Vitamins tolerable upper intake level

G.7 Tolerable Upper Intake Levels, Vitamins (Reprinted with permission from the National Academy of Sciences, Courtesy of the National Academies Press, Washington, D.C.)... 

Due to bleeding risk, individuals on anticoagulant therapy or individuals who are vitamin K-deficient should not take vitamin E supplementation without close medical supervision. Absent of that, vitamin E is a well-tolerated relatively non-toxic nutrient. A tolerable upper intake level of 1,000 mg daily of a-tocopherol of any form (equivalent to 1,500 IU of RRR a-tocopherol or 1,100 IU of all-rac-a-tocopherol) would be, according to the Food and Nutrition Board of the Institute of Medicine, the highest dose unlikely to result in haemorrhage in almost all adults. 

Vieth, R. (2006). Critique of the considerations for establishing the tolerable upper intake level for vitamin D Critical need for revision upwards. /. Nutr. 136,1117-1122. 

EFSA, European Food Safety Authority, Tolerable upper intake levels for vitamins and minerals. EFSA, Parma, Italy, February 2006. 

ScientiE>c Committee on Food, Guidelines of the Scientil>c Committee on Food for the development of tolerable upper intake levels for vitamins and minerals SCF/CS/ NUT/UPPLEV/11 FINAL, 28 November 2000 http //ec.europa.eu/food/fs/sc/scf/ out80a en.pdf... 

Johnston CS (1999) Biomarkers for establishing a tolerable upper intake level for vitamin... 

Scientific Committee on Food (2000) Opinion of the Scientific Committee on Food on the Tolerable Upper Intake Level of Vitamin Bg. Brussels European Commission Health and Consumer Protection Directorate-General. 

The optimal dietary requirements of vitamin E for humans are not yet known, especially with the emergence of new paradigms regarding adequate levels of dietary micronutrients (Chalem, 1999). Recommendations in the United States and Canada have been reevaluated, and a new concept of Dietary Reference Intake (DRI, 2000) was issued for vitamin E and other antioxidants. The DRI recommendation should prevent specific deficiency disorders, support health in general ways and minimize the risk of toxicity, which carries more tasks than the previous recommendations (DRI, 2000). Accordingly, the recommendations for intakes were set to higher levels than previously. Estimated Average Requirements (EAR) for adults, both men and women, were set to 12 mg a-tocopherol/day, RDA to 15 mg/day and Tolerable Upper Intake Level (UL) to 1000 mg/day. Moreover, the EAR and RDA are based only on the 2R-stereoisomeric forms of a-tocopherol, because the other vitamers... 

The findings of these and other studies have led the Food and Nutrition Board of the U.S. Institute of Medicine to recommend a tolerable upper intake level of3000 tg/day of preformed vitamin A for men of 19 years and older, with lower levels for women of child-bearing age, infants, children, and adolescents. Carotenemia results from a chronic excessive intake of carotene-rich foods, principally carrots. This condition, in which yellowing of skin is observed, is benign, because the excess carotene is deposited rather than converted to vitamin A. 

No adverse effects have been associated with excess vitamin Bi2 intake from food or supplements in healthy people. Daily oral doses of up to 2 mg of cyanocobalamm can be used for treatment of deficiency in those who can tolerate oral supplementation. There are insufficient data in the literature to propose a tolerable upper intake level for vitamin Bj2. ... 

A Tolerable Upper Intake Level (UL). The UL is the maximum intake by an individual that is unlikely to pose risks of adverse health effects in almost all (97-98%)individu-als. It includes intake of a nutrient from all sources (food, fortified food, water, and sup-dements). Water can include fluoride and minerals depending on the source of water. "Tolerable" is used to "avoid implying any possible beneficial effect." It is the amount of vitamin that can be "tolerated" without the person s exhibiting or experiencing adverse reactions. The UL should not be considered the upper dose for those who self-dose with megadoses of vitamins. 

Hypervitaminosis K. Although it is possible to overdose with this vitamin, the fact that it is available only over the counter in small doses in multivitamin preparations has resulted in little knowledge of any toxicities. Toxicities do not appear in animals administered large doses. It is known that excess intake of the vitamin does not promote clot formation. There is no Tolerable Upper Intake Level. 

Hypervitaminosis Thiamine. The vitamin is considered very safe. There are no Tolerable Upper Intake Levels. Possibly the rate-limiting phosphorylation step in the intestinal mucosa reduces the risk of toxicity. The percentage of thiamine absorbed decreases as the dose increases. 

Hypervitaminosis Niacin. Niacin is considered nontoxic, and there are no Tolerable Upper Intake Levels based on its use as a vitamin. These refer only to niacin and niaci-... 

Hypervitaminosis Pyridoxine. A certain mystique has built up around this vitamin, resulting in individuals overdosing themselves with commercial vitamin supplements. Serious neurological problems have been seen in doses of 2-6 g/day for 2 0 months (62-64). Megadosing below 2 glday seems safe, but all of this information is based mostly on anecdotal reports. There is a Tolerable Upper Intake Level, but the UL to RDA ratio is a comfortable 50-60. 

There have been no reports of toxicity and no Tolerable Upper Intake Levels. Because its active transport is saturable, excessive uptake is doubtful. Also, this vitamin does not have the mystique that would prompt marketing "high potency" formulations. 

Hypervitaminosis B, 2. The vitamin is considered nontoxic. There has been some concern that the presence of the CN anion in the commercial vitamin might cause problems with megadoses. However, 1000 fig of cyan-ocobalamin contains only 0.02 mg of CN. There are no Tolerable Upper Intake Levels. 

HypervitaminosisC. The vitamin is considered very safe. At one time, many of the over-the-counter products contained significant amounts of sodium ascorbate, which would be contraindicated in people on low sodium diets. Today s products are virtually sodium free unless labeled otherwise. Nevertheless, there are intermittent reports of adverse reactions associated with high doses. Therefore, there are Tolerable Upper Intake Levels, but these are very high relative to the RDAs. The UL to RDA ratio averages about 20. 

A Tolerable Upper Intake Level (UL) is the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects to almost all individutils in the general population. Unless otherwise specified, the UL represents total intake from food, water, and supplements. Due to alack of suitable data, ULs could not be established for vitamin K, thiamin, riboflavin, vitamin B, pantothenic acid, biotin, and carotenoids. In the absence of a UL, extra caution may be warranted in consuming levels above recommended intakes. Members of the general population should be advised not to routinely exceed the UL. The UL is not meant to apply to individuals who are treated with the nutrient under medical supervision or to individuals with predisposing conditions that modify their sensitivity to the nutrient As preformed vitamin A only... 

The adverse effects of vitamin A in so-called tolerable upper intake levels have been reviewed [1 ]. Chronic hypervitaminosis A is relatively rare. Its effects are varied and non-specific. In adults they include central nervous system effects, skin disorders, conjunctivitis, nausea, vomiting, teratogenicity, and hepatotoxicity. In infants and young children, skeletal and intracranial (e.g. transient bulging fontanelle) abnormalities can occur. There are conflicting data on the risks of bone fractures from high chronic dosing in industrialized countries. 

Kraemer K, Waelti M, de Pee S, Moench-Pfanner R, Hathcock JN, Bloem MW, Semba RD. Are low tolerable upper intake levels for vitamin A undermining effective... 

The amount of vitamin E required by the body depends upon its size and the amount of polyunsaturated fats in the diet, as vitamin E is needed to protect these fats from oxidation. The requirement for vitamin E depends upon intake of refined oils, fried foods, or rancid oils. Supplemental estrogen or estrogen imbalance in women increases the need for vitamin E, as does air pollution. The recommended dietary allowance (RDA) for vitamin E is really quite low, many people do not consume this in their diet alone. Table 19.1 lists the RDAs and tolerable upper intake levels (ULs) for vitamin E. The new recommendations for vitamin E are expressed as milligrams of RRR-a-tocopherol equivalents. Dietary supplements of vitamin E are labeled in terms of international units (lU). 1 mg of synthetic vitamin E (a//-rac-a-tocopheryl acetate is equivalent to 1 lU vitamin E, but only 0.45 mg RRR-a-tocopherol. 1 mg of natural vitamin E (RRR-a-tocopherol) provides 1.5 lU. For the LIE, the Food and Nutrition Board recommended 1000 mg of any a-tocopherol form, which is equivalent to 1500 lU RRR- or 100 lEI all-rac-a-tocopherol (Food and Nutrition Board, 2000 Hathcock et al., 2005 Combs, 2008). 

Recommended Dietary Allowances and Tolerable Upper Intake Levels for Vitamin A... 

Recommended dietary allowances (RDA) for the US and Canada were recently revised by the Institute of Medicine (lOM). Owing to the serious, potentially irreversible, effects caused by an excess of vitamin A, guidelines were also established for a tolerable upper intake level (UL), defined as the highest intake of a nutrient that is likely to pose no risk of adverse health effects in nearly all healthy individuals. The 2001 RDA and UL for vitamin A for various life stages are listed in Table 2. 

Table 2 Recommended dietary allowances (RDA) for vitamin A in micrograms ( g), retinol activity equivalents (RAE) and international units (lU), and tolerable upper intake levels (UL, pg retinol day" ) for children and adults ...

Tolerable Upper Intake Levels and Vitamin D Intoxication... 

Abnormal accumulation in tissues and overloading of normal metabolic pathways, leading to signs of toxicity and possibly irreversible lesions. Niacin (Section 8.7.1), and vitamins A (Section 2.5.1), D (Section 3.6.1), and Bg (Section 9.6.4) are all known to be toxic in excess (see Section 1.2.4.3 for a discussion of tolerable upper levels of intake). 

Tolerable Upper Levels of Intake A number of the vitamins are known to be toxic in excess. For most, there is a considerable difference between reference intakes that are more than adequate to meet requirements and the intake at which there may he adverse effects, although for vitamins A (Section 2.5.1) and D (Section 3.6.1) there is only a relatively small margin of safety. 

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