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Vitamin Mega-Doses

Can you get too much of a good thing?

Every year Americans spend billions of dollars on vitamins, minerals and herbal supplements. Usually, the amounts we take are within safe limits. Occasionally, however, fads come along that advocate mega-doses as the latest cure-all. But more isn't always better. In fact, mega-doses can cause more problems than they claim to cure. For healthy adults, here are the latest safe upper limits for many nutrients established by the Institute of Medicine at the National Academy of Sciences. (If you have medical problems, discuss the vitamins and other supplements you take with your doctor; these limits may not be safe for your situation.)

Following are the:

• nutrient names,
• the upper limits per day and
• the critical adverse effect(s):

Calcium
2,500 mg
Hypercalcemia, a disorder in which the level of calcium in the blood is too high; the most common symptoms are feeling tired, difficulty thinking clearly, lack of appetite, pain, frequent urination, increased thirst, constipation, nausea and vomiting.

Folate (folic acid)
1,000 ug
Can mask the presence of anemia caused by Vitamin B12 deficiency.

Magnesium
350 mg
Diarrhea, abdominal pain, loss of appetite and irregular heartbeat.

Niacin
35 mg
Flushing, itching, headaches, cramps and nausea; more serious adverse effects can include liver damage, high blood sugar and irregular heartbeats.

Selenium
400 ug
Selenosis - symptoms include gastrointestinal upsets, hair loss, white blotchy nails and mild nerve damage.

Vitamin B6
100 mg
Nerve damage in the arms and legs that is usually reversible when supplementation is stopped.

Vitamin C
2,000 mg
Diarrhea and abdominal pain.

Vitamin D
50 ug
Hypercalcemia (see Calcium above).

Vitamin E
1,000 mg
Bleeding, especially for people on blood-thinning medications, and gastrointestinal complaints.

Zinc
40 mg
Reduced "good" high-density lipoprotein (HDL) cholesterol, suppressed immune system function, diarrhea, heartburn, nausea, vomiting and abdominal pain.

*mg = milligram; 1,000 mg = 1 gram
ug = microgram; 1,000 ug = 1 mg; 1,000,000 ug = 1 gram

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Reprinted with the permission of Today's Seniors. More helpful solutions can be found online at www.A-Guide-for-Seniors.com.

Source of Upper Daily Limit: Dietary Reference Intakes; Applications in Dietary Assessment, Institute of Medicine, National Academy of Sciences, 2000.

The Memorial Sloan-Kettering Cancer Center is an excellent source for information about herbs, botanicals and other dietary supplements. Their special website contains information about 140 products. To visit it, simply click here.