On our quest to be healthy, sometimes we don’t realize that too much of a good thing can be bad. Forty-four percent of Americans take vitamins and dietary supplements daily and as many as 84% of Americans consider vitamins and supplements to be safe. This is a perception that increases their risk for vitamin toxicity since more than 60,000 instances of vitamin toxicity are reported annually to US poison control centers. Taking vitamin or mineral supplements without consulting a doctor can leave us with other more serious health issues. Taking a standard multivitamin combined with a healthy diet is perfectly safe but when we combine those with additional vitamin or mineral supplements- we may be increasing our risk of serious illnesses and side effects. Let’s explore what is too much and the side effects that an overdose can cause.
The recommended daily allowance (RDA) of vitamin B3 is between 14-16 milligrams and it is water soluble so it is not stored in the body. Deficiencies are rare because of the abundant food sources that contain vitamin B3 (niacin). Many people supplement this because it can lower your cholesterol and risk of cardiovascular disease but this should always be done at the instruction of a doctor. Doses of 35 mg or more daily cause blood-vessel dilation, which can result in tingling, itching, and flushing of the face, neck, and chest — a condition called niacin flush which is uncomfortable but not dangerous. Other side effects include hair loss, dry skin, liver toxicity, heart palpitations, joint pain, muscle cell damage, glucose intolerance, headache, seizures, mental changes and fainting. High doses could pose risks such as liver damage, gastrointestinal problems including vomiting, cramping, and diarrhea. Long term vitamin B3 overdose toxicity has also been shown to cause gout.
The RDA of vitamin B6 is 1.3 – 1.7 mg and it is water soluble so it is not stored in the body so toxic levels are hard to obtain unless a dietary supplement is taken. Vitamin B-6 supplements had been recommended in large doses for treatment of health issues such as carpal tunnel syndrome, premenstrual syndrome (PMS), improved cognitive function and for the reduction of homocysteine (a protein that is often elevated when a person is at a high risk for heart disease or dementia). Doses of one to six grams for more than one year can lead to a range of minor to debilitating symptoms. Some symptoms of toxicity include muscle spasms, muscle cramps, headaches, severe fatigue, mood changes, skin lesions, light sensitivity and gastrointestinal symptoms, such as nausea and heartburn. While these symptoms can be reversed with discontinued supplementation, long term dosages of 100 mg or more can lead to permanent nerve damage including loss of bodily functions.
The RDA of vitamin E is 15 mg and because it is fat soluble, it is stored in the liver. While vitamin E has been recommended for a wide range of reasons including prevention of eye disorders, improving skin elasticity, controlling diabetes and cancer prevention-taking too much can be dangerous. Researchers hypothesize that cumulative free-radical damage to neurons over time contributes to cognitive decline and neurodegenerative diseases, such as Alzheimer’s disease. High doses of vitamin E from supplements may also cause serious bleeding in the brain known as a hemorrhagic stroke. The tolerable upper limit of vitamin E for adults is 1,000 milligrams, or 1,500 international units, per day, but your doctor will determine what a safe upper limit is for you.
Manganese is essential for healthy bone structure and prevention of osteoporosis. While there is no RDA for it, it is said to be LIKELY safe in amounts up to 11 mg per day. More than 11 mg per day might not be safe and can cause serious side effects, including symptoms resembling Parkinson’s disease, such as shaking (tremors). People who have trouble getting rid of manganese from the body, such as people with liver disease, may experience side effects when taking less than 11 mg per day.
While there are many reasons and benefits of supplementing specific vitamins and minerals, it is important to know what the safe daily intake for each is. Consult your doctor prior to implementing dietary supplements into your daily routine.