Too much vitamin D can lead to vitamin D side effects. There are some basic signs of vitamin D toxicity in the body such as poor appetite, nausea, vomiting, weakness, weight loss, constipation, confusion, disorientation, and heart rhythm issues. Note that these symptoms may also be indications of other health issues and therefore, it is wise not to jump to conclusions that these are vitamin D overdose symptoms. However, if taking vitamin D in supplements and the above symptoms are being experienced, then too much vitamin D may be in your system.
Vitamin D side effects and vitamin D toxicity almost always occur because of supplement use or overuse of supplements. Most foods do not provide the amount of vitamin D that will cause a vitamin D overdose, unless very large amounts of foods rich in vitamin D are consumed. Too much sun exposure will also not lead to too much vitamin D in the body. This is because the body naturally limits the amount of vitamin D produced via sun exposure of the skin. Once a certain amount of vitamin D is produced by sun exposure via the skin route, then no more vitamin D is produced for a period of time as regulated by the body. Some health conditions such as hyperparathyroidism will cause vitamin D toxicity problems as well. This is a good reason why a physician should be consulted if considering increasing the daily intake of vitamin D.
The questions are: what is too much vitamin D in the body and what are the safe limits of vitamin D intake to avoid any vitamin D side effects and vitamin D toxicity issues. Some recent (in 2010) tolerable daily upper intake levels have been published by the National Academy of Sciences. The levels vary based on the age of the individual. For infants there are two categories for the tolerable daily upper intake levels of vitamin D: from 0 to 6 months of age it is 1,000 IUs and 6 to 12 months of age it is 1,500 IUs. For the children and adolescent categories the following daily levels exist: 1 to 3 years old is 2,500 IUs of vitamin D, 4 to 8 years old is 3,000 IUs of vitamin D, and finally 9 to 18 year old individuals have a limit of 4,000 IUs daily. For adults over 19 years of age, the vitamin D tolerable daily limit is 4,000 IUs and the same applies to pregnant or lactating women. As a comparison, the recommended daily intake for vitamin D is in the 400 to 800 IUs range.
These high vitamin D values are a guide and are based on the average healthy individual. Some people may experience vitamin D side effects at levels lower that the ones stated above. In order to avoid vitamin D toxicity issues or a vitamin D overdose, it is best to consult a physician when considering taking vitamin D at levels higher than the recommended daily intake value.
Other vitamin D effects are potential damage to the kidneys, formation of kidney stones, and the creation of high levels of calcium in the blood leading to impaired heart and lung function due to calcium deposition in these soft tissues.
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