Quick Answer. The effects of caffeine start within 10 minutes after it is consumed, according to ScienceDaily. However, caffeine requires 45 minutes to reach its maximum concentration in the blood. Continue Reading.
The heart, blood, and blood vessels are the three structural elements that ... These nutrients enter the bloodstream by passing through the walls of the intestine.he heart, blood, and blood vessels are the three structural elements that ... These nutrients enter the bloodstream by passing through the walls of the intestine.
For the most part, the B vitamins are absorbed directly into the bloodstream in your stomach or small intestines. The exception is vitamin B-12, which must be bound to something called intrinsic factor for absorption.itamin C in red peppers is absorbed into your bloodstream in the small intestines. Photo Credit Design Pics/Design Pics/Getty Images. Most of the nutrients in the food you eat -- such as protein, fats, carbohydrates and fat-soluble vitamins -- need to undergo some amount of digestion before they can be absorbed.