Association between plasma homocysteine concentrations and extracranial carotid-artery stenosis

BACKGROUND

Epidemiologic studies have identified hyperhomocysteinemia as a possible risk factor for atherosclerosis. We determined the risk of carotid-artery atherosclerosis in relation to both plasma homocysteine concentrations and nutritional determinants of hyperhomocysteinemia.

METHODS

We performed a cross-sectional study of 1041 elderly subjects (418 men and 623 women; age range, 67 to 96 years) from the Framingham Heart Study. We examined the relation between the maximal degree of stenosis of the extracranial carotid arteries (as assessed by ultrasonography) and plasma homocysteine concentrations, as well as plasma concentrations and intakes of vitamins involved in homocysteine metabolism, including folate, vitamin B12, and vitamin B6. The subjects were classified into two categories according to the findings in the more diseased of the two carotid vessels: stenosis of 0 to 24 percent and stenosis of 25 to 100 percent.

RESULTS

The prevalence of carotid stenosis of > or = 25 percent was 43 percent in the men and 34 percent in the women. The odds ratio for stenosis of > or = 25 percent was 2.0 (95 percent confidence interval, 1.4 to 2.9) for subjects with the highest plasma homocysteine concentrations (> or = 14.4 mumol per liter) as compared with those with the lowest concentrations (< or = 9.1 mumol per liter), after adjustment for sex, age, plasma high-density lipoprotein cholesterol concentration, systolic blood pressure, and smoking status (P < 0.001 for trend). Plasma concentrations of folate and pyridoxal-5'-phosphate (the coenzyme form of vitamin B6) and the level of folate intake were inversely associated with carotid-artery stenosis after adjustment for age, sex, and other risk factors.

CONCLUSIONS

High plasma homocysteine concentrations and low concentrations of folate and vitamin B6, through their role in homocysteine metabolism, are associated with an increased risk of extracranial carotid-artery stenosis in the elderly.

Effect of vitamin C supplementation on lipoprotein cholesterol, apolipoprotein, and triglyceride concentrations

Plasma ascorbic acid (AA) frequently is positively correlated with high-density-lipoprotein (HDL) cholesterol and inversely related to total cholesterol concentration. To determine if vitamin C intake can alter cholesterol concentration, we examined the effect of vitamin C supplementation (1 g/d) on lipoprotein cholesterol and triglyceride levels in 138 subjects, aged 20 to 65 years, who completed an 8-month randomized, double-blinded, placebo-controlled trial. Individuals with higher levels of plasma AA (> 80 mumol/L for men and > 90 mumol/L for women), HDL cholesterol (> 1.4 mmol/L for men and > 1.7 mmol/L for women), and total cholesterol (> 6.7 mmol/L) were excluded from this trial. We observed no overall effect of supplementation on plasma concentrations of HDL, LDL, or total cholesterol, apolipoprotein (apo) B, or triglyceride. We did observe a marginally significant (P < 0.10) increase of 1.9 mumol/L (5.3 mg/dL) in apo A-I concentration with supplementation and a significant (P < 0.05) difference of 0.10 mmol/L (3.8 mg/dL) in HDL cholesterol concentration between vitamin C and placebo treatment in a nonrandomized subgroup of individuals (n = 43) and a baseline plasma AA level less than 55 mumol/L. Although the apo A-I concentration increase was only marginally significant with supplementation, change in plasma AA concentration was significantly (P < 0.05) correlated with change in apo A-I concentration in the entire sample. The overall results of this trial were negative, but our data do not allow us to rule out the possibility that vitamin C supplementation might increase HDL cholesterol or apo A-I concentrations among individuals with lower plasma AA levels.

High dose ascorbate supplementation fails to affect plasma homocyst(e)ine levels in patients with coronary heart disease

Pharmacologic doses of folate, in the absence of clinical folate deficiency, can reduce plasma levels of the putatively atherothrombotic amino acid, homocysteine (H(e)). Data suggesting that H(e) may accumulate in experimental scurvy prompted us to explore the efficacy of high dose ascorbate supplementation as a H(e)-lowering treatment, in the absence of clinical ascorbate deficiency. A randomized, placebo-controlled trial of 12 weeks of high dose (4.5 g/day) ascorbate supplementation was completed by 44 patients with established coronary heart disease. No significant change in mean fasting total plasma H(e) levels was demonstrable despite a marked increase in mean fasting plasma ascorbate levels amongst those patients randomized to active treatment. Ascorbate supplementation to prevent the development of fasting hyperhomocysteinemia may only be relevant at scorbutic levels of plasma ascorbate.

Ascorbic acid and plasma lipids

We examined the association between plasma lipids and total ascorbic acid in 256 men and 221 women age 20-65 years. Among men, we observed that high-density lipoprotein (HDL) cholesterol was 2.1 mg per dl higher, total:HDL cholesterol was 5.4% lower, total cholesterol was 4.8 mg per dl lower, low-density lipoprotein (LDL) cholesterol was 5.6 mg per dl lower, and triglyceride was 5.2% lower for each 0.5 mg per dl increment in ascorbic acid. The association between ascorbic acid and total:HDL cholesterol ratio in men was modified by glucose concentration. Among women, we observed that HDL cholesterol was 14.9 mg per dl higher for women with ascorbic acid levels < or = 1.05 mg per dl and 0.9 mg per dl lower for women with ascorbic acid levels > 1.05 mg per dl for each 0.5 mg per dl increment in ascorbic acid. Total:HDL cholesterol ratio was 10.9% lower for women with ascorbic acid concentrations < or = 1.45 mg per dl and 0.6% higher for women with ascorbic acid concentrations > 1.45 mg per dl for each 0.5 mg per dl increment. The associations among ascorbic acid concentration, total and LDL cholesterol, and triglyceride concentrations were weak or absent among women. These results are consistent with earlier observations relating ascorbic acid and HDL cholesterol and indicate that ascorbic acid might also be related to total and LDL cholesterol concentrations in men.

Effects of dietary intakes on plasma lipids, lipoproteins, and apolipoproteins in free-living elderly men and women

Plasma lipid and apolipoprotein (apo) A-I and B concentrations and habitual dietary intakes were determined in 306 free-living elderly individuals (119 men and 187 women, age range 60-100 y). Plasma lipid and apo A-I concentrations were significantly higher in women than in men. In older men, plasma triglyceride, total cholesterol, and apo B concentrations were significantly lower than in younger men, whereas a significant trend towards lower LDL-cholesterol concentrations was observed in older women. Energy intake and percent macronutrient intake were not influenced by age. Higher carbohydrate intake was associated with lower HDL cholesterol and apo A-I concentrations, whereas higher total fat intake was associated with higher apo A-I concentrations. Higher vitamin A intake was associated with higher plasma concentrations of HDL cholesterol and apo A-I. Our data indicate that both dietary and plasma concentrations of vitamin A, body mass index, age, and sex are important determinants of plasma lipid concentrations in the elderly.

Vitamin status and intake as primary determinants of homocysteinemia in an elderly population

OBJECTIVE

To describe the distribution of plasma homocysteine concentrations in an elderly population and to analyze the relationship between homocysteine level and intake of vitamins and serum levels of vitamins that serve as coenzymes in homocysteine metabolism.

DESIGN

Cross-sectional analysis of homocysteine levels and vitamin blood levels and intake in elderly participants in the Framingham Study.

SETTING

Population-based cohort in Framingham, Mass.

PARTICIPANTS

A total of 1160 adult survivors, aged 67 to 96 years, from the original Framingham Heart Study cohort.

MAIN OUTCOME MEASURES

Plasma homocysteine concentration correlated with plasma folate, vitamin B12, pyridoxal-5'-phosphate (PLP), and oral intakes of these vitamins, and the contribution of these vitamins to the prevalence of elevated homocysteine in the population.

RESULTS

Homocysteine levels were positively correlated with age after controlling for vitamin concentrations. After controlling for age, sex, and levels of other vitamins, homocysteine exhibited a strong inverse association with plasma folate. When subjects were grouped by deciles of plasma folate, mean homocysteine was significantly higher in the lowest two folate deciles (15.6 and 13.7 mumol/L, respectively) than in the highest decile (11.0 mumol/L). Homocysteine demonstrated weaker, inverse associations with plasma vitamin B12 and PLP. Similar inverse associations were demonstrated between homocysteine and intakes of folate and vitamin B6, but not vitamin B12. Prevalence of high homocysteine (> 14 mumol/L) was 29.3% in this cohort, and was greatest among subjects with low folate status. Inadequate plasma concentrations of one or more B vitamins appear to contribute to 67% of the cases of high homocysteine.

CONCLUSIONS

These results indicate a strong association between homocysteine concentration and folate, vitamin B12, and vitamin B6 status, as well as age. It is possible that a substantial majority of the cases of high homocysteine in this older population can be attributed to vitamin status.

Nutritional and economic advantages for homeless families in shelters providing kitchen facilities and food

Food habits were examined in homeless families in Boston-area hotels and family shelters. Reported household income, food expenditures, food sources, and attitudes were analyzed for 77 caretakers grouped according to kitchen facilities provided and amount of food provided. Diets were analyzed using a 4-week semiquantitative food frequency questionnaire for 71 female respondents grouped by type of residence (hotel or shelter). Median monthly income was $589 and was similar among groups. Mean monthly food expenditures were lower for those who lived in shelters that provided standard kitchen facilities and substantial food support compared with those who lived in hotels without these amenities ($93 vs $244; P < .05). Compared with others, respondents who lived in hotels reported purchasing food more frequently (P < .05), were more likely to use food pantries (P < .01), and had fewer food items on hand (P < .01). They were less likely to be satisfied with their diets, access to food, and cooking and food storage facilities (P < .05). Nutrient intakes were frequently below two thirds of the Recommended Dietary Allowance for vitamin B-6 (63% of respondents), calcium (44%), and iron (44%). Vitamin A intakes were lower in hotel residents, as were vitamin B-6, vitamin C, and zinc per 1,000 kcal (P < .05). We conclude that services provided to homeless families in shelters and hotels may influence food expenditures, food procurement, and women's diets. Nutrition professionals should consider the availability of kitchen facilities and food when counseling homeless families.

Comparison of micronutrient intake measured by a dietary questionnaire and biochemical indicators of micronutrient status

We compared the intake of 12 micronutrients as reported on a semiquantitative food frequency questionnaire with corresponding biochemical indicators of nutrient status in a sample of 57 males and 82 females aged 40-83 y. Age-, sex-and energy-adjusted correlation coefficients ranged from near zero for thiamin, vitamin A, and zinc to 0.63 for folate. Correlation coefficients between intake and the biochemical measures were > 0.30 for carotenoids, vitamin D, vitamin E, vitamin B-12, folate, and vitamin C. Differences of 50% or more were observed between extreme quartiles of intake for mean plasma concentrations of folate, vitamin B-12, and vitamin C. Excluding nutrient supplement users generally reduced the correlations. These data demonstrate that food frequency questionnaires can provide valid information on intake for a number of micronutrients.

Long-term morbidity and mortality of overweight adolescents. A follow-up of the Harvard Growth Study of 1922 to 1935

BACKGROUND

Overweight in adults is associated with increased morbidity and mortality. In contrast, the long-term effect of overweight in adolescence on morbidity and mortality is not known.

METHODS

We studied the relation between overweight and morbidity and mortality in 508 lean or overweight adolescents 13 to 18 years old who participated in the Harvard Growth Study of 1922 to 1935. Overweight adolescents were defined as those with a body-mass index that on two occasions was greater than the 75th percentile in subjects of the same age and sex in a large national survey. Lean adolescents were defined as those with a body-mass index between the 25th and 50th percentiles. Subjects who were still alive were interviewed in 1988 to obtain information about their medical history, weight, functional capacity, and other risk factors. For those who had died, information on the cause of death was obtained from death certificates.

RESULTS

Overweight in adolescent subjects was associated with an increased risk of mortality from all causes and disease-specific mortality among men, but not among women. The relative risks among men were 1.8 (95 percent confidence interval, 1.2 to 2.7; P = 0.004) for mortality from all causes and 2.3 (95 percent confidence interval, 1.4 to 4.1; P = 0.002) for mortality from coronary heart disease. The risk of morbidity from coronary heart disease and atherosclerosis was increased among men and women who had been overweight in adolescence. The risk of colorectal cancer and gout was increased among men and the risk of arthritis was increased among women who had been overweight in adolescence. Overweight in adolescence was a more powerful predictor of these risks than overweight in adulthood.

CONCLUSIONS

Overweight in adolescence predicted a broad range of adverse health effects that were independent of adult weight after 55 years of follow-up.

Effects of vitamin C on high-density lipoprotein cholesterol and blood pressure

Diet has been linked to cardiovascular disease risk by its influence on low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and blood pressure (BP). Recent evidence suggests that vitamin C may play a role in regulation of cholesterol and BP. The cross-sectional relationships of plasma ascorbic acid (PAA) with cholesterol and BP are described in three Boston area samples: 1) 249 males and 447 females (aged 60-100 years), 2) 100 Chinese-American males and 159 Chinese-American females (aged 60-96 years), and 3) 225 male and 192 female participants (aged 20-60 years) in a randomized field trial of vitamin C supplementation. Results indicate 3.7-9.5% higher levels of HDL-C, 4.1% lower levels of LDL-C, and 1.9-5.5% lower levels of BP with each 30 mumol/L increment in PAA. These relationships may be stronger at lower levels of PAA.

Relationship in humans between ascorbic acid consumption and levels of total and reduced ascorbic acid in lens, aqueous humor, and plasma

The relationships between plasma, aqueous humor and lens ascorbic acid levels are examined in 131 samples from 127 patients. Mean ascorbate intake for nonsupplemented individuals was 148 mg/day or over two times the recommended daily allowance. A subset of 44 patients participated in a trial to assess the impact of vitamin C supplementation of 2 grams per day on aqueous and lens ascorbic acid levels. Such supplementation significantly increased both total and reduced ascorbic acid levels in plasma and aqueous and total ascorbic acid in the lens. Correlation coefficients relating total and reduced ascorbic acid levels in the three tissues ranged from 0.42 to 0.19 (p less than 0.05 for all correlation coefficients). Over 60% of the ascorbate was present in the reduced form in plasma and aqueous, and about 50% of the lens ascorbate was in the reduced form.

Epidemiologic evidence of a role for the antioxidant vitamins and carotenoids in cataract prevention

The relationship between antioxidant nutrient status and senile cataract was examined in 77 subjects with cataracts and 35 control subjects with clear lenses. Subjects with low (below the 20th percentile) and moderate (20th-80th percentiles) plasma nutrient and nutrient intake levels of vitamin C, vitamin E, and carotenoids were compared with subjects with high levels (above the 80th percentile). The odds ratio (OR) of cortical (CX) cataract among subjects with low plasma carotenoid levels was 7.2 (P less than 0.05) and the OR of posterior subcapsular (PSC) cataract for persons with low plasma vitamin C was 11.3 (P less than 0.10). Low vitamin C intake was associated with an increased risk of CX (OR = 3.7, P less than 0.10) and PSC (OR = 11.0, P less than 0.05) cataract. Subjects who consumed fewer than 3.5 servings of fruit or vegetables per day had an increased risk of both CX (OR = 5.0, P less than 0.05) and PSC cataract (OR = 12.9, P less than 0.01).

Descriptors of alcohol consumption among noninstitutionalized nonalcoholic elderly

This paper describes relationships between reported alcohol consumption and selected sociodemographic and health variables. Two hundred and four men and 367 women aged 60-95 years were examined as part of a nutritional status survey of elderly. Fifty-three percent of men and 44% of women reported drinking at least 2 g of alcohol per week. Men were more likely to drink than women, and the level of alcohol consumption decreased with age. Drinking was positively associated with education (p less than 0.01) and negatively associated with recent medical care (p less than 0.01), history of MI (p less than 0.05), and denture use (p less than 0.05). Among drinkers, reported alcohol intake was higher for subjects less than age 70 (p less than 0.01), males (p less than 0.01), the college educated (p less than 0.01), and smokers (p less than 0.05). Level of alcohol intake was lower for those who had received medical care in the year preceding study participation (p less than 0.05). Identical results were observed for alcohol intake expressed as percent of total calories. Intake ranged from 3.8% of total calories among subjects 80+ years old to 6.2% of total calories among 60-69-year-olds.

Moderate alcohol intake and nutritional status in nonalcoholic elderly subjects

Three hundred and seventy-three female and 213 male nonalcoholic subjects, aged 60-100 y, who had participated in a nutritional status survey of elderly people in the Boston area were grouped according to usual alcohol intake: 0-4, 5-14, or 15+ g/d. The age- and sex-adjusted mean intake of calories, fat, protein, carbohydrate, and 10 micronutrients and the mean levels of 14 nutrient and 22 nonnutrient biochemical indices were compared for the three categories of alcohol intake. The mean micronutrient intakes were also adjusted for total caloric intake and the mean nutrient biochemical concentrations were also adjusted for the corresponding nutrient intakes. The results suggest that caloric intake and blood concentrations of retinol, iron, ferritin, HDL cholesterol, AST, and ALT increased with increasing alcohol intake whereas folate and phosphorus intakes and blood measures of riboflavin, copper, zinc, urea nitrogen, and creatinine decreased with increasing alcohol intake.