Medical Nutrition Therapy for Disorders of Lipid MetabolismManual of Clinical Nutrition Management C- 45 Copyright © 20 13 Compass Group, Inc.
antioxidant-rich foods, such as fruits, vegetables, and whole grains, from which antioxidants were derived (29).
Because so many nutrients are contained in these foods, it is difficult to directly link the antioxidant nutrients to
the reduction in CHD risk. Antioxidants such as vitamin E, vitamin C, and beta carotene (or carotenoids) should
be specifically planned into a cardioprotective dietary pattern (Grade III) (5). The AHA recommends increased
consumption of antioxidant-rich fruits, vegetables, and whole grains, which is associated with reduced disease
risk (Grade III) (5,29). There is limited evidence to support the use of antioxidant supplements for disease
prevention, even though this topic has been an issue of considerable debate (29). Vitamin E, vitamin C, and beta
carotene supplements should not be recommended to reduce the risk of cardiovascular disease because they
have shown no protection for cardiovascular disease events or mortality (Grade II) (5). The observation that
adequate consumption of vitamin E may be difficult to achieve by dietary means leads the debate regarding
vitamin E supplementation (26,27). Recent trials provide stronger evidence that vitamin E supplementation does
not reduce cardiovascular disease or all-cause mortality; in some cases, vitamin E supplementation may lead to
negative health outcomes including increased risk of death from hemorrhagic stroke (30-34). The Cambridge
Heart Antioxidant Study (32) demonstrated a benefit of vitamin E in secondary prevention; however, the GISSI
trial (14) and Heart Outcomes Prevention Evaluation Study (33) showed no beneficial effects of vitamin E at doses
of 300 mg and 400 mg, respectively. Supplemental vitamin E, vitamin C, beta carotene, and selenium should not
be taken with the simvastatin/niacin drug combination because of possible blunting of HDL2 (the HDL
subfraction that is thought to be most protective) and an increased percentage of stenosis demonstrated in one
study (Grade II) (5). Supplemental beta carotene cannot be recommended for individuals who smoke because of an
increased risk for lung cancer in these individuals (Grade II) (5,28,29,34).
Folic acid and vitamins B 6 and B 12 : Homocysteine, an amino acid in the blood, appears to oxidize LDL
cholesterol (16). A high level of serum homocysteine, independent of other cardiac risk factors, is associated
with increased risk for coronary artery disease. Conversely, low homocysteine levels are associated with
reduced risk. (Grade II) (5,16). An increase in blood total homocysteine levels of 5 μmol/L elevates the risk of
coronary artery disease as much as does a 20 mg/dL increase in total cholesterol (16). Factors that influence
blood homocysteine levels include: deficiencies of folate, B 6 , and B 12 ; age; sex; menopausal status; renal
function; and certain medications. Folate is required for the conversion of homocysteine to methionine, an
amino acid. Serum folate levels have an inverse relationship with total homocysteine levels (35-37). Although
supplemental folate (0.5 to 2.5 mg) taken alone or in combination with B 6 (10 to 25 mg) and B 12 (0.4 mg)
reduced homocysteine levels by 17% to 34%, it did not reduce the risk for coronary events after a period of 6
months to 2 years in stable coronary artery disease patients, post-stroke patients, or post-angioplasty patients
that had normal baseline homocysteine levels and total cholesterol levels (Grade II) (5,38,39). Folate, vitamin B 6 , and
vitamin B 12 should be included in the cardioprotective dietary pattern to meet the Dietary Reference Intakes.
Based on current evidence the supplementation of these vitamins to lower cardiovascular risk is not
recommended (5).
Alcohol: Alcohol does not affect LDL cholesterol concentrations, but it does increase serum triglycerides
concentrations and HDL cholesterol levels in many individuals. The mechanism for the rise in HDL cholesterol
is not known. It is also not known whether the higher level of HDL affords any protection against CHD.
Population and cohort studies, primarily of men, suggest that one or two drinks of alcohol-containing beverages
per day are associated with reduced risk of cardiovascular disease, while excessive consumption of alcohol is
associated with increased CHD (Grade I) (5,40-42 ). The NCEP report and the AHA do not specifically recommend
alcohol consumption for CHD prevention (1,5). Most data do not support an association the between type of
alcoholic beverage (wine, beer, or liquor) and protection against cardiovascular disease (Grade II) (5,40-42). The
cardiovascular disease benefits of alcohol may be realized when alcohol is consumed with meals (Grade II) (5,40-42).
Observational studies have found a relationship between high alcohol intake (more than three drinks per day)
and elevated blood pressure (3,5). The AHA Guidelines 2000 are consistent with the US Dietary Guidelines in
recommending that daily alcohol consumption be limited to two drinks for men and one drink for women.
Phytochemicals: Phytochemicals are nutritive substances found in plants. Nuts, whole grains, fruits, and
vegetables contain a variety of phytochemicals. Epidemiologic studies show a relationship between the intake of
phytochemicals, primarily plant sterols, flavonoids, and plant sulfur compounds, and CHD. Plant sterols found in
rice bran decrease cholesterol levels (43). Flavonoids found in tea, onions, soy, and wine have antioxidant
properties. Plant sulfur substances found in garlic, onions, and leeks decrease serum cholesterol (44). Studies are
difficult to interpret because food sources containing phytochemicals have multiple compounds, and results
distinguishing a specific cause and effect to the atherosclerotic process have been limited. Studies are currently
assessing the relationship of phytochemicals to CHD.