Fat-Soluble Vitamins: Functions, Sources, and Deficiency Risks

Vitamins encourage your body to function appropriately. These are essential for various bodily processes such as growth and development, immune system function, cell function, strong bones, improved vision, wound healing, energy production, and metabolism etc. Vitamins are categorized as water-soluble vitamins and fat-soluble vitamins. Vitamin C and B Vitamins are water-soluble vitamins. Vitamins A, D, E, and K are fat-soluble vitamins. A lack of vitamins can cause deficiencies and various health problems. Your body obtains vitamins from a variety of healthy foods as part of your dietary intake; however, you can consider supplements depending on your medical conditions and consultation with a doctor.

This article highlights the fat-soluble vitamins, their functions, various food sources, and deficiency risks, so don’t miss out on the valuable information.

Vitamins are divided into two groups. Water-soluble and fat-soluble vitamins have different functions in the body depending on bodily requirements. Fat-soluble vitamins (Vitamins A, D, E, and K) are stored in the body's fatty tissue and liver in the body, making it particularly important for individuals with fat malabsorption syndromes . These vitamins are best absorbed with healthy fats.

Water-soluble vitamins are Vitamin C and B vitamins, including B1 (Thiamin), B2 (Riboflavin), B3 (Niacin), B4 (Pantothenic acid), B6 (Pyridoxine), B7 (Biotin), B9 (Folic acid or folate), and B12 (Cobalamin). The body doesn’t store water-soluble vitamins. The leftover or excess amounts of these vitamins are released through the urine. For that reason, these should be consumed regularly to prevent lower amounts or deficiencies. Exceptionally, B12 is stored in the liver for some years.

Fat-soluble vitamins, including Vitamin A, Vitamin D, Vitamin E, and Vitamin K, do not dissolve in water. These are absorbed in the presence of fats and stored in the liver and fatty tissue. These vitamins can remain in your body’s fat and can be stored for up to 6 months until your body requires and uses them, which is essential for maintaining healthy teeth . Each fat-soluble vitamin has a significant function and is found in various foods.

Fat-soluble vitamins are found in dairy and animal-based products, along with fruits and vegetables. These vitamins play a significant role in your vision health, immunity, bone health, blood clotting, and can also impact the risk of heart disease. The optimal absorption of fat-soluble vitamins necessitates dietary fats. Fat-soluble vitamins dissolve in oils and fats. If you consume fat-soluble vitamin-rich foods, the fat in those foods encourages absorption and transports them into the bloodstream.

After absorption, fat-soluble vitamins are wrapped into chylomicrons, fat-containing particles that convey them through the lymphatic system into the bloodstream, potentially offering protection against skin cancer. Your body stores these vitamins in the liver and fatty tissues and reserves the supply when required.

Let us explore the list of fat-soluble vitamins and understand their functions, dietary sources, and deficiency risks.

Vitamin A is also called Retinol and plays various important roles in the body. Usually, this fat-soluble vitamin is associated with eye health and vision. Vitamin A can be derived from provitamin A carotenoids.

• Vitamin A is vital for proper vision.
• It aids reproductive functions.
• It encourages cell growth and organ maintenance.

Sources: Vitamin A is found in both animal-based products as well as plant-based products, particularly in the form of beta carotene . Eat plenty of vegetables to meet your Vitamin A needs. The top Vitamin A sources are dairy products (yogurt, cheese, and cream), liver, beef, some fish, egg yolk, fortified grains, carrots, broccoli, squash, cantaloupe, dark-colored fruits, and dark green leafy vegetables.

Deficiency risks and symptoms: Although Vitamin A deficiency is rare, it is found in people lacking food variety and those dominated by white potatoes and rice. Vitamin A deficiency symptoms include night blindness, vulnerability to infections, impaired immune system, and severity may lead to blindness. The risk factors for vitamin A deficiency include insufficient intake of Vitamin A-containing food, malabsorption, infants, children, pregnant women, and breastfeeding mothers, and people with liver conditions.

Vitamin D is also known as the “Sunshine Vitamin”. It supports your bone health and immune function. Vitamin D collaborates with calcium to strengthen your bones, and it helps muscle function and improves immune health. As you age, your body requires more Vitamin D to maintain healthy muscles and bones. Vitamin D has a crucial role in sustaining overall well-being. It is calcium absorption, immune function, cognitive function, and muscle function.

• It supports calcium and phosphorus absorption.
• Vitamin D helps in bone mineralization.
• It reduces the risk of developing autoimmune diseases.
• It prevents muscle weakness.

Sources: Your body creates Vitamin D as sunlight hits your skin directly. Vitamin D sources are sun exposure, fortified foods, cod liver oil, egg yolk, fatty fish (salmon, herring, mackerel), fortified cereals, and fortified dairy products.

Risk of deficiency: Mild deficiency or insufficiency of Vitamin D is common in older adults and hospitalized patients. Severe Vitamin D deficiency is uncommon. Risk factors of Vitamin D deficiency include older age, darker skin tone, obesity, low sun exposure, and medical conditions that impair fat absorption. Common consequences of Vitamin D deficiency include weak muscles, soft bones, and a greater risk of bone fractures. Symptoms of deficiency include impaired wound healing, hair loss, depression, and fatigue.

Vitamin E is a powerful antioxidant that protects cells from free radicals and plays an important role in skin health and immune function. It supports immune health and prevents blood clots. Vitamin E helps fight carcinogens and certain cancer-causing agents.

• It aids healthy blood flow.
• It neutralizes free radicals.
• It strengthens the defense system of the body.
• It prevents blood clot formation in arteries.

Sources: Vitamin E is found in leafy greens, vegetable oils (wheat germ, safflower, and sunflower), margarine, nuts, seeds, fortified foods, red bell peppers, spinach, avocados, mango, and papaya.

Risks of deficiency and effects: Vitamin E deficiency is rare and is never detected in otherwise healthy people. Although it's not common, it may cause various health problems such as a weakened immune system, vision problems, muscle damage, and nerve damage. Vitamin E deficiency symptoms include tremors, muscle weakness, walking difficulty, numbness, vision problems, and poor immunity.

Vitamin K is important for bone formation and blood clotting; however, a deficiency in vitamin K can lead to serious health issues. It acts as a cofactor for proteins engaged in these processes and also contributes to heart health and cognitive function. A lack of Vitamin K can make you vulnerable to easy bruises and bleed more. It is essential for bone metabolism, which helps maintain strong bones, especially in older adults.

• Vitamin K may aid cognitive function.
• Evidence shows that it can improve heart health.
• It is vital for wound healing due to its involvement in blood clotting.

Sources: Green leafy vegetables, cabbage, cauliflower, broccoli, Brussels sprouts, cereals, fermented foods, blueberries, figs, dairy products, meat, fish, beef, liver, and eggs.

Deficiency risks: Unlike other fat-soluble vitamins, Vitamin K is not significantly stored in the body. Thus, lacking a Vitamin K-rich diet may lead to deficiency. Mainly, people who cannot digest and absorb fat efficiently have a greater risk of experiencing Vitamin K deficiency. Intake of broad-spectrum antibiotics can also increase the risk of Vitamin K deficiency. Low levels of Vitamin K are associated with reduced bone density and a greater risk of fractures in women. Vitamin K deficiency in patients taking blood-thinning medication (Warfarin) can cause increased bruising and bleeding. Symptoms of low levels of Vitamin K include excessive bruising or bleeding, bone problems (osteoporosis), and internal bleeding in infants that can be fatal.

Vitamins are mainly classified as fat-soluble (Vitamin A, D, E, and K) and water-soluble vitamins (Vitamin C and B Vitamins) depending on the way these are absorbed stored, and eliminated by the body. Fat-soluble vitamins are stored in fatty tissues and the liver and necessitates dietary fats for absorption while water-soluble vitamins are not stored in the body and the extra amounts are eliminated through urine.

Water-soluble vitamins (Vitamin C and B-complex vitamins) are vital for several bodily functions such as nerve function, immune health, and energy metabolism. B vitamins work as coenzymes and support various metabolic processes, including red blood cell formation, energy production, and nerve function.

• Thiamin (B1): Nerve function and carbohydrate metabolism.
• Riboflavin (B2): Healthy skin and vision, and energy metabolism.
• Niacin (B3): Energy production, proper nervous system function, and healthy skin.
• Pantothenic acid (B5): Hormone production and energy production.
• Pyridoxine (B6): Nerve function, red blood cell formation, and protein metabolism.
• Biotin (B7): Energy metabolism and healthy hair, skin, and nails.
• Folate (B9): Cell growth, red blood cell formation, and DNA synthesis
• Vitamin C (Ascorbic Acid): collagen production, wound healing, and better immune function.

People with malabsorption disorders, certain medical conditions, limited sun exposure, and those who consume a diet that lacks food variety are at risk of developing fat-soluble vitamin deficiencies.

• Malabsorption disorders (liver disease, cystic fibrosis, inflammatory bowel disease).
• Limited sun exposure (dark skin people and elderly people).
• Certain health conditions (chronic pancreatitis).
• Diets lacking a variety of foods.
• Children and infants.
• Pregnant and breastfeeding women.
• Elderly people with a reduced ability to produce Vitamin D.

Various vitamin deficiencies can cause various health conditions, and the exact symptoms of vitamin deficiencies depend on the particular vitamin lacking in the body. However, common symptoms of vitamin deficiencies include vision problems, anemia, skin changes, weakness, fatigue, anemia, clotting issues, bone loss, and immune dysfunctions.

Vision problems (night blindness, dryness in eyes, risk of blindness), Skin problems (dry, damaged skin and skin infections), hair thinning, improper bone growth, slow wound healing, and increased risk of infections can occur, especially if there is too much vitamin from supplement .

Muscle weakness, bone pain, increased risk of fractures, fatigue, lack of energy, weakness, mood swings, anxiety, depression, vision problems, immune system problems, hair loss, frequent illness, and loss of appetite.

Neurological problems, vision problems, dry skin, brittle hair, slow wound healing, immune dysfunction, muscle weakness, anemia, difficult body movements, fatigue, upset stomach.

Excessive bleeding, easy bruising, internal bleeding, prolonged bleeding after injury, bone problems, fatigue, irritability, and sleep disturbance.

You should not take too many fat-soluble vitamins as there are risks of high doses of fat-soluble vitamins, which can interfere with the body’s ability to synthesize vitamin properly . High doses can be toxic and symptoms may include birth defects, organ damage, skin issues, fatigue, and nausea.

Excessive intake of Vitamin A, particularly through supplements can cause Hypervitaminosis A involving symptoms such as nausea, headaches, dizziness, blurred vision, liver damage, intracranial pressure, and even coma. Long-term high doses may cause hair loss, dry and itchy skin, fatigue, weight loss, anorexia, and bone and joint pain.

Excessive intake of Vitamin D leads to hypercalcemia, and abnormally high levels of calcium in blood and the symptoms include nausea, vomiting, excessive thirst, frequent urination, and constipation. It can cause weak bones, bone pain, kidney stones, fatigue, and muscle weakness.

Too much intake of Vitamin E can meddle with blood clotting processes, potentially causing hemorrhaging. Other symptoms include fatigue, nausea, diarrhea, and stomach cramps.

Vitamin K is vital for blood clotting, and excessive consumption can interact with the effects of certain medications, including anticoagulants, leading to an increased risk of bleeding. Other symptoms include fatigue, nausea, diarrhea, and stomach cramps.

Fat-soluble vitamins are absorbed in the presence of healthy dietary fat that is healthy such as nuts, seeds, olive oil, avocados, and vegetable oil. The recommended dietary allowance for adults is 700- 900 mcg RAE for Vitamin A, 15 mcg for Vitamin D, 15 mg for Vitamin E, and 70-120 mcg for Vitamin K.

Vitamin A: 700 mcg RAE per day for women and 900 mcg RAE for men. The tolerable upper intake level for adults is 3000 mcg RAE per day.

Vitamin D: The recommended daily intake for adults is 15 mcg per day and for older adults 20 mcg per day.

Vitamin E: The recommended daily allowance is 14mg alpha-tocopherol equivalents per day. The tolerable upper intake for adults is 1000 mg per day.

• Malabsorption syndromes (liver diseases, cystic fibrosis, celiac disease, and Crohn’s disease).
• Chronic diseases (chronic, renal, heart, or respiratory failure, and cancer).
• Protein losses (nephrotic syndromes, exudative enteropathies).
• Chronic inflammatory conditions (systemic lupus erythematosus, Sjögren’s syndrome, acquired immunodeficiency syndrome).
• Medications affecting absorption (orlistat, corticosteroids, antiepileptic drugs, and mineral oils)
• Blood thinning medications (warfarin)
• Unbalanced or insufficient diets
• Pregnancy and breastfeeding
• Excessive alcohol consumption

Eat a balanced diet including dairy products, eggs, leafy greens, oily fish, fruits, vegetables, good proteins, whole grains, and healthy fats to obtain fat-soluble vitamins in adequate amounts.

Fat-soluble vitamins need dietary fats for absorption and are stored in the liver and fatty tissues, so you don’t need to eat them daily. Eat a healthy and nutrient-rich diet incorporating healthy fats, fatty fish, dairy products, certain oils, fruits, and leafy green vegetables. Exces