ROLE OF DIET AND EXERCISE IN TREATMENT OF HYPERLIPIDEMIALifestyle interventions, in the form of dietary modification and exercise, are effective means of managing and treating high serum levels of cholesterol and triglycerides in individuals diagnosed with dyslipidemia. Such interventions should always be attempted as the initial step in the management and treatment of lipid abnormalities, especially when total cholesterol levels, low-density lipoprotein (LDL) levels, or triglyceride serum levels are just above the reference range.
EFFECT OF EXERCISE ON DYSLIPIDEMIA
The acute effects of exercise on serum lipid levels are greatest with respect to elevating the levels of high-density lipoprotein (HDL). Various studies have shown HDL levels to increase by 4-43% with exercise. A reduction in triglyceride (TG) levels also occurs 18-24 hours after an acute bout of exercise and can persist for up to 72 hours. This effect is greatest in those with the highest pre-exercise TG values and does not appear to require a threshold of exertion to be demonstrated. The chronic effects of exercise were studied among endurance athletes. It was noted that they frequently had serum HDL cholesterol concentrations 10-20 mg/dL or 40-50% higher than their sedentary counterparts. Their triglyceride levels were also lower by 20%, and their LDL cholesterol concentrations were lower by approximately 5-10%.
The Health, Risk Factors, Exercise, Training, and Genetics (HERITAGE) Family Study showed that regular endurance exercise training was particularly helpful in men who have low HDL cholesterol levels, elevated TG levels, and central or abdominal obesity. The increase in HDL levels was usually noticed at 12 weeks or more and not seen at 10 weeks or less. Increased training volume predictably yielded greater results. The increase in HDL levels was more profound when exercise was combined with caloric restriction.
The effect of chronic exercise on LDL levels is less definitive. Prolonged exercise generally induces a small reduction in LDL levels. Such decrease was shown to be around 8%. The addition of a weight-reducing, low-fat diet to exercise significantly enhances the LDL-lowering effect.
EFFECT OF DIET ON DYSLIPIDEMIA
Although the diet commonly recommended for patients with dyslipidemia is low in saturated fat (<10% of caloric intake), low in cholesterol (<300 mg/d), and high in soluble fibers, several other diets have also been tried with reasonable success. Among them, the Mediterranean diet was a particularly effective alternative. This diet is low in red meat; high in fruits, vegetables, whole grains, beans, nuts, and seeds; and low to moderate in fish, poultry, and dairy products. Another suggested diet alternative contains diverse cholesterol-lowering components. This diet is low in saturated fat and high in plant sterols, soy protein, viscous fibers, and almonds. The level of LDL reduction with this second alternative diet was not statistically significant from a diet very low in saturated fat plus 20 mg/d of lovastatin. Meanwhile, increasing the percentage of monounsaturated fat intake and reducing caloric intake from carbohydrates to around 40% was also shown to reduce both fasting and postprandial triglyceride levels and increase HDL levels.
DIETARY SUPPLEMENTS AND DYSLIPIDEMIA
Several over-the-counter dietary supplements are frequently selected by dyslipidemic patients or are taken upon the recommendation of health care professionals.
Fish oil
Most of the data used to support the intake of fish oil concentrate were derived from studies that used high daily doses (>6 g/d). These studies conclusively showed significant reduction in serum triglyceride levels through inhibition of very low-density lipoprotein (VLDL) triglycerides and apolipoprotein B synthesis. In hypertriglyceridemic subjects, a dose of 15 g/d of fish oils lowered serum triglyceride levels by approximately 50%. Although many trials support the cardioprotective effects of fish oil, recent epidemiologic evidence, unfortunately, does not. The precise reasons for these controversial findings have yet to be determined.
Variations in the apolipoprotein E (apoE) genotype may play a role in an
individual’s specific response to fish oil therapy. In particular, an
increase of LDL-C levels and a trend in the direction of reduced HDL-C
levels after fish oil supplementation were observed in subjects
possessing the apoE4 allele, compared to individuals possessing the
homozygous apoE3 allele profile. Additionally, individuals possessing
the apoE2 allele have shown improved responses to reduction of expected
serum triglyceride elevations after meals.
Oat bran supplement
Beta-glucan (the main soluble fiber component of oat bran) may decrease the absorption of ingested nutrients and bile acids by increasing the viscosity of intestinal contents. Several studies have demonstrated evidence that oat bran supplements have a substantial hypocholesterolemic effect. A daily dose of 3 grams or more is required to produce clinically relevant reductions in both total cholesterol (TC) and LDL concentrations. Combining oat bran supplementation with exercise showed consistent and substantial reduction of serum lipid levels.
Plant sterols
Compounds that are structurally similar to cholesterol were shown to lower serum lipid levels by inhibiting intestinal cholesterol absorption. Plant sterols include vegetable oils, seeds, and nuts. A meta-analysis of 21 trials that used plant sterol supplements showed that a dose of 2 g/d reduced serum LDL levels by approximately 10%. Although plant sterols consistently lower TC and LDL concentrations, evidence suggests that these nutritional supplements have no effect on HDL or TG levels. Combining plant sterols of 1.8 g/d with 25-40 minutes of endurance physical exercise 3 times per week resulted in universal reduction of TC, LDL, and TG levels and an increase in HDL levels.
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