What are Water Soluble Vitamins? (And Why it Matters for You)

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    As a family, vitamins come in two classes: water-soluble and fat-soluble. The difference is how the vitamin behaves within the body.

    9 water-soluble vitamins to consider taking for optimal health:

    1. Vitamin C

    Vitamin C is one of the most popular micronutrients, thanks to its many known benefits for healthy immune system function, antioxidant activity, energy metabolism, and support for iron absorption. It is also known as ascorbic acid.

    Your body needs vitamin C in a daily supply because the body does not store it.

    Natural sources of vitamin C

    Vitamin C has a plethora of food sources — virtually all fruits and vegetables contain some of this essential vitamin.

    The foods that contain the highest amounts of vitamin C are:

    • Bell peppers
    • Citrus fruits
    • Melons like cantaloupe
    • Strawberries
    • Brassica vegetables like broccoli
    • Kiwi
    • Potatoes
    • Tomatoes
    • Tropical fruits like mangoes

    There are other sources of vitamin C, too. Acerola cherries are an abundant source of this nutrient, which is why Care/of uses it to formulate our vitamin C supplement. By providing vitamin C with the natural bioflavonoids that it’s paired with in foods, the body can easily absorb and recognize it as a useful source of this nutrient.

    Recommended vitamin C daily dosage

    The recommended dietary allowance (RDA) of vitamin C each day is:

    • 75 mg for adults born female
    • 85 mg for pregnancy
    • 120 mg for lactation
    • 90 mg for adults born male
    • +35 mg daily for adults who use tobacco

    While there are plenty of food sources of vitamin C, you may not get enough from your diet if you don’t eat a lot of fruits and vegetables, have food restrictions, or have gastrointestinal challenges. Cooking with heat or for longer lengths of time can decrease the vitamin C concentration in foods, too.

    Because vitamin C is water-soluble, it can be consumed at higher amounts, especially from foods, without any negative effects. The tolerable upper limit (TUL) for all adults is 2,000 mg. If you plan to supplement with higher intakes, always check with your medical provider first.

    2. Vitamin B1 (Thiamine)

    Thiamin, also known as vitamin B1, is needed for energy metabolism, cellular function, and healthy growth and development. Your body needs it specifically as a cofactor to metabolize and create energy from amino acids, fats, and glucose from the foods that you eat.

    Natural sources of vitamin B1

    There are many foods that provide thiamin and it is also added to some in a process called fortification.

    The highest natural dietary sources of vitamin B1 are:

    • Pork chops
    • Trout
    • Black beans
    • Mussels
    • Tuna
    • Acorn squash

    Most breakfast cereals are fortified to provide some percentage of thiamin to support reaching the daily recommended allowance, and many other foods like egg noodles, English muffins, and macaroni also have B1 added to them.

    Recommended vitamin B1 daily dosage

    Like other water-soluble vitamins, the body can’t store much thiamin — less than a day’s worth. You need to replenish it everyday.

    The RDA for thiamin is:

    • 1.1-1.2 mg for adults
    • 1.4 mg for pregnancy and lactation

    In most cases, you can easily get enough thiamin from food, but it’s also found in B-complex supplements.

    3. Vitamin B2 (Riboflavin)

    Riboflavin or vitamin B2, like many B vitamins, is an essential nutrient for your body’s healthy energy metabolism. It is also needed for metabolizing fats and medications and to convert amino acids in the body. How your body uses other nutrients, like folate, niacin, iron, and vitamin B6, is also somewhat dependent on the enzyme activity of riboflavin.

    Natural sources of vitamin B2

    Riboflavin is found in many foods, including:

    • Beef liver
    • Dairy products like yogurt, milk, and cheese
    • Meat, poultry, and seafood like beef, chicken, and clams
    • Almonds
    • Mushrooms
    • Eggs
    • Quinoa

    An interesting fact about riboflavin is that your intestines can make some of it, particularly after you eat meals with vegetables. Most breakfast cereals are also fortified with various percentages of the daily value for riboflavin. Other foods, like instant oats, are also fortified with smaller amounts of vitamin B2.

    Recommended vitamin B2 daily dosage

    The RDA for riboflavin is:

    • 1.1 mg for adults born female
    • 1.4 mg for pregnancy
    • 1.6 mg for lactation
    • 1.3 mg for adults born male

    The body only stores small amounts of riboflavin. If extra amounts are consumed, they are eliminated from the body via urine, so you can’t bank riboflavin. You need to consume it daily. Riboflavin is commonly found with other B vitamins in supplements, since they have a synergistic effect.

    4. Vitamin B3 (Niacin)

    Niacin, known as vitamin B3, is necessary for energy metabolism alongside other B vitamins. Over 400 enzymes in the body rely on niacin, making it necessary to perform more coenzyme operations than any other vitamin. Niacin also helps fuel the catabolic reactions that convert the food you eat into usable cellular energy as adenosine triphosphate (ATP).

    Other functions of niacin include support for DNA integrity, epigenetic expression (how your genes respond to and interact with the environment), and cell communication. Derivatives of niacin are also needed for anabolic reactions, like fatty acid synthesis and antioxidant defenses in cells.

    Natural sources of vitamin B3

    Niacin is found in many foods. Natural sources include:

    • Beef liver
    • Poultry like chicken and turkey
    • Marinara sauce
    • Seafood like salmon and tuna
    • Pork
    • Beef
    • Brown rice

    Some breakfast cereals can be fortified with about 25% daily value of niacin, while enriched white rice and breads contain smaller amounts.

    The body can produce some bioactive niacin metabolites from tryptophan, an amino acid found in foods like chicken and turkey. Tryptophan on its own is considered to contribute to the dietary intake of niacin since tryptophan can be converted to nicotinamide (NAD).

    Recommended vitamin B3 daily dosage

    Niacin deficiency is uncommon. The RDA for vitamin B3 is:

    • 14 mg for adults born female
    • 18 mg for pregnancy
    • 17 mg for lactation
    • 16 mg for adults born male

    Nicotinic acid, a supplement form of niacin, can cause a side effect known as the niacin flush. This short-lived effect, while generally considered to be harmless, can be alarming if it’s never happened to you. Other supplement forms of niacin, like nicotinamide, do not cause this reaction. The upper limit for adults is 35 mg, but intakes lower than this could still lead to flushing if you take the nicotinic acid form.

    Niacin is commonly found in B-complex formulations and some multivitamins. It can also be taken as a standalone supplement.

    5. Vitamin B5 (Pantothenic acid)

    Pantothenic acid, known as vitamin B5, is a vital nutrient for energy production because it helps to synthesize important carrier proteins for fatty acid synthesis. Along with other B vitamins, it’s necessary for anabolic and catabolic activity and general metabolic wellness.

    Natural sources of vitamin B5

    Vitamin B5 is one of the few nutrients that is found in almost all foods in varying amounts. Natural sources include:

    • Beef liver
    • Mushrooms
    • Sunflower seeds
    • Chicken
    • Tuna
    • Avocado
    • Milk
    • Potatoes
    • Eggs

    Breakfast cereals are fortified with varying percentages of the recommended dietary allowanceof pantothenic acid.

    Recommended vitamin B5 daily dosage

    Most people probably get enough vitamin B5 because it is available in so many different foods. The RDA is:

    • 5 mg for all adults
    • 6 mg for pregnancy
    • 7 mg for lactation

    Vitamin B5 is also found in B-complex vitamins as well as some multivitamins.

    6. Vitamin B6 (Pyridoxine)

    Pyridoxine, which is more commonly known as vitamin B6, is necessary for more than 100 enzyme reactions in the body. It supports metabolic activity for proteins, amino acids, carbohydrates, lipids, and one-carbon units. B6 supports neurotransmitter synthesis, healthy immune system function, hemoglobin formation, and energy storage.

    Natural sources of vitamin B6

    Vitamin B6 is naturally present in many foods:

    • Chickpeas
    • Beef liver
    • Seafood like tuna and salmon
    • Poultry like chicken and turkey
    • Potatoes
    • Bananas
    • Marinara

    Some breakfast cereals are also fortified with 25% of the daily value while others can have more, less, or no fortification whatsoever.

    Recommended vitamin B6 daily dosage

    The RDA for vitamin B6 is:

    • 1.3 mg for adults through age 50
    • 1.9 mg for pregnancy
    • 2 mg for lactation
    • 1.5 mg for adults born female over age 50
    • 1.7 mg for adults born male over age 50

    While most people get enough B6, certain factors make it more likely that serum levels of the bioavailable form of this nutrient are low, including:

    • Frequent alcohol use
    • Higher body weight
    • Pregnancy
    • Gastrointestinal conditions

    Vitamin B6 is typically found in dietary supplements as pyridoxine or the active form, pyridoxal 5’ phosphate (PLP). It is usually in B-complex formulas, multivitamins, and prenatal vitamins. It is sometimes taken on its own and some research has found that B6 can help with pregnancy morning sickness.

    7. Vitamin B7 (Biotin)

    Biotin is a B vitamin that supports metabolic energy production from carbohydrates, proteins, and fats. It’s also needed for gene regulation and cell signaling. Biotin is popularly considered a nutrient for hair, skin, and nails, but clinical evidence doesn’t link it to those direct benefits. Biotin deficiency, while uncommon, has been associated with hair loss.

    Natural sources of vitamin B7

    Biotin is found in many foods, including:

    • Beef liver and beef
    • Egg
    • Seafood like salmon and tuna
    • Pork
    • Sunflower seeds
    • Almonds
    • Vegetables like spinach, broccoli, and sweet potato

    Recommended vitamin B7 daily dosage

    There is no official RDA for biotin, but the adequate intake (AI) has been set at:

    • 30 mcg for all adults and for pregnancy
    • 35 mcg for lactation

    Biotin deficiency is very rare. Factors that may benefit from biotin support include:

    • Frequent alcohol use
    • Pregnancy
    • Breastfeeding

    There is no upper limit set for biotin because even at high amounts, it hasn’t been shown to cause toxicity. However, biotin can interfere with many types of laboratory test results. Taking more than 10 mg of biotin even once can impact certain lab tests for several days, so be sure to check with your medical provider before you start biotin supplements.

    8. Vitamin B9 (Folate)

    Vitamin B9 is more commonly known as folate or folic acid. It is an important nutrient for the synthesis of DNA and the metabolism of amino acids. Without adequate folate, numerous biochemical processes in the body won’t function properly.

    Folate is also vital in the early days and weeks of pregnancy to support healthy neural development. Because deficiency can lead to potential birth defects, folic acid is added to many foods. It’s recommended that all adults born female who could become pregnant ensure that they get at least 400 mcg of folic acid each day. The most important need for folate in pregnancy happens before most people even know they’ve conceived.

    Natural sources of vitamin B9

    Folate is found in many foods. Natural sources that contain the highest amounts include:

    • Beef liver
    • Vegetables like spinach, asparagus, Brussels sprouts, broccoli, and romaine lettuce
    • Black-eyed peas
    • Avocado
    • Kidney beans

    Breakfast cereals can be fortified with folic acid but the amount varies. Some are fortified with 25% of the daily value for folic acid. Other foods that are commonly enriched with folic acid include bread, flour, cornmeal, pasta, rice, and other grain products.

    Recommended vitamin B9 daily dosage

    The RDA for folate is:

    • 400 mcg DFE for all adults
    • 600 mcg DFE for pregnancy
    • 500 mcg DFE for lactation

    Prenatal vitamins, multivitamins, B-complex supplements, and standalone folate supplements can all be additional sources of this important nutrient.

    Dietary supplements may also contain folate in its methylated form, known as L-5 MTHF. Active folate, as it’s also known, has a bioavailability that is the same as or greater than folic acid. For some people with certain gene variants, it may provide a superior form of the nutrient.

    The tolerable upper limit for folate has been set at 1,000 mcg for all adults. Consuming higher amounts of supplemental folate can conceal a vitamin B12 deficiency or lead to other potential health consequences. Always consult your healthcare provider before using high-dose folate or folic acid supplements or before starting any new products.

    9. Vitamin B12

    Vitamin B12 is one of the most well-known and widely researched nutrients. It’s crucial for neurological function because it supports healthy nerve myelination, but it’s also needed for DNA synthesis, amino acid conversion, healthy neural tube development during pregnancy, and many other aspects of health.

    Because vitamin B12 is so essential, it is the one water-soluble vitamin that the body can store. The liver retains about 1-5 mg of B12, or about 1,000-2,000 times as much as is typically needed on a daily basis. But because of this, symptoms of deficient intake may not show up for years. Vitamin B12 should still be consumed daily to support dietary needs.

    Natural sources of vitamin B12

    Vitamin B12 is found in many foods, but most of them are derived from animal sources. People who follow vegan and vegetarian diets typically need to supplement with B12 to prevent deficiency, which can cause irreversible nerve issues after long periods of inadequate intake.

    Natural food sources of vitamin B12 include:

    • Meats like liver, beef
    • Seafood like clams, salmon, and tuna
    • Dairy products like milk, yogurt, cheese
    • Eggs
    • Turkey

    Breakfast cereals are sometimes fortified with 25% of the daily value for vitamin B12. Nutritional yeast may also be fortified with B12, but if you’re taking it as a main source of this vitamin, be sure to read the label to know how much you are getting.

    Recommended vitamin B12 daily dosage

    The RDA for vitamin B12 is:

    • 2.4 mcg for all adults
    • 2.6 mcg for pregnancy
    • 2.8 mcg for lactation

    Vitamin B12 is commonly found in multivitamins, prenatal vitamins, and B-complex supplements. It is also often found in standalone supplements. People who are most likely to have inadequate B12 levels are those who are older than age 60, follow plant-based diets, take certain medications, or have digestive conditions. Genetic variants can also impact B12 digestion and absorption.

    There is no established upper limit for B12 because it has not been associated with toxicity. It’s still important to check with your doctor before consuming very high intakes of any single nutrient.

    What are the functions of water-soluble vitamins?

    Water-soluble vitamins meet many basic nutritional requirements. They each have unique functions, but also work together to support overall well-being. Water-soluble vitamins can be absorbed on an empty stomach when taken as dietary supplements or with food sources. Vitamin C and the B-complex family of nutrients are needed for healthy immune system function, neurological health, cognition, energy metabolism, and much more.

    Water-soluble vitamin supplements: what you need to know

    Water-soluble vitamins have many food sources, but there are also many reasons why you may want or need to supplement your food intake with dietary supplements. Because the body cannot store most of them, they need to be consumed on a daily basis.

    Water-soluble micronutrients are found in many different supplements. Some are included in multivitamin and prenatal vitamins, while others can be taken as standalone nutritional supplements. B-complex supplements may also contain most or all of the B vitamins. When looking for water-soluble supplements, especially B vitamins, you want them to be in active forms, since the body can more readily put them to use.

    Care/of formulates our high-quality, third-party tested nutritional supplements with bioavailability and absorption in mind.

    The difference between water-soluble and fat-soluble vitamins

    Water-soluble nutrients absorb in the digestive tract in the presence of water, and can also be excreted from the body via the kidneys and intestines. For most of these types of vitamins, there’s low potential for toxicity because the body uses what it needs each day and eliminates the rest. But this is also why they need to be consumed on a daily basis, since the body cannot store most of them. Water-soluble vitamins include vitamin C and the B vitamins.

    Fat-soluble vitamins need to be eaten and absorbed with meals that contain healthy fats. The body stores them, and because of this, toxicity is a possibility if they are consumed at high amounts for longer periods of time. The body has no easy way to eliminate excess fat-soluble vitamins, especially from supplements. In most cases, normal dietary intake from foods does not cause issues with fat-soluble nutrients. Fat-soluble vitamins include vitamins A, D, E, and K.

    Only your healthcare provider can determine what nutrients your body needs. Before starting supplements, especially those at higher intakes, always work with a provider to create a personalized plan for your nutritional well-being.

    Is vitamin D water-soluble?

    No, vitamin D is a fat-soluble vitamin, not a water-soluble nutrient. It can be synthesized in the body after outdoor sunlight exposure from UVB rays. It can also be obtained from foods like fatty coldwater fish, egg yolks, and fortified milk or butter products. Dietary supplements represent a common source of vitamin D, and are best absorbed when taken with foods that contain healthy fat.

    How to tell if you have a water-soluble vitamin deficiency

    Many nutrients have labs that can be run to determine your levels, and nutrition professionals can conduct dietary analyses to see what nutrients may be inadequate in your diet. Each type of nutrient may present different symptoms, and many of them cause no symptoms at all or they may take years to show up.

    Because symptoms can be varied or present differently, any changes to your health should always be discussed with your medical provider.

    The bottom line

    Water-soluble vitamins are essential for your health. Except for vitamin B12, the body cannot store them—but all of them need to be consumed daily to support healthy nutrient balance. Fruits, vegetables, meats, dairy products, nuts, seeds, and whole grains contain water-soluble nutrients. If you eat a wide variety of foods, you’re likely getting much of what you need. If you have food allergies, have a restricted food plan, or can’t eat certain food groups, you may need to supplement to support adequate intake of important water-soluble vitamins.

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    Dr. Carla Montrond Correia ND, CNS
    Medical Content Manager
    Dr. Montrond-Correia is a licensed naturopathic physician and a certified nutrition specialist (CNS). She holds degrees from University of Bridgeport, Georgetown University, and University of Saint Joseph, and supplemented her education with internships in the health and wellness space. She's focused on research, herbal medicine, nutrigenomics, and integrative and functional medicine. She makes time for exercise, artistic activities, and enjoying delicious food.
    Mia McNew, MS
    Freelance Contributor
    Mia McNew is a nutrition science researcher with bachelor's and master's degrees in nutrition science and biochemistry. She holds additional certifications in clinical nutrition and formerly managed a private nutrition practice focusing on fertility and the management of chronic health and autoimmune disorders. She is currently pursuing a PhD in human nutrition with a research focus on disability, underserved populations, and inequities in popular nutrition therapy approaches. She has extensive experience as a fact-checker, researcher, and critical research analyst and is passionate about science and health communications that provide practical support.