Sara Salvatore

Total antioxidant capacity of the diet is inversely and independently related to plasma concentration of high-sensitivity C-reactive protein in adult Italian subjects

Inflammation, a risk factor for cardiovascular disease, is associated with low plasma levels of antioxidant vitamins. In addition to vitamins, other antioxidants modulate the synthesis of inflammatory markers in vitro and contribute to the total antioxidant capacity (TAC) of a diet. However, the relationship between dietary TAC and markers of inflammation has never been evaluated in vivo. We investigated the relationship between dietary TAC and markers of systemic (high-sensitivity C-reactive protein (hs-CRP), leucocytes) and vascular (soluble intercellular cell adhesion molecule-1) inflammation in 243 non-diabetic subjects. General Linear Model (GLM) analysis showed a significant (P=0.005) inverse relationship between hs-CRP and quartiles of energy-adjusted dietary TAC, even when recognized modulating factors of inflammation, namely alcohol, fibre, vitamin C, alpha-tocopherol, beta-carotene, BMI, waist circumference, HDL-cholesterol, hypertension, insulin sensitivity and plasma beta-carotene, were included in the model as covariates (P=0.004). The relationship was stronger for subjects with hypertension (P=0.013 v. P=0.109 for normotensive individuals). Among dietary factors, TAC was significantly higher (5.3 (sd 3.0) v. 4.9 (sd 2.7) mmol Trolox/d; P=0.026) in subjects with low plasma hs-CRP (range: 0.0-4.1 mg/l) than in subjects with high plasma hs-CRP (range: 4.2-27.8 mg/l). We conclude that dietary TAC is inversely and independently correlated with plasma concentrations of hs-CRP and this could be one of the mechanisms explaining the protective effects against CVD of antioxidant-rich foods such as fruits, whole cereals and red wine. This could be of particular significance for subjects with high blood pressure.

Bioavailability and catabolism of green tea flavan-3-ols in humans

OBJECTIVE The aim of this study was to investigate green tea flavan-3-ol catabolism and plasma pharmacokinetic and urinary excretion by high-performance liquid chromatography with tandem mass spectrometry to evaluate their absolute bioavailability by taking into account all known and some unknown catabolites deriving from their interaction with the gastrointestinal tract and its host microflora. METHODS A feeding study was carried out in 20 healthy human volunteers who ingested 400 mL of a ready-to-drink green tea containing approximately 400 μmol of flavan-3-ols. Urine and plasma were collected for 4 and 24h, respectively, and 39 relevant catabolites were identified in these biological fluids by tandem mass spectrometry. RESULTS In biological fluids, 39 relevant flavan-3-ol catabolites were identified. In plasma, (-)-epigallocatechin-3-gallate was the only unmetabolized compound and the highest in absolute concentration compared with (-)-epigallocatechin and (-)-epicatechin conjugates. Colonic microflora-derived polyhydroxyphenyl-γ-valerolactones were by far the main urinary catabolites, averaging 10 times greater concentratin than flavan-3-ol conjugates. The calculated bioavailability was equal to 39% and it is interesting to notice the great variability in urinary excretion of colonic metabolites among participants, probably related to differences in their own colonic microflora. CONCLUSION This study demonstrates that green tea catechins are more bioavailable than previously observed when colonic ring fission metabolites are taken into consideration. Regular consumption of ready-to-drink green tea containing flavan-3-ols allows a non-marginal exposure of the human body to these catabolites, somehow justifying the numerous beneficial actions described as linked to green tea intake.

Effect of domestic cooking methods on the total antioxidant capacity of vegetables

As well as tables of food composition, total antioxidant capacity (TAC) databases—developed in past years for investigating health effects of antioxidant-rich foods in epidemiological and nutritional studies—have been created on the basis of analytical data from raw plant material. However, most vegetables are commonly cooked before consumption. With the aim of completing a previously developed TAC database, the effect of the major domestic practices (i.e. boiling, pan-frying and deep-frying) on the TAC of commonly consumed cooked vegetables was evaluated. Based on dry weight, boiling generally resulted in positive TAC changes whereas a general negative effect on the TAC was observed in pan-fried vegetables. Deep-frying produced a TAC increase of potato, artichoke and aubergine but a TAC reduction of mushroom and onion. The present study clearly indicates that cooking is not always a detrimental process when the TAC is used as an index to evaluate the nutritional characteristics of vegetables.

The total antioxidant capacity of the diet is an independent predictor of plasma β -carotene

Objective:To investigate the contribution of the total antioxidant capacity (TAC) of the diet to plasma concentrations of β-carotene.Design:Cross-sectional study.Setting:Department of Public Health and Department of Internal Medicine and Biomedical Sciences, University of Parma.Subjects:A total of 247 apparently healthy adult men (n=140) and women (n=107).Methods:A medical history, a physical exam including height, weight, waist circumference and blood pressure measurements, a fasting blood draw, an oral glucose tolerance test and a 3-day food record.Results:We observe a negative trend across quartiles of plasma β-carotene for most biological variables clustering in the insulin resistance syndrome, as well as for traditional and new risk factors for type II diabetes and cardiovascular disease (CVD), including C-reactive protein and γ-glutamyltranspeptidase (P<0.05). Regarding dietary characteristics, energy-adjusted intake of fat, fiber, fruits, vegetables, β-carotene, vitamin C, vitamin E and dietary TAC significantly increased with increasing plasma β-carotene (P<0.05), whereas alcohol intake decreased (P=0.013). Adjusted geometric means (95% confidence interval) of plasma β-carotene significantly increased across quartiles of dietary TAC, even when single dietary antioxidants were considered in the model (QI=0.087 mg/dl (0.073–0.102); QII=0.087 mg/dl (0.075–0.103); QIII=0.114 mg/dl (0.098–0.132) and QIV=0.110 mg/dl (0.093–0.130); P for linear trend=0.026). When the population was divided on the basis of alcohol consumption, this trend was also observed in subjects drinking <20 g alcohol/day (P=0.034), but not in those with higher alcohol intake (P=0.448).Conclusions:Dietary TAC is an independent predictor of plasma β-carotene, especially in moderate alcohol drinkers. This may explain, at least in part, the inverse relationship observed between plasma β-carotene and risk of chronic diseases associated to high levels of oxidative stress (i.e., diabetes and CVD), as well as the failure of β-carotene supplements alone in reducing such risk.Sponsorship:Supported by the European Community IST-2001–33204 ‘Healthy Market’, the Italian Ministry of University and Research COFIN 2001 and the National Research Council CU01.00923.CT26 research projects.