Is it Safe to Take Two Multivitamins in One Day?
Tip
Taking two multivitamins a day can put your health in danger and cause severe toxicity. When consumed in large doses, certain nutrients may affect the kidneys, increase the risk of bleeding and promote the formation of calcium stones, among other side effects.
Additionally, dietary supplements, including multivitamins, may interact with prescription drugs. Discuss your options with a medical professional. If your diet is balanced, you might not need a daily multivitamin at all.
Are Multivitamins Really Necessary?
More than 75 percent of Americans take dietary supplements, according to the Council for Responsible Nutrition (CRN). About 83 percent of adults aged 18 to 34 and 75 percent of those aged 35 to 54 take multivitamins. These pills are designed to fill nutrient gaps and prevent deficiencies. However, their effectiveness is subject to debate.
Some dietary supplements contain too much of certain vitamins and minerals, which can lead to side effects. Large doses of vitamin A, for example, may cause nausea and vomiting, blurry vision, dizziness and other mild adverse reactions. Over time, you may experience more serious side effects, such as liver damage, joint pain and bone thinning.
Iron supports the formation of red blood cells and protects against anemia. Low levels of this mineral in the bloodstream can affect immune function, cognition and learning abilities. Too much iron, on the other hand, may cause fluid buildup in the lungs, low blood pressure, irregular heartbeat, liver damage, convulsions, fever and coma.
If you have a balanced diet, you probably don't need to take a daily multivitamin. However, there are cases when these supplements can help.
Crohn's disease, for instance, reduces the absorption of vitamins and minerals in the body, which may result in severe deficiencies and malnutrition. Multivitamin supplements can benefit those who have this inflammatory bowel disorder.
Real Help or Marketing Hype?
The scientists reviewed several clinical trials conducted on more than 400,000 participants and concluded that multivitamins have no effect on the risk of cancer, heart disease or early death. On the contrary — certain nutrients, such as vitamin A, vitamin E and beta-carotene may increase the risk of death, especially when consumed in large doses. Researchers have found no association between multivitamins and chronic disease prevention.
Johns Hopkins nutrition experts conducted their own research. After analyzing several studies and reviews, including the one cited above, they concluded that multivitamins don't protect against cardiovascular problems, mental decline, heart attack or premature death. The only exception is folic acid, which may benefit pregnant women.
More Isn't Better
Multivitamins appear to be safe for long-term use. Too much of anything can be harmful, though — and dietary supplements are no exception. Taking two multivitamins a day may cause severe toxicity.
Read more: 5 Vitamins Related to Skin Irritations
When used in large doses, these supplements can affect every system in your body. Potential side effects include joint, bone and muscle pain, eye irritation, frequent urination, irritability, fatigue, mood swings and changes in bowel habits, as reported by the U.S. National Library of Medicine. You may also experience the following symptoms:
- Unintentional weight loss
- Lack of appetite
- Intestinal bleeding
- Hair loss
- Dry skin
- Seizures
- Confusion
- Cloudy urine
- Bloody diarrhea
Except for niacin, water-soluble vitamins (such as riboflavin and folic acid) are unlikely to cause serious side effects because the excess is eliminated in the urine. Vitamin B3, or niacin, may produce a temporary sensation of heat that lasts up to eight hours, according to the U.S. National Library of Medicine. Other nutrients, though, may have life-threatening side effects when consumed in excess.
Calcium, for example, is essential for teeth and bone health. It also plays a vital role in nerve and muscle function. However, large doses of calcium supplements may lead to kidney stones, constipation and poor absorption of iron and zinc. Additionally, multivitamins containing calcium may interact with antibiotics, thyroid medications, anticonvulsants and other drugs.
As the Mayo Clinic notes, elevated calcium levels in the blood can also affect the kidneys, bones, muscles, heart and brain. This condition, known as hypercalcemia, may cause gastrointestinal symptoms, weaken your bones and depress your mood. Irregular heartbeat, fatigue and excessive thirst are common side effects.
Multivitamin supplements often contain zinc. This mineral supports your natural defenses, contributes to protein synthesis and accelerates wound healing, among other functions. Too much of it can affect copper absorption, reduce good cholesterol levels and affect your immune system. You may also experience nausea and vomiting, abdominal pain, diarrhea and other digestive symptoms.
Read more: 10 Weird Signs You're Not Getting Enough Nutrients
Another example is vitamin E, a fat-soluble nutrient with antioxidant effects. When used in adequate doses, it keeps your immune system strong, protects against free radical damage, maintains the integrity of cell membranes and fights inflammation. However, it may increase the risk of bleeding when consumed in excess.
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