If you buy something through a link on this page, we may earn a small commission. How this works. Fat-soluble vitamins are vitamins A, D, E, and K. They are present in foods containing fats. The body absorbs these vitamins as it does dietary fats. They do not dissolve in water. Vitamins help the body function effectively. There are two types: water-soluble and fat-soluble vitamins. The water-soluble vitamins are vitamins B and C. Most vitamins come from food, but sunshine contributes to vitamin D. Some people need or choose to take supplements that provide extra vitamins. The body absorbs fat-soluble vitamins best when a person eats them with higher-fat foods. This article looks at the types, functions, and sources of fat-soluble vitamins, and what can happen if a person has too much or too little.

Vitamin A Share on Pinterest Carrots are a dietary source of vitamin A. Vitamin A helps maintain healthy vision. Without vitamin A, a person could experience vision problems and possibly vision loss. Types Vitamin A is not a single vitamin but a collection of compounds known as retinoids. Retinoids occur naturally in the human body, and they are present in some dietary sources. Some foods provide retinols, which the body can use directly as vitamin A. Others provide provitamin A, compounds that the body converts into vitamin A. Function Vitamin A supports several functions throughout the body, including: vision

the immune system Learn more here about why we need vitamin A. Dietary sources People can obtain vitamin A through dietary sources. Animal sources provide preformed vitamin A, or retinols. This type is ready for the body to use. Plant sources provide carotenoids, such as beta-carotene, which is a powerful antioxidant. The body can convert these into vitamin A. For this reason, lists of ingredients often show vitamin A content as “vitamin A RAE.” RAE means “retinol activity equivalents.” Animal sources of vitamin A include: fish liver oil

beef liver

cheese, milk, and other dairy products

Sources of beta carotene include:

sweet potato

kale, spinach, and other green, leafy vegetables

carrots

cantaloupe

black-eyed peas

fortified breakfast cereals Find out more here about dietary sources of vitamin A. Recommended intake Nutritionists measure some vitamins in two ways: micrograms (mcg) RAE

international units (IU) Food packages usually show the amounts in IU. A diet that contains 900 mcg RAE of vitamin A, which is the recommended intake for males over 14 years of age, would provide around 3,000–36,000 IU of vitamin A, according to the Office of Dietary Supplements (ODS). Anyone who has concerns about their vitamin A intake should seek advice from a health professional, who will help them understand these measures. The recommended intake of vitamin A varies by age and sex. The 2015–2020 Dietary Guidelines for Americans recommend consuming the following amounts each day. Amounts are in mcg RAE. Age (years) 1–3 4–8 9–13 14 and over Female 300 400 600 700 Male 300 400 600 900

Deficiency Vitamin A deficiency is rare in the United States, but it can affect a person who: follows a plant-based diet

has cystic fibrosis A long-term deficiency can lead to a loss of night vision and possibly a total loss of vision. Overdose Too much vitamin A can be toxic. It can affect: people who take vitamin A supplements

those with a high intake of fish liver oil

people who take medications that contain retinoids, such as acitretin (Soriatane), a treatment for psoriasis During pregnancy, high levels of vitamin A can harm a growing fetus. Symptoms of an overdose include: headaches

fatigue

nausea

dizziness In severe cases, coma and death can result. Vitamin A supplements are available for purchase online. However, people should speak to a doctor before taking these or other supplements. The time a person takes a vitamin can affect its impact. Find out more here about when to take different vitamins.

Vitamin D People obtain vitamin D: naturally through exposure to sunlight or in the diet

through fortified foods

as supplements The body obtains the compounds it needs to make vitamin D from food. It also produces vitamin D when ultraviolet (UV) light meets the skin. Types Vitamin D is not a single substance but a group of compounds collectively known as calciferol. The body absorbs calciferol into the bloodstream and then converts it to calcitriol. Two types occur naturally: vitamin D-3, found in animal fats

vitamin D-2, found in plants, such as mushrooms Function Vitamin D has two main roles in the body: It maintains bone health.

It supports the immune system. Find out more about the health benefits of vitamin D. Dietary sources A person can obtain some vitamin D from the sun, but most people will also need to use other sources, too. The main alternative is food. Dietary sources include: oily fish and fish oils

fortified dairy products, plant-based milks, and cereals

beef liver

eggs How can you get more vitamin D from the sun? Click here to find out. Recommended intake Experts measure vitamin D in international units (IU). Current guidelines recommend that people of all ages intake of 600 IU of vitamin D daily. This is hard to measure, however, as it is not easy for a person to know how much vitamin D they obtain from sunlight. Deficiency A vitamin D deficiency can affect: older adults and children who do not spend much time out of doors

people with darker skin

some people with chronic health conditions

those who live far from the Equator, where winter days are short

those with obesity The main effects of vitamin D deficiency include: osteoporosis, or loss of bone mass osteomalacia, when bones become soft

rickets, when a child’s bones do not develop as they should

increased risk of infection and autoimmunity Learn more about vitamin D deficiency. Overdose It is rare for a person to have too much vitamin D, but using supplements could trigger this. Having too much vitamin D could lead to high levels of calcium in the blood. This can lead to: nausea

headaches

low appetite and weight loss

a buildup of calcium in tissues and blood vessels

heart or kidney damage

high blood pressure Vitamin D supplements are available for purchase in pharmacies and online. A person should speak to their doctor before using these supplements, however.

Vitamin E Vitamin E is an antioxidant that can help the body destroy free radicals. Free radicals are unstable atoms that can cause oxidative stress. Oxidative stress can lead to cell damage, and this can result in cancer and other diseases. Vitamin E may help protect the body from a range of health issues. Types There are eight forms of vitamin E, but only alpha-tocopherol meets humans’ needs, according to the ODS. Function Some reasons why the body needs vitamin E are: as an antioxidant

to boost the immune system

to dilate blood vessels and help prevent clotting Dietary sources Good sources of vitamin E include: wheat germ oil

sunflower seeds and oil

almonds, hazelnuts, and peanuts

spinach and broccoli

kiwi fruit and mango Which foods are good sources of vitamin E? Find out here. Recommended intake Current guidelines recommend people consume the following amounts of vitamin E. Experts measure vitamin E intake in milligrams (mg) AT, but packaging currently uses international units (IU). Age (years) 1–3 4–8 9–13 14 and over Female 6 mg (9IU) 7 mg (10.4 IU) 11 mg (16.4 IU) 15 mg (22.4 IU) Male 6 mg (9IU) 7 mg (10.4 IU) 11 mg (16.4 IU) 15 mg (22.4 IU) The ODS note that, during breastfeeding, a female should consume 19 mg (28.4 IU) each day. Deficiency Vitamin E deficiency is rare, but it can affect people with Crohn’s disease or cystic fibrosis. These conditions affect the liver’s ability to absorb vitamin E. A deficiency can result in: nerve and muscle damage that affects movement and coordination

vision problems

a weakened immune system As vitamin E is an antioxidant, a long-term deficiency could increase the overall risk of various diseases. Click here to find out how to recognize a vitamin E deficiency. Overdose Obtaining vitamin E through natural sources is unlikely to lead to an overdose, although supplement use can increase this risk. People who use blood-thinning medication, such as warfarin (Coumadin) should ask their doctor before taking vitamin E supplements, as these may interfere with blood clotting. Vitamin E supplements are available for purchase in pharmacies and online.

Vitamin K Vitamin K helps the body form blood clots. Blood clotting is essential to prevent excessive bleeding. Types There are several types of vitamin K. The two most common groups are: Vitamin K-1 (phylloquinone), present in green, leafy vegetables and some other plant sources

Vitamin K-2 (menaquinones), present in animal sources and fermented foods There are also synthetic forms and other forms that the body makes. Function Apart from blood clotting, vitamin K may also: lower the risk of heart disease

enhance bone health

reduce the buildup of calcium in the blood Learn more here about why we need vitamin K and where to get it. Dietary sources Food sources of vitamin K-1 and K-2 include: kale

liver

spinach

parsley

butter

egg yolks Learn about 40 foods that provide vitamin K. Recommended intake Experts do not have enough evidence to recommend a specific intake of vitamin K suitable to meet the needs of 97-98% of healthy individuals. Instead, they recommend an adequate intake (AI), an amount assumed to provide nutritional adequacy, as follows: Age (years) 1–3 4–8 9–13 14–18 19 and over Female 30 55 60 75 90 Male 30 55 60 75 120 Deficiency The body is not able to store as much vitamin K as it does vitamin A or D. This means a person needs a regular intake of vitamin K, and there is a higher chance of a deficiency. A vitamin K deficiency may result in: excess bleeding

lower bone density, in the long term Learn more about a vitamin K deficiency here. Overdose Taking high quantities of vitamin K does not appear to lead to adverse effects. However, it can interfere with the use of blood-thinning medications, such as warfarin (Coumadin). Vitamin K supplements are available for purchase in pharmacies and online. However, people should speak to a doctor before using them, especially if they use blood thinners or have a condition that affects blood clotting.