Too Much of a Good Thing Can be Harmful
added 04/04/11
by Mary Saucier Choate, M.S., R.D., L.D.
Dietitian and Co-op Food and Nutrition Educator
Did you know that there is a Tolerable Upper Intake Level (UL) for certain nutrients, and that consuming more than this level on a regular basis places an individual at potential risk of harmful side effects?
ULs were researched and published as part of the new Dietary Reference Intakes partly in response to the increasingly common practice of fortifying foods with nutrients and partly due to the growing use of dietary supplements. The levels of nutrients in dietary supplements are not regulated, so the amounts that a manufacturer decides to put in a supplement may be at an insignificant, safe, or excessive level. It’s left up to the consumer to read the label carefully for the supplement serving size and amount of nutrients.
The undesirable effects from regularly exceeding the UL vary in seriousness for each nutrient. It is important to note, however, that these upper limits are intended for healthy people and apply to daily or habitual use. People who are suffering from certain nutrition-related diseases or health problems might require treatment with higher levels of nutrients than the UL. In these cases, a health professional should closely monitor their treatment.
Are You Overdoing It?
If you think you may be taking too much of a supplement, or if you have no idea what amount is safe to take, the following steps can help.
The Institute of Medicine’s Dietary Reference Intakes Tables list the recommended levels and UL of nutrients by age and gender. Check out their website.
With your calculator in hand, along with your supplement bottles, fortified drinks, cereals, and sports bars, add up the nutrients you are taking in, every day, and compare these to the levels listed in the table below to be sure you’re not getting too much of a good thing.
| Tolerable Upper Intake Levels (ULs) of Vitamins and Trace Minerals for Adults | |||
| Nutrient | Source of Nutrient | Tolerable Upper Limit (UL) per day for adults1 | Increased risk of these adverse effects resulting from regularly exceeding the daily Tolerable Upper Limit level. 2 |
| Vitamin A | Food, fortified foods, supplements | 3,000 mcg | Liver abnormalities and birth defects |
| (retinol) | (10,000 IU) | UL does not apply to vitamin A in the form of beta-carotene. | |
| Vitamin B6 | Food, water, and supplements | 100 mg | Sensory neuropathy (nervous system damage) and skin lesions |
| (pyridoxine) | |||
| Vitamin C | Food, supplements | 2,000 mg | Diarrhea and related gastrointestinal disturbances |
| Calcium | Food, water, and supplements | 2,500 mg | Milk-alkali syndrome (high blood calcium levels and kidney insufficiency) |
| Choline | Food, water, and supplements | 3,500 mg | Hypotension (abnormally low blood pressure); fishy body odor |
| Copper | Food, water, and supplements | 10,000 mcg | Liver damage |
| Vitamin D | Food, water, and supplements | 50 mcg | Hypercalcemia (abnormally high levels of calcium in the blood) which can lead to kidney disorders and abnormal calcium deposits in the kidneys, blood vessels, heart, and lungs |
| (2,000 IU) | |||
| Vitamin E (alpha-tocopherol) | Fortified foods, supplements | 1,000 mg | Increased tendency for hemorrhagic effects (abnormal bleeding) |
| Folate | Fortified foods, supplements | 1,000 mcg | May cause or make worse the neuropathy (nervous system damage) of vitamin B12 deficiency |
| Fluoride | Food, water, and supplements | 10 mg | Tooth enamel fluorosis (discoloration and defects in tooth enamel, occurs before teeth have erupted from the gums) and skeletal fluorosis (a crippling chronic bone and joint disease -extremely rare in US) |
| Iodine | Food, water, and supplements | 1,100 mcg | Thyroid dysfunction |
| Iron | Food, water, and supplements | 45 mg | Gastrointestinal distress |
| Magnesium | Supplements; pharmacological agents | 350 mg | Diarrhea |
| Manganese | Food, water, and supplements | 11 mg | Elevated blood manganese concentration and neurotoxicity (disruption in normal functioning of the nervous system) |
| Molybdenum | Food, water, and supplements | 2,000 mcg | Based upon impaired reproduction and fetal development in rats and mice, because of the lack of sufficient human data |
| Niacin (nicotinic acid; niacinamide; nicotinamide) | Fortified foods, supplements | 35 mg | Flushing (burning, tingling sensation and flush on face, arms, and chest) |
| Phosphorus | Food, water, and supplements | 4,000 mg | Elevated blood levels of phosphorus |
| Problematic in kidney disease and certain other conditions | |||
| Selenium | Food, water, and supplements | 400 mcg | Selenosis (brittleness and loss of hair and nails) |
| Zinc | Food, water, and supplements | 40 mg | Adverse effect on copper status |
1 Children have a different UL for certain nutrients.
2 Not all side effects listed, just the ones used to set the UL.
Celebrate Cooperatives
A co-op is owned by, and operated for, the people who use its services. Learn more here about the International Year of Cooperatives and check out a great video from our friends at NCGA!
