The Most Bioavailable Forms of Each Vitamin

Do you ever wonder why there are so many different forms of vitamins on the market? And how do you know which one is best for you? Well, we’ve got the answer for you!

Different vitamin forms have differing levels of bioavailability which refers to how much of that particular nutrient is absorbed and utilized in the body. This is important because it allows us to get as much out of our supplements as possible.

Supplements are a great way to fill nutrition gaps that cannot be met through food but it is important to realize that just because a supplement claims to provide a specific amount of a particular nutrient does not mean it will all be absorbed. We have compiled together the ultimate list of the most bioavailable forms of each vitamin to hopefully make it easier for you to pick out the best supplement! This post contains affiliate links.

Fat Soluble Vitamins 

Vitamins A, D, E, and K are all fat soluble vitamins and therefore, can be toxic to the body if they are overconsumed and stored in excess. If a diet is well balanced, then it is unlikely that these vitamins will need to be supplemented. However, if supplementation is desired or needed, it is important to understand which form of the vitamin will be most bioavailable for meeting nutritional needs. To make it easier for you, we have bolded what to look for on the nutrition label when shopping for supplements. 

• Vitamin A – Vitamin A helps maintain healthy skin, good eyesight, and functions in reproductive and immune health. There are two forms of vitamin A: the preformed vitamin A called retinol (or retinyl esters) which is found in animal products and the provitamin A called carotene which is found in foods of plant origin. Preformed vitamin A is the most bioavailable form because it is already in the preferred form that the body likes to absorb whereas carotenoids must undergo an extra conversion step to be absorbed. Look on the supplement nutrition label for preformed vitamin A, retinyl acetate, and retinyl palmitate. 

• Vitamin D – Known as the sunshine vitamin, vitamin D is highly important for strong bones and the immune system. Vitamin D has 2 forms: Vitamin D2 (ergocalciferol) which is present in plants and D3 (cholecalciferol) which can be obtained from animal products or sun exposure. While both forms of vitamin D are absorbed equally in the body, studies have shown that Vitamin D3 is more effective at increasing the vitamin D levels in the blood and may be the preferred form of supplementation. Few foods naturally contain vitamin D and supplementation may be advised, especially if sun exposure is not achieved regularly. Look on the supplement nutrition label for vitamin D3, cholecalciferol. 

• Vitamin E – Vitamin E is an antioxidant that helps boost immunity, widen blood vessels to prevent clotting, and improve brain and heart health. There are eight forms of vitamin E but only one is recognized as being biologically active in the human body which is known as alpha-tocopherol. However, recent evidence suggests that gamma-tocopherol is more effective at increasing the anti-inflammatory properties of vitamin E supplements than simply alpha-tocopherol alone. If vitamin E supplementation is desired, look for a mixed tocopherol supplement that may list alpha and gamma tocopherols on the nutrition label.

• Vitamin K – Vitamin K is required for proper blood clotting and healthy bones. This vitamin has three primary forms: K1 (phylloquinone), K2 (menaquinone), and K3 (dihydrophylloquinone). Of the three forms, MK-7 vitamin K2 has been shown to be the most bioavailable form of vitamin K because it is accessible for a longer period of time in the body’s circulation allowing for increased absorption. The K2 form of vitamin K has been linked to decreased risk of chronic diseases and can be consumed in dairy products, meats, and fermented foods. For supplementation, look on the nutrition label for vitamin K2 and menaquinone-7 or MK-7. 

Water-Soluble Vitamins

Vitamin C and the B vitamins are categorized as water soluble and are readily eliminated from the body. These vitamins must be frequently replenished through diet or supplementation and will rarely accumulate to toxic levels in the body. Check out our list of the most bioavailable forms of each water soluble vitamin!

• Vitamin C – Vitamin C is one of the most popular supplements because of the widespread belief in its immune boosting and anti-aging powers. Vitamin C is most commonly found as ascorbic acid in supplements. Some vitamin C supplements are paired with bioflavonoids, plant chemicals, to mirror the natural makeup of vitamin C in fruits and vegetables and potentially increase the absorption of vitamin C in the body. When choosing a vitamin C supplement look on the nutrition label for a complete C complex of ascorbic acid, bioflavonoids that contain hesperidin and rutin, and rose hips or acerola cherry which provide additional vitamin C and enzymes for better absorption. 

• Vitamin B1 (Thiamin) – Thiamin is known as the “morale vitamin” for its highly important role in producing energy for the body, stimulating the brain, and improving mental attitudes. It should be noted that all B vitamins are more effective when taken together in a B-complex supplement. However, there is an additional form of thiamin that is fat-soluble and more bioavailable known as benfotiamine which is actually transformed into thiamin once ingested into the body. Look on the nutrition label for benfotiamine or a complete B-complex supplement. 

• Vitamin B2 (Riboflavin) – Riboflavin is another extremely important B vitamin for the proper growth and functioning of the cells in the body. Riboflavin, like all other B vitamins, is also best taken in a complete B-complex supplement form and may be labeled as simply riboflavin or riboflavin 5-phosphate on the nutrition label. Although there is no proven bioavailability difference between the two forms, some believe that riboflavin 5-phosphate may be more bioavailable since it is already in the active form that the body needs. 

• Vitamin B3 (Niacin) – Niacin, another B vitamin involved in the growth and production of energy in cells, is specifically known for reducing cholesterol levels. There are three forms of niacin that may be found in supplements: nicotinic acid, nicotinamide (niacinamide), and nicotinamide riboside. Nicotinic acid is known for causing a red flush on the face while nicotinamide does not, and is therefore, the preferred form of supplementation. Nicotinamide riboside has been shown to increase the levels of the essential niacin-containing energy molecule in the body far better than either of the two other niacin forms. If niacin is supplemented alone, then look for nicotinamide riboside on the nutrition label, and if it is supplemented in a complete B-complex vitamin, look for nicotinamide (or niacinamide). 

• Vitamin B5 (Pantothenic Acid) – Panthothenic acid is rarely deficient in America since it is in most foods, but it is part of most complete B-complex supplements as calcium pantothenate as adding the mineral helps with shelf stability. Pantothenic acid is also available in the form of pantethine which has been shown to lower cholesterol while the calcium pantothenate form does not. 

• Vitamin B6 – Vitamin B6 is important for normal brain and immune function and is also unlikely to be deficient in Americans as this vitamin is present in a variety of foods. There are two common supplement forms of vitamin B6: pyridoxine which is present in most complete B-complex supplements and pyridoxal 5-phosphate which is the active form of vitamin B6 in the body. Both forms show similar bioavailability. To prevent deficiency in other B vitamins, make sure B1 and B2 are in equal amounts to B6 in a B-complex supplement. 

• Folate – Folate is a B vitamin that is absolutely essential during pregnancy for normal development of the fetus as well as throughout the lifespan for red blood cell production. Interestingly, the supplemental form of folate known as folic acid, is more bioavailable than the folate present in foods. Folate is considered most bioavailable in the form of 5-methyltetrahydrofolate (5-THF) because it can be absorbed despite metabolic disorders or pH changes in the stomach. 

• Vitamin B12 – Vitamin B12 is one of the most commonly deficient nutrients due to age, diet, and certain medical conditions. There are four vitamin B12 supplement forms but it has been shown that methylcobalamin and adenosylcobalamin work best together as the most bioavailable form of this vitamin. A sublingual tablet in which the vitamin directly enters the bloodstream is recommended as vitamin B12 does not absorb well in the stomach. 

• Biotin – Finally, the last member of the B vitamin family, biotin. Biotin is great for maintaining the health of hair, skin, and nails and because of this, it is often seen in multivitamin supplements. Biotin is simply found in its free form and is 100% absorbed when taken orally. It should be noted that biotin works best when combined with vitamins B2, B6, niacin, and A.