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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. 

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]

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