From 1985 to 1995 a group of doctors set out to test a theory—that high doses of beta-carotene and retinol, two A vitamins with cancer-fighting properties, could greatly reduce our risk of getting cancer. They put study participants on 30 milligrams of beta-carotene and 25,000 International Units (IU) of retinol each day. But instead of turning their bodies into cancer-fighting machines, the vitamins actually caused some participants to get cancer. The doctors stopped the trial nearly two years early because of the results. "We should step back and ask ourselves whether there might be a lesson to take from this sad experience of actually causing cancer with high vitamin intake," says Tim Byers, MD, professor of epidemiology at the Colorado School of Public Health. Byers, one of the original researchers in the trial, recently led a forum at the American Association for Cancer Research reviewing this and other studies that all found increased cancer risk with vitamin overdose.
"I think the lesson is one that says a little nutrient is good, a lot may not be better," he says. It's an easy lesson, but one many do not obey. At the first sign of a cold, we guzzle orange juice and vitamin C powders, take vitamin C tablets or suck on vitamin C infused cough drops—despite research that overloading your body with Vitamin C does nothing to get rid of your cold. It usually doesn't cause any harm either, though, which may be why people continue to take it. Vitamin C is a water-soluble vitamin, meaning any extra hangs around in the water in your body until it's flushed out in your urine. So taking too much once in a while isn't really a problem. MORE: Do You Just End Up Peeing Out All The Vitamins You Take? But not all vitamins are water-soluble, and the ones that are lipid-soluble, meaning they like to hang around in your body's fat, don't get flushed out. Instead, if you take too much of a lipid-soluble vitamin over a few weeks to a month, they sit in the liver and can build up to toxic levels, causing problems ranging from weak bones to liver damage, according to Katherine Zeratsky, a registered dietician nutritionist at the Mayo Clinic.
Scientists are still trying to figure out exactly how much of a vitamin is too much for our bodies to handle, but in the meantime the Institute of Medicine has a list of Upper Tolerable Intake Levels, which is the best bet given the research so far. How much is too much: More than one a day. If you're a health-conscious person in the United States today, chances are you take a multivitamin. And one a day, even if you're already getting enough nutrients in food, won't hurt you. But more than one a day over a long period of time will. The most serious risk, according to the National Institute of Health, comes from multivitamins that include iron or calcium. Calcium toxicity can cause abdominal pain, weak bones, constipation, irregular heartbeat, and depression among other symptoms. Iron is one of the most dangerous minerals to overdose on, and can cause problems ranging from diarrhea and liver damage to low blood pressure and coma. How much is too much: 2000 mg. Since vitamin C is water-soluble, excess that your body doesn't need just gets flushed out in your urine.
But, The Mayo Clinic warns, large doses of vitamin C can cause problems like diarrhea, nausea, vomiting, heartburn, cramps, headache, insomnia, and kidney stones. The average person needs only 65 to 90 mg of vitamin C every day, which you can find in one large orange or a cup of chopped bell peppers. Let's Stay In Touch Keep this field blank Enter your email address You may unsubscribe at any time. MORE: 4 Vitamins You're Probably Not Getting Enough Of Vitamin A: How much is too much: 3000 IU Vitamin A is fat-soluble, which means it gets processed through your liver. Too much vitamin A will stick around until it can get processed—and taking too much every day for a month can lead to toxic levels. Other than studies like the one above showing both the beta-carotene and retinol forms of vitamin A can cause cancer, too much retinol has been linked with birth defects, weak bones, and liver damage. How much is too much: 1100 IU This is another one that has been linked to cancer.
Vitamin E is fat-soluble and easy to get in your diet from foods like meat, eggs, and vegetables—so it's rare for people to have vitamin E deficiency. The average person only needs 15 mg a day, but can tolerate much more. Too much vitamin E can cause problems with blood clotting, and poses risk of hemorrhage. High doses have also been associated with both lung and prostate cancers. How much is too much: 4000 IU, according to the IOM, but recent evidence suggests we may actually need more than 8000 IU to avoid Vitamin D deficiency. Unlike vitamin E, vitamin D deficiency is common. Doctors estimate three out of every four people are vitamin D deficient; so taking a vitamin D supplement might not be a bad thing. But be careful not to overdo it. Taking 50,000 IU of vitamin D a day can lead to toxicity, according to the Mayo Clinic. Vitamin D toxicity builds calcium in your blood and lead to weak bones, kidney stones, nausea, kidney problems, and calcification of soft tissue. MORE: Is A Vitamin Deficiency Making You Gain Weight?
How much is too much: 1 to 1.3 mg There are many different forms of vitamin B, but the Institute of Medicine only lists limits for folic acid (vitamin B9) and vitamin B6. Although B vitamins are water-soluble like vitamin C, they can cause problems when taken in large doses. Folic acid, for example, has also been linked to cancer in high doses. It's also been known to cause stomach problems, trouble sleeping, rash, and seizure. And doctors believe taking more than 200 or 300 mg of vitamin B6 can cause nerve damage.Vitamin D is essential for healthy bones, and to control the amount of calcium in our blood. It is important at every stage of life, but especially for rapidly growing infants and teenagers and for pregnant and breastfeeding women. Most people get little Vitamin D in their diet. Only a few natural foods such as oily fish and eggs (20 – 40 units per egg) contain significant amounts of Vitamin D. A few foods are fortified with small amounts of Vitamin D (e.g. some yoghurts and breakfast cereals).
All formula milks are fortified, but plain cow’s milk is not fortified in the UK. Breast milk generally contains little Vitamin D. Sunshine is the main source of Vitamin D. However, Vitamin D can only be made in our skin by exposure to sunlight when the sun is high in the sky. Therefore in most of the UK from November to March, and in Scotland from October to April, Vitamin D can not be made from sunshine. A daily dose of 400 units Vitamin D is safe for all age groups, and is consistent with the recommendations of the UK Scientific Advisory Committee on Nutrition (SACN) (1), the National Osteoporosis Society (2) the British Paediatric and Adolescent Bone Group (BPABG) (3) and a Global consensus statement based on a recent literature review (4). Pregnant and breastfeeding mothers should take 400 units daily. If a breastfeeding mother was not taking these supplements, or is known to be deficient herself, her baby should start Vitamin D supplements soon after birth. A healthy term baby born to a mother who is taking appropriate supplements can wait until a month of age before starting supplements.
The recommended dose for babies is 300 – 400 units daily. Note: A dose of 10 micrograms of Vitamin D is 400 units. Disclaimer: The RCPCH does not endorse any particular commercial product; those listed are examples of products in usage in the UK. Check your local Trust guidelines for specific recommendations. There are two types of Vitamin D: Ergocalciferol (Vitamin D2) and Colecalciferol (Vitamin D3). For daily treatment, both D2 and D3 are equally effective (consensus statement 4). Vitamin D2 is a plant product and Vitamin D3 is obtained from fish or mammals. Nevertheless many sources of Vitamin D3 are acceptable to vegetarians and those adhering to a Halal or Kosher diet as the main commercial source is lanolin. Lanolin is the oil of sheep's wool and most religious authorities do not class it as a meat product. Whether ingested orally or made in the skin under the action of Ultraviolet light, Vitamin D is converted to 25(OH)Vitamin D in the liver. This is then converted in the kidney and other body tissues to 1,25-(OH)2VitaminD, which is also known as Calcitriol and is the form with metabolic effects.
“Activated Vitamin D” preparations such as Calcitriol or Alfacalcidol SHOULD NOT BE USED for the treatment of simple Vitamin D deficiency. They should only be used for the treatment of complex cases by specialists. They are ineffective in treating simple Vitamin D deficiency and can cause severe adverse effects, particularly hypercalcaemia. Simple Vitamin D is safe and is the treatment for D deficiency. A dose of 400 units daily is appropriate for most children. Most children do not need a medical assessment or blood test. Advice should be given that all children require Vitamin D from sun, diet or supplement. If a child has risk factors for deficiency or symptoms suggesting rickets or other rare deficiency syndromes then medical assessment is required. * Lifestyle Advice: Vitamin D and the Sun Consensus statement 2010 This represents the unified views of the British Association of Dermatologists, Cancer Research UK, Diabetes UK, the Multiple Sclerosis Society, the National Heart Forum, the National Osteoporosis Society and the Primary Care Dermatology Society:
Vitamin D is essential for good bone health and for most people sunlight is the most important source of vitamin D. The time required to make sufficient vitamin D varies according to a number of environmental, physical and personal factors, but is typically short and less than the amount of time needed for skin to redden and burn. Enjoying the sun safely, while taking care not to burn, can help to provide the benefits of vitamin D without unduly raising the risk of skin cancer. Vitamin D supplements and specific foods can help to maintain sufficient levels of vitamin D, particularly in people at risk of deficiency. Blood levels of Vitamin D do not need to be measured routinely. The recommended dosage (400 units daily) is safe and should be given to all children. The only children requiring blood levels are those with rare disorders such as rickets or unexplained symptoms including seizures and cardiomyopathy in infants, and poor growth in children and muscle weakness at any age.
If a blood test is required 25hydroxyVitaminD should be measured as it is the only reliable marker of body stores. The blood test requires about 2ml of serum and costs approximately £20. Basic bone biochemistry (calcium, phosphate and alkaline phosphatase) is often normal despite significant Vitamin D deficiency. High alkaline phosphatase implies rickets. The units for 25hydroxyVitaminD are nmol/L in the UK, but ng/ml in the USA. A blood level of 25hydroxyVitaminD below 25nmol/L is called deficient. A blood level above 50 nmol/L is generally regarded as sufficient, although some laboratories give reference ranges up to 75 or 80. In practice symptoms of Vitamin D deficiency in individuals with blood levels more than 50nmol/L are rare, so 50 nmol/L is becoming widely accepted as the appropriate blood level to aim for. In the few children that require a blood test it can be helpful to measure Parathyroid hormone (PTH) on the same blood specimen. PTH is produced in the neck glands when the parathyroid calcium-sensing receptors detect a low level of blood calcium.
Therefore PTH levels are a helpful measure of calcium and Vitamin D status. A high level of PTH in children is usually due to Vitamin D deficiency or a lack of calcium in the diet. Other causes (e.g. parathyroid tumours or renal failure) are rare. Although sunshine is the usual source of Vitamin D, diet is the source of calcium. It is particularly important to prevent Vitamin D deficiency in children with limited calcium intake. Children with allergies or fussy diets, and especially young people with autism, are at risk of rickets due to calcium / Vitamin D deficiency. Children with rickets, hypocalcaemia or other significant symptoms due to Vitamin D deficiency, and children with blood levels below 25 nmol/L should be prescribed treatment doses of Vitamin D before starting long term supplements. The same effect may be achieved by multiplying the dose by 7 and giving it weekly. In older children, especially if compliance is a concern, a single dose can be used (multiply daily dose by 30).
It is essential to check the child has a sufficient dietary calcium intake, and that a maintenance Vitamin D dose follows the treatment dose (see Standard Vitamin D supplement dose above) and is continued long-term. Follow-Up: Some recommend a clinical review a month after treatment starts, asking to see all vitamin and drug bottles. A blood test can be repeated then if it is not clear that sufficient vitamin has been taken. Vitamin D is prescribable as Colecalciferol Liquid 3,000 units/ml. Tablets or capsules of 400, 1,000, 10,000, 20,000 units are also prescribable (e.g. Fultium, InvitaD3). Combined “Calcium and Vitamin D” tablets are available but unless the patient has insufficient calcium intake it is often better, and cheaper, to prescribe a pure Vitamin D product.those listed are examples of products in the UK. Check your local trust guidelines for specific recommendations. After treatment, children who were deficient or insufficient should continue long term supplements at least until completion of growth, unless lifestyle changes to provide a reliable intake from diet and sun exposure.
If a patient is diagnosed with Vitamin D deficiency the family should be screened or treated. As a minimum, screening should take place by taking a history, and prevention advice given. Investigation of other family members by blood testing is seldom indicated. Adverse effects of Vitamin D overdose are rare but care should be taken with multivitamin preparations as Vitamin A toxicity is a concern. Multivitamin preparations often contain a surprisingly low dose of Vitamin D. Vitamin D toxicity is exceedingly rare below serum concentrations of 375nmol/L. Massive overdose causes hypercalcaemia but there is no agreement on the threshold concentration or amount of Vitamin D that results in toxicity. In adults, prolonged daily intake of Vitamin D up to 10,000 IU or serum concentrations of 25(OH)D of up to 240 nmol/L appear to be safe. SACN has accepted the European Food Safety Authority recommendations of a safe upper limit of 1,000 units/day for infants up to 1 year of age, 2,000 units/day for children aged 1-10 years and 4,000 units/day for those older than 10.