beginner's guide to fat-soluble vitamins: all you need to know

One of the biggest food myths in the world revolves around nutrient absorption. Most assume the foods we put into the body are entirely digested, absorbed, and stored, however, this isn’t the case. As food is eaten, the body immediately starts breaking it down into smaller molecules that we can use and store. Due to the complexity of the human body, these molecules must travel through various pathways to reach their final destination. The utilization rate of each molecule depends on the path used, but 100% of the vitamin or mineral is generally not absorbed or stored.

This is particularly true for multivitamin supplements as they’re absorbed differently than natural vitamins from whole foods. Supplements are created in a lab and are synthetic; therefore the body is not designed to absorb these vitamins as they would a whole food. For specific populations with vitamin deficiencies, restricted diets, pregnant women, and elderly people, these multivitamins are necessary. For the more general population, consuming vitamins from whole foods is more beneficial as they’re absorbed better into the body. Of course, vitamins and supplements can be beneficial to all but think of them more as nutrition insurance rather than your first line of defense.

Let’s do a quick overview of the pathway …

1. Digestion

   1. Where? The stomach (small amount occurs in the mouth).

   2. What? The breakdown of whole foods into smaller molecules for absorption.

2. Absorption

   1. Where? Mainly in the small intestine.

   2. What? The broken-down molecules are taken up into the cells.

3. Storage or excretion

   1. Where? Throughout the entire body (bones, fat tissue, liver, etc.).

   2. What? Any excess of these molecules is either stored in their storage site or excreted from the body through human waste.

Now, let’s circle back to vitamins …

There are two classes of vitamins, water-soluble and fat-soluble. What’s the main difference? Well, I’ll give you a hint, it’s in the name!

Water-soluble vitamins are transported through the body with water, they do not require any other nutrients to be absorbed or stored. Water-soluble vitamins include all the B vitamins and vitamin C.

Fat-soluble vitamins are different, they require fat to be transported, absorbed, and stored. Fat-soluble vitamins include A, D, E, and K, and each of them contributes to different functions in the body. Though they have different roles, they all rely on fat.

Here’s how it works (1) …

Eat a whole food with fat-soluble vitamins and a fat source → enzymes in the stomach break up the contents of the whole foods → fat-soluble vitamins combine with ingested fat to form fat globules → fat globules holding the vitamin travel to the small intestine → enzymes from the small intestine free the bound vitamin from fat → enzymes digest the vitamin and place them into a micelle (made up of stomach bile and fat) → micelles can cross through the cell walls (these vitamins can not cross the walls without the fat) → absorption into the small intestine → excess is stored in fat tissue or excreted.

The bottom line of this complex process is that dietary fat is required to digest, absorb, and store fat-soluble vitamins (1).

Now, if any fat will help with this process, why extra virgin olive oil (EVOO)?

While it’s true that any fat could do the trick, EVOO is a monounsaturated fat, making it the healthiest form of fat to consume. EVOO has cardioprotective functions and antioxidant properties. It also fights type 2 diabetes, inflammation, neurological decline, and much more. More about the benefits of EVOO can be found here. Consuming the right kind of fat with these fat-soluble vitamins is good practice to take care of your health. And it’s easier than you may think.

Try this easy recipe incorporating EVOO into a smoothie!

Tropical Green Smoothie

• ½ banana

• ½ cup mango

• ½ cup pineapple

• 1 cup spinach

• 1 scoop vanilla protein

• 1 scoop collagen peptides

• 1-2 tsp extra virgin olive oil

• ½ cup coconut milk (or milk of choice)

• ½ cup coconut water

Place all ingredients in a blender and puree until smooth.

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Written by Chloe Morrill

Reviewed by Kelly Powers, MA, RDN, a Registered Dietitian Nutritionist who takes a holistic approach to nutrition and health. Kelly is a recipe developer with a food blog highlighting whole foods, simple recipes, and her life in San Francisco. She’s the creator of Weeknight Dinners, a weekly meal plan program that helps users get back in the kitchen and feed themselves well.

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References

1. Gropper, S. S. & Smith, J. L. (2018). Advanced Nutrition and Human Metabolism: Seventh edition. Cengage Learning.