1(1), 59-70 (2013) Table 5: Interventional trial data on lipid lowering effects of flaxseeds (RCT-randomized control trial, TCTotal cholesterol, LDL-Clow density lipoprotein, HDLhigh density lipoprotein, TG-triglycerides; ↓: Reduced; P<0.05: Statistically significant) 64 MADAN & NARSARIA, Curr Res Nutr Food Sci. Jour., Vol. 1(1), 59-70 (2013) proteins are studied as all the discussed food items are a good sources of this bioactive components. Epidemiological data on dietary fiber and risk of ASCVD are extensive and suggest in general an inverse correlation between them. Several observational trials have found positive correlation between soy proteins and n-3 fatty acids and secondary prevention of ASCVD. Also observational studies revealed that lignans may reduce ASCVD morbidity and mortality. The following section describes data from human studies that addresses the Quantity and Effects of soy, flax, oats and psyllium and their bioactive components on CV risk factors dyslipidemia and others like inflammation, blood pressure and glycemic control. Bioactive Components Enriched Food Items Soy Soy (glycine max) is a species of legume native to East Asia. The beans contain significant amounts of proteins (38%), isoflavones, dietary fiber (25-30%) and phytic acid. The principle carbohydrates (30-32%) of mature soybeans are the disaccharide sucrose (2.5-8.2%), trisaccharde raffinose (0.1-1.0%) and the tetrasaccharide stachyose (1.4-4.1%). The majority of soybean carbohydrates can be classed as belonging to dietary fiber. The Food Drug and Administration (FDA) have approved soy as an official cholesterollowering food, along with other heart and health benefits35. The major bioactive components that are responsible for improving the lipid profile on soy interventions are dietary fiber, phytoestrogens and soy proteins and articles related to these are discussed in table 4. To Summarize The bulk of the evidence from five clinical trials36-41. Suggest that soy proteins (20-40g/d) or soy isoflavones (30-150mg/d) can modestly but significantly (p=<0.05) reduce total and LDL cholesterol in both normal and hypercholesterolemic subjects, without a significant effects on HDL-c and TG’s. Effects were more prominent in post menopausal women or in subjects with initial mild to moderate hypercholesterolemia. Desroches S., et al., concluded that soy was also effective in shifting LDL particle size to a less atherogenic pattern. Thus, replacing foods high in saturated fats, trans fats & cholesterol; by soy products containing 30-150 mg/d of isoflavones or 20-40g/d of soy protein have a positive effects against coronary risk factors and related co morbidities e.g.: type2 DM ,hypertension and others. Flaxseeds Flaxseed (linseed) is a smooth, flat and reddish-brown in color is native to the region extending from the eastern Mediterranean to INDIA. Whole flaxseeds contain 28% dietary fiber (7-10% soluble fiber, 11-18% insoluble fiber); 40% fats (57% of omega 3 fatty acids) and 21% proteins. it is also the richest source of phtoestrogenslignans42. Consumption of flaxseeds have shown to reduce total and LDL cholesterol as well as platelet aggregation43,44. The major bioactive components responsible for hypolipidemidic action of flaxseeds are dietary fiber, omega3 fatty acids and lignans and human trials related to these are discussed in detailed in table 5. To Summarize The results of the above discussed 5 clinical trials43-48 suggest that flaxseeds (20-50g/d whole or partially defatted respectively) are efficacious in improving the lipid profile in both normal and mild-moderate hypercholesterolemic subjects. This can be due to the bioactive components in flax like fiber, n-3 fatty acids and lignans which via several mechanisms as discussed earlier have shown to have a positive association with reductions in serum total and LDL cholesterol. The effects of flax seeds were more prominent in subjects with initial hypercholesterolemia like in postmenopausal women. They have also shown to have beneficial effects on other CVD risk factors like ratios of TC: HDL, LDL: HDL reductions in Apo B 100 and also Lp (A) a strong predictor of CVD. Thus daily incorporation of 20-50g of whole or partially defatted seeds respectively is effective in improving lipid profile. Oats Oats most commonly are available as 65 MADAN & NARSARIA, Curr Res Nutr Food Sci. Jour., Vol. 1(1), 59-70 (2013) Table 6: Interventional trial data on lipid lowering effects of oats (RCT-randomized control trial, TCTotal cholesterol, LDL-Clow density lipoprotein, HDLhigh density lipoprotein, TG-triglycerides; RTE:Ready-To-Eat ;SCFA: Short chain fatty acid; ↓: Reduced; P<0.05: Statistically

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Cite this paper

@inproceedings{Madan2013HypolipidemicDC, title={Hypolipidemic Dietary Components}, author={Jagmeet Madan and ANKITA NARSARIA}, year={2013} }