Lycopene and beta-carotene are bioavailable from lycopene 'red' carrots in humans.

OBJECTIVE: The purpose of this study was to determine if lycopene and beta-carotene are bioavailable from lycopene red carrots and if lycopene absorption is affected by carrot fiber. DESIGN: Two crossover studies in humans attempted to compare the relative bioavailability of lycopene and beta-carotene from tomato paste to a genetically selected lycopene red carrot during chronic feeding. Each study contained three treatment groups. The vehicle of administration was muffins. INTERVENTION AND METHODS: Study 1 (n=9) used white carrots (0 mg lycopene/day), red carrots (5 mg/day), and tomato paste (20 mg/day). Study 2 (n=10) used red carrots (2.6 mg/day), tomato paste (5 mg/day), and tomato paste plus white carrots (5 mg/day). Each intervention lasted 11 days with a 10-day washout period between treatments. Serum lycopene and beta-carotene were measured by HPLC. RESULTS: Statistical analysis indicated a significant effect of muffin type in study 1 (P<0.001), and a significant treatment by sequence interaction in study 2 (P=0.04). The response to increasing amounts of lycopene is linear at the levels fed in these studies (r=0.94). The data suggest that maintenance of serum lycopene concentrations at 0.3 micromol/l occurs at about 2 mg/day of lycopene from mixed dietary sources and a serum plateau occurs at >/=20 mg/day. CONCLUSIONS: These results show that lycopene and beta-carotene are bioavailable from red carrots and lycopene absorption seems to be affected by carrot fiber. Making inferences from both studies, the lycopene in the red carrot is about 44% as bioavailable as that from tomato paste. Red carrots provide an alternative to tomato paste as a good dietary source of lycopene and also provide bioavailable beta-carotene.

Natural abundance deuterium and 18-oxygen effects on the precision of the doubly labeled water method.

The doubly labeled water method for measuring total energy expenditure is subject to error from natural variations in the background 2H and 18O in body water. There is disagreement as to whether the variations in background abundances of the two stable isotopes covary and what relative doses of 2H and 18O minimize the impact of variation on the precision of the method. We have performed two studies to investigate the amount and covariance of the background variations. These were a study of urine collected weekly from eight subjects who remained in the Madison, WI locale for 6 wk and frequent urine samples from 14 subjects during round-trip travel to a locale > or = 500 miles from Madison, WI. Background variation in excess of analytical error was detected in six of the eight nontravelers, and covariance was demonstrated in four subjects. Background variation was detected in all 14 travelers, and covariance was demonstrated in 11 subjects. The median slopes of the regression lines of delta2H vs. delta18O were 6 and 7, respectively. Modeling indicated that 2H and 18O doses yielding a 6:1 ratio of final enrichments should minimize this error introduced to the doubly labeled water method.

The role of exercise in the treatment of obesity.

The prevalence of obesity in the USA has increased dramatically in the past decade. This foreshadows an increase in the rates of morbidity and mortality from obesity-related diseases and increases in the number of individuals undergoing weight-loss therapy. Although exercise has long been recommended for inclusion in such therapy, the present review has found that it has had little or no effect on weight loss per se when the exercise is limited to the typically prescribed 3-5 h/wk of moderate or vigorous activity. However, further review has shown that exercise helps to preserve and at times even increase fat-free mass during weight loss. At the same time, fat loss is generally increased. Neither type nor amount of exercise appears to have much effect during treatment, with the possible exception of resistance training, which is associated with the best outcome for fat-free mass. The most important role of exercise, however, is in the maintenance of the weight loss. In this respect, the volume of exercise seems to be important because several lines of evidence have indicated that exercise must expend roughly 2500 kcal/wk to maintain weight loss. Studies of weight maintenance, however, have generally not included randomized controls; thus, further research is required to solidify these conclusions.