Why can people consume large amounts of foods with beta-carotene ...

[jace]

Why can people consume large amounts of foods with beta-carotene without any ill effects but cannot consume large amounts of foods with active vitamin A without risk of serious toxic effects?

Question 2

Which individual's activity had the highest calorie cost?
 a. Sara, who weighs 145 lb and did step aerobics (0.062 cal/lb/min) for 35 minutes
 b. Ben, who weighs 180 lb and walked on the treadmill (0.048 cal/lb/min) for 25 minutes
 c. Mary, who weighs 120 lb and rode her bike (0.076 cal/lb/min) for 20 minutes
 d. Andrew, who weighs 163 lb and swam (0.058 cal/lb/min) for 30 minutes
 e. Kia, who weighs 185lb and ran on the treadmill (0.061cal/lb/min) for 25 minutes

[Dominic]

Answer to Question 1

The liver converts beta-carotene into active vitamin A. The diet must supply 12 micrograms of beta-carotene to produce 1 microgram of active vitamin A, and this conversion is not efficient enough to result in a toxic level of active vitamin A. The only sign of excess beta-carotene intake is a bright yellow color of the skin due to a buildup of beta-carotene in the fat beneath the skin.
Certain animal foods, such as liver, contain very high levels of active vitamin A. When these foods are ingested, all of the vitamin A is sent directly into the body and its fat tissues. The amount of active vitamin A can quickly reach toxic levels that can cause digestive upset as well as possible damage to the liver.

Answer to Question 2

a

[jace]

Excellent

[gcook]

Thanks for the timely response, appreciate it