Since vitamins and minerals are naturally found in foods, it may be easy to assume that you can’t overdo it when it comes to taking them in supplement form. The fact that they are readily available to the consumer without a prescription is another factor that may give a false sense of security. Adequate amounts of vitamins and minerals are essential for health. But it’s important to keep in mind that you can have “too much of a good thing” when it comes to dietary supplements.
Roughly 60,000 cases of vitamin toxicity are reported to U.S. poison control each year. Some vitamins and minerals have a greater risk of toxicity than others and often simply reading warnings and dosing instructions on the label can go a long way in preventing an overdose. But it’s also important to 1) do your own research before starting a new supplement and 2) always mention all of your supplements when giving your health history to a healthcare provider.
The Irony of Iron
While iron deficiency is the most common nutrient deficiency worldwide, iron supplements are more likely to cause an overdose than any other vitamin or mineral supplement. Adverse effects can occur at dosages greater than 20 mg/kg of body weight, while 180-250 mg/kg is considered a lethal dose. However, fatalities have occurred at much lower doses. Iron toxicity is the biggest cause of poisoning deaths among children under the age of six. Thankfully, this statistic is coming down due to warning labels now required on all iron-containing supplements. Iron toxicity occurs in 4 stages, beginning with symptoms such as nausea and vomiting and progressing to organ failure, coma, convulsions, and sometimes death.
Fat-soluble vitamins include vitamins D, A, E, and K. These nutrients have the potential to accumulate in the body and cause toxicity in large amounts. Take vitamin D for example. Taking more than 10,000 IU daily (and especially more than 40,000 IU) for more than 3 months can lead to high levels of 25(OH)D in the blood which results in high blood levels of calcium. This can also occur if over 300,000 IU are ingested within 24 hours. This condition, known as hypercalcemia, causes symptoms such as confusion, loss of appetite, fatigue, weakness, digestive upset, and bone pain.
Toxicity can also occur with large amounts of supplemental preformed vitamin A, such as retinoic acid and retinol. While these forms of vitamin A come from animal sources, it is very unlikely to overdose from food sources of vitamin A. Hypervitaminosis A can cause blurred vision, confusion, bone loss, hair loss, irritability, peeling skin, and liver damage. If taking a multi-vitamin, it is best to take one that contains all (or mostly) plant-based sources of vitamin A, which are called carotenoids. Beta-carotene is one example. Therapeutic doses of preformed vitamin A are sometimes used in the treatment of various health conditions, but this should only be done under the supervision of a doctor.
Sodium, potassium, calcium, magnesium, and chloride are minerals that are called electrolytes because they have an electric charge. They play important roles in the body and need to be in the correct balance with each other to maintain things like proper fluid balance, heart rhythms, and muscle contractions. These nutrients can become depleted or out of balance as a result of exercise, sweating, excessive urination, diarrhea, or vomiting, as well as certain health conditions, cancer treatments, and medications. Antibiotics, diuretics, hormonal pills, laxatives, and blood pressure medications are a few pharmaceuticals that can also affect electrolyte balance.
Because of the delicate balance of electrolytes and the potentially fatal consequences of severe electrolyte imbalances, it’s important to be cautious about supplementing with these nutrients, particularly doses that exceed recommended daily values. If you are an athlete or suspect a chronic deficiency of any of these nutrients, it’s best to work with a professional to see if supplementation is warranted and safe. Symptoms of electrolyte imbalance include anxiety, thirst, dizziness, fever, headaches, confusion, insomnia, heart palpitations, and muscle cramps or weakness. Immediate medical attention is needed in severe cases – blood levels are tested and intravenous electrolytes may be used for treatment.
Vitamin and mineral supplements can be essential in preventing nutrient deficiencies, particularly in developing countries where they are common and often severe due to poverty and lack of access to nourishing foods. Even in developed countries where over-farming, the use of herbicides, and poor diets have contributed to nutrient deficiencies, supplements can be very helpful in maintaining optimal health. However, these examples serve as good reminders to exercise caution even when taking “natural” substances. Treat supplements like medications by being transparent with your healthcare providers about what you are taking. Also, do your research on proper dosing and possible interactions, carefully read labels, and buy good quality products.