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December 6, 2004

38 Min Read
Cardiovascular Health

Cardiovascular Health

by HeatherGranato

It has been said that blood is life. As such, it is notsurprising that one of every 2.6 deaths is attributed to diseases of thecardiovascular system, with its responsibility for moving nutrients and oxygenthrough the body and removing waste products.

Cardiovascular disease (CVD) is not just one disease, but ahost of interrelated conditions affecting the heart, blood vessels and bloodcells. Degenerative conditions include atherosclerosis, congestiveheart failure (CHF), coronary heart disease (CHD) and hypertension (high bloodpressure). These are contributing factors to other acute events including strokeand myocardial infarction. It is estimated that one in five Americans has one ormore types of CVD, including 50 million with hypertension, 13.2 million with CHDand 5 million with CHF.

With such prevalence in the population, it is no wonder thatthe costs associated with CVD are staggering. In 2004, the estimated direct andindirect cost of CVD was $368.4 billion, according to the American HeartAssociation (AHA).

As with all disease prevention, ensuring a healthy lifestyleis critical. Researchers suggest incorporating regular physical activity,avoiding smoking, maintaining a healthy body weight and following a diet rich inwhole grains, fruits and vegetables, omega-3 essential fatty acids (EFAs) andunsaturated fats as the predominant form of dietary fat could prevent themajority of CVD in Western populations.1 Such a diet has shown significantbenefits compared with the more predominant Western pattern dietcharacterized by high intakes of processed meats, eggs, red meats and high-fatdairy products; that Western diet appears to increase inflammation, insulin and glycated hemoglobin, raising CVD risk.2

In addition, consuming certain specialty foods appears tofurther lower the risk of CVD.The National Cholesterol Education Program and theAHA suggest the use of viscous fibers, plant sterols, soy protein and nuts; astudy in 46 hyperlipidemic adults found the combination reduced lowdensitylipoprotein (LDL or bad) cholesterol by 30 percent, significantly reducingCHD risk.3 In fact, the diet lowered LDL as effectively as the use of thepharmaceutical lovastatin. Similar results were reported in a study of 25hyperlipidemic subjects following the portfolio diet or a control, low saturatedfat diet.4 The portfolio diet reduced LDL by 35 percent and also significantlyimproved the ratio of LDL-to-HDL (high-density lipoprotein, the goodcholesterol that removes plaque from arteries).

Another well known diet for its cardiovascular benefits is theMediterranean diet, characterized by olive oil as the dominant fat source, ahigh consumption of fruit and vegetables, fiber, fish and legumes, plus winewith meals. Dutch researchers noted the Mediterranean diet is low in saturatedfat and high in monounsaturated fatty acids, antioxidants, fiber and folic acid,and intervention studies support the use of the diet to improve the coronaryrisk profile.5 In particular, data from the GISSIPrevenzione clinical trial,which included 11,323 men and women with myocardial infarction, found adherenceto a Mediterranean diet significantly reduced the risk of premature mortality.6

Researchers have also investigated the impact of addingcertain foods to the diet with the goal of reducing CVD risk. For example, nutsare drawing a great deal of interest of late for theirbeneficial effects. A review from the Bundaberg Specialist Centre in Australianoted 1 oz. of daily nut ingestion may reduce the risk of fatal CHD by 45percent when substituted for saturated fat, and by 30 percent when substitutedfor carbohydrate intake.7 The author pointed out nuts are a good source of arginine, vitamin E, folate, fiber, potassium, magnesium, tannins andpolyphenols, and may also have a satiating effect in the diet. Nuts fattyacid profile is also of interest, as most nuts are high in oleic acid, linoleicacid and linolenic acid, with additional phytosterols and tocopherols.8 Dietaryintervention studies have found the addition of peanuts (replacing an equalamount of other fat) reduces triacylglycerol and increases serum magnesiumlevels,9 while adding walnuts (in place of other dietary fat) to the diet of hypercholesterolemic subjects can reduce total and LDL cholesterol and improve endothelial function.10

Increasing the quantity of dietaryfiber also appears beneficial. Researchers from Tulane University in New Orleans investigatedthe relationship between total and soluble fiber intake and the risk of CHD andCVD in 9,776 adults over a 19-year follow up.11 Compared with the lowestquartile of dietary fiber intake, participants in the highest quartile had a 12percent reduced risk of CHD and an 11 percent reduction in CVD events. Similarresults were reported from a population study of 3,588 older men and women, inwhich subjects in the highest quintile of cereal fiber intake had a 21 percentlower risk of incident CVD compared with those in the lowest quintile.12 Cerealfiber intake was particularly associated with lower risk of stroke and ischemicheart disease death. A pooled analysis of cohort studies, which included datafrom 91,058 men and 245,186 women, found each 10 g/d increment of total dietaryfiber was associated with a 14 percent decrease in risk of all coronary events and a 27 percent decrease in risk of coronary death.13

The benefits of fiber intake led FDA to allow a health claimlinking higher intake of dietary fiber, particularly soluble fiber, to a reducedrisk of heart disease, as well as a separate claim on the relationship betweensoluble fiber from oats and psyllium seed and a reduced risk of heart disease. Oatsas a source of dietary fiber and the soluble fiber betaglucanhave been extensively studied for their benefit onheart health. Intervention studies have shown a hypocaloric diet containingoats significantly decreases cholesterol and lowers blood pressure compared to asimilar diet without oats,14 and may even improve blood pressure control to thepoint that patients can reduce the dosage of antihypertensive medications.15 Tothat end, researchers at Tulane recruited 110 subjects with untreated, buthigher than optimal blood pressure or stage 1 hypertension to receive 8 g/d ofwater-soluble fiber from oat bran or a control intervention.16 Three months of the fiberintervention had a moderate effect on both systolic and diastolic bloodpressure.

On the cholesterol side, oat bran and other sources of dietaryfiber appear to lower total and LDL cholesterol. A randomized study in 235 malepatients with hypercholesterolemia found the administration of a fatmodifieddiet with 35 g/d to 50 g/d of oat bran significantly decreased total and LDLcholesterol, as well as apolipoprotein B (apoB).17 And a study in 36 overweightmen who received oat or wheat cereal (each providing 14 g/d of dietary fiber),found only the oat diet produced lower concentrations of the moreatherosclerotic small, dense LDL and LDL particle number, while improving the HDL-to-LDL ratio.18

Another FDA health claim in the heart health arena linksconsumption of soy with hearthealth. Approved in 1999 after a petition from the Solae Co., the claim linksthe intake of 25 g/d of soy protein with a reduced risk of CHD. A review fromthe University of Illinois noted soy consumption appears to improve plasmalipids, reduce LDL oxidation and improve vascular reactivity.19 Further reviewssuggest the benefits of soy include its vegetable protein, high soluble fibercontent, absence of saturated fat with high levels of polyunsaturated fats, and major phytoestrogencontent.20

A great deal of the initial work in the soy field was done inAsian populations, which generally have a much greater intake of soy foods thanWestern cultures. Researchers at Vanderbilt University examined the relationshipbetween soy food intake and incidence of CHD among 64,900 Chinese women participating in the Shanghai Womens HealthStudy.21 There was a dose-response relationship between soy food intakeand risk of total CHD, with an adjusted relative risk of 0.25 observed for womenin the highest versus the lowest quartile of total soy protein intake. A laterEuropean study in 1,033 pre- and postmenopausal women included 361nonvegetarians, 570 vegetarians and 102 vegans; soy protein intake was inverselyassociated with total and LDL cholesterol concentrations, and with the ratio of total-to-HDL cholesterol.22

Intervention diet studies have found relatively positiveresults on CVD risk factors. A randomized, placebo-controlled crossover trialcomparing soy-based milk and yogurt with equivalent dairy products for fiveweeks each in 26 mildly hypercholesterolemic and/or hypertensive subjects foundsoy intake significantly improved total cholesterol and LDL cholesterol inequol-positive subjects.23 Another study in 61 men with relatively higher bloodpressure and/or total cholesterol found 20 g/d of soy protein in the dietreduced both systolic and diastolic blood pressure and total cholesterol.24 Anda three-month study comparing the impact of soy milk (500 mL twice daily) onblood pressure found chronic soy milk ingestion had modest but significanthypotensive action in hypertensive men and women.25

Isolated soy protein has also netted good results. Researchersat the University of Illinois at Urbana-Champaign investigated the impact of 0.5g/kg/d isolated soy protein consumption on serum lipids in 14 Type II diabeticmen.26 Over the course of the study, which included two eightweek interventionperiods and two four-week washout periods, isolated soy protein consumptionsignificantly improved the total-to-HDL ratio and HDL cholesterol levels.Another study found the use of 30 g/d or 50 g/d of isolated soy protein in 130subjects significantly reduced LDL cholesterol concentrations.27 And when usedin place of animal protein in the diet of 42 subjects with moderatehypercholesterolemia, 25 g of soy protein appears to modestly reduce LDL andtotal cholesterol to more normal levels.28

One pending question remains the significance of soys isoflavoneson cardiovascular risk factors. A recent Canadianstudy involved 20 hyperlipidemic subjects who underwent a four-phase,randomized, crossover trial using diets with isolated soy protein or animalprotein (25 g/1,000 kcal), with or without isoflavones.29 Soy protein reducedtriglycerides by 12 percent, total cholesterol by 4 percent and LDL by 5 percentcompared to animal protein; isoflavones had no significant effect ontriglyceride, HDL or LDL levels, though there was a slight reduction in totalcholesterol associated with isoflavone intake. Another Canadian study involved41 hyperlipidemic men and women following three different diets for one montheach: low fat dairy (control), high-isoflavone (50 g soy protein with 73 mgisoflavones daily) and low-isoflavone (52 g soy protein and 10 mg isoflavonesdaily).30 Both soy diets resulted in significantly lower total cholesterol andestimated CHD risk, and positive changes in the ratio of LDL-to-HDL cholesterol,with no significant differences between the isoflavone groups. However, ameta-analysis from Tokyo University of Agriculture involving eight studiescomparing high- and low-isoflavone comparisons found with identical soy proteinintake, higher levels of isoflavone led to greater decreases in LDL levels.31

This is supported by data from the Framingham Offspring Study,analyzed by researchers from the University Medical Center in Utrecht, TheNetherlands, who examined the association between dietary phytoestrogen intakeand metabolic CVD risk factors in 939 postmenopausal women.32 Higher intake of isoflavones and lignans were associated with lower triglyceride levels, as wellas a reduced cardiovascular risk factor metabolic score. Another review ofdietary phytoestrogen intake in 403 postmenopausal women found increasing isoflavone intake was associated with decreased aorticstiffness.33

Animal research has suggested soy isoflavones may havespecific benefits in the cardiovascular system. An isoflavone-rich soysupplement provided to mice slightly mitigated the plasma cholesterol increasesassociated with adding cholesterol to the diet, and also appeared to keep plasmatriglycerides lower.34 Soy isoflavones were also found in a diabetic rat modelto reduce the atherosclerotic index and inhibit lipid peroxidation compared tocontrol rats that did not receive added isoflavones.35 Also, 5 mg/kg body weightof soy isoflavones caused significant decreases in the concentrations of freeradicals in the bodies of male New Zealand white rabbits, and decreased levelsof plasma total lipids, total cholesterol, triglycerides, LDL, very low-densitylipoprotein (VLDL) and the LDL-to-HDL ratio.36

Isoflavones are not only consumed through soy. Supplementaldosages of red clover appearto have effects on plasma lipid levels as well. A 12-week, randomized, doubleblind, placebo-controlled trial in 252 menopausal women investigated the impactof two different red clover dietary supplements (Promensil, 82 mg totalisoflavones, and Rimostil, 57.2 mg total isoflavones) or placebo on lipids and boneturnover.37 Women taking the red clover supplements had greater meanincreases in HDL cholesterol and a significant decrease in triglyceride levels.Another study using a supplement with 43.5 mg isoflavones or placebo in 177women found supplementation in perimenopausal women reduced triglycerides, totalcholesterol and LDL cholesterol, suggesting menopausal status may impactefficacy of the supplement.38 However, red clover supplements may also benefitmen, as a study in 46 middle-aged men and 34 postmenopausal women foundadministration of 40 mg/d of red clover isoflavones for six weeks reduced LDL inthe men but not in the women.39

Another source of dietary phytoestrogens as lignans is flaxseed.A review from the University of Pennsylvania, Philadelphia, noted flaxseed maymodestly reduce serum total and LDL cholesterol and decrease some markers ofinflammation.40 Researchers from Oklahoma State University, Stillwater,investigated the impact of flaxseed on the prevention of ovariectomy-inducedrise in total cholesterol and atherosclerotic lesions in hamsters.41 Over fourmonths, the three doses of flaxseed (7.5 percent, 15 percent or 22.5 percent ofthe diet) significantly reduced the fatty acid streak area, and prevented the ovariectomy-induced rise in total cholesterol seen in the control animals. Thesame researchers investigated the impact of 40 g/d of ground flaxseed oncholesterol levels

in postmenopausal women not on hormone therapy.42Flaxseed significantly lowered serum total cholesterol and non-HDL cholesterol.

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