Though vitamin D plays a crucial role in your health -- keeping bones and teeth in good shape -- too much is toxic. However, you generally do not get vitamin D from food. Instead, your body makes it via a reaction in your skin to natural sunlight. By taking too many vitamin D supplements you may go beyond what your body will accept.
Vitamin D Toxicity
Vitamin D helps your body to absorb the mineral calcium, critical for building strong bones. However, too much vitamin D leads to hypervitaminosis D. This can cause a buildup of calcium in your blood, leading to decreased bone density and kidney problems. However, it takes a lot of vitamin D to get to this point. The Linus Pauling Institute says that it takes over 50,000 IU of vitamin D per day. Hypervitaminosis D may occur at lower levels, though usually no less than 10,000 IU each day.
Dosage
The Food and Nutrition Board sets the recommended daily limits for vitamin D at well below 10,000 IU. The figures refer to tolerable upper limits, so they're not necessarily a daily target. Children over nine years old and adults should take no more than 4,000 IU of vitamin D daily. Children from four to eight years old should get no more than 3,000 IU per day. Prolonged doses significantly higher than that could lead to grogginess, fatigue and even fatality.
Infants
Babies and young children are at particular risk of a vitamin D overdose. Breast-fed babies should get no more than 400 IU of vitamin D from supplements each day. This also applies to partially breast-fed infants. The FDA points out that using liquid vitamin D can lead to vitamin D overdose in babies. Liquid doses are harder to measure out accurately. A vitamin D overdose in babies leads to symptoms such as vomiting, weakness, thirst, stomach pain and in serious cases kidney failure.
Considerations
Remember that multi-vitamins may also contain vitamin D. So, if you're taking a specific vitamin D supplement make sure that your multivitamin isn't pushing your daily dose over the limit. The Linus Pauling Institute suggests that adults over 50 need more vitamin D than younger people. This is because the body loses its ability to effectively make vitamin D via the sunlight on the skin. Aim for a dose of 2,000 IU each day if you're over 50 to help prevent osteoporosis and similar age-related conditions.
References
- FDA; Infant Overdose Risk With Liquid Vitamin D; June 15, 2010
- Linus Pauling Institute; Vitamin D; Jane Higdon, Ph.D.; 2004
- Harvard Health Publications; Vitamin D and Your Health: Breaking Old Rules, Raising New Hopes; February 2007
- Office of Dietary Supplements: Dietary Supplement Fact Sheet: Vitamin D;
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