There are four types of fat-soluble vitamins in the human diet – vitamin A, D, E and K. They are stored in the body for a longer period of time as compared to water-soluble vitamins. Thus, they pose a greater risk of toxicity when consumed in excess amounts. Eating a well-balanced and wholesome diet will not lead to toxicity in healthy individuals. (1)
Let’s get down to the details of fat-soluble vitamins:
Vitamin A is a fat-soluble vitamin which is extremely important for healthy eyes and skin. It is available in two forms in nature; retinol which is the active form of vitamin A and it can be directly used by the body when vitamin A rich foods or supplements are consumed.
Beta-carotene is the indirect form which gets converted to the active form of vitamin A in the body. Once both forms get active, they play various essential roles in the body, such as-
Vitamin A contains chemical structures that promote healthy vision, protect the cornea and reduce the risk of cataracts, dry eyes and age-related macular degeneration (AMD). These chemical structures trigger light sensors in the eye and enable vision and improve visual acuity.
Vitamin A promotes growth and regeneration of skin cells. It improves blood flow towards the skin and prevents premature aging of the skin. It is also required for quick wound healing and cell growth.
Studies have found that deficiency of vitamin A is associated with poor immunity and high risk of acquiring infections. Regular consumption of vitamin A regulates immune cells and lowers the level of inflammation and inflammatory mediators. (2, 3, 4)
The recommended dietary allowance for retinol for adults is 600 micrograms/ day and for beta-carotene is 4800 micrograms/ day.
Also Read: 7 Amazing Health Benefits of Vitamin A
Signs and Symptoms of Vitamin A Deficiency
- Xerophthalmia- dryness, and inflammation of the cornea and conjunctiva
- Night blindness
- Bitot’s spots- build-up of keratin in the conjunctiva
- Poor immunity
- Dry, scaly and rough skin
- Respiratory and gastrointestinal tract infections
Read in Detail Here: Vitamin A Deficiency Symptoms
Dietary Sources of Vitamin A
Foods rich in Vitamin A include:
- Organ meat
- Fish liver oil
- Whole milk
- Curd made from whole milk
- Dark green leafy vegetables
- Sweet potato
- Yellow-orange bell peppers
Vitamin D or the ‘sunshine vitamin’ is crucial for healthy bones. It enhances the absorption of calcium and thus along with calcium, it helps in keeping the bones strong.
Besides maintaining bone health, vitamin D plays a vital role in strengthening the immune system. Deficiency of vitamin D is linked to the onset of various infections and illnesses. It enhances protective immunity and protects the body against attack by harmful foreign particles.
Vitamin D is also known as a potent anti-cancer agent. Studies have revealed that vitamin D might help in the management of prostate, colon and breast cancers. It inhibits the growth of cancer cells and suppresses the formation of tumors. Furthermore, it reduces the circulation of inflammatory compounds in the body. (5, 6)
The recommended dietary allowance for vitamin D for adults is 10 IU/ day.
Also Read: 9 Amazing Health Benefits of Vitamin D
Signs and Symptoms of Vitamin D Deficiency
- Muscle pain
- Tiredness and fatigue
- Depression and anxiety
- Poor bone health and bone loss
Read in Detail Here: Vitamin D Deficiency Symptoms
Dietary Sources of Vitamin D
- Organ meat
- Fatty fish such as salmon, mackerel, and tuna
- Egg yolks
- Foods fortified with vitamin D
Vitamin E, a fat-soluble vitamin is a potent antioxidant in nature. It protects the cells against free radical damage and prevents the onset of diseases induced by oxidative stress.
Vitamin E is present in nature in 8 different forms and alpha-tocopherol is the only form which is preferentially absorbed and used by the body.
Attack by the free radicals can break down healthy eye tissue and damage the vision. As vitamin E is a powerful antioxidant, it scavenges the free radicals and delays cataract formation.
Oxidative stress can damage the brain cells, impair memory, decline cognitive function and may lead to mood swings. Consuming foods rich in vitamin E can protect the brain cells against damage caused by oxidative stress. Vitamin E further improves cognitive performance and boosts memory.
Vitamin E improves skin elasticity, restores hydration, moisturizes skin and protects it against free radical attack. Thus, it prevents premature skin aging and fights signs of aging such as fine lines, dark spots, and wrinkles. (7, 8, 9)
The recommended dietary allowance for vitamin E for adults is 8-10 milligrams tocopherol/ day.
Also Read: 7 Amazing Health Benefits of Vitamin E
Signs and Symptoms of Vitamin E Deficiency
- Muscle weakness
- Lack of coordination of muscles
- Poor cognitive function
- Hair loss
- Rough and scaly skin
Read in Detail: Vitamin E Deficiency Symptoms
Dietary Sources Of Vitamin E
- Sunflower seeds
- Wheat germ
- Vegetable oils
Vitamin K, a fat-soluble vitamin is named after ‘KOAGULATION’, a German word for blood clotting. It is present in three different forms in nature:
- Vitamin K1 or phylloquinone, which is found in plant-based foods.
- Vitamin K2 or menaquinone, which is made from vitamin K1.
- Vitamin K3 or menadione, which is synthesized from bacteria and micro-organisms.
Vitamin K is best known for its role in normal blood coagulation. When your skin gets punctured or when you bleed, blood clots become necessary to stop bleeding. The protein coagulation factors that play a vital role in blood clotting require vitamin K for their activity.
Low vitamin K status is associated with low bone mineral density, high risk of osteoporosis and easy bone fractures. Vitamin K inhibits the excess formation of ‘osteoclasts’, a type bone cell that breaks down bone tissue and promotes demineralization. Bones contain proteins that depend on vitamin K for their proper functioning. Vitamin K further improves the bone turnover profile and positively affects calcium balance. (10, 11)
Also Read: 8 Amazing Health Benefits of Vitamin K
Signs and Symptoms of Vitamin K Deficiency
- Easy fractures and poor bone health
- Excessive blood loss from wounds
- Easy bruising
- Heavy menstrual periods
- Nose bleeding
- Bleeding within the gastrointestinal tract
Read in Detail Here: Vitamin K Deficiency Symptoms
Dietary Sources Of Vitamin K
- Mustard greens
- Collard greens
- Turnip greens
- Beet greens
- Brussels sprouts
Note: These fat-soluble vitamins are absorbed in the body in the presence of fat. Hence, while cooking foods rich in fat-soluble vitamins, a source of fat, such as cooking oil should be added to it.