Most of the vitamins needed by humans dissolve in water. But there are four fat-soluble vitamins: they are much better absorbed into the bloodstream when consumed with fat: These are vitamins A, D, E, and K. I will explain what their health benefits are and what are the main sources.
Vitamin A
This vitamin supports many functions of the body:
– vision (necessary for the light-sensitive cells of the eyes and for the formation of lacrimal fluid);
– immune function;
– cell growth;
-Hair Growth (deficiency leads to hair loss);
– reproductive function and importance for the development of the fetus.
Food sources
Vitamin A is found only in animal food sources, mainly liver, fish oil and butter:
Provitamin A can be obtained from carotenoids, which are antioxidants found in plants. The most effective beta-carotene is found in abundance in carrots, kale, spinach, red, yellow and orange vegetables, and some dark green leafy vegetables.
Consumption rate
The recommended daily intake of vitamin A is 900 mcg for men and 700 mcg for women. For infants under one year old – 400-500 mcg, for children from 1 to 3 years old – 300 mcg, from 4 to 8 years old – 400 mcg, from 9 to 13 years old – 600 mcg.
Vitamin A deficiency
Vitamin A deficiency is rare in developed countries.
However, it can be experienced by vegans, as vitamin A, ready for consumption, is found only in animal food sources. Although provitamin A is found in fruits and vegetables, it is not always efficiently converted to Retinol, the active form of vitamin A (effectiveness depends on a person’s genetics).
A diet based on refined rice and potatoes, with a lack of fat and vegetables, can cause a lack of this vitamin.
Sign of early deficiency – night blindness (poor twilight vision). Deficiency consequences: dry eye syndrome, blindness, hair loss, skin problems (hyperkeratosis, or goose bumps); suppression of immune function.
Overdose
Hypervitaminosis A is rare, but with serious consequences. The main reasons are excessive intake of vitamin A from dietary supplements, liver or fish oil. But the consumption of provitamin A does not cause hypervitaminosis.
The main symptoms are: fatigue, headaches, irritability, abdominal pain, joint pain, lack of appetite, vomiting, blurred vision, skin problems and inflammation in the mouth and eyes, liver damage, bone loss, hair loss.
The upper limit of consumption is 900 mcg per day for adults.
Vitamin D
There are two well-known functions of vitamin D (and in fact there are many more):
– maintenance of bone tissue: Vitamin D helps in the absorption of calcium and phosphorus from the diet and regulates the levels of these most important minerals for bones;
– strengthening the immune system.
Types
Vitamin D, or calciferol, is a collective term for several fat-soluble compounds. It exists in two main forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).
Once absorbed into the blood, the liver and kidneys convert calciferol to calcitriol, a biologically active form of vitamin D. It can also be deposited in the body for later use as calcidiol.
Sources of Vitamin D
The body produces the right amount of vitamin D3 when a significant portion of the skin is regularly exposed to sunlight. But many people spend little time in the sun or fully clothed even in hot, sunny weather. And sunscreen, while recommended for everyone, reduces the amount of vitamin D produced by the skin. For example, for several years now I have lived exclusively in hot sunny countries and nevertheless experienced a lack of vitamin D. I described this in more detail in a separate article.
As a result, vitamin D needs to be replenished from the diet.
Few foods naturally contain vitamin D. The best food sources are oily fish, fish oil, and eggs (vitamin B3). Mushrooms exposed to UV light may also contain vitamin D2.
Some of the most powerful sources of vitamin D are:
Consumption rate
For children and adults, the daily intake of vitamin D is 15 mcg, for the elderly – 20 mcg.
Vitamin deficiency D
Severe vitamin D deficiency is rare.
Risk factors for “mild” deficiency include: dark skin color, old age, obesity, lack of exposure to sunlight, and diseases that interfere with fat absorption.
Consequences of vitamin D deficiency: decreased bone density, weak muscles, increased risk of fractures, weak immunity. Signs also include fatigue, depression, hair loss, and slow wound healing.
Vitamin overdose D
Toxicity is very rare. Long-term exposure to the sun does not cause hypervitaminosis, but a large amount of supplementation can lead to hypercalcemia – an excessive amount of calcium in the blood.
Symptoms: headache, nausea, loss of appetite and weight, fatigue, kidney and heart damage, high blood pressure, fetal abnormalities in pregnant women. The upper limit of the daily intake for adults is 100 mcg.
Vitamin E
A powerful antioxidant, vitamin E protects cells from premature aging and free radical damage. Antioxidant properties are enhanced by vitamins C, B3 and selenium. In large quantities, vitamin E thins the blood (reduces blood clotting).
Types
Vitamin E is a family of eight antioxidants: tocopherols and tocotrinols. Alpha-tocopherol is the most abundant form of vitamin E, accounting for about 90% of this vitamin in the blood.
Sources of
The most powerful sources of vitamin E are certain vegetable oils, seeds and nuts, avocados, peanut butter, oily fish, and fish oil.
Consumption rate
For adults, the recommended daily intake of vitamin E is 15 mg, for children and adolescents, the dosage ranges: 6-7 mg for children 1-8 years old, 11 mg for children 9-13 years old, 15 mg for children 14-18 years old.
Vitamin E deficiency
Deficiency is rare, usually in conditions that prevent the absorption of fat or vitamin E from food (cystic fibrosis, liver disease).
Vitamin E deficiency symptoms: muscle weakness, difficulty walking, tremors, vision problems, weak immune function, numbness.
Long-term deficiency can lead to anemia, heart disease, severe neurological problems, blindness, dementia, impaired reflexes, and an inability to fully control body movements.
Vitamin E overdose
Overdose is unlikely, it occurs only due to the large number of additives. Potential consequences are blood thinning, reduced effectiveness of vitamin K, and heavy bleeding. People taking blood-thinning medications should avoid high doses of vitamin E.
Vitamin K
Vitamin K plays a key role in the blood clotting process. Without it, you risk dying from bleeding. It also supports healthy bones and helps prevent calcification of blood vessels, reducing the risk of heart disease.
Types
Vitamin K is a compound divided into two main groups. Vitamin K1 (phylloquinone) is the main form of vitamin K in the diet, and vitamin K2 (menaquinone).
Food sources
Vitamin K1 is found in plant-based food sources (primarily green leafy vegetables):
And vitamin K2 is found in small amounts in fatty animal products (egg yolk, butter, liver) and in fermented soy products. It is also produced by gut bacteria in the colon.
Vitamin K intake
Adequate vitamin K intake is 90 mcg for women and 120 mcg for men. For children, the value ranges from 30 to 75 mcg, depending on age.
Vitamin K deficiency
Unlike vitamins A and D, vitamin K does not accumulate in the body. A lack of vitamin K in the diet leads to a deficiency in just a week.
In the risk zone, first of all, people whose body is not able to effectively absorb fats (due to celiac disease, inflammatory bowel disease, cystic fibrosis).
Broad-spectrum antibiotics and very high doses of vitamin A, which reduce vitamin K absorption, can increase the risk of deficiency.
Excessive doses of vitamin E can counteract the effects of vitamin K on blood clotting. Without vitamin K, blood will not clot, and even a small wound can lead to irreparable bleeding.
Low vitamin K levels are also associated with decreased bone density and the risk of fractures in women.
Vitamin overdose K
Natural forms of vitamin K are non-toxic.