Consumer Tips

May 5, 2009
If the label of a food or dietary supplement indicates 100% of the "Daily Value" for vitamin A, then one serving of the product contains about 200% of the daily intake currently recommended by the Institute of Medicine. Since high vitamin A intake may promote bone loss and birth defects, revision of labeling regulations is long overdue.
Too much vitamin A can be toxic
May 11, 2009
Less than 2 milligrams of vitamin B-6 is all that is needed to meet an adult’s daily needs; only 200 milligrams consumed daily can cause nerve damage over time. Check that your dietary supplement does not contain toxic levels of this essential nutrient.
Though B6 is important, don't overdose
July 14, 2009
Adequate calcium is good for bone health, but it is possible to get too much. The Institute of Medicine considers 2500 mg/day to be the upper limit. Indiscriminate use of calcium- fortified foods plus supplements can easily go over that limit.
How much is too much calcium?
July 24, 2009
Vitamin B-6 is needed to make blood, keep the nervous and immune systems functioning properly, and regulate blood glucose levels. But, high doses of this vitamin can damage nerves - especially those in the arms, hands, legs and feet.
Though B6 is important, don't overdose
August 6, 2009
It is important to consume adequate amounts of all essential nutrients. However, because excessive intake of some nutrients can be harmful, a “Tolerable Upper Intake Level” has been established for many nutrients. These values represent the maximum daily amount of a nutrient thought to not cause harm.
Vitamin limits hard to set
September 5, 2009
Vitamin B-6 is required in tiny amounts measured in thousandths of a gram. Many foods contain vitamin B-6, so it is unlikely to be too low unless your diet is extremely limited in variety or total food consumed. B-6 supplements in high doses, however, can cause nerve damage.
Though B6 is important, don't overdose
October 13, 2009
Fiber can help to prevent constipation. Excessively high fiber intake, however, can interfere with essential mineral absorption and can even cause constipation if inadequate fluids are consumed.
Balancing the facts on fiber
December 22, 2009
High-fat meals may increase the risk of a heart attack for several hours because arteries narrow and blood flow slows. Enjoy the higher fat holiday foods, but in moderation.
Switch from fat phobia to fat smarts
April 8, 2010
The theory that heart disease is caused by too much iron in the body has been refuted by a number of studies. Too much iron is mainly a concern for those with the genetic condition called hemochromatosis.
Iron level is important to good health
August 10, 2010
Foods and food components that show potential for preventing cancer are not necessarily beneficial during the treatment of cancer. A review of clinical trials reported that supplementation with vitamins C and E and beta carotene should not be used during chemotherapy.
Not too much ... not too little ... but enough
August 24, 2010
Too much of a good thing can be bad. This applies to nutrients and even exercise. “Tolerable Upper Intake Levels” have been established for many nutrients to help people know how much is too much.
How much is too much?
September 22, 2010
Vitamin A is needed for normal growth, reproduction, bone health, blood cell production, skin health and immune function, but too much vitamin A (just 2 to 3 times the current recommended vitamin A intake) has been linked to increased bone loss and birth defects.
Too much vitamin A can be toxic
March 9, 2011
An old medical condition called "milk alkali syndrome" has resurfaced and researchers are recommending a new name: "calcium alkali syndrome." Overuse of calcium supplements and calcium-containing antacids can cause high blood pressure and even kidney failure. Researchers recommend keeping total calcium intake below 1200 to 1500 mg per day.
Calcium Supplements: Too Much of a Good Thing?
July 7, 2011
Over time, excess consumption of fat and sugar have been found to lead to increased rates of cell death in organs like the liver and kidneys. This is thought to be a key factor in the development of conditions like type 2 diabetes. New research is finding that 3 specific small RNA molecules increase in the lipid overload condition and cause cell death.
Surprising Culprits Behind Cell Death from Fat and Sugar Overload
July 15, 2011
It is difficult to drink too much water, but it is possible. The Institute of Medicine points out that the maximal adult kidney excretion rate is 0.7 to 1.0 liters of water per hour. Unless the rate of sweat loss is substantial, consuming water at or above this rate could be harmful and even deadly.
Waterlogged America: Do We Drink Too Much?
March 27, 2012
Using a human cell culture technique, researchers found that some antioxidants such as resveratrol and genistein can damage DNA. This may prove to be another example of the "dose making the poison" since moderate intake of these antioxidants from foods seems to protect DNA from damage.
High-Throughput Screening Finds Surprising Properties for Antioxidants: Some Compounds Can Damage DNA, but May Treat Cancer
March 3, 2013
Although meeting essential nutrient needs during pregnancy is needed for optimal infant health, excessive intake of a nutrient also may cause problems. A recent study found that infants with high blood levels of vitamin D at birth were more likely to develop allergies within their first 2 years of life.
Too Much Vitamin D During Pregnancy Can Cause Food Allergies, Research Suggests
June 5, 2013
Tea is a source of fluoride in the diet that may benefit dental and bone health. However, proving that too much of a good thing can be bad for you, a woman who consumed very large amounts of concentrated tea for about 20 years suffered from fluoride toxicity that was serious enough to cause her to lose her teeth.
Woman's Tea Addiction Led to Loss of Teeth
January 31, 2014
Supplementation of adult men with vitamin D2 (3800 IU/day) for 6 weeks caused an increase in blood markers of muscle damage. Based on this study, high dose supplementation with vitamin D may have detrimental effects in athletes.
Taking vitamin D2 is a poor choice for athletes, research shows
February 2, 2014
Too much of a good thing can be bad. A new study found that feeding mice supplemental amounts of the antioxidants N-acetylcysteine (NAC) and vitamin E markedly increased tumor progression and reduced survival. This result is similar to the effects seen in smokers taking beta-carotene supplements.
Antioxidants may speed up lung cancer progression
February 22, 2014
Consuming adequate amounts of folic acid is important to overall health. However, taking high dose folic acid supplements can interfere with the timely diagnosis of vitamin B-12 deficiency that is common in older people and strict vegetarians.
Taking folate supplements not for all
May 27, 2014
Studies in mice show that supplementing the diet with the alpha-tochopherol form of vitamin E improves lung function, but the gamma-form worsens lung function. A newly published study of over 4500 people followed for 20 years found a similar relationship in humans. Other studies have found health benefits associated with both the alpha and gamma forms of vitamin E. Therefore Including a variety of vegetable oils in the diet is likely the best option to maintain a balanced intake of the various forms of vitamin E.
Vitamin E-rich oils linked to lung inflammation
January 17, 2015
Tanning Beds and Vitamin D: It generally is assumed that sun exposure cannot lead to excessive vitamin D levels in the body. However, a recent case study of a white woman indicated that her excessively high blood level of vitamin D (hypervitaminosis D) was caused by tanning bed use three to four times a week. When she ceased using the tanning bed, her blood level of vitamin D (25-hydroxyvitamin D) returned to a normal level within a month.
Vitamin D Highlights: Too Much Tanning
February 16, 2015
Folic Acid Excess: A study conducted with rats found that high folic acid intake (20 times recommended intake) before, during, and after pregnancy caused their babies to become overweight and insulin resistant in adulthood. This effect was more pronounced in female offspring. How this may translate to humans is not clear, but it supports heeding the U.S. folic acid tolerable upper intake level that is about twice the RDA.
Taking too much folic acid while pregnant may put daughters at risk of diabetes and obesity
July 17, 2015
Drinking During Exercise: When people drink too much during very long endurance events, they can dangerously lower their blood sodium level - a condition called hyponatremia. A new consensus statement cautions athletes against drinking before they are thirsty and recommends using thirst as their guide to drink during long bouts of exercise. However, it should be recognized that waiting for thirst can lead to dangerous dehydration in hot and humid situations in which the rate of water loss in sweat can exceed the rate at which water can be absorbed by the intestine.
Overhydration potentially deadly for athletes, experts warn Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015
July 25, 2015
Vitamin B-6 is needed to make blood, keep the nervous and immune systems functioning properly, and regulate blood glucose levels. But, high doses of this vitamin can damage nerves - especially those in the arms, hands, legs and feet.
Though B6 is important, don't overdose
August 8, 2015
Essential Nutrients and Balance: It is important to consume adequate amounts of all essential nutrients. However, because excessive intake of some nutrients can be harmful, a “Tolerable Upper Intake Level” has been established for many nutrients. These values represent the maximum daily amount of a nutrient thought to not cause harm.
Vitamin limits hard to set
October 16, 2015
Oxidative Stress and Cancer: A new study indicates that the cancer cells that spread cancer throughout the body by metastasis are less likely to survive when exposed to oxidative stress. Consequently, researchers think that consuming large amounts of antioxidants from the diet and/or supplements may actually promote the spread of cancer. Again, too much of a good thing is not good.
The latest study about antioxidants is terrifying. Scientists think they may boost cancer cells to spread faster.
January 24, 2016
Potential Selenium Toxicity in Nuts: Brazil nuts are an excellent source of selenium. However, moderation is the key since only five nuts a day can contain more selenium than the tolerable upper intake level established by the Institute of Medicine.
The dark side of healthful 'superfoods'
September 27, 2016
Zinc and Infection: All essential nutrients are part of a balancing act. Too little and too much of a nutrient are both potentially bad. A new study, using a mouse model, found that high zinc intake altered the lower intestinal bacterial ecology in a way that favored the development of the bacterium Clostridium difficile. This bacteria can cause infections that are highly resistant to treatment.
Excess dietary zinc worsens C. diff infection
October 18, 2016
Folic Acid Excess and Vitamin B12 Function: High folic acid intake has been associated with neurological damage when vitamin B12 status is low. A new study found that people with a fairly common gene alteration for a vitamin B-12 transport protein are much more likely to develop peripheral neuropathy, especially when folic acid intake is high.
High folate intake linked with nerve-damage risk in older adults with common gene variant
September 25, 2017
Excess Dietary Manganese and the Heart: Manganese is an essential nutrient that is found in many "healthy" foods." However, it is possible to exceed the "tolerable upper intake level" of manganese when foods that are rich in the mineral make up a large part of the diet. Excess manganese is known to affect the brain with a Parkinson's disease-like condition. Now, a new study with mice found that high dietary manganese levels altered immune function to allow the pathogenic bacterium Staphylococcus aureus to infect the heart. How this might relate to humans is currently unknown.
Excess dietary manganese promotes staph heart infection
October 7, 2017
Excess Nutrients: Too much of a good thing isn’t always good. For example, high intake of calcium and vitamin D increased the risk of poor cognitive function in elderly.
High Calcium And Vitamin D Intakes Associated WIth Higher Risk Of Cognitive Impairment In Elderly
August 14, 2018
Pantothenic Acid Toxicity: No tolerable upper intake level has been established for pantothenic acid (vitamin B5) due to its apparent safety within a wide range of intakes. However, very high doses of pantothenic acid supplements (such as 10,000 mg per day) have caused upset stomach and diarrhea. Excess intake from food sources has not been reported and is highly unlikely.
Pantothenic Acid Fact Sheet for Consumers
August 17, 2018
Calcium Excess: The Tolerable Upper Intake Level for calcium, established by the Institute of Medicine in 2010, is 2500 mg/day for adults 19-50 years of age and 2000 mg/day for adults 51 years and older. Since these values were established, additional research related to risks of prostate cancer suggests that it may be best to limit calcium intake (from food and supplements combined) to 1000 to 1200 mg/day.
Calcium Fact Sheet for Consumers
August 24, 2018
Potassium Excess: a tolerable upper intake for potassium was not set by The Food and Nutrition Board of the Institute of Medicine because adverse effects from high dietary potassium has not been documented in healthy individuals. Those in individuals with kidney problems or those consuming excessive potassium supplements can have serious gastrointestinal problems, muscle problems and abnormal heart rhythm.
Potassium Fact Sheet for Consumers
August 31, 2018
Vitamin A Toxicity: Besides being an essential nutrient, vitamin A can also be consumed in excess, causing dizziness, headaches, nausea, skin irritation, joint pains and bones, coma, and can cause congenital birth defects. Vitamin A can accumulate in the liver with high levels of liver consumption but most excessive vitamin A comes from dietary supplements.
Vitamin A - Fact Sheet for Health Professionals
September 7, 2018
Excess Vitamin C: Excess vitamin C from supplements can cause diarrhea in some individuals, but generally excess vitamin C is excreted by the body in urine. When people have been taking more than 1000 mg vitamin C daily, it is important to slowly decrease the dose over time to prevent what is called rebound scurvy.
Vitamin C - Fact Sheet for Consumers
September 14, 2018
Excess Vitamin B1: No toxic effects from excess thiamin in food or dietary supplements (up to 200 mg/day) have been recorded. Large intravenous doses of B1 have caused life-threatening anaphylactic reactions in a few individuals. There is no established Tolerable Upper Intake Level for thiamin, however, the Expert Group on Vitamins and Minerals of the Food Standards Agency, United Kingdom recommends not to exceed 100 mg per day from dietary supplements.
Thiamin Fact Sheet for Consumers
September 16, 2018
Essential Nutrients and Normal Growth: During pregnancy, good nourishment of a woman's body provides an adequate supply of nutrients to the developing fetus and supports milk production after birth to meet the baby's needs. Poor nutrition of the mother can impair normal development in ways that are irreversible and can have serious adverse effects that persist even into adult life.
Good nutrient consumption sets stage for healthy child
September 19, 2018
Chromium Excess: The toxicity of chromium is relatively low compared to recommended intake levels. No Tolerable Upper Intake Level has been established by the Institute of Medicine. However, the Expert Group on Vitamins and Minerals in the United Kingdom provided an adult "Guidance Level" of no more than 10 mg per day from dietary supplements.
Chromium Dietary Supplement Fact Sheet
September 28, 2018
Riboflavin Excess: The toxicity of riboflavin (vitamin B2) is very low and no Tolerable Upper Intake Level has been established by the Institute of Medicine. The Expert Group on Vitamins and Minerals in the United Kingdom provide an adult "Guidance Level" of no more than 40 mg per day from dietary supplements.
Riboflavin - Fact Sheet for Consumers
October 5, 2018
Iron Excess: The Tolerable Upper Intake level for iron is set at 45 mg/day because doses much higher than this can cause gastrointestinal irritation and related symptoms. People with a hereditary condition called hemochromatosis can accumulate excessive amounts of iron over time due to a lack of the normal regulation of iron absorption that protects most people from iron overload.
Iron Fact Sheet for Consumers
October 19, 2018
Copper Excess: The adult RDA for copper is just under one mg per day and the Tolerable Upper Intake Level is 10 mg per day. Although consuming copper at this level is uncommon, there is some concern that 10 mg/day might be too high because of some evidence that men consuming 7.8 mg/day of copper for 147 days experienced some adverse changes in measures of immune function and antioxidant status.
Copper in diets
October 26, 2018
Excess Vitamin B6: Although it is unlikely than anyone would get excess levels of B6 from food, this is not the case with supplements. Excess B6 can cause severe nerve damage resulting in pain and numbness of the extremities. B6 excess also can result in nausea, heartburn, and skin sensitivity to sunlight. The Tolerable Upper Intake Level for B6 is 100 mg per day.
Vitamin B6 Fact Sheet for Consumers
November 2, 2018
Fluoride Excess: Excess fluoride intake is identified by slightly different signs: mild fluoride excess is detectable by small opaque white flecks on teeth; moderate fluoride excess causes mottling and mild staining of the teeth; severe fluoride excess is marked staining and pitting of teeth. Risk of excess fluoride increases especially when fluoride supplementation is used by people living in areas where the water contains significant amounts of fluoride.
Fluoride in diet
November 16, 2018
Iodine Excess: Like an iodine deficiency, iodine excess can also cause thyroid issues. If an individual is low in iodine, excess iodine can cause a hyperthyroid reaction. If an individual has normal iodine status, excess iodine can produce a hypothyroid condition and the formation of a goiter.
NIH - Iodine Fact Sheet for Consumers
November 23, 2018
Folate Excess: Under most conditions, high folate intake has a low risk of adverse effects. However, if vitamin B12 status is low, high folate intake can mask the usual diagnostic sign of B12 deficiency by preventing megaloblastic anemia. Meanwhile, the hidden B12 deficiency is causing irreversible nerve damage.
Folate Fact Sheet for Consumers
November 30, 2018
Magnesium Excess: High magnesium intake is primarily due to the use of magnesium supplements. The most common concern is that excess magnesium can cause diarrhea. Consequently, the tolerable upper intake level (UL) for magnesium is 350 mg/day from supplements. Intake of supplemental magnesium in greater amounts is likely to pose a risk of diarrhea or other gastrointestinal disturbances.
Magnesium Fact Sheet for Consumers
December 6, 2018
Biotin Excess: Although there is no evidence that excess dietary biotin has caused any harm. There is however evidence that excess biotin from supplements may cause false lab test results, including altered thyroid tests.
Biotin Fact Sheet for Consumers - Office of Dietary Supplements
December 14, 2018
Manganese Excess: Manganese is unusual in the sense that it is not difficult to exceed the Tolerable Upper Intake Level from food sources alone. Over time, excess dietary manganese can cause neurological damage that results in symptoms similar to Parkinson's Disease. Many of the "superfoods" like blueberries, whole grains, and nuts are high enough in manganese that substantial over-consumption of these foods can exceed the Tolerable Upper Intake Level.
Manganese
December 21, 2018
Excess vitamin D can be toxic primarily from suppllements. In addition to various stomach upset issues, excess vitamin D has been shown to be related to kidney stones and problems with heart rhythm. Excessive sun exposure does not cause vitamin D poisoning.
NIH - Vitamin D - Fact Sheet for Consumers
January 10, 2019
Excess Vitamin E: Supplement doses of vitamin E greater than 1,100 IU/day for adults has been shown to reduce the ability to form blood clots after an injury and could cause serious bleeding in the brain, also known as a hemorrhagic stroke. Even lower levels of supplemental vitamin E may be problematic for children.
Vitamin E Fact Sheet
January 19, 2019
Sodium Excess: Chronic excess sodium consumption can lead to edema or water retention. For salt sensitive individuals, excess sodium has been shown to be one factor involved in the development of high blood pressure.
Sodium and the Diet
February 1, 2019
Phosphorus Excess: The food supply is abundant in phosphorus. Excessive blood phosphorus from dietary sources is rare and generally only occurs in people with severe kidney disease or problems with calcium regulation.
Phosphorus in diet
February 8, 2019
Selenium Excess: Selenium is an essential dietary mineral but can also be toxic in high doses. Selenium accumulates overtime and excessive selenium can cause gastrointestinal disturbances, hair and nail problems, skin rashes and nervous system problems. Although Brazil nuts are considered to be a high selenium risk food, this is true only in areas with selenium-rich soils. Plants from Allium (garlic and onion) and Brassicaceae families (broccoli and cauliflower) are also plants that are considered selenium accumulators.
Selenium Fact Sheet for Consumers
February 15, 2019
Zinc Excess: Excess zinc consumption from foods is unlikely unless zinc dietary supplements are consumed in excess. However zinc excess in the form of nasal sprays and gels has been linked to a permanent loss of the sense of smell.
Zinc - Fact Sheet for Consumers