Lutein and zeaxanthin are xanthophyll carotenoids found particularly in dark-green leafy vegetables and in egg yolks. They are widely distributed in tissues and are the principal carotenoids in the eye lens and macular region of the retina. Epidemiologic studies indicating an inverse relationship between xanthophyll intake or status and both cataract and age-related macular degeneration suggest these compounds can play a protective role in the eye. Some observational studies have also shown these xanthophylls may help reduce the risk of certain types of cancer, particularly those of the breast and lung. Emerging studies suggest as well a potential contribution of lutein and zeaxanthin to the prevention of heart disease and stroke. Even as the evidence for a role of lutein and zeaxanthin in disease prevention continues to evolve, particularly from human studies directed to their bioavailability, metabolism, and dose-response relationships with intermediary biomarkers and clinical outcomes, it is worth noting that recommendations to consume foods rich in xanthophylls are consistent with current dietary guidelines.

Objective: To assess the effects of consuming foods containing oat b-glucan on blood pressure, carbohydrate homeostasis and biomarkers of oxidative stress. Design: A randomized, double-blind, controlled clinical trial. Setting: The trial was conducted at two clinics. Subjects and interventions: Ninety-seven men and women with resting systolic blood pressure 130-179 mm Hg and/or diastolic blood pressure 85-109 mm Hg were randomly assigned to consume foods containing oat b-glucan or control foods for 12 weeks. Resting blood pressures, insulin and glucose values before and after standard breakfast meals, and four biomarkers of oxidative stress were measured before and at the end of the treatment period. Results: Changes from baseline to week 12 in mean peak insulin and incremental area under the insulin curve differed significantly between groups (P ¼ 0.037 and 0.034, respectively), with the b-glucan group showing declines and the control group remaining essentially unchanged. Blood pressure responses were not significantly different between groups overall. However, in subjects with body mass index above the median (31.5 kg/m 2 ), both systolic (8.3 mm Hg, P ¼ 0.008) and diastolic (3.9 mm Hg, P ¼ 0.018) blood pressures were lowered in the b-glucan group compared to controls. No significant differences in biomarkers of oxidative stress were observed between treatments. Conclusions: The results of the present trial suggest beneficial effects of foods containing b-glucan from oats on carbohydrate metabolism, and on blood pressure in obese subjects.

A reduced-fat spread containing plant sterol esters incorporated into a low-fat diet is a beneficial adjunct in the dietary management of hypercholesterolemia.

The effect of vitamin B-6 deficiency on immune response was studied in eight healthy elderly adults. The protocol consisted of a 5-d baseline (BL) period; a vitamin B-6-depletion period of less than or equal to 20 d; three stages of vitamin B-6-repletion, each lasting 21 d; and a 4-d final phase. The amounts of vitamin B-6 ingested during the different phases of the study were 3.00, 15.00, 22.50, and 33.75 micrograms.kg body wt-1.d-1, respectively. During the final phase the subjects ingested 50 mg vitamin B-6/d. Fasting blood was collected at the end of each period. Vitamin B-6 depletion significantly decreased percentage and total number of lymphocytes, mitogenic responses of peripheral blood lymphocytes to T- and B-cell mitogens, and interleukin 2 production. These indices returned to BL values after the third vitamin B-6-repletion period, when the total vitamin B-6 intakes were 1.90 +/- 0.18 mg/d for women and 2.88 +/- 0.17 mg/d for men. Vitamin B-6 deficiency impairs in vitro indices of cell-mediated immunity in healthy elderly adults. This impairment is reversible by vitamin B-6 repletion.

This placebo-controlled study examined in healthy women the effects of ingestion of a single large dose of beta-carotene (120 mg) on the concentrations of beta-carotene and lycopene in plasma and skin, and the effects of UV light exposure on the concentrations of beta-carotene and lycopene in the skin. Ingestion of beta-carotene increased plasma beta-carotene concentration by 127%, from 0.26 +/- 0.06 (mean +/- SEM) to 0.59 +/- 0.07 mumol/L after 1 d, and the level remained elevated at 0.54 +/- 0.11 mumol/L after 5 d. beta-Carotene in skin, analyzed after 6 d, increased by 23%, from 1.41 +/- 0.74 to 1.74 +/- 0.72 nmol/g. beta-Carotene ingestion had no effect on the lycopene concentrations of plasma (0.37 +/- 0.11 mumol/L) or skin (1.60 +/- 0.62 nmol/g). A single exposure of a small area of one volar forearm to a dose of solar-simulated light (three times the individually determined minimal erythema dose) resulted in 31 to 46% reductions in skin lycopene concentration compared with an adjacent non-exposed area. The same UV dose did not result in significant changes in skin beta-carotene concentration. We conclude that a single 120-mg dose of beta-carotene increases plasma and skin beta-carotene concentrations and has no effect on plasma and skin lycopene concentrations. The amounts of lycopene in plasma and skin are comparable to or even greater than those of beta-carotene. When skin is subjected to UV light stress, more skin lycopene is destroyed compared with beta-carotene, suggesting a role of lycopene in mitigating oxidative damage in tissues.

Carotene-rich yellow and green leafy vegetables, when ingested with minimal fat, enhance serum carotenoids and the total-body vitamin A pool size and can restore low liver vitamin A concentrations to normal concentrations.

Vitamin A deficiency is a major global public health problem. Among the variety of techniques that are available for assessing human vitamin A status, evaluating the provitamin A nutritional values of foodstuffs and estimating human vitamin A requirements, isotope dilution provides the most accurate estimates. Although the relative expense of isotope dilution restricts its applications, it has an important function as the standard of reference for other techniques. Mathematical modelling plays an indispensable role in the interpretation of isotope dilution data. This review summarises recent applications of stable isotope methodology to determine human vitamin A status, estimate human vitamin A requirements, and calculate the bioconversion and bioefficacy of food carotenoids.

Three-day DRD can detect changes in the body pool size of vitamin A, although a predictive equation to quantitate total body stores of vitamin A with the use of 3-d data needs to be developed. Bioconversion of plant carotenoids to vitamin A varies inversely with vitamin A status; improvement in status after dietary interventions is strongly influenced by total body stores of vitamin A and is influenced little or not at all by serum retinol.