Fat-Soluble And Water-Soluble Vitamins: What It All Means

Vitamins can take two forms; fat-soluble or water-soluble. Solubility refers to how vitamins are absorbed, dissolved, metabolized, and transported. As the name suggests, fat-soluble vitamins do not dissolve in water and need fat in order to be digested and utilized. Just as water-soluble vitamins need water to be dissolved and metabolized for various biological functions throughout the body. 

What Vitamins Are Fat-Soluble?

Fat-soluble vitamins are best absorbed and provide more bioavailability when taken with foods higher in fat.  That means, when these specific vitamins are not taken with enough fat, they pass through the GI tract, without much effect or absorption. Thus it’s crucial that when taking fat-soluble vitamins, you ingest them with foods higher in fat.

Vitamins A, D, E, and K are all classified as fat-soluble vitamins. Once these vitamins are ingested, they couple with lipid or fat-based structures, such as our cell membranes [R].

Vitamin A contains carotenoids and provitamins, meaning they are converted to vitamins in the body. Carotenoids are the chemicals that give carrots, peppers, sweet potatoes, and beets their distinct bright yellow, orange, and red color. Vitamin A is involved in many biological functions such as immune function, wound healing, red blood cell development, and synthesizing proteins [R].

Vitamin D is synthesized through the skin and absorbed from the sun. But if you live in a cloudy climate such as the Pacific Northwest like me, then you get most your Vitamin D through supplements. Vitamin D is really classified as a group of prohormones, and can benefit a positive mood state, bone health, and promote a healthy heart. Studies have shown that Vitamin D may also have an effect on regulating stress and anxiety. But you’ll need some fat to absorb it as well, which will also help you absorb calcium. Ever heard the saying, that milk does the body good? Now you know why.

fat soluble vitamins

Vitamin E is comprised of 8 antioxidants, and can help prevent oxidative stress, or free-radical damage.

Vitamin K is a family of two fat-soluble vitamins, K1 and K2. Vitamin K helps the body form natural blood clots to help with the body’s natural healing process. Vitamin K also assists in bone health, amino-acid metabolism, regulating calcium, and reducing the risk of heart disease [R].

What Vitamins Are Water-Soluble?

Water-soluble vitamins are best absorbed when taken with water. These vitamins are both actively and passively absorbed through the GI tract, via carrier proteins and active transport. Since we are continuously cycling through water, these vitamins are not stored in large quantities, like fat-soluble vitamins.

B Vitamins and Vitamin C are water soluble vitamins.

Fat-Soluble & Water-Soluble Vitamins: Takeaway

Despite the solubility of a vitamin, micronutrients are involved in nearly every biological process throughout your body. Vitamins work synergistically to keep you vibrant and healthful. Without the recommended amounts of vitamins obtained from food, supplements, and outside sources like the sun, your immune system can become comprised and weakened. Include micronutrient-rich foods, such as colorful fruits and vegetables, as well as lean proteins, quality complex carbohydrates, and healthy fats.


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