Complementary Alternative Cardiovascular Medicine

60 Alternative Cardiovascular Medicine
high levels reactive oxygen and nitrogen species can be damaging to
cells and contribute to disease. Among the chronic diseases in which
oxidative stress plays a significant role is CVD. It has been proposed that
oxidation of low-density lipoproteins (LDLs) may be a key step in the
development of atherosclerosis (3–5). Oxidized LDL cholesterol is
believed to have different properties than LDL that is not oxidized.
Oxidized LDL accumulates in the cells that line the blood vessels. These
lead to fatty streaks and later to atherosclerotic lesions. The concept that
oxidatively modified LDL is proatherogenic and exists in vivo is supported
by a growing body of data. In animal models, antioxidant supplementation
inhibits atherosclerosis progression (6). The nutrients studied
in these experiments were ascorbic acid, α-tocopherol and β-carotene.
Vitamin C
The prospective studies that relate ascorbic acid (Vitamin C) to CVD
are not consistent. A significant inverse relationship was found between
plasma vitamin C and coronary artery disease (CAD) in epidemiological
studies (7). Ascorbate concentrations were also lower in the aortas of
people with atherosclerosis, diabetes, and CAD and in smokers and
nonsmokers when compared with unaffected controls. It has been hypothesized
that low ascorbate concentrations in the arterial wall may predispose
LDL to oxidation, which could promote atherogenesis. In the
NHANES Study, which included 11,349 US men and women, there was
an inverse association between cardiovascular mortality and ascorbic
acid intake of at least 50 mg/d through diet or supplement (8). A large,
more than 4-yr prospective study of 19,496 men and women in Norfolk,
United Kingdom, showed that plasma ascorbic acid was inversely related
to mortality from all causes and from CVD and ischemic heart disease in
men and women (9). Studies such as these have several confounders:
elevation of plasma ascorbic acid might indicate that foods that contribute
vitamin C may also contribute nutrients, such as potassium, folate,
calcium, magnesium, and isoflavones, that might confer cardiovascular
benefits. Studies conducted on large cohorts (10,11) did not show association
between vitamin C intake and mortality.
Observational studies suggest that vitamin C plays a role in the etiology
of CVD, but there are no completed interventional trials of this
vitamin alone. The Recommended Dietary Allowance (RDA) for vitamin
C is 75 mg/d for women and 90 mg/d for men. The recommendation
for smokers is an additional 35 mg/d because of increased oxidative
stress and other metabolic differences. The Upper Limit (UL) for vitamin
C is 2000 mg/d (12).