You know that vitamin C can promote optimal immune function, vitamin D supports healthy teeth and bones, and vitamin A plays a role in supporting normal eye health.* 

But, did you know that each vitamin is structurally different? There are two different categories into which vitamins are classified, which determine how the body absorbs them: fat soluble and water soluble.

Let’s dive into fat-soluble vs. water-soluble vitamin differences and how they can affect the way our bodies utilize vitamins. 

Difference between fat-soluble and water-soluble vitamins 

What are water-soluble and fat-soluble vitamins?

There are two distinct groups of vitamins in our diets (and supplements): fat-soluble vitamins, which are best absorbed with and easily stored in fat, and water-soluble vitamins, which dissolve in water and generally cannot be stored in the body for later use. To describe some general differences between fat-soluble and water-soluble vitamins: When it comes to fat-soluble vitamins, because we can store them in our bodies for later use, there is a small, although not impossible, risk of deficiency. In contrast, with water-soluble vitamins, since we don’t store these, if you are not consuming them in adequate amounts, it’s easier to become deficient. 

Humans do not naturally synthesize either water-soluble or fat-soluble vitamins, so both must be obtained exogenously from diet, supplementation, or, in the case of vitamin D, most prominently, from exposure to the sun.1,2 

So, which are water-soluble vitamins? And which are fat-soluble vitamins? Is vitamin C fat soluble? Is vitamin B12 water soluble or fat soluble? What are the most important fat-soluble vitamins?

Water-soluble vitamins include all B vitamins and vitamin C, while the fat-soluble vitamins are vitamins A, D, E, and K. Water-soluble vitamins are essential for normal cellular function, growth, and development, and they play a role in the health of the skin, the proper function of the nerves and heart, immune function, and red blood cell formation. Fat-soluble vitamins play a crucial role in maintaining vision, supporting bone health, benefiting immune function, supporting cardiovascular health, and promoting the ability for blood to clot.

Structure and absorption of vitamins 

Structurally how are water-soluble and fat-soluble vitamins different?

Water-soluble and fat-soluble vitamins are very different from one another, and even within the two categories, each vitamin has a different structure. Water-soluble vitamins are polar molecules, meaning they can be dissolved in water, whereas fat-soluble vitamins are non-polar, meaning that they are not able to dissolve in water and need more help being absorbed into the body. 

How are water-soluble vitamins absorbed?

When we consume a water-soluble vitamin, such as vitamin C, that vitamin is dissolved in water when it enters the body. It then goes on to get absorbed in the small intestine, facilitated by various carrier-mediated mechanisms. 

How are fat-soluble vitamins absorbed?

Fat-soluble vitamins are absorbed through the creation of lipid clusters that are formed in the small intestine. This process of creating lipid clusters and absorbing fat-soluble vitamins relies on the production and release of bile and pancreatic enzymes from the gallbladder and pancreas, respectively. After this, fat-soluble vitamins are repackaged into what’s called a chylomicron, which is then secreted into the lymphatic system before entering the bloodstream.1,2 

What about minerals? 

Similar to vitamins, minerals cannot be made by the human body and must be obtained through diet or supplementation, but they are essential for numerous physiological functions. Minerals are either classified as major (macro) or trace, depending on how much of them we need each day. Major minerals include sodium, potassium, chloride, calcium, phosphorus, magnesium, and sulfur, and we typically need these in larger quantities within our diet. Trace minerals include iron, copper, zinc, selenium, iodine, chromium, and others, of which we usually need less. 

So, are minerals fat soluble or water soluble? Is magnesium water or fat soluble? 

Minerals are generally water-soluble, although their solubility can vary, and do not require enzymatic digestion, as they are absorbed directly into the bloodstream. 

Where do I get vitamins? Can fat-soluble and water-soluble vitamins be taken together?

Vitamins are found in an abundance of food sources in our diet, but most commonly we can find them in fruits and vegetables – foods rich in color! They can also be fortified or added to products like milk and cereal, where, in the case of milk, we need vitamin D to absorb its calcium.   

Water-soluble vitamins: 

  • B vitamins can be found primarily in grains like cereals and breads, nuts and seeds, eggs, meat and fish, leafy green vegetables, sweet potatoes, and tomatoes. Thorne offers a few different B vitamin supplements, including Basic B Complex and individual B vitamins like Vitamin B12 and 5-MTHF (active folate), all in their tissue-ready and most absorbable forms. 
  • Vitamin C can be found in strawberries, citrus fruit, bell peppers, kiwi, broccoli, cantaloupe, Brussels sprouts, and kale. If you need an extra boost of vitamin C, try Thorne’s Vitamin C with Flavonoids. Flavonoids are also known as “Vitamin P.” What is vitamin “P”? P stands for polyphenols, packed with antioxidants known for their ability to support a healthy inflammatory response.* 

Fat-soluble vitamins: 

  • Vitamin A can be found in foods like liver, salmon, eggs, cheese, oysters, milk, butternut squash, collard greens, mango, and cantaloupe. 
  • While we make most of our vitamin D from exposure to the sun, we can also obtain it from fatty fish such as salmon, tuna, and sardines, as well as egg yolks and mushrooms. It can be hard to maintain a consistent level of vitamin D year-round, depending on where you are in the world. Try Thorne’s Vitamin D-5,000, especially for those times when you are seeing less sunlight throughout the day. 
  • Vitamin E is found in plant-based oils, almonds, peanuts, sunflower seeds, asparagus, red bell pepper, avocados, mangoes, and pumpkin. Vitamin E can also be found in Thorne’s Ultimate-E, a supplement that provides antioxidants for cardiovascular support.* 
  • Vitamin K can be found in dark leafy greens like spinach, kale, and Swiss chard, broccoli, cabbage, cauliflower, blueberries, figs, prunes, soybeans, vegetable oils, and eggs. For a supplement containing vitamin K, look to Thorne’s Vitamin K, with both K1 and K2 to support healthy blood vessels and help maintain bone density.*  

For a more comprehensive option, containing both water- and fat-soluble vitamins, check out Thorne’s multi-vitamin and mineral suite, where you can find a multivitamin suited to you and your health goals.

We hope this article has answered your questions like “What is the difference between fat-soluble and water-soluble vitamins?” 

References 

  1. Water soluble: Lykstad J, Sharma S. Biochemistry, Water Soluble Vitamins. [Updated 2023 Mar 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538510/ [Accessed July 3, 2025]
  2. Fat soluble: Reddy P, Jialal I. Biochemistry, Fat Soluble Vitamins. [Updated 2022 Sep 19]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534869/ [Accessed July 3,2025]