What are Fat soluble vitamins?
Last updated on March 7th, 2023 at 08:48 am
10 minutes read.
Overview
Vitamins are vital micronutrients that cannot be synthesized by your body and the only principal means by which you get vitamins is through your diet.
Vitamins can classify as fat-soluble or water-soluble. Fat-soluble meaning they easily dissolve in fatty substances. For example, fat-soluble which include vitamins A, D, E, and K can easily dissolve in your bloodstream, small intestine, skin tissues, organs, and bone marrow.
As a result, they are found in abundance in animal food like meat, fatty fish, liver, egg, butter, and plants such as dark green vegetables, avocados, bullet pears, carrots, mangoes, red palm oil, and yellow corn. (1)
This article highlights the four fat-soluble vitamins and the food source you can eat to get them in abundance. Feel free to skip ahead:
Vitamin A
Vitamin A plays a key role in maintaining your vision. When your lack vitamin A for a couple of weeks or months your first notice the symptoms in your vision. Symptoms like eye itching, increased eye worms, and eye pain. (2)
Types
Vitamin A is not a single compound. Rather, it is a group of fat-soluble compounds collectively known as retinoids.
The most common dietary form of vitamin A is retinol. Other forms — retinal and retinoic acid — are found in the body, but absent or rare in foods.
Vitamin A2 (3,4-dehydroretinal) is an alternative, less active form found in freshwater fish. (2)
Main role and function of vitamin A
Vitamin A supports many critical aspects of your body function, including:
Vision maintenance. Vitamin A is essential for maintaining the light-sensing cells in your eyes and for the formation of tear fluid. (3)
Immune function. Vitamin A deficiency impairs your immune function, increasing susceptibility to infections. (4, 5)
Body growth. Vitamin A is necessary for cell growth in your body. Deficiency may slow or prevent growth in children. (6)
Hair growth. It is also vital for hair growth. Deficiency leads to alopecia or hair loss. (7)
Reproductive function. Vitamin A maintains fertility and is vital for fetal development. (8,
Source of Vitamin A
There are two main sources of vitamin A: animal sources and plant sources. All the sources of vitamin A need some fat in the diet to aid dissolution.
Plant sources of vitamin A include mangos, papaya, many squashes, carrots, sweet potatoes, and maize (but not the white varieties). Other good sources of vitamin A are red palm oil and Beirut palm oil. (Note: if these oils are boiled to remove their color the vitamin A is destroyed.)
Plant sources contain vitamin A in the form of carotenoids which have to be converted during digestion into retinol before your body can use it. Carotenoids are the pigments that give plants their green color and some fruits and vegetables their red or orange color. (9)
Studies show that overcooking normally reduces the vitamin A contents of these foods. So if you want to get vitamin A in this food don’t overcook them. (9)
In animal sources, vitamin A is found as retinol, the ‘active’ form of vitamin A. Liver, including fish liver, is a very good source.
Other animal sources are egg yolk (not the white) and dairy products such as milk (including human breast milk), cheese, and butter. Meat, from the animal’s muscles, is not a good source.
Vitamin A deficiency
Vitamin A deficiency is rare in developed countries but may be common in developing countries.
However, vegans may be at risk since preformed vitamin A is only found in animal-sourced foods.
Although provitamin A is abundant in many fruits and vegetables, it is not always efficiently converted into retinol, the active form of vitamin A. The efficiency of this conversion depends on your genetics. (10, 11)
A common symptom of early deficiency includes night blindness. As it progresses, it may lead to more serious conditions, such as:
Dry eyes. Severe deficiency may cause xerophthalmia, a condition characterized by dry eyes caused by reduced tear fluid formation (4)
Blindness. Serious vitamin A deficiency may lead to total blindness. In fact, it is among the most common preventable causes of blindness in the world. (12)
Hair loss. If you are vitamin A deficient, you may start to lose your hair. (13)
Skin problems. Deficiency leads to a skin condition known as hyperkeratosis, or goose flesh (14)
Poor immune function. Poor vitamin A status or deficiency makes you prone to infections (5)
Vitamin A toxicity
Overdosing on vitamin A leads to an adverse condition known as hypervitaminosis A. It’s rare but may have serious health effects.
Its main causes are excessive doses of vitamin A from supplements, liver, or fish liver oil. In contrast, a high intake of provitamin A does not cause hypervitaminosis.
At extremely high doses, vitamin A can be fatal. (15)
Healthcare professionals advise against exceeding the upper limit for intake, which is 3,000 mcg of preformed vitamin A per day for adults.
Higher amounts may cause acute hypervitaminosis A in adults. Children can experience harmful effects at much lower amounts. (16)
Individual tolerance varies considerably. Children and people with liver diseases like cirrhosis and hepatitis are at an increased risk and need to take extra care.
Pregnant women should also be especially careful, since high doses of vitamin A may harm the fetus. (17)
Vitamin D
Sources of Vitamin D
Some people call it the sunshine vitamin, vitamin D is produced when your skin when is exposed to sunlight.
It is best known for its beneficial effects on bone health. Deficiency makes you highly susceptible to bone fractures.
Types
Vitamin D is a collective term used to describe a few related fat-soluble compounds.
Also known as calciferol, vitamin D comes in two main dietary forms:
Vitamin D2 (ergocalciferol). This form is found in mushrooms and some plants.
Vitamin D3 (cholecalciferol). This form is found in animal-sourced foods, such as eggs and fish oil, and is produced when your skin is exposed to sunlight.
The main role and function of vitamin D
Vitamin D has numerous roles and functions, but only a few are well-researched. These include the following:
Bone maintenance. Vitamin D regulates the circulating levels of calcium and phosphorus, which are the most important minerals for bone growth and maintenance. It promotes the absorption of these minerals from your diet.
Immune system regulation. It also regulates and strengthens your immune system function. (18)
Once absorbed into the bloodstream, your liver and kidneys change calciferol into calcitriol, which is the biologically active form of vitamin D. It can also be stored for later use in the form of calcidiol.
Vitamin D3 is more efficiently converted into calcitriol than vitamin D2. (19, 20)
Source of vitamin D
Vitamin D is found primarily in two forms, D2 and D3. Vitamin D2 (ergocalciferol) is present in certain foods such as salmon, tuna, and mackerel.
Smaller quantities are present in beef liver, cheese, and egg yolks. Many countries fortify natural milk with vitamin D.
This is a practice implemented to decrease the prevalence of rickets and osteomalacia. Vitamin D3 (cholecalciferol) is synthesized in the skin after exposure to sunlight, hence its nickname the “sunshine vitamin.” (1, 21)
The richest natural sources of vitamin D include fatty fish, fish oil, and mushrooms that have been exposed to sunlight or ultraviolet light.
Vitamin D deficiency
Severe vitamin D deficiency is rare, but mild forms of deficiency or insufficiency are common among people who are hospitalized as well as older adults.
The most well-known consequences of vitam in D deficiency include soft bones, weak muscles, and an increased risk of bone fractures. This condition is called osteomalacia in adults and rickets in children. (22 )
Vitamin D deficiency is also associated with poor immune function, increased susceptibility to infections, and autoimmune diseases. (23, 24)
Other signs of deficiency or insufficiency may include fatigue, depression, hair loss, and impaired wound healing .
Observational studies have also linked low vitamin D levels or deficiency with an increased risk of dying from cancer and an elevated risk of heart attacks. (25, 26)
Vitamin D deficiency is traditionally associated with osteomalacia in adults or rickets in children. Both diseases are characterized by brittle or soft bones.
Vitamin D toxicity
Vitamin D toxicity is very rare.
While spending a lot of time in the sun does not cause vitamin D toxicity, taking high amounts of supplements may harm you.
The main consequence of toxicity is hypercalcemia, a condition characterized by excessive amounts of calcium in the blood.
People are generally advised to avoid exceeding the upper limit of vitamin D intake, which is 4,000 IU per day for adults.
Higher amounts, ranging from 40,000–100,000 IU (1,000–2,500 mcg) per day, may cause symptoms of toxicity in adults when taken daily for 1 or 2 months. Keep in mind that much lower doses may harm young children.
Vitamin E
As a powerful antioxidant, vitamin E protects your cells against premature aging and damage by free radicals.
Types
Vitamin E is a family of eight structurally similar antioxidants that are divided into two groups:
Tocopherols: alpha-tocopherol, beta-tocopherol, gamma-tocopherol, and delta-tocopherol
Tocotrienols: alpha-tocotrienol, beta-tocotrienol, gamma-tocotrienol, and delta-tocotrienol
Alpha-tocopherol is the most common form of vitamin E. It makes up around 90% of the vitamin E in the blood.
Role and function of vitamin E
Vitamin E’s main role is to act as an antioxidant, preventing oxidative stress and protecting fatty acids in your cell membranes from free radicals. (27)
These antioxidant properties are enhanced by other nutrients, such as vitamin C, vitamin B3, and selenium.
In high amounts, vitamin E also acts as a blood thinner, reducing the blood’s ability to clot. (28)
Sources of Vitamin E
Naturally occurring sources of vitamin E include vegetable oils, seeds, nuts, and whole grains. (29)
Other rich sources include avocados, peanut butter, margarine, fatty fish, and fish liver oil.
Vitamin E deficiency
Vitamin E deficiency is uncommon and is never detected in people who are otherwise healthy.
It happens most often when diseases that impair the absorption of fat or vitamin E from food, such as cystic fibrosis and liver disease, are present.
Severe, long-term deficiency may lead to anemia, heart disease, serious neurological problems, blindness, dementia, poor reflexes, and the inability to fully control body movements. (30, 31)
Vitamin E toxicity
Overdosing vitamin E is difficult when it is obtained from natural dietary sources. Cases of toxicity have only been reported after people have taken very high doses of supplements.
Yet, compared to vitamins A and D, overdosing on vitamin E appears to have a less harmful effect, but it still requires medical intervention.
It may have blood-thinning effects, counteracting the effects of vitamin K and causing excessive bleeding. Thus, people who take blood-thinning medications should avoid taking large doses of vitamin E. (32, 33, 34)
Additionally, at high doses of more than 1,000 mg per day, vitamin E may have pro-oxidant effects. That is, it can become the opposite of an antioxidant, potentially leading to oxidative stress. (35)
Vitamin K
Vitamin K plays a key role in blood clotting. Without this essential vitamin, there’s a higher risk of excessive bleeding, which could lead to death.
Types
Vitamin K is actually a group of fat-soluble compounds divided into two main groups:
Vitamin K1 (phylloquinone). Found in plant-sourced foods, phylloquinone is the main form of vitamin K in the diet. (36)
Vitamin K2 (menaquinone). This variety of vitamin K is found in animal-sourced foods and fermented soy products, like natto. Vitamin K2 is also produced by gut bacteria in the colon (37, 38)
Additionally, there are at least three synthetic forms of vitamin K. These are known as vitamin K3 (menadione), vitamin K4 (menadiol diacetate), and vitamin K5.
Role and function of vitamin K
Vitamin K plays an essential role in blood clotting. In fact, the “K” stands for “coagulation,” the Danish word for coagulation, which means clotting.
But vitamin K has other functions as well, including supporting bone health and helping prevent the calcification of blood vessels, potentially reducing the risk of heart disease. (39)
Sources of Vitamin K
Vitamin K has two primary forms, K1 and K2. Vitamin K1 (phylloquinone) is present in green leafy vegetables, cabbage, and cauliflower. Lesser quantities are in fish, meat, and some fruits. The gut microflora synthesizes vitamin K2 (menaquinone). (40)
Vitamin K deficiency
Unlike vitamins A and D, vitamin K is not stored in the body in significant amounts. For this reason, consuming a diet lacking in vitamin K may lead you to become deficient in as little as a week. (41)
People who do not efficiently digest and absorb fat are at the greatest risk of developing vitamin K deficiency. This includes those who have celiac disease, inflammatory bowel disease, and cystic fibrosis.
The use of broad-spectrum antibiotics may also raise the risk of deficiency, as well as very high doses of vitamin A, which seem to reduce vitamin K absorption.
Mega-doses — very large doses — of vitamin E may also counteract the effects of vitamin K on blood clotting (42, 43)
Without vitamin K, your blood will not clot, which increases the risk that even a small wound could cause unstoppable bleeding. Fortunately, vitamin K deficiency is rare, since the body only needs small amounts to maintain blood clotting.
Low levels of vitamin K have also been linked with reduced bone density and increased risk of fractures in women. (44)
Vitamin K toxicity
Unlike the other fat-soluble vitamins, natural forms of vitamin K have no known symptoms of toxicity.
As a result, scientists have not been able to establish a tolerable upper intake level for vitamin K. Further studies are needed.
In contrast, a synthetic form of vitamin K, known as menadione or vitamin K3, may have some adverse effects when consumed in high amounts. (45, 46)
Conclusion
There are four fat-soluble vitamins in the human diet: A, D, E, and K. They are essential for health and play many important roles in the body.
With the exception of vitamin D, most of them are easy to get from a diet that includes a variety of foods, especially if you eat plenty of nuts, seeds, vegetables, fish, and eggs.
These vitamins tend to be abundant in fatty foods, and you can enhance their absorption by adding fat or oil to an otherwise low-fat meal.
Few foods are naturally rich in vitamin D. It’s abundant in fatty fish and fish oil but also formed by your skin when you’re exposed to sunlight.
For this reason, vitamin D deficiency can occur in people who do not eat a diet filled with a variety of nutrient-rich foods and regularly spend time indoors, which may be due to a variety of factors, including medical reasons or personal choice.
While you generally do not need to supplement with vitamins A, E, and K, taking vitamin D supplements is widely recommended.
For optimal health, make sure you get all the fat-soluble vitamins in adequate amounts. If you have questions about your vitamin intake or you’re considering supplementation, talk with a healthcare professional.
I hope you get the value worth your time. I appreciate the time you spend with me. Leave a comment if you find this article helpful. Do you have any questions as regards this topic I didn’t touch here? Feel free to share with me in the comment below.
MEDICAL DISCLAIMER
The content provided in living Good Blog is for informational and educational purposes only. It’s not intended to provide medical advice or take the place of such advice or treatment from a personal doctor. All readers/viewers of this content are advised to consult their qualified health professionals regarding specific health questions. Living Good Blog takes no responsibility for possible health consequences of any person(s) reading or following the information in this educational content. Viewers of this content, especially those taking prescription or over-the-counter medication, should consult their physicians before beginning any nutrition, supplement, or lifestyle program.
