What are fat-soluble and water-soluble vitamins?

            Vitamins are a micronutrient that we get from food required for our overall health and body functioning (1). Vitamins come in two different varieties – fat-soluble and water-soluble. Fat-soluble vitamins include vitamins A, D, E, and K and are absorbed and transported like fats when consumed. They are best absorbed when fat is present, and water is very little (2). These vitamins are necessary for many functions in our body, including reproduction and growth (3). Water-soluble vitamins include biotin, niacin, vitamin C, and folate (among others). Unlike fat-soluble vitamins, which do not dissolve in water (picture oil in water – never quite mixing and staying completely separate, no matter how much you mix it), water-soluble vitamins dissolve easily in liquid (4). They are found in vegetables, beans, legumes, seeds, and other foods that many consume daily (3). While multivitamins are a great addition to your diet, they are not a substitute for fresh fruits, vegetables, and other food groups essential for our nutrient intake, including vitamins (5).

Some examples of water-soluble and fat-soluble vitamins include:

Water-soluble vitaminsFat-soluble vitamins
Ascorbic acid (Vitamin C)Vitamin A
ThiaminVitamin D
NiacinVitamin E
Vitamin B6Vitamin K
Vitamin B12 
Water- and Fat- soluble vitamins

Vitamins are essential for good health!

            Water-soluble vitamins form part of a complex system in our gut, involving our gut microbiome (the bacteria that inhabit our gut and help us digest food and fight disease) and influence so many parts of our body. Vitamins are absorbed in the large intestine, which has many ways to absorb water-soluble vitamins produced by our gut microbes (these microbes break down food into its many smaller components, and one of those components is vitamins) (6).

Vitamin deficiencies cause a number of health problems

A lack of vitamins (fat- or water-soluble) can cause many conditions, including scurvy (caused by a lack of vitamin C, this condition causes a decrease in red blood cell counts, bleeding, sore arms and legs, and weakness), ulceration, and malnutrition (7). A study following Japanese men and women found that dietary intake of vitamin C, B2, and folate (all water-soluble fats) was directly associated with reduced risk of diabetes (8).

            One very important water-soluble vitamin is biotin (also called Vitamin H). Humans have lost the ability to synthesize biotin, so we have to get it from our diet. Biotin deficiencies can result in neurological disorders, growth problems, and skin diseases, among many other health problems. We must absorb enough biotin in our intestinal tract to keep our body running normally. When we eat foods that contain biotin (including eggs, fish, meat, seeds, nuts, and vegetables such as sweet potatoes), our gut microbes break those foods down and extract the micronutrients, including biotin, which is absorbed in our intestines and sent where it is needed (9, 10).

            Vitamin C deficiency (another water-soluble vitamin) has been a controversial topic for quite some time. While we know diseases like scurvy form when it is in short supply, the effects of vitamin C works in our body remain largely unknown (11). Vitamin C helps us recover from infections, functions as an antioxidant (getting rid of those damaging free oxygen radicals that go on to disrupt DNA and can cause cancer), and may have a role in preventing environmental temperature-related stress (12).

            B-vitamins are another group of water-soluble vitamins that are thought to be very involved with bone health and fractures’ resistance. Many studies have suggested increasing vitamin B enriched foods may protect the elderly from bone fragility and associated fractures, but more studies are needed (13). They are also suspected to improve celiac disease symptoms, and studies suggested extra B vitamins may be useful for those living with celiac disease, following a gluten-free diet (14). Vitamin B12, one of the B vitamin families, is also suspected to play a role in cognitive function. Still, many further studies are needed in this area, as we are just on the cusp of learning about this interesting relationship (15).

There is such a thing as too much of a good thing

            While vitamin deficiencies are bad for our health (which we now know firsthand), too much of most vitamins is also a bad thing. Many vitamins are stored until they are needed, which is a survival tactic our body has developed for use in times of vitamin and nutritional shortages. Vitamins A, B12, and D are stored primarily in the liver, while vitamins A and D are stored primarily in our fat cells. Also, “Vitamin D Could Lower The Risk Of Mortality And Severity Of Coronavirus (COVID-19).”

We only need small amounts of vitamins, and deficiencies can take more than a year to show symptoms and fully develop because of our efficient storage mechanisms (16). Overdosing on certain vitamins can cause nausea, diarrhea, stomach cramps, and organ problems. Water-soluble vitamins are eliminated in our urine and more likely to be destroyed when cooked (17).

As we have now seen, water-soluble vitamins are essential for our well-being and overall health. While too much can be a bad thing for our health, shortages of these vitamins cause a host of health problems and medical conditions. Multivitamins are a good start, but you should focus on getting the majority of your water-soluble vitamins from whole foods, uncooked when possible (to maximize the nutritional benefits). Good luck in discovering a whole new world of nutritional potential in the foods you thought you knew so well. Have a look at “10 Healthy Foods And 10 Not So Healthy.”

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