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Calcium-fortified orange juice. Vitamin-enhanced waters. Fortified cereals and energy bars. Everywhere you turn, new products are showing up on supermarket shelves touting added vitamins and minerals.
But if you already take a multi-vitamin and mineral tablet, add a calcium or vitamin E supplement on top of that, and eat a few fortified food products along with a fairly healthy diet, can you overdo it? Is it possible to get too many vitamins and minerals?
Yes, said Cynthia Sass, a registered dietitian and spokeswoman for the American Dietetic Association.
"Americans tend to think that more is better, or that if it's natural, it can't harm you, and that is particularly true when it comes to vitamins and minerals," Sass said.
But that's not always the case. In her practice, she has seen some patients who habitually overdo it with vitamins and minerals and suffer the consequences-albeit not life-threatening ones.
David Klurfeld, a professor of nutrition at Wayne State University in Detroit and founder of NutritionNewsFocus.com, agreed with Sass' concerns. "It can be an issue for some people, particularly the subset of the population who is very health conscious," he said.
People may not be poisoning themselves with vitamins and minerals, but in some cases, they are overdosing.
For example, while most people don't get enough calcium in their diets, the health-focused consumer will seek out ways to get more calcium-and that's not hard to do these days. Besides drinking milk and eating yogurt, they might consume a glass of calcium-fortified orange juice, a bowl of fortified breakfast cereal, an energy bar, one or two bottles of enhanced water, a multivitamin/mineral supplement and a couple of calcium supplements. That could easily push them past the upper limit of 2,500 milligrams.
Professional athletes frequently go beyond recommendations for vitamins and minerals, said Chris Rosenbloom, an associate dean and professor of nutrition at Georgia State University and a spokesman for the American Dietetic Association. Weekend warriors and dedicated exercisers may also seek out large quantities of supplements and fortified foods in an effort to boost performance.
Overconsumption of vitamins or minerals is possible, according to Jeffery Blumberg, professor of nutrition at Tufts University, but he said it's usually supplements-not fortified foods-that push people over the edge of reasonable intake.
Most fortified foods generally provide 100 percent or less of the daily recommended values for vitamins and minerals. Blumberg's bigger concern is inadequate intake, particularly of nutrients such as calcium-not with people getting too much.
"The risk is at very high levels, much higher than most people get through the foods they eat," he said. "So I don't see this as a major problem."
Blumberg added that in his research with older people, if it were not for fortified foods like breakfast cereals, there would be real problems with nutrient deficiencies.
"We add vitamins A and D to milk, B vitamins and folic acid to grain products. These are public health approaches that underwent a lot of scrutiny because people are quite simply not getting enough through their typical diet and because of that are at risk for deficiencies," he said.
The National Academy of Sciences has determined upper limits for most vitamins and minerals. This is the maximum-not the recommended-amount people can safely take without ill side effects. The recommended dietary allowance (RDA) is the minimum amount of vitamins and minerals you should strive to get each day-preferably through food but supplements as well, if needed. Blumberg points out that the RDA is not necessarily the optimal amount-many researchers believe that the amounts for certain vitamins and minerals-such as the antioxidant vitamins C and E-should be higher to help prevent disease.
The upper limit is typically set at 10 to 40 times the RDA, noted Blumberg, so you would need to eat a lot of foods before you veer toward danger. He points to vitamin B12 as an example of the wide chasm between the RDA and upper limit. No upper limit has been established because there is no known toxicity for vitamin B12; the RDA is 6 micrograms (1 microgram is 1 millionth of a gram). Yet for some conditions, physicians may recommend up to 400 micrograms, he explained.
Although there is considerable leeway in many cases for intakes above the upper limit, there still is little justification or benefit to consumers to take in enormous quantities.
Water-soluble vitamins are a good example, said Sass. "Most people think if they take too many water-soluble vitamins (like B vitamins and vitamin C) they will just get washed out in the urine, which is true-but it can put extra stress on the kidneys and liver."
A more serious problem with water-soluble vitamin B6, she said, is that, over time, it can cause nerve damage if taken in excessive amounts.
Vitamin C is another that people tend to take in large quantities, mainly in the form of supplements-and often in an attempt to stave off colds and illness.
"At 2,000 milligrams or greater, it can cause digestive upset, and people don't typically associate stomach upset with the fact that they are taking vitamin C," said Sass. Klurfeld added that because vitamin C enhances iron absorption, research has shown excess amounts may increase the risk of liver cancer and heart disease in people with iron overload.
All of the experts interviewed agree that overconsumption of vitamin A is the most dangerous. That is nearly impossible to do by eating foods but easily accomplished if taking excessive amounts of supplements. The window of safety for vitamin A is the most narrow of all the vitamins. Some research suggests that consuming just two to three times the RDA may be dangerous, Blumberg said. Klurfeld said that in high amounts, beta carotene (a precursor to vitamin A) has been shown to promote incidence of lung cancer and fatal heart disease in smokers; in pregnant women, excess consumption carries a risk of fetal malformations.
Because vitamin A and its precursors are found in different forms-retinol, provitamin A carotenoids like beta carotene among them-consumers may not be aware of their consumption levels. Some supplements will list the form of vitamin A, so it helps to read the label to know how much you are getting.
Unfortunately, many Americans do not eat a varied enough diet, so taking a multivitamin and mineral supplement or including fortified foods in their diet is probably warranted.
"With some breakfast cereals, it's like taking a multivitamin and mineral supplement in and of itself, so it may be wise to look at what foods and fortified foods you are eating regularly in your diet and figure out what-if any-additional supplements you may need, such as calcium or folic acid," Rosenbloom recommended.
Sass concurred. "Too much or too little can be harmful in terms of vitamins and minerals," she said. "People have to ask themselves, `Is it worth spending money on fortified foods or can I do OK by eating a good diet and taking a multivitamin?' "
(c) 2003, Chicago Tribune. Distributed by Knight Ridder/Tribune News Service.