We often have patients drop by the pharmacy to ask us questions about how much of a certain vitamin they need to stay healthy. There are so many different choices when it comes to vitamins and doses, which can make it confusing to choose what is right for you. With that in mind, I want to go over the basics about each vitamin and how much of each you should be getting daily, as well as the best ways to include these vitamins in your diet.
Click Here For Recommended Daily Vitamin Doses
Vitamin Values
The Food and Nutrition Board and the Institute of Medicine have established recommended values for each type of vitamin. These values are called Dietary Reference Intakes (DRI) and include the Recommended Dietary Allowance (RDA) and the Upper Intake Levels (UL). The RDA is defined as the average daily level of intake that is sufficient to meet nutrient needs of about 97-98% of the healthy population. The UL values are the maximum daily intake that is unlikely to cause any negative health effects. Although the minimum recommended daily intake levels have been well-established, there are some vitamins and minerals that do not have upper levels of intake. It is still important to make sure that you don’t excessively supplement those vitamins.
You may have heard of water-soluble and fat-soluble vitamins. Fat-soluble vitamins are stored in the body for greater amounts of time, so it’s easier to get too much of these vitamins. The fat-soluble vitamins are vitamins A, D, E, and K. You will also often see these vitamins measured in International Units (IU) on bottles and food labels.
Water-soluble vitamins dissolve in water, are usually eliminated from the body in urine, and are not stored in the body for long periods of time. It is more difficult to get too much of these vitamins, though it is still possible. The water-soluble vitamins are B vitamins and vitamin C. These vitamins are measured in milligrams (mg) and micrograms (mcg).
It’s important to know what foods are good sources for vitamins, as we get a lot of vitamins from our diet. Generally, good sources of vitamins should say that they have at least 20% of your daily value of that vitamin on its nutrition label.
Vitamin A
Vitamin A – one of the vitamins you may not think of very often – plays roles in bone growth, reproductive health, vision, and skin health, depending on its form. You may have heard of a few of the different forms of vitamin A, including retinol, retinal, and retinoic acid. There are also carotenes, which are vitamin A precursors that are changed to usable forms in the body. These carotenes are good for visual health and include lycopene (found in tomatoes and watermelon), zeaxanthin (found in paprika, saffron, and kale), and lutein (found in kale and brussels sprouts).
So where does vitamin A come from in our diet? Vegetables are the best source of vitamin A, but you can also get it from meat, fish, and poultry. The Institute of Medicine does not currently recommend additional supplementation of beta-carotene, which is a type of Vitamin A.
Vitamin A deficiency is more common in developing countries and is actually pretty rare in the United States. Some people who may be at some risk for decreased vitamin A levels are those with celiac disease, pancreatic disease, Crohn’s disease, alcoholics, and vegetarians. Some key signs and symptoms of deficiency include night blindness and dry cornea (the clear membrane that covers your eye). Treatment usually includes a vitamin A oil that is swallowed or an injection.
B Vitamins
There are quite a few B Vitamins. Some of the B vitamins require other B vitamins to be absorbed or activated in the body. It’s common to see a lot of B vitamins bundled together in a Vitamin B complex, although it is still possible to get most of them individually too.
Vitamin B1: Thiamine
Thiamine is used by the body for energy production, which is why you may have had your doctor recommend a B vitamin complex if you’re feeling tired all the time. It helps with the conversion of carbohydrates to energy, so the more carbs you consume, the more thiamine you need. Thiamine also helps convert glucose into energy that is used by the brain.
The general rule with thiamine is that it’s important to replace what is degraded daily by our bodies. About 1 mg per day is degraded in adults, so we want to replace that. Thiamine intake is also based on your caloric consumption, and it’s recommended to get about 0.2-0.3 mg per 1000 calories consumed.3
We generally get enough thiamine from our diets, but people who are on certain diuretics like furosemide (Lasix), oral contraceptives, or those who have cirrhosis may require a supplement.
Vitamin B2: Riboflavin
Riboflavin has roles in general metabolism, respiration, and healthy maintenance of vision, skin, nails and hair. Riboflavin is necessary for the activation and production of another one of the B vitamins, vitamin B6. Some good sources of riboflavin are fortified foods, yogurt, cheddar cheese, milk, eggs, and almonds.
Some reasons for added supplementation in your diet might be the use of oral contraceptives, certain diuretics like hydrochlorothiazide, and some multivitamins that contain copper, zinc, or iron.
Vitamin B3: Niacin
Niacin helps the body convert proteins and fats into energy. It also helps with healthy skin maintenance. At higher doses, Niacin can potentially help with lowering cholesterol levels. It helps with DNA production, so a deficiency of niacin can cause damage to DNA.
People who take oral contraceptives, have irritable or inflammatory bowel disease, or diarrhea may need to take a niacin supplement. Some good sources of niacin are peanuts, chicken (white meat), canned tuna, and salmon.
Vitamin B6: Pyridoxine
Pyridoxine helps with protein metabolism and helps maintain healthy nervous and immune systems. It’s very easy to get in our diet, and therefore there is never a real need to supplement. Bananas, baked potatoes, oatmeal, and salmon are some good sources of pyridoxine.
Pyridoxine can actually be used with another drug (doxylamine) to help with nausea and vomiting during pregnancy.
Vitamin B12: Cyanocobalamin
Cyanocobalamin helps our body with processing another B vitamin, folic acid. It helps store and absorb folic acid. Cyanocobalamin also helps with maintaining a healthy nervous system, and with the creation of new red blood cells (to some extent).
Getting enough cyanocobalamin can be a problem for some people, especially vegetarians, because plant sources are generally inconsistent or unreliable. Good sources of this vitamin include steamed clams, oysters, fortified breakfast cereal, yogurt, and (surprisingly) fast food cheeseburgers. It’s important to know that calcium is required for our body to absorb cyanocobalamin.
Besides vegetarians, there are a few other reasons you may need a Vitamin B12 supplement. Some medications, including those that help reduce stomach acid for people with heartburn or acid reflux, and metformin are the most common reasons for supplementation. Someone who has stomach issues or a certain type of anemia may also need supplementation.
Folic Acid
Folic acid is another of the B vitamins. It is involved in the production of our DNA, so it’s very important to get enough of it. It is also crucial for brain and spinal cord development, which makes it an important supplement for pregnant women and women of child-bearing age.
Some good food sources of folic acid are fortified foods such as cereal, many vegetables, legumes, and nuts. However, there are some reasons for additional supplementation. People who take oral contraceptives, antacids, aspirin, and metformin may have less absorption of folic acid from their diet. Pregnant women will also need a supplement, sometimes found in prenatal vitamins.
Vitamin C
Almost everyone has heard of vitamin C. It acts as an antioxidant in our bodies to get rid of DNA-damaging free radicals. Did you know that consuming at least 500 mg of vitamin C per day can decrease your risk of developing cataracts? It is also important in preventing bruising and helping our bodies to create collagen, a type of tissue that holds together our bones, muscles, and skin. Collagen is also used by our bodies to create scar tissue, so a deficiency in vitamin C may actually impair wound healing.
Many people have heard that taking vitamin C supplements can prevent the common cold, but scientific evidence on this varies. Some studies show that it can potentially help decrease the duration of the cold but may not prevent it. Regardless, it still may be a smart idea to supplement if you feel you’re getting sick.
We are actually one of the few species that doesn’t create our own vitamin C. We get all our vitamin C from our diet. Fruits and vegetables such as papaya, cantaloupe, and oranges are the best sources of vitamin C. Excess vitamin C is stored in the liver, so it’s difficult to develop a deficiency. Additional supplementation is recommended in smokers, those with poor nutritional intake, pregnant women, and people with inflammatory diseases.
Even though vitamin C is water-soluble, it is still possible – though difficult – to get too much in one day. Daily doses of 2000 mg or higher can cause nausea, diarrhea, nose bleeds, and even kidney stones over time.
Vitamin D
Vitamin D is another vitamin most people have heard of. Its main role in the body is to help maintain and build strong bones and teeth by making sure we have enough calcium and phosphate in our body. Vitamin D helps children build strong bones and can help to prevent osteoporosis in the elderly. Vitamin D also helps us maintain a healthy immune system.
One of the best ways to get vitamin D is through sun exposure, specifically UV-B rays. However, any sunscreen that is over an SPF level of 8 will block the UV rays our body needs to make vitamin D. As an alternative to sunlight, it is pretty easy to get vitamin D in our diets. Milk and cereals are usually fortified with it. Beef and salmon are also good food choices for those looking to increase their vitamin D intake.
Deficiency can result in people with a chronic gastrointestinal disease such as celiac or Crohn’s disease, if they have a milk allergy, if they are a strict vegetarian, or if they spend less time outdoors. Some signs and symptoms of a deficiency include lower back pain for women, muscle weakness, and possibly throbbing bone pain in the lower back or pelvis when pressure is applied to certain areas of the body. People with a deficiency in vitamin D can be at risk for osteoporosis (for the elderly) and age-related macular degeneration. Having a vitamin D deficiency is more common than the other vitamins, so there are a few different choices to supplement your dietary intake.
There are two different forms of Vitamin D you may have seen. D3, also called cholecalciferol, is animal-based, and not the best choice for vegetarians. D2 is plant-based, however, it is not absorbed as well as the D3 form. Vitamin D comes in many different doses, so it’s important to make sure you choose the right supplement strength for your age.
Ask Our Pharmacists About Your Vitamin Intake
It can be overwhelming to figure out what supplements you need based on your age, diet, and activity levels. Feel free to ask one of our pharmacists for help choosing the right vitamin supplement for you! If you need regular dosing information, check out the handy tables listed below!
If you need regular dosing information, check out the handy tables listed below!
Adult (19+) Daily Vitamin Intake
| Vitamin | Dietary Reference Intake | Upper Level of Intake | |||
| Women | Men | Women | Men | ||
| Vitamin A | 2310 IU | 3000 IU | 10,000 IU | ||
| Vitamin D | 400-1000 IU | 4000 IU | |||
| Vitamin B1 à Thiamine | 1.1 mg | 1.2 mg | Not established | ||
| Vitamin B2 à Riboflavin | 1.1 mg | 1.3 mg | Not established | ||
| Vitamin B3 à Niacin | 14 mg | 16 mg | 35 mg | ||
| Vitamin B6à Pyridoxine | 19-50 years: 1.3 mg
50+: 1.5 mg |
19-50 years: 1.3 mg
50+: 1.7 mg |
100 mg | ||
| Vitamin B12 à Cyanocobalamin | 2.4 mcg | Not established | Not established | ||
| Folic Acid | 400 mcg | 1000 mcg | |||
| Pantothenic Acid | 5 mg | Not established | |||
| Biotin | 30 mcg | Not established | |||
| Vitamin E (alpha-tocopherol) | 22.5 IU | 1000 IU | |||
| Vitamin C (ascorbic acid) | 60 mg | 90 mg | 2000 mg | ||
Teenager (14-18) Daily Vitamin Intake
| Vitamin | Dietary Reference Intake | Upper Level of Intake | ||
| Female | Male | Female | Male | |
| Vitamin A | 2310 IU | 3000 IU | 9240 IU | |
| Vitamin D | 200-400 IU | 4000 IU | ||
| Vitamin B1 à Thiamine | 1.0 mg | 1.2 mg | Not established | Not established |
| Vitamin B2 à Riboflavin | 1.0 mg | 1.3 mg | Not established | Not established |
| Vitamin B3 à Niacin | 14 mg | 16 mg | 30 mg | |
| Vitamin B6à Pyridoxine | 1.2 mg | 1.3 mg | 80 mg | |
| Vitamin B12 à Cyanocobalamin | 2.4 mcg | Not established | Not established | |
| Folic Acid | 400 mcg | 800 mcg | ||
| Pantothenic Acid | 5 mg | Not established | Not established | |
| Biotin | 25 mcg | Not established | ||
| Vitamin E (alpha-tocopherol) | 22.5 IU | 800 IU | ||
| Vitamin C (ascorbic acid) | 75 mg | 2000 mg | ||
Children (9-13) Daily Vitamin Intake
| Vitamin | Dietary Reference Intake | Upper Level of Intake |
| Vitamin A | 2000 IU | 5610 IU |
| Vitamin D | 200-400 IU | 4000 IU |
| Vitamin B1 à Thiamine | 0.9 mg | Not established |
| Vitamin B2 à Riboflavin | 0.9 mg | Not established |
| Vitamin B3 à Niacin | 12 mg | 20 mg |
| Vitamin B6à Pyridoxine | 1.0 mg | 60 mg |
| Vitamin B12 à Cyanocobalamin | 1.8 mcg | Not established |
| Folic Acid | 300 mcg | 600 mcg |
| Pantothenic Acid | 4 mg | Not established |
| Biotin | 20 mcg | Not established |
| Vitamin E (alpha-tocopherol) | 16.5 IU | 600 IU |
| Vitamin C (ascorbic acid) | 45 mg | Not established |
Children (4-8) Daily Vitamin Intake
| Vitamin | Dietary Reference Intake | Upper Level of Intake |
| Vitamin A | 1320 IU | 3000 IU |
| Vitamin D | 200-400 IU | 2000 IU |
| Vitamin B1 à Thiamine | 0.6 mg | Not established |
| Vitamin B2 à Riboflavin | 0.6 mg | Not established |
| Vitamin B3 à Niacin | 8 mg | 15 mg |
| Vitamin B6à Pyridoxine | 0.6 mg | 40 mg |
| Vitamin B12 à Cyanocobalamin | 1.2 mcg | Not established |
| Folic Acid | 200 mcg | 400 mcg |
| Pantothenic Acid | 3 mg | Not established |
| Biotin | 12 mcg | Not established |
| Vitamin E (alpha-tocopherol) | 10.5 IU | 300 IU |
| Vitamin C (ascorbic acid) | 25 mg | Not established |
Children (1-3) Daily Vitamin Intake
| Vitamin | Dietary Reference Intake | Upper Level of Intake |
| Vitamin A | 1000 IU | 2000 IU |
| Vitamin D | 200-400 IU | 2000 IU |
| Vitamin B1 à Thiamine | 0.5 mg | Not established |
| Vitamin B2 à Riboflavin | 0.5 mg | Not established |
| Vitamin B3 à Niacin | 6 mg | 10 mg |
| Vitamin B6à Pyridoxine | 0.5 mg | 30 mg |
| Vitamin B12 à Cyanocobalamin | 1.0 mcg | Not established |
| Folic Acid | 150 mcg | 300 mcg |
| Pantothenic Acid | 2 mg | Not established |
| Biotin | 8 mcg | Not established |
| Vitamin E (alpha-tocopherol) | 9 IU | 300 IU |
| Vitamin C (ascorbic acid) | 15 mg | Not established |
Resources:
General
Vitamin A
Vitamin B
- https://ods.od.nih.gov/factsheets/Thiamin-Consumer/
- https://ods.od.nih.gov/factsheets/Riboflavin-Consumer/
- https://medlineplus.gov/ency/article/002409.htm
- https://ods.od.nih.gov/factsheets/VitaminB6-Consumer/
- https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/
- https://ods.od.nih.gov/pdf/factsheets/Folate-Consumer.pdf#search=%22folic%20acid%22
Vitamin C
- https://ods.od.nih.gov/factsheets/VitaminC-Consumer/
- Ran L, Zhao W, Wang J, et al. Extra dose of vitamin C based on a daily supplementation shortens the common cold: a meta-analysis of 9 randomized controlled trials. Biomet Red Int. 2018;1-12.
- Douglas R, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold: review. Cohcrane Database Syst Rev. 2000;2.
Vitamin D
