The Difference Between Water-Soluble and Fat-Soluble Vitamins
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By Dale Mayo, March 24, 2022
Our bodies need vitamins for many biochemical functions and to maintain optimal health. Vitamins are either water-soluble (not easily stored and easily washed out) or fat-soluble (easily stored in fat upon absorption).[1]
What Are Fat-Soluble and Water-Soluble Vitamins?
Water-soluble vitamins (vitamin B complex and vitamin C) dissolve in water and are readily absorbed into tissues but not stored in the body. For this reason, they do not build up in your body in toxic levels. Too much vitamin C, however, can cause diarrhea. Fat-soluble vitamins (vitamins A, D, E, and K) are dissolved in fats and are distributed in your bloodstream. Because they are stored in the liver and fatty tissues, they can accumulate to toxic levels if ingested in excess.[2]
Fat-Soluble Vitamins
- Vitamin A (beta carotene) is important for healthy eyes, bone and tissue growth, reproduction, and for regulating your immune system. Vitamin A deficiency is rare in the United States. Vitamin A is better absorbed by your body if it comes in meat rather than plants, so vegetarians need to eat 5 servings to meet the daily requirements. People who have trouble absorbing vitamin A (those with celiac or Crohn’s disease or pancreatic disorders) may need supplements. Warning: While it is not possible to get too much vitamin A from food, too much vitamin A from supplementation may increase the risk of birth defects, liver abnormalities and reduced bone density.
- Vitamin D (calciferol) helps your body absorb calcium, which is important for the development and maintenance of healthy teeth and bones. It also helps regulate levels of calcium and phosphorus in your blood. Your skin produces vitamin D after exposure to sunshine. Vitamin D helps slow osteoporosis and may reduce the risk of cardiovascular disease. In the United States, vitamin D deficiency is not uncommon and supplementation is recommended for many people.
- Vitamin E (tocopheral) protects red blood cells and may play a role in immune function, DNA repair and other metabolic functions. While getting enough vitamin E in your diet is good, some research indicates that vitamin E supplementation in high doses may increase the risk of heart failure or death. [3]
- Vitamin K is important for blood clotting and healthy bones.
Water-Soluble Vitamins
Vitamin B1 (thiamin) is part of an enzyme needed for energy metabolism and is important to nerve function.
Vitamin B2 (riboflavin) is part of an enzyme needed for energy metabolism and is important for normal vision and skin health.
Vitamin B3 (niacin) helps your body convert food to energy and helps improve blood circulation and cholesterol levels. Deficiency is rare in the United States but can show up in alcoholics and the malnourished. Deficiency can result in pellagra (diarrhea, dermatitis, and dementia).
Vitamin B5 (pantothenic acid) is used in energy production and hormone formation.
Vitamin B6 (pyridoxine) helps your body use protein, form red blood cells, and maintain brain function. Serious deficiencies in vitamin B6 are rare.
Vitamin B7 (biotin) is needed to metabolize protein, fats, and carbohydrates. Deficiency can lead to muscle pain, heart problems, anemia, and depression. Biotin is a contributor to keratin and has become a popular supplement for improving hair, skin, and nail quality. Large doses of biotin can skew a number of clinical tests, including thyroid tests T3 and T4 (but not TSH) levels.
Vitamin B9 (folate) is important in red blood cell formation, healthy cell growth, and for a developing fetus during pregnancy.
Vitamin B12 (cobalamin) plays essential roles in red blood cell formation, cell metabolism, and nerve function. Deficiency may lead to pernicious anemia.
Vitamin C (ascorbic acid) is important for collagen growth, wound healing, bone formation, and enhancing the immune system. It helps your body absorb iron, strengthen blood vessels, and acts as an antioxidant. Deficiency can result in scurvy.
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Where Do You Get Water-Soluble and Fat-Soluble Vitamins?
A balanced diet usually provides enough of both fat- and water-soluble vitamins. People older than 50 and some vegetarians may need to use supplements to get enough B12.
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Fat-soluble vitamins |
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Nutrient |
RDA |
Sources |
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Vitamin A (beta carotene) |
2,330 IU/day (adult women) 3,000 IU/day (adult men)
Supplements are not recommended |
Vitamin A from animal sources (retinol): fortified milk, cheese, cream, butter, fortified margarine, eggs, liver, shrimp, fish. Beta-carotene (from plant sources): Leafy, dark green vegetables; dark orange fruits (apricots, cantaloupe) and vegetables (carrots, winter squash, sweet potatoes, pumpkin). One small carrot (5”) provides about 6,000 IU of vitamin A |
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Vitamin D (calciferol) |
200 IU/day (adults 19-50) 400 IU/day (adults 51-70) 600 IU/day (adults 71+) |
Egg yolks, liver, fatty fish, fortified milk, fortified margarine. When exposed to sunlight, the skin can make vitamin D. 8 ounces of fortified milk contains 100 IU of vitamin D. |
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Vitamin E (tocopheral) |
15mg/day (adults) Supplements: 22 IU natural sources 33 IU synthetic sources |
Polyunsaturated plant oils (soybean, corn, cottonseed, safflower); leafy green vegetables; wheat germ; whole-grain products; liver; egg yolks; nuts and seeds. One ounce of almonds has more than 7 mg of vitamin E. |
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Vitamin K |
No RDA, but Adequate Intake (AI) is as follows: 90 mcg/day (women 19+) 120 mcg/day (men 19+)[4] |
Leafy green vegetables such as kale, cabbage, collard greens, and spinach; green vegetables such as broccoli, brussels sprouts, and asparagus; also produced in intestinal tract by bacteria. Drizzle salad with olive oil or add avocado to improve absorption. |
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Water-soluble vitamins |
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Nutrient |
RDA |
Sources |
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Vitamin B1 (thiamin) |
1.1 mg/day (women 19+) 1.2 mg/day (men 19+) 1.4 mg/day (pregnant and breastfeeding women) |
Found in all nutritious foods in moderate amounts: pork, whole-grain or enriched breads and cereals, legumes, nuts and seeds, watermelon, acorn squash. |
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Vitamin B2 (riboflavin) |
1.1 mg/day (women 19+) 1.2 mg/day (men 19+) 1.4 mg/day (pregnant) 1.6 mg/day (breastfeeding) |
Milk and milk products; leafy green vegetables; whole-grain, enriched breads and cereals; lean beef and pork, eggs, salmon. |
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Vitamin B3 (niacin) |
14 mg/day (adult women) 16 mg/day (adult men) |
Meat, poultry, fish, whole-grain or enriched breads and cereals, vegetables (especially mushrooms, asparagus, and leafy green vegetables), potatoes, peanut butter. 3 ounces of tuna (canned in water) has 11 mg of niacin. |
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Vitamin B5 (pantothenic acid) |
5 mg/day (adults 19+) 6 mg/day (pregnant) 7 mg/day (breastfeeding) |
Widespread in foods: salmon, chicken, organ meat, whole grains, broccoli, avocados, mushrooms. |
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Vitamin B6 (pyridoxine) |
1.3 mg/day (adults 19-50) 1.5 mg/day (women 51+) 1.7 mg/day (men 51+) |
Meat, fish, poultry, vegetables, fruits, legumes, tofu, bananas. One medium banana contains about 0.4 mg of vitamin B-6. |
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Vitamin B7 (biotin) |
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Widespread in foods: Whole grains, eggs, soybeans, fish. Also produced in intestinal tract by bacteria. |
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Vitamin B9 (folate) |
400 mcg/day (adults) 600 mcg/day (pregnant women) 500mcg/day (breastfeeding women) |
Leafy green vegetables and legumes, asparagus, spinach, broccoli, seeds, orange juice, and liver; now added to most refined grains. Half a cup (4 ounces) of cooked spinach contains 130 micrograms (mcg) of folate. |
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Vitamin B12 (cobalamin) |
2.4 mcg/day (adults) |
Meat, poultry, fish, seafood, eggs, milk and milk products; not found in plant foods. 3 ounces of salmon contains about 5 mcg of vitamin B-12. |
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Vitamin C (ascorbic acid) |
75 mg/day (adult women) 90 mg/day (adult men) |
Found only in fruits and vegetables, especially citrus fruits, vegetables in the cabbage family, cantaloupe, strawberries, peppers, tomatoes, potatoes, spinach, lettuce, papayas, mangoes, kiwifruit. 1 medium orange has about 70 mg of vitamin C. |
How Best to Get the Most Vitamins in Your Diet?
Add more fruits and vegetables to your diet – they are low in calories and high in nutrients. People who consume lots of vegetables have lower rates of heart disease, hypertension, diabetes, eye problems and even cancer. Eat the recommended daily amount of at least five servings (a serving is one half cup of raw fruit or vegetable or a small piece of fruit). If you maintain your weight on a 2,000 calorie per day diet, this translates into nine servings (or 4.5 cups) per day.[5] Easy ways to do this is to add berries to your cereal, eat a piece of fruit or some easy to eat vegetables (carrots, celery) instead of chips.
Vary your menu – eating only raw fruits and vegetables may rob you of some important nutrients. For example, levels of lycopene (a potent antioxidant), a carotenoid found in tomatoes and other red-pigmented vegetables are higher in processed than fresh tomatoes. It’s also important to add spices and healthy fats to vegetables – the fats not only help you absorb more nutrients, but also make them taste good so that you’ll want to eat them again. Nutrient-rich foods are easy to find and represent the five basic food groups, which makes it simple to develop a balanced, healthy eating pattern. Healthline’s list of the 11 most nutrient foods on the planet includes salmon, kale, seaweed, garlic, shellfish, potatoes, liver, sardines, blueberries, egg yolks, and dark chocolate.[6]
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Food vs. supplements
Whole foods (fruits, vegetables, grains, and dairy products) have benefits you can’t find in a pill, including a variety of nutrients your body needs — not just one (like you’d get in a supplement). Whole foods also provide fiber, which is needed in digestion and in the prevention of certain diseases. Soluble fiber (found in beans, some grains, and some fruits and vegetables) and insoluble fiber (found in whole grains and some fruits and vegetables) may help prevent heart disease, diabetes, and constipation. Many foods contain phytochemicals which may help protect you against cancer, heart disease, osteoporosis, and diabetes.[7]
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Warning: You can get too much. Please talk to your doctor before taking supplements. While it is almost impossible to get too many vitamins from your food, it is easy to take too much in a supplement – especially among the fat-soluble vitamins A, D, E, and K. |
References
[1] Lykstad, J., Sharma, S. (2021). Biochemistry, Water Soluble Vitamins. [Updated 2021 Mar 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK538510/
[2] Alma, L. (2021). Fat-soluble vs. water-soluble vitamins. August 19, 2021. https://www.verywellhealth.com/fat-vs-water-soluble-998218
[3] Vitamins and Minerals What You Should Know About Essential Nutrients. Mayo Clinic Women’s HealthSource Special Report (2009) Mayo Foundation for Medical Education and Research, Rochester, MN. https://www.mayoclinic.org/documents/mc5129-0709-sp-rpt-pdf/doc-20079085
[4] https://www.hsph.harvard.edu/nutritionsource/vitamin-k/
[5] Parker-Pope, T. (2008) Finding the best way to cook all those vegetables. The New York Times. May 20, 2008. https://www.nytimes.com/2008/05/20/health/nutrition/20well.html?searchResultPosition=10
[6] https://www.healthline.com/nutrition/11-most-nutrient-dense-foods-on-the-planet
[7] Vitamins and Minerals What You Should Know About Essential Nutrients. Mayo Clinic Women’s HealthSource Special Report (2009) Mayo Foundation for Medical Education and Research, Rochester, MN. https://www.mayoclinic.org/documents/mc5129-0709-sp-rpt-pdf/doc-20079085
