Explain the difference between water soluble and fat soluble vitamins

Fat-soluble vitamins and supplements are dissolved by fats in the body. They include vitamins A, D, E, and K. Water-soluble vitamins, including vitamin C and vitamin B elements found in food or supplements, are dissolved in water.

Fat-soluble vitamins deliver nutrients to the body in different ways from the water-soluble ones. They may be stored and are excreted from the body at different rates.

This article discusses the types of vitamins and their differences. It explains why your body needs them as well as the possibility that you can take too many of these vitamins.

Water-Soluble Vitamins

Water-soluble vitamins are those that are dissolved in water and readily absorbed into tissues for immediate use. Because they are not stored in the body, they need to be replenished regularly in the diet.

Any excess of water-soluble vitamins is quickly excreted in urine and will rarely accumulate to toxic levels. With that being said, certain types of water-soluble vitamins, such as vitamin C, can cause diarrhea if taken in excess.

The water-soluble vitamins include the B-complex group and vitamin C, each of which offers the following health benefits:

• Vitamin B1 (thiamine) helps to release energy from foods and is important in maintaining nervous system function.
• Vitamin B2 (riboflavin) promotes good vision and healthy skin, and it is also important in converting the amino acid tryptophan into niacin.
• Vitamin B3 (niacin) aids in digestion, metabolism, and normal enzyme function as well as promoting healthy skin and nerves.
• Vitamin B5 (pantothenic acid) aids in metabolism and the formation of hormones. It may help to control cholesterol and have anti-inflammatory benefits.
• Vitamin B6 (pyridoxine) aids in protein metabolism and the production of red blood cells, insulin, and hemoglobin.
• Vitamin B7 (biotin) helps release energy from carbohydrates and aids in the metabolism of fats, proteins, and carbohydrates from food.
• Vitamin B9 (folate or folic acid) also aids in protein metabolism and red blood cell formation, and it may reduce the risk of neural tube birth defects.
• Vitamin B12 (cobalamin) aids in the production of normal red blood cells as well as the maintenance of the nervous system.
• Vitamin C (ascorbic acid) is central to iron absorption and collagen synthesis. It aids in wound healing and bone formation while improving overall immune function.

Water-Soluble Vitamin Food Sources

Water-soluble vitamins dissolve in water right away. Once the body has as much of one as it needs, the rest gets flushed out of the body by the kidneys. Fresh fruits, including citrus and berries, as well as tomatoes and peppers, are excellent vitamin C sources. B-complex vitamins are found in a range of foods, including meat and dairy.

Fat-Soluble Vitamins

Fat-soluble vitamins are dissolved in fats. They are absorbed by fat globules that travel through the small intestines and are distributed through the body in the bloodstream.

Unlike water-soluble vitamins, excess fat-soluble vitamins are stored in the liver and fatty (adipose) tissues for future use. They are found most abundantly in high-fat foods and are better absorbed if eaten with fat.

Fat-Soluble Vitamins and Toxicity

Fat-soluble vitamins can accumulate to toxic levels if taken in excess. Where a well-balanced diet can't cause toxicity, overdosing on fat-soluble vitamin supplements can. Symptoms and side effects of fat-soluble vitamin toxicity vary depending on the vitamin. They range from nausea and vomiting to slowed growth and birth defects.

There are four types of fat-soluble vitamins, each of which offers different benefits:

• Vitamin A is integral to bone formation, tooth formation, and vision. It contributes to immune and cellular function while keeping the intestines working properly.
• Vitamin D aids in the development of teeth and bone, by encouraging the absorption and metabolism of phosphorous and calcium.
• Vitamin E is an antioxidant that helps fight infection and keeps red blood cells healthy.
• Vitamin K is central to blood clotting and also keeps bones healthy.

The easiest way to remember which vitamins are which is to memorize the fat-soluble ones, as there are only four: vitamins A, D, E, and K. All others are water-soluble.

A Word From Verywell

Vitamin supplements may offer health-boosting benefits, but they can sometimes interact with medications or cause complications with an existing health condition. Be sure to let your healthcare provider know if you're taking vitamins or have questions about them in your diet.

Frequently Asked Questions

• Can fat-soluble or water-soluble vitamins cause weight gain?

  There's little research about fat soluble vitamins causing weight gain. It's water-soluble B-complex vitamins that are usually associated with it. Researchers began seeing this trend when foods, like cereal, became fortified with vitamins. Some suggest that vitamin intake from natural or fresh foods may be an adequate source.

• How much vitamin A is safe to take?

  The daily tolerable upper intake level for vitamin A supplements according to age are:

  • Babies and children under 3: 300 micrograms (mcg)
  • Children 4 to 8: 900 mcg
  • Tweens 9 to 13: 1700 mcg
  • Teens 14 to 18: 2800 mcg
  • Adults 10 to 70 and older: 3000 mcg

• Is it possible to get too much of water-soluble vitamins?

  Yes. Several have upper limits for consumption, meaning that even though they aren't stored, they could cause problems if too much is circulating in the body. For example, a high level of vitamin B6 for an extended period of time is associated with nerve damage that cannot be reversed.

• What happens if you don't get enough fat soluble vitamins?

  It's hard to have a fat-soluble vitamin deficiency in the United States. Most people get adequate vitamins A, D, E, and K in their diets. Some health conditions can cause deficiencies. For instance, liver cirrhosis may cause vitamin A deficiency.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

By Lori Alma
Lori Alma, RN, is a registered nurse and cystic fibrosis expert who assists families in a Florida Department of Health program for special needs children.

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