Fat-soluble vitamins are those that are digested and absorbed in the presence of fat. They include vitamins A, D, E, and K. These vitamins are mainly found in foods that contain fats.
Vitamins are usually classified as either water-soluble or fat-soluble. Water-soluble vitamins do not dissolve in fat and are only absorbed in media of water. They include vitamins B complex and C. The four fat-soluble vitamins are perfectly absorbed into your bloodstream when eaten with fatty meals. They help your body function effectively, alongside other health benefits. This article will discuss all the fat-soluble vitamins, their roles in the body, dietary sources, and deficiency symptoms.
Vitamin A is well known for its role in maintaining eyesight. Its deficiency is often associated with night blindness. Contrary to what people know, vitamin A is not a single compound. Instead, it refers to a collection of fat-soluble compounds collectively known as retinoids. The main type of vitamin A is retinol. Retinal and retinoic acid are other forms of this vitamin and are not found easily in foods. Your body produces them naturally.
Vitamin A has several functions in the body. The main function is maintaining vision and stimulating the tear gland to synthesize tear. It also improves immune system, preventing infections. This vitamin is also needed for the growth of hair and body. Its deficiency can lead to hair loss and stunted growth respectively, in children. Vitamin A is solely found in animal-based foods, including butter, liver, and fish liver oil. It can also be found in plant foods including spinach, carrots, and kales.
Just like any other nutrient, vitamin A should be taken in moderation. The recommended daily intake (RDI) of this vitamin varies across ages. Infants should take a maximum of 1667 IU, children should take 1000 IU and not to exceed 2000 IU. Women aged 19-70 years should take 2300 IU, while men of the same age should take 3000 IU. Vitamin A deficiency is characterized by dry eyes, blindness, hair loss, compromised immunity, hyperkeratosis and other skin problems. Vitamin A toxicity or hypervitaminosis A, is a rare condition but a fatal one. To avoid it, stick to the right dosage.
Vitamin D is believed to be obtained from sunlight, and its even tagged ‘sunshine vitamin.’ Its synthesis is triggered by exposing your skin to sunlight. It is needed for various bodily functions including formation of healthy bones. Easy fracturing is the main symptom for its deficiency. Same to vitamin A, vitamin D is used to refer to compounds which are soluble in fat, known as calciferol. They include ergocalciferol (vitamin D2) found in plant foods, and cholecalciferol (vitamin D3) fish oil and eggs. Vitamin D3 is produced when your skin is hit directly by sunlight.
Researchers believe that vitamin D has numerous functions in the body. However, they have only been able to prove few of them. First, vitamin D is used to control the levels of calcium and phosphorus in the blood – two minerals that are essential in bone formation. Vitamin D absorbs them from the eaten food. Second, vitamin D helps in regulating the immune system. Readily available vitamin D in the bloodstream can be converted into calcitriol for immediate use or calcidiol, which is stored for future use.
Your body is able to manufacture enough vitamin D it needs, provided that you expose your skin to sunlight. Unfortunately, many people do not expose themselves to sunlight, and even when they do so, they are fully clothed. Some even use sunscreen to prevent sunburn. While it is healthy to use sunscreen, it only reduces the amount of vitamin D synthesized by the skin. For this reason, dietary sources remain the best source of vitamin D. These include fish oil, mushrooms, and fatty fish. The RDI for vitamin D in both children and adults is 600 IU or 15 mcg.
Vitamin D deficiency is very rare. However, when it gets to severe cases, the individual will need to be hospitalized for management clinically. Certain factors may lead to vitamin D deficiency, including dark skin, low exposure to sun, old age, obesity, and health conditions that inhibits fat absorption. The main symptoms of vitamin D deficiency include easy fracturing, muscle weakness, and brittle bones. Excess intake of vitamin D may be harmful leading to conditions like hyperkalemia and kidney problem.
Vitamin E is a powerful antioxidant. It neutralizes the effects of free radicals, preventing premature aging. It groups together eight antioxidants with similar characteristics, and are divided into tocopherols and tocotrienols. Tocopherols include alpha-, beta-, gamma-, and delta-tocopherol, whereas, tocotrienols include alpha-, beta-, gamma-, and delta-tocotrienol. Up to 90% of vitamin E is made up of alpha-tocopherol.
The main function of vitamin D, is acting as an antioxidant – molecules which are known for prevention of oxidative stress and damaging the free radicals. The antioxidant properties of vitamin D are complemented by vitamin B3, vitamin C, and selenium. It also prevents the blood from clotting by making it thinner. The main dietary sources of this vitamin include nuts, seeds, and vegetable oils. Adults should not exceed 23 IU of vitamin D per day. Lack of vitamin D is characterized by muscle weakness, shuffling gait, and compromised immunity.
Vitamin K is widely known for its role in the process of clot formation. It is used to refer to vitamin K1 (phylloquinone) and vitamin K2 (menaquinone), which are found in plant foods and animal foods, respectively. Other forms of vitamin K are vitamin K3 (menadione), vitamin K4 (menadiol diacetate), and vitamin K5. The main function of vitamin K is coagulation. In fact, the word “K” is for “koagulation.” Other functions include maintenance of bone health and supporting heart health. Its main sources include lettuce, parsley, spinach, and Brussels sprouts. The RDI for vitamin K in women is 90 mcg and in men is 120 mcg.
Fat-soluble vitamins are four and they include vitamin A, vitamin D, vitamin E, and vitamin K. They have different functions in the body, including vision maintenance, bone health maintenance, immune strengthening, and formation of blood clots.