Fat Soluble Vitamins (DAKE) Science, Foods and Benefits
Fat soluble vitamins (A, D, E, K) are crucial for brain function, heart health, and mineral absorption throughout the body. These essential nutrients dissolve in fat and can be stored in the liver and fatty tissues, supporting everything from vision and immunity to bone strength.
Fat Soluble Vitamins
Fat-soluble vitamins (A, D, E, and K) are essential nutrients that dissolve in fat and can be stored in the body’s fatty tissue and liver. These vitamins play crucial roles in maintaining overall health and bodily functions.
These vitamins work synergistically to help transport and use minerals in the body, supporting energy creation, tissue recovery, and muscle function. Deficiency in vitamins like D, A, K, and E reduces the body’s ability to create energy and function properly. These fat-soluble vitamins work together to maintain optimal health, supporting everything from vision to immunity to bone strength.
What are fat vs water-soluble vitamins?
Storage: Fat-soluble vitamins dissolve in fat and can be stored in the body’s liver and fatty tissues, while water-soluble vitamins dissolve in water, are excreted through urine, and instead of being stored in the body.
Absorption: Fat-soluble vitamins require fat for proper absorption, while water-soluble vitamins are directly absorbed into the bloodstream.
Toxicity: Fat-soluble vitamins pose a greater risk for toxicity when consumed in excess because they accumulate in the body.
What helps absorb fat-soluble vitamins?
Dietary fat is essential for the absorption of fat-soluble vitamins. These vitamins are absorbed along with dietary fats in the small intestine. Interestingly, you don’t need to consume fat simultaneously with the vitamins – research shows you can consume fat up to 12 hours after vitamin intake and still achieve absorption. (1) (2)
What are the 4 main fat-soluble vitamins?
The four fat-soluble vitamins are:
- Vitamin A
- Vitamin D
- Vitamin E
- Vitamin K
What happens to excess fat-soluble vitamins?
Excess fat-soluble vitamins are stored in the body’s liver and fatty tissues rather than being excreted. (3) (4) Because of this storage capability, taking megadoses of fat-soluble vitamins (especially through supplements) can lead to toxicity. This can cause various health problems depending on the vitamin.
What happens if you don’t get enough fat-soluble vitamins?
Deficiencies in fat-soluble vitamins can cause various health problems: (5)
Vitamin A deficiency: Night blindness, reduced immunity, dry skin, and susceptibility to infections
Vitamin D deficiency: Bone pain, fractures, osteomalacia, rickets, muscle weakness, and increased fall risk
Vitamin E deficiency: Neuropathy, impaired vision, and slower wound healing
Vitamin K deficiency: Hemorrhagic syndrome (bleeding disorders), osteopenia, and muscle weakness
What is the role of fat soluble vitamins?
Each fat-soluble vitamin serves specific functions:
Vitamin A: Essential for vision, immune function, reproduction, cell differentiation, and bone growth
Vitamin D: Maintains bone health, supports immune function, helps muscles move, and reduces inflammation
Vitamin E: Acts as an antioxidant protecting cells from damage, boosts immune function, and prevents blood clotting in vessels
Vitamin K: Enables blood clotting and helps make proteins for healthy bones and tissues
Which foods are highest in fat soluble vitamins?
Vitamin A
- Animal sources: Liver, beef, fish, egg yolks, dairy products
- Plant sources: Sweet potatoes, carrots, dark leafy greens, mangoes, squash
Vitamin D
- Fatty fish (salmon, mackerel, sardines)
- Fish liver oils (cod liver oil)
- Fortified milk and cereals
- Egg yolks
Vitamin E
- Vegetable oils (wheat germ, sunflower, safflower)
- Nuts and seeds
- Avocados
- Dark green vegetables
- Wheat germ
Vitamin K
- Dark leafy greens (spinach, kale)
- Broccoli, Brussels sprouts, cabbage
- Cauliflower
- Fish, liver, beef, eggs
Vitamin D
Vitamin D, often called the sun vitamin, supports numerous functions in the body. This fat-soluble vitamin exists in multiple forms, with vitamin D3 (cholecalciferol) being the primary type produced in human skin upon sun exposure.
Functions in the Body
Vitamin D’s primary function is promoting calcium absorption in the gut and maintaining adequate calcium and phosphate concentrations. This enables normal bone mineralization and prevents muscle spasms (6). Without sufficient vitamin D, bones become thin, brittle, or misshapen, resulting in poor bone development and higher risk of injury.
Beyond skeletal health, vitamin D has several other vital roles:
- Immune System Support: Vitamin D triggers immune cells to produce antibodies, modulating both innate and adaptive immune responses. (7)
- Muscle Function: There’s a correlation between vitamin D deficiency and muscle weakness, pain, and atrophy (8). Vitamin D supplementation has shown positive impacts on physical performance and injury prevention, particularly in deficient individuals. (9)
- Cellular Processes: Vitamin D modulates cell growth, neuromuscular function, and glucose metabolism. (6)
Vitamin D Deficiency
Vitamin D deficiency is a global health concern. A comprehensive study analyzing data from > 7 million participants across 81 countries found that 15.7% of people have severe deficiency (<30 nmol/L), 47.9% have deficiency (<50 nmol/L), and 76.6% have insufficient levels (<75 nmol/L). (10)
Symptoms of deficiency include: (11) (12)
- Bone pain, weakness and deformity
- Muscle aches and weakness
- Fatigue or tiredness
Long-term deficiency increases the risk of:
- Osteoporosis
- Certain cancers
- Type 2 diabetes
- High blood pressure
- Infectious diseases
- Autoimmune diseases
Source of Vitamin D
Sunlight
The sun is the most natural and effective source of vitamin D. When skin is exposed to UVB radiation (290-315 nm), 7-dehydrocholesterol in the epidermis absorbs this energy and converts to previtamin D3, which then isomerizes into vitamin D3 (13).
Several factors affect vitamin D production from sunlight:
- Time of day: Midday sun produces more vitamin D
- Skin exposure: More exposed skin means more vitamin D production
- Skin color: Darker skin requires longer exposure
- Season and latitude: Northern regions and winter months provide less UVB radiation (14)
For most people with lighter skin, 10-15 minutes of daily sun exposure during summer months can provide sufficient vitamin D. Those with darker skin may need 25-40 minutes (15). However, prolonged exposure should be avoided to prevent sunburn and skin cancer risk.
Food Sources
Few foods naturally contain significant amounts of vitamin D. The richest sources include:
- Oily fish: Salmon, sardines, herring, mackerel, and rainbow trout
- Red meat and liver
- Egg yolks
- Fortified foods: In many countries, products like milk, plant-based milks, breakfast cereals, yogurt, margarine, and orange juice are fortified with vitamin D.
Supplements
Vitamin D supplements are widely available in two forms: D2 (ergocalciferol) and D3 (cholecalciferol). Most evidence suggests D3 is more effective at raising blood levels of vitamin D, particularly in higher doses or for longer-term use.
Most health authorities recommend maintaining serum 25-hydroxyvitamin D (25OHD) concentrations above 50 nmol/L (20 ng/mL) for optimal bone health. Severe deficiency is typically defined as levels below 30 nmol/L (12 ng/mL). (16)
While supplementation benefits those with deficiency, large clinical trials like VITAL, ViDA, and D2d (involving over 30,000 participants) have shown that vitamin D supplementation in already vitamin D-replete adults (>50 nmol/L) does not prevent certain diseases like cancer, type 2 diabetes, or cardiovascular events. (16)
Conclusion
Vitamin D is essential for multiple bodily functions, from bone health to immune system regulation. While sunlight remains the most natural source, dietary intake and supplements are important, especially for those with limited sun exposure or increased risk factors for deficiency.
Understanding your vitamin D status through blood testing and consulting healthcare providers about appropriate supplementation can help maintain optimal levels of this crucial nutrient.
Vitamin E
Vitamin E is a fat-soluble vitamin that plays crucial roles in the body, primarily as an antioxidant. It comprises eight chemical forms, with alpha-tocopherol being the most biologically active form in humans.
Functions in the Body
Vitamin E serves multiple essential functions:
- Antioxidant Protection: It protects cells from damage caused by free radicals, which are believed to play a role in aging-related conditions (6) (17).
- Immune System Support: It helps maintain a strong immune system against viruses and bacteria (17).
- Blood Health: Vitamin E aids in forming red blood cells and widening blood vessels to prevent blood clotting (17).
- Cell Signaling: It facilitates cell-to-cell interactions and regulates gene expression (6).
- Anti-inflammatory Effects: Research shows vitamin E supplementation, particularly α-tocopherol, can reduce inflammatory markers like C-reactive protein (CRP) (18).
- Membrane Protection: It increases the orderliness of membrane lipid packaging, allowing tighter packing and greater cell stability (19).
Vitamin E Benefits
Vitamin E has been associated with several health benefits
- Cardiovascular Health: Studies are mixed, with some showing no effect and others showing a 24% and 26% decrease in cardiovascular death and major cardiac events, respectively. (20) (21)
- Cognitive Function: Vitamin E may delay the progression (and slow down functional decline) of Alzheimer’s disease, especially during mild to moderate stages. (22) (23)
- Reproductive Health: Studies suggest that pregnancy complications like miscarriage and premature birth may be associated with vitamin E deficiency. (22) (24)
- Skin Health: Vitamin E may protect and moisturize the skin, and prevent sun damage, contributing to its overall health. (25)
Vitamin E Deficiency
Vitamin E deficiency is uncommon but can occur due to certain conditions that affect fat absorption, as the vitamin requires dietary fat for proper absorption. (26)
Deficiency symptoms include:
- Muscle weakness
- Coordination and walking difficulties
- Numbness and tingling (peripheral neuropathy)
- Vision deterioration
- Immune system problems
Premature infants are particularly at risk due to their immature digestive systems, which can interfere with fat and vitamin E absorption. (26)
Source of Vitamin E
Vitamin E is found in various foods, particularly:
| Food Source | Category | Serving Size | Vitamin E Content | % Daily Value |
|---|---|---|---|---|
| Wheat germ oil | Plant-based Oil | 1 tablespoon (14g) | 20mg | 135% |
| Sunflower oil | Plant-based Oil | 1 tablespoon (14g) | 5.75mg | 38% |
| Safflower oil | Plant-based Oil | 1 tablespoon (14g) | 5mg | 31% |
| Sunflower seeds | Nuts/Seeds | 28g (1 oz) | 7.4mg | 49% |
| Almonds | Nuts/Seeds | 23 nuts | 7mg | 47% |
| Brazil nuts | Nuts/Seeds | 10 nuts | 5mg | 33% |
| Peanuts | Nuts/Seeds | 28g | 2mg | 13% |
| Avocados | Fruit | 100g | 2.4-3mg | 16-20% |
| Kiwi | Fruit | 100g | 1.4-1.46mg | 9-10% |
| Mangoes | Fruit | 100g | 1mg | 7% |
Supplementation
While vitamin E is essential for health, excessive supplementation can be harmful. High doses may cause abnormal bleeding, muscle aches, diarrhea, and vomiting. (26) Additionally, it can interact with blood thinners and chemotherapy medications.
While recent meta-analyses suggest inflammation lowering effect of alpha-tocopherol, (18) there’s still not a strong consensus of vitamin E use for preventing CVD. (27)
Vitamin K
Vitamin K is a fat-soluble vitamin that performs multiple functions in the human body. While primarily known for its role in blood clotting, research has revealed its importance for bone health and heart function.
Functions in the Body
Blood Clotting: Vitamin K’s most well-established role is in blood coagulation, where it helps make four of the 13 proteins needed for blood clotting. This process is essential for healing wounds and preventing excessive bleeding. (28) (29)
Bone Strength: Vitamin K strengthens bones by helping produce osteocalcin, a protein that prevents low bone density. (28) (30) Women who consume at least 110 mcg of vitamin K daily are 30% less likely to experience hip fractures compared to those with lower intake. (29) (31) A meta-analysis showed that vitamin K2 supplementation (45 mg/day) significantly reduced hip fractures by 77%, vertebral fractures by 60%, and all non-vertebral fractures by 81%. (32)
Heart Protection: It plays a vital role in preventing arterial calcification by activating matrix Gla protein (MGP), the most potent arterial calcification inhibitor known. (32) This helps maintain blood pressure and reduces the risk of stroke by preventing mineral buildup in arteries. (33)
Emerging research suggests vitamin K may have additional benefits:
Vitamin K Deficiency
Vitamin K deficiency is rare in healthy adults but can occur in certain populations: (37)
- Newborn babies (vitamin K doesn’t cross the placenta well)
- People with malabsorption disorders like celiac disease or cystic fibrosis
- Those taking certain antibiotics or blood-thinning medications
- Individuals with liver disease (38)
Symptoms of Deficiency
The primary signs of vitamin K deficiency include:
Source of Vitamin K
Vitamin K exists in two main forms: K1 (phylloquinone) found in plant foods, and K2 (menaquinone) found in animal products and fermented foods.
Foods that contain vitamin K (39)
| Food Source | Vitamin K Type | Amount | % of Daily Value |
|---|---|---|---|
| Mustard greens (cooked) | K1 | 1 serving | 346% |
| Swiss chard (raw) | K1 | 1 leaf | 332% |
| Collard greens (cooked) | K1 | ½ cup | 254% |
| Natto (fermented soybeans) | K2 | 1 serving | 238% |
| Kale (cooked) | K1 | ½ cup | 205% |
| Spinach (raw) | K1 | 1 cup | 121% |
| Broccoli (cooked) | K1 | ½ cup | 92% |
| Brussels sprouts (cooked) | K1 | ½ cup | 91% |
| Pepperoni sausage | K2 | 3 ounces | 30% |
| Kiwi | K1 | 1 fruit | 23% |
| Soybean oil | K1 | 1 tablespoon | 21% |
| Avocado | K1 | ½ medium fruit | 18% |
| Chicken wings | K2 | 1 wing | 12% |
| Blackberries | K1 | ½ cup | 12% |
| Blueberries | K1 | ½ cup | 12% |
| Chicken liver | K2 | 3 ounces | 5% |
Practical Considerations
Consuming vitamin K with foods that contain fat ensures optimal absorption, as vitamin K is fat-soluble.
People taking blood-thinning medications like warfarin should be cautious in maintaining consistent vitamin K intake, as sudden changes can affect the medication’s effectiveness (28) (29).
The recommended daily intake for adults is 120 mcg for men and 90 mcg for women, which can easily be achieved through a balanced diet rich in green vegetables (40).
Vitamin A
Vitamin A is a fat-soluble vitamin that exists in two primary forms:
- preformed vitamin A (retinol) from animal sources like fish, meat, and dairy
- provitamin A (mainly beta-carotene) from plant sources, particularly orange-colored foods like carrots, sweet potatoes, and pumpkin (41) (42).
This vital nutrient plays critical roles in vision, immune function, cellular communication, reproduction, and the proper functioning of various organs in the body (43).
Function in the Body
It supports vision by combining with the protein opsin to form rhodopsin, a molecule necessary for color vision and low-light vision. (44) This nutrient also protects and maintains the cornea (the outermost layer of the eye) and the conjunctiva (the membrane covering the eye). (45)
Beyond vision, vitamin A is integral to immune function by maintaining mucosal barriers in the skin, respiratory tract, and gut. It stimulates immune responses that protect from infections by supporting the creation of immune cells, including B cells and T cells. Vitamin A deficiency therefore is linked to weaker immunity. (46)
Vitamin A also plays a vital role in cellular communication and growth during embryonic development. It contributes to proper reproduction in both males and females and supports the metabolism of iron in our bodies. At the cellular level, vitamin A is converted to retinoic acid, which activates hundreds of genes, influencing numerous physiological processes.
Benefits of Vitamin A
Skin Health: Vitamin A and its derivatives can significantly improve skin health by supporting hydration, skin elasticity, and aiding in repairing the barrier. Additionally, vitamin A has anti-aging properties, supporting skin regeneration and wound healing. (47) The skin’s barrier function is reinforced by vitamin A, which is considered crucial for maintaining proper and healthy skin conditions. (48)
Immune Function: Fat-soluble vitamins play an important immunoregulatory role. Vitamin E (and D) can contribute to dendritic cell function and maturation, important components of immunity. To an extent, this explains the link between low levels of vitamin A and increased susceptibility to infections. (49)
Reproductive Health: Vitamin A was first recognized in 1922 as an antioxidant for female reproductive health. (50) In animal models, vitamin A (avocado oil) has shown positive effects on reproductive parameters (sperm production). (51) Studies in animals suggest a potential decrease in the negative impact of environmental toxins on reproductive health. (52)
Vitamin A Deficiency
Vitamin A deficiency (VAD) is rare in developed countries but remains common in developing nations where access to vitamin A-rich foods is limited. This deficiency can lead to severe health complications, particularly affecting vision and immune function, potentially causing night blindness. (54)
Vitamin A deficiency also significantly weakens the immune system and the integrity of epithelial barriers, making individuals more susceptible to infections and diseases. (55)
Globally, vitamin A deficiency affects hundreds of thousands of children and pregnant women in low-income countries.
Source of Vitamin A
Vitamin A comes from both animal and plant sources, with animal sources providing preformed vitamin A and plant sources offering provitamin A carotenoids that the body converts to active vitamin A.
| Animal Source (Food) | Type of Vitamin A | Plant Source (Food) | Type of Vitamin A |
|---|---|---|---|
| Liver and liver pâté | Preformed Vitamin A | Orange and yellow vegetables (carrots, sweet potatoes, butternut squash) | Provitamin A |
| Fish and fish oils (particularly cod liver oil) | Preformed Vitamin A | Dark leafy greens (kale, collard greens, spinach, Swiss chard) | Provitamin A |
| Eggs (especially egg yolks) | Preformed Vitamin A | Tomato products | Provitamin A |
| Dairy products (cheese, whole milk, butter) | Preformed Vitamin A | Fruits (mangoes, apricots) | Provitamin A |
| Fortified foods (margarine, some cereals) | Preformed Vitamin A | Some vegetable oils | Provitamin A |
The body can absorb 75% to 100% of retinol from animal sources, while the absorption rate for beta-carotene from plant foods ranges from 10% to 30%. (53)
Supplementation Considerations
The Recommended Dietary Allowance (RDA) for vitamin A is 900 mcg for men and 700 mcg for women per day. (54) These levels are relatively easy to achieve through consumption of whole foods, with most people in developed countries achieving these levels without supplementation.
In cases of deficiency, vitamin A supplements may be recommended, typically in the range of 25,000–50,000 IU for adults at high deficiency. (55) However, caution is necessary as vitamin A is stored in the body’s fatty tissues, and excessive intake can lead to toxicity.
Exceeding the tolerable upper intake level of 3,000 mcg may lead to hypervitaminosis A, causing symptoms like nausea, headaches, and more severe complications. (56)
