There are numerous essential vitamins that we need to obtain from our diet.
These vitamins include vitamins A, B1, B2, B3, B5, B6, B12, C, D, E, K, folate, and biotin.
Four of these vitamins are fat-soluble: vitamins A, D, E, and K.
The remaining vitamins are water-soluble.
In this article, we will briefly explain the importance of each essential vitamin. Further, we will look at the recommended daily allowance (RDA) and the best food sources for each one.
All RDA figures are sourced directly from the US National Institutes of Health.
Vitamin A
There are two primary ways to get vitamin A from our diet.
Pre-formed vitamin A, otherwise known as retinol, is available from animal-based foods such as liver and eggs (1).
In contrast, we can also convert carotenoids found in plant-based foods to vitamin A.
However, this conversion rate can vary depending on the person and the specific food (2).
Some of these carotenoids, including astaxanthin, lutein, and lycopene, may have further benefits due to their antioxidant properties (3).
Vitamin A is fat-soluble, and it is particularly important for the optimal functioning of the immune system. The vitamin also plays a crucial role in vision (4, 5).
Similar to other B vitamins, vitamin B2 is important for producing energy from the food we eat, and it is necessary for the optimal absorption of carbohydrates, fat, and protein (10).
Vitamin B2 is better known as riboflavin, and it is a water-soluble vitamin.
Niacin is an important vitamin for the digestive and nervous systems, and like other B vitamins, it also plays a role in converting food into energy (13).
We can find this vitamin in a wide range of animal-based and plant-based foods.
Vitamin B6, also known as pyridoxine, is available from both animal-based and plant-based foods.
However, it is important to note that the vitamin’s relative bioavailability is lower in plant foods.
Animal sources of B6 have a near-100% bioavailability, but the presence of fiber and pyridoxine glucoside in plant foods decreases the bioavailability (21).
Vitamin B6 has vital functions for brain and cellular development, energy metabolism, and supporting the nervous and immune systems (22).
Vitamin B12 is probably the most famous of all the B vitamins.
This essential vitamin is of great importance to our health, and inadequate intake can potentially lead to anemia, nerve damage, and other serious consequences (25).
Vitamin B12 is only available from animal foods, so vegans need to supplement with either B12 tablets, nutritional yeast, or other fortified food (26, 27).
Biotin is a little-known B vitamin that is also called vitamin B7 and may sometimes be referred to as ‘vitamin H’ (34).
This vitamin has a role in cell signaling, gene expression, energy metabolism, and the nervous system (35).
There is currently no set RDA for biotin due to a lack of available data to determine a recommended level.
However, the Food and Nutrition Board at the National Academies of Sciences, Engineering, and Medicine set an adequate intake (AI) level at 30 mcg for adults (36).
To learn more about biotin and see a list of the best dietary sources, see this guide:
Bell peppers, berries, citrus fruit, leafy green vegetables, tomatoes, certain organ meats (41)
Vitamin D
Sometimes referred to as ‘the sunshine vitamin,’ vitamin D is one of the four fat-soluble vitamins. It is also unique in that we can obtain it from either our diet or sunlight exposure (42).
The most common dietary forms of vitamin D are vitamin D2 (ergocalciferol) and D3 (cholecalciferol). We can find D2 in plant foods like mushrooms, and UV-enriched mushrooms can be a very significant source of vitamin D. In contrast, we can find vitamin D3 in animal foods, and oily fish contains particularly high levels (43, 44).
Vitamin D has many important functions within the human body, and maintaining adequate levels may help to lower the risk of certain chronic diseases (45, 46).
Vitamin K is a fat-soluble vitamin that is available in two dietary forms (54):
Vitamin K1 (phylloquinone)
Vitamin K2 (menaquinones)
Vitamin K1 is the plant form, and the best dietary source is green vegetables. In contrast, vitamin K2 is available from animal foods such as aged cheese and meat (menaquinone-4) and fermented foods, such as natto (menaquinone-7) (54).
Initial research suggests that vitamin K2—particularly menaquinone-7—may have the best bioavailability (55, 56).
Maintaining adequate levels of vitamin K is thought to have a beneficial role in cardiovascular health and preserving healthy bones (57).
Lastly, choline is not currently classed as a vitamin, although it has vitamin-like properties. Despite not officially being a vitamin, choline is an essential nutrient, and we need to obtain it from our diet (60, 61).
Additionally, choline appears to haves some potential benefits for human health. Among these, the nutrient appears to have a protective effect on the liver, and low-choline diets may even increase the risk of fatty liver disease (62, 63).
Further research suggests that choline may also be necessary for optimal brain development and cognitive health (64, 65).
There is no recommended daily allowance for choline, but an adequate intake level has been set.
While we often hear about the importance of a particular vitamin, the truth is that they are all important.
There are many different vitamins, and they are essential for a reason: we need them in sufficient quantities to maintain optimal health.
An omnivorous diet focusing on whole foods is the best way to ensure we get a wide range of essential vitamins.
Regarding more restrictive diets, such as the vegan diet, supplementation is an important consideration to ensure a sufficient intake of essential vitamins.
Michael works as a nutritionist in a community setting and holds a Master's Degree in Clinical Nutrition. He is a Registered Associate Nutritionist with the Association for Nutrition.
