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Absorption of Micronutrients and Water into the Bloodstream

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  • 0:02 What Are Micronutrients?
  • 1:19 Role of the Small Intestine
  • 2:11 Micronutrient Absorption
  • 4:33 Water Absorption
  • 5:17 Lesson Summary
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Lesson Transcript
Instructor: Donna Ricketts

Donna Ricketts is a health educator with 15 years of professional experience designing health and wellness programs for adults and children.

In this lesson, you will gain a deeper understanding of how and where absorption of micronutrients and water take place in your body. You will also learn how and where it enters your bloodstream.

What Are Micronutrients?

Your body absorbs two types of nutrients: macronutrients and micronutrients. Macronutrients (carbohydrates, proteins, and fats) are your body's direct source of fuel or energy, while micronutrients, which are commonly referred to as vitamins and minerals, are needed in minimal amounts. But, just because you only need a little doesn't mean that they don't pack a punch.

Micronutrients are vital for the proper functioning of all your body's systems. They include such minerals as iron, which helps your body produce red blood cells, and calcium, which aids with blood clotting. Micronutrients also include vitamins such as vitamin A (essential for vision health), while vitamin C is essential for healthy teeth, gums, and bones.

In addition, micronutrients indirectly serve as the catalyst to release the energy from the macronutrients. Without them you couldn't get the energy out of carbohydrates and fats or convert the protein you eat into your own lean body mass. Unless vitamins and minerals are efficiently absorbed, none of the nutrients can function properly.

The Role of the Small Intestine

Micronutrients are released from food by digestion and then absorbed mainly in the small intestines. A little bit is absorbed in the stomach and large intestines, but mainly in the small intestines. The inside surface of the small intestine contains many folds covered by villi, very thin, long projections on the inside of the intestinal wall. These projections contain muscle, so they are constantly moving in a wave-like motion. Their purpose is to increase the absorption potential of the small intestine by increasing its surface size. On each villi are even tinier microvilli that are nutrient-specific; this is where absorption occurs.

Micronutrient Absorption

During the process of absorption, nutrients that come from the food (including carbohydrates, proteins, fats, vitamins, and minerals) pass through channels in the small intestine into the bloodstream. The blood works to distribute these nutrients to the rest of the body. There are two primary ways that nutrients cross through the walls of the small intestine and enter the bloodstream: passive diffusion and active transport absorption.

Passive diffusion can be thought of as pouring liquid through a cheesecloth. It's a simple process where nutrients move from an area of high concentration (like the inside of the intestine) to an area of low concentration (like the bloodstream). Active transport absorption means that the nutrient requires a helper, or carrier molecule, to get it through the intestinal wall into the bloodstream.

Some micronutrients are more inclined to one type of absorption than the other, but all vitamins, including fat-soluble ones (like A, D, E, and K) and water-soluble ones (like C and most of the Bs), are absorbed through passive diffusion. Fat-soluble vitamins are mostly absorbed passively and must be transported with dietary fat into the lymphatic system and then into the bloodstream. If you don't eat enough dietary fat, your body will not properly absorb these vitamins. A very low-fat diet can lead to deficiencies of fat-soluble vitamins.

Water-soluble vitamins can be directly absorbed into the bloodstream from the intestine by both passive and active mechanisms. Vitamin B-12 relies on 'carriers,' namely sodium, for transport into the bloodstream. Minerals like calcium and magnesium, on the other hand, are transported actively. Many micronutrients can be absorbed more readily than others, depending on what kind of food they're coming from, and also on your body's current status and need for that nutrient.

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