Vitamin supplements have many health benefits, but improper use can lead to serious side effects. A previous article discussed the side effects of vitamin supplements for Vitamin C, Vitamin E, Calcium and Zinc. This article covers the side effects of two additional common vitamin supplements: Vitamin A and Vitamin D.
Vitamin A: Daily Recommendations and Side Effects
Vitamin A is an antioxidant that supports the immune system, especially in response to respiratory infections. It is required by the body for the proper growth and development of bones, skin, hair, teeth and gums. Vitamin A is well known for supporting healthy vision. Vitamin A is also known as retinol and is commonly referred to by that name when used in facial care products.
The recommended daily dosages for Vitamin A are:
Ages 0-6 months – 400 micrograms (1,333 IU)
Ages 7-12 months – 500 micrograms (1,667 IU)
Ages 1-3 years – 300 micrograms (1,000 IU)
Ages 4-8 years – 400 micrograms (1,333 IU)
Ages 9-13 years – 600 micrograms (2,000 IU)
Ages 14-18 years – 900 micrograms (3,000 IU) (boys) and 700 micrograms (2,333 IU) (girls)
Men 19 years of age or older – 900 micrograms (3,000 IU)
Women 19 years of age or older – 700 micrograms (2,333 IU)
Pregnant teens (18 years of age or younger) – 750 micrograms (2,500 IU)
Pregnant adults (19 years of age or older) – 770 micrograms (2,567 IU)
Breastfeeding teens (18 years of age or younger) – 1,200 micrograms (4,000 IU)
Breastfeeding adults (19 years of age or older) – 1,300 micrograms (4,333 IU)
Side effects of Vitamin A include fatigue, decreased appetite, nausea, vomiting, headache, irritability, dry or cracking lips and skin, hair loss.
The Food and Nutrition Board (FNB) of the U.S. Institute of Medicine of the National Academy of Sciences set new limits for Vitamin A consumption in January 2001. The FDA uses the much higher 1968 guidelines for acceptable limits of Vitamin A in supplements. While signs of Vitamin A toxicity generally do not occur until levels of 8,000 micrograms (25,000 IU) or above have been reached, research is showing some members of the population (elderly, alcohol abusers, people prone to high cholesterol) may show the signs at lower amounts. Due to the high number of foods fortified with Vitamin A, it is best to look for vitamin supplements that contain as little Vitamin A as possible.
Total Vitamin A intake (Vitamin A supplements and food) should not exceed:
Ages 0-12 months – 600 micrograms (2,000 IU)
Ages 1-3 years – 600 micrograms (2,000 IU)
Ages 4-8 years – 900 micrograms (3,000 IU)
Ages 9-13 years – 1,700 micrograms (5,667 IU)
Ages 14-18 years – 2,800 micrograms (9,333 IU)
Ages 19 years and up – 3,000 micrograms (10,000 IU)
Toxic level side effects of Vitamin A include the side effects mentioned above, as well as dizziness, malaise, blurred vision, joint or bone pain and swelling, yellowing of the skin, decreased growth, intracranial pressure, intense itching, eye damage, liver damage, high calcium levels, and intrahepatic homeostasis (bile cannot flow into the intestines). Infants with Vitamin A toxicity may develop symptoms similar to a brain tumor, including a bulge in the fontalle (the soft spot on the head).
Toxic levels of Vitamin A can occur from one large dose or a long-term use of Vitamin A supplements. Seek medical attention if you have taken an extremely high dose of Vitamin A or are displaying signs of Vitamin A toxicity.
High doses of Vitamin A during pregnancy have been linked to birth defects, especially malformations of the central nervous system. Pregnant women should not exceed 3,000 micrograms (10,000 IU) per day. As many foods are fortified with Vitamin A, pregnant women should look for prenatal vitamins that contain 1,500 micrograms (5,000 IU) or less. Vitamin A is excreted through breast milk and can cause signs of toxicity in nursing babies.
Due to an increased risk of osteoporosis from high doses of Vitamin A, senior adults taking Vitamin A supplements or a multi-vitamin supplement should look for one that contains 750 micrograms (2,500 IU) or less.
The risk of Vitamin A toxicity is increased if Vitamin A supplements are used with the following drugs: Soriatane, Coumadin, Targentin, ATRA, Vesanoid, Tegison, Accutane, Amnesteen, Vesaboid, Avita, Renova, Retin-A, and Altinac. Avoid using a Vitamin A supplement while on these or similar medications. Always tell your doctor or pharmacist if you are using a Vitamin A supplement or a multi-vitamin containing Vitamin A.
People using tetracycline antibiotics, especially minocycline (Minocin), while using a Vitamin A supplement may develop intracranial hypertension (abnormal pressure in the cerebrospinal fluid). Tell your doctor or pharmacist if you have been using a Vitamin A supplement or a multi-vitamin containing Vitamin A when being prescribed an antibiotic.
Vitamin A can reduce the effectiveness of the vaccine for measles. Do not take Vitamin A supplements if you will be receiving that vaccination.
Oral contraceptives can increase blood levels of Vitamin A. Speak to your doctor or pharmacist on how to adjust your Vitamin A supplementation to avoid toxicity.
Isotretinoin (Accutane), which is a synthetic derivative of Vitamin A used to treat acne, has been shown to cause serious birth defects. It should be avoided before and during pregnancy. Tretinoin (Retin-A) is a topical Vitamin A derivative that should be avoided during pregnancy due to risk of absorption into the blood stream.
Vitamin D: Daily Recommendations and Side Effects
Vitamin D is used by the body to absorb calcium, which helps build strong bones and teeth. It also helps regulate the heartbeat, aids in normal blood clotting, protects against muscle weakness, and is needed for proper functioning of the thyroid.
There are several types of Vitamin D, but the most frequently supplemented forms are Vitamin D2 and Vitamin D3. Vitamin D2 (ergocalciferol), which is found in plant sources, is the form most often added to milk and used in multi-vitamins. Vitamin D3 (cholecalciferol) is found in animal food sources and is the form the body produces in response to sunlight. It is stronger than Vitamin D2 and is frequently used in individualized Vitamin D supplements.
The body produces almost all the Vitamin D it needs when the skin is exposed to sunlight. Ten to 15 minutes of sunlight each day should be enough to meet the Vitamin D requirements of the body. The Food and Nutrition Board (FNB) of the U.S. Institute of Medicine of the National Academy of Sciences has set the daily recommended daily values based on the assumption a person has zero Vitamin D synthesis due to lack of sun exposure.
The recommended daily dosages for Vitamin D are:
Ages 0-12 months – 5 micrograms (200 IU)
Ages 1-50 years – 5 micrograms (200 IU)
Ages 51-70 years – 10 micrograms (400 IU)
Ages 71 years and up – 15 micrograms (600 IU)
The American Academy of Pediatrics feels these levels are too low and recommends 10 micrograms (400 IU) for infants, children and teens.
Vitamin D3 is generally well tolerated when taken at or below the recommended levels. One study showed a side effect of daytime sleepiness.
The toxic level side effects of Vitamin D are quite severe. This has prompted the Food and Nutrition Board to set the upper limits for supplemental Vitamin D intake low as a precaution.
Supplemental Vitamin D daily intake should not exceed:
Ages 0-12 months – 25 micrograms (1,000 IU)
Ages 1 year and up – 50 microgram (2,000 IU)
There is no toxic limit for Vitamin D produced through sunlight exposure.
The toxic level side effects of Vitamin D are hypercalcemia (abnormally high levels of calcium) and bone loss. Early symptoms of hypercalcemia include appetite loss, nausea and vomiting. These symptoms are followed by headache, drowsiness, fatigue, weakness, dry mouth, excess thirst, excess urination, abdominal pain, metallic taste in the mouth, ringing in the ears, vertigo, and unsteadiness. Calcium deposits may form in various organs, such as the heart, lungs, and especially the kidneys. If left untreated, hypercalcemia can lead to kidney failure, abnormal heartbeat, and nervous system dysfunction (confusion, dementia and coma), and death. Seek medical attention if you have taken excessively high doses of Vitamin D or are showing any toxic side effects.
Vitamin D should be used with caution when taking digitalis (Digoxin) or herbal supplements with the same properties due to the risk of hypercalcemia causing irregular heart rhythms.
The risk of hypercalcemia is increased in hypoparathyroid patients who take Vitamin D supplements and thiazide diuretics. Inform your doctor or pharmacist if you are taking a Vitamin D supplement.
Using a Vitamin D supplement and taking a magnesium-containing antacid can lead to a condition called hypomagnesaemia (high magnesium levels in the blood), which can have dangerous side effects in people with kidney problems.
Linus Pauling Institute’s Micronutrient Information Center, Oregon State University:
National Institutes of Health National Library of Medicine – Medline Plus:
Nutritional Supplement Educational Centre: