Four food-frequency categories of fruit intake as a predictor of plasma ascorbic acid level in middle-aged Japanese men.

PURPOSE: Plasma levels of ascorbic acid are assumed to be determined not only by dietary amount of ingested vitamin C, but also by other dietary and nondietary factors. To assess the predictability of plasma ascorbic acid level in Japanese men, we examined its association with dietary sources of vitamin C and other lifestyle factors. METHODS: In a cross-sectional study of 621 healthy men aged 40-49 years who were sampled randomly from five areas in Japan, the weekly intake frequency of foods rich in vitamin C (< 1, 1-2, 3-4, > or = 5 days/week), alcohol consumption per week, use of vitamin C supplements, and smoking were assessed by use of a food-frequency questionnaire (FFQ) (all subjects) and a 3-day weighed dietary record (DR) from 203 volunteers. RESULTS: In univariate analyses of FFQ data, the intake frequency of fruit (R2 = 0.12), pickled vegetables (R2 = 0.03), potatoes (R2 = 0.01), and alcohol consumption (R2 = 0.02) were significant determinants of plasma ascorbic acid in addition to supplement use and study area. In a multivariate analysis, four FFQ categories of fruit intake accounted for 19% of the variation in plasma ascorbic acid among nonsupplement users after adjustment for study area and alcohol intake. The association between plasma ascorbic acid level and quartile of dietary vitamin C intake (mg/day) measured by DR was weaker (R2 = 0.04) than the association between plasma ascorbic acid level and dietary intake of fresh fruit (g/day) (R2 = 0.09). CONCLUSION: The predictability of plasma ascorbic acid by a four-category FFQ assessment of fruit intake was superior to calculated vitamin C or fruit intake assessed by detailed DR.

Antioxidant vitamins in prevention.

The authors are aware that there is still a need for much research to elucidate the possible preventive effects of antioxidant vitamins with regard to degenerative and neoplastic diseases. There must also be vigorous examination of the evidence that antioxidant vitamins can play a crucial part in a large number of other disorders (Alzheimer's disease, Parkinson's disease, diabetes, chronic and acute inflammations, airway disorders, reperfusion syndrome). The aim of prevention-oriented medical research must be to develop suitable measures able to make a considerable contribution to the overall prevention policy. Although there is still uncertainty about the mode of action and the optimal dosage of antioxidant nutrients and dietary constituents, particularly because of the safety when the dosage is correct, more information must be provided about early prevention of an inappropriate, low antioxidant intake; intake in the diet should definitely be preferred to supplementation because of the other beneficial effects of the recommended foodstuffs.

Helicobacter pylori, dietary factors, and atrophic gastritis in five Japanese populations with different gastric cancer mortality.

In a cross-sectional study of 634 men aged 40 to 49 years, randomly selected from five areas of Japan with different rates of gastric cancer mortality, 121 men of 624 evaluated were diagnosed as having atrophic gastritis through serum pepsinogen I < 70 ng/ml and the pepsinogen I (PGI)/pepsinogen II (PGII) ratio < 3.0. We examined the relation of Helicobacter pylori (H. pylori) antibodies and dietary factors, including plasma level of antioxidant micronutrients, to the presence of atrophic gastritis. Presence of H. pylori IgG antibodies was associated with increased risk of atrophic gastritis (odds ratio [OR] = 1.9, 95 percent confidence interval [CI] = 1.1-3.3). As the level of plasma beta-carotene increased, we found a steady decrease in the risk of atrophic gastritis (OR for second quartile = 0.7, third quartile = 0.6, fourth quartile = 0.4, with CI = 0.2-0.8). Frequent intake of yellow vegetables also was associated with lower risk, while frequent intake of soybean products was related to increased risk. Although H. pylori antibodies, beta-carotene level, and intake of soybean products were all significant in the multivariate analysis, these factors did not explain the differences in atrophic gastritis prevalence among the five regions. The analysis of these risk factors in relation to each pepsinogen marker showed that although both H. pylori infection and low plasma beta-carotene were associated with the decreased level of serum PGI/II ratio, the former was derived from the increase of PGII, which is common in early stage of atrophic gastritis, and the latter from the decrease of PGI, which is specific to severe atrophic gastritis.(ABSTRACT TRUNCATED AT 250 WORDS)

Cross-sectional study with multiple measurements of biological markers for assessing stomach cancer risks at the population level.

A cross-sectional study to determine correlations between measurable biologic markers and mortality from stomach cancer was performed in various areas of Japan. Blood and urine were collected from randomly selected 40- to 49-year-old men and their spouses in four areas with different rates of mortality from stomach cancer. The samples were analyzed for levels of the micronutrients vitamins A, C, and E, beta-carotene, and lycopene in plasma and for levels of NaCl, nitrate, and N-nitrosamino acids (N-nitrosoproline, N-nitrosothioproline [NTPRO] and N-nitrosomethylthioproline [NMTPRO]) in 24-hr urine. A significant, strong correlation was found between the amount of salt excreted in urine and stomach cancer mortality in both men and women. Although the amounts of nitrate and of the three N-nitrosamino acids in 24-hr urine were not correlated with stomach cancer rates, the low excretion levels of NTPRO and NMTPRO in the lowest risk area for stomach cancer were noteworthy, regardless of the high level of nitrate excretion in the same area. This suggests a lesser degree of endogenous nitrosation in the body. No protective effect of micronutrients was observed in this correlation study; there was, however, a negative correlation between plasma lycopene level and stomach cancer mortality. Salt intake was thus confirmed to play an important role in the development of stomach cancer and is likely to be a rate-regulating factor in Japanese populations. N-Nitrosamino acids and lycopene may also be related to stomach cancer mortality.

Preventive potential of antioxidative vitamins and carotenoids on cancer.

Epidemiological and experimental research indicated some time ago that vitamins might act as protective agents in carcinogenesis. However, only more recently prospective studies proved a significant inverse correlation between certain vitamins and cancer at different site. The Basel Study (comprising 3756 healthy adult volunteers) is unique in its immediate measurement of the plasma vitamins at the time of the clinical assessment (1971-1973). The complete mortality follow-up allows testing of several hypotheses regarding the molecular basis of cancerogenesis. Among these mechanisms, aggressive oxygen species have been implicated. By analyzing plasma concentrations of essential antioxidants in cancer cases and survivors, we demonstrated a significantly negative inverse correlation between plasma beta-carotene and all cancer (n = 102, p less than .01), cancer of the lung (n = 37, p less than .01) and stomach (n = 17, p less than .05). Low retinol was related only to gastric cancer (p less than .01); low vitamin C and low vitamin E was related to all cancer and gastric cancer (p less than .05). The estimated antioxidant potential calculated as the molar product of vitamins C, E and beta-carotene showed a highly significant inverse correlation with all cancer and cancer of the lung and the stomach (p less than .01). These data and other newer studies strongly support the antioxidants in a role as natural inhibitors which may act on cancer initiation or promotion. Finally the convergence of results of the many epidemiological and experimental studies allow more soundly based conclusions with regard to dosage and time of vitamin intake in cancer.

Stability of plasma fatty acids at -20 degrees C and its relationship to antioxidants.

The fatty acid composition of cholesteryl esters (CE), triglycerides (TG) and phospholipids (PL) was analysed with gas chromatography before and after 3 years' storage of EDTA plasmas at -20 degrees C. In the three lipid fractions the proportion of polyunsaturated fatty acids (PUFA) with 3 or more double bonds decreased by 14% to 46%, while the proportions of saturated and monounsaturated fatty acids and also of linoleate (18:2 omega 6) showed an increasing trend. The changes tended to be relatively greatest in TG and smallest in PL. The initial concentration of vitamin A correlated negatively with reductions of all 20- to 22-carbon PUFA in CE and with that of arachidonate (20:4 omega 6) and docosahexaenoate (22:6 omega 3) in TG. The change in CE-18:2 omega 6 tended to be inversely correlated with vitamin A. The initial concentration of beta-carotene and the change in CE- and TG-18:3 omega 3 and CE-22:6 omega 3 showed also inverse correlations. Vitamin C, alpha-tocopherol and selenium had only occasional and mostly insignificant associations with the fatty acid alterations. In freshly analysed samples the concentration of vitamin A correlated negatively with the percentage of 18:2 omega 6 in plasma CE, TG and PL and with that of 20:4 omega 6 in platelets, and beta-carotene and alpha-tocopherol had positive correlations with 18:2 omega 6 in most plasma lipid fractions and platelets. Vitamin C and selenium correlated positively with 22:6 omega 3 in plasma, and selenium also with that in platelets.(ABSTRACT TRUNCATED AT 250 WORDS)