Relation of serum ascorbic acid to serum lipids and lipoproteins in US adults

To examine the relation of serum ascorbic acid level to serum lipid and lipoprotein levels among a random sample of the US adult population.

Using linear regression, the relation of serum ascorbic acid level to serum lipid and lipoprotein levels was examined among 5,412 women and 5,116 men enrolled in the Second National Health and Nutrition Examination Survey (NHANES II), 1976-1980. Age, race, body mass index, level of physical activity, level of education, alcohol intake, and dietary energy, cholesterol, and fat intakes, and other potential confounders were included in the multivariate models.

Serum ascorbic acid level was independently associated with high-density lipoprotein cholesterol (HDL-C) among women; each 1 mg/dl increase in serum ascorbic acid level (range 0.1 to 2.7 mg/dl) was associated with a 2 mg/dl increase in HDL-C level (p = 0.001). Because other investigators have demonstrated an inverse relation between ascorbic acid intake or blood levels and total serum cholesterol in individuals with elevated total serum cholesterol levels, we analyzed four subgroups of NHANES II participants with total serum cholesterol levels > 200 mg/dl. Among women with total serum cholesterol levels > or = 200 mg/dl, each 1 mg/dl increase in serum ascorbic acid level was independently associated with an increase of 2 to 3 mg/dl in HDL-C level (p < or = 0.05). Serum ascorbic acid level was not significantly associated with other serum lipids or lipoproteins.

If the observed associations are linked causally, they would suggest that ascorbic acid is a factor in cholesterol homeostasis among women and may be particularly important for women at increased risk for coronary heart disease.