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"Vitamins: What do fat and water soluble mean?"

Let’s break down how vitamins break down.

What is solubility?

Solubility refers to the way that a vitamin dissolves in another substance. Vitamins need to be soluble in order for our body to be able to use the food that we eat. When we describe vitamins in terms of solubility, it helps us understand better how to break them down into their nutritional components, or their smaller parts.

The soluble property of a vitamin indicates how it will be stored in the body. For example, a water soluble vitamin can easily transport to the bloodstream. Fat-soluble vitamins are first dissolved into the dietary fat they are consumed with and then absorbed by the body.

Fat-soluble Vitamins

Fat-soluble vitamins are those that are easily stored in fat, and they are soluble in the fatty tissues of the body. For optimal absorption, fat-soluble vitamins should be consumed with fatty foods (click here for reference). Don’t worry, we will be covering each vitamin individually and so I’ll elaborate on the reasoning behind this as we explore the fat-soluble vitamins.

Water-Soluble Vitamins

Water soluble vitamins are soluble in water or water-like substances. As you might predict, water-soluble vitamins are washed out of the body more quickly than their fat-soluble counterparts. However, the B-complex and C vitamins are found in many foods and regular intake and a healthy lifestyle is usually sufficient to avoid deficiency. Lack of these vitamins is often due to malnutrition, and is prevented easily in developed countries. These vitamins are vital for proper functioning of the nervous system, and usually a combined deficiency is usually more common than malnutrition of a single vitamin. While deficiency is relatively rare in developed countries, it is still important to be aware of the diverse symptoms that can appear from deficiency, malabsorption, or toxicity-- especially as a healthcare provider.

Bite-sized Facts

Absorption Alterations (Am I at risk?)

Certain people can be at risk for problems with absorbing vitamins properly. Be sure to ask your doctor about potential concerns if you:

  • Have certain medical conditions

  • Have certain genetic mutations (i.e. MTHFR)

  • Are trying to conceive

  • Are pregnant or lactating

  • Are an older adult

  • Have had weight loss surgery

  • Have IBD (Crohn’s or UC)

  • Have or are at risk for osteoporosis

  • Have an autoimmune or inflammatory disease

We’ll be going over the fat-soluble vitamins first: A, D, E, and K, starting with Vitamin A next week! Be sure to check out the new prints and products available in the shop if you want to sport your knowledge of nutrients.


FREE Patient References

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  3. Lykstad J, Sharma S. Biochemistry, Water Soluble Vitamins. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2020.

  4. Chawla J, Kvarnberg D. Hydrosoluble vitamins. Handb Clin Neurol. 2014;120:891-914. doi:10.1016/B978-0-7020-4087-0.00059-0

  5. Clifford J, Kozil A. Fat-Soluble Vitamins: A, D, E, and K-9.315. Colorado State University Extension. Accessed at

  6. Clifford J, Curely J. Water-Soluble vitamins: B-Complex and Vitamin C-9.312. Colorado State University Extension. Accessed at

  7. Tello M. What Patients- and Doctors-- need to know about vitamins and supplements. Harvard Health Publishing. Harvard Medical School. 2018. Accessed at

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