A member of my wife’s family was diagnosed with colon cancer a while ago. We have been looking at the value of various supplements in support of the treatment she is reading. Several studies have linked low vitamin D levels to reduced risk of many diseases, including colon cancer.

My training as a pharmacist warned me that vitamin D can be dangerous if taken at very high levels. What levels are dangerous? I found a study that was published in the journal Anticancer Research in February of this year. The researchers believe that intake of up to 40,000 international units/day are not likely to result in signs of significant toxicity (poisoning). This is a huge dose, and closer reading of the abstract shows that the dose required to get the serum 25(OH)D level above 40 ng/mL was almost 10,000 international units/day.

The full article was available at no charge. So I took a look at it. The authors enrolled more than 3600 patients and measured their 25(OH)D levels. They found that most people were taking less than 500 international unit each day. The authors noted that this is the first analysis of a relation between vitamin D levels and vitamin D supplements measured in a community of patients. The patients were not taking a single brand of vitamin D, so it is not possible to say which brand anyone should take. The study raises a lots of questions, but they made it clear that what was thought to be a high dose a few years ago may actually be what most people need.

Of course, an individual should not be taking the second day without consulting with a physician. There are just too many things that should be considered to be able to suggest a dose that will work for everyone. Some of the things include where you live, how much time you spend in the sunshine, and any dietary sources of vitamin D. Other research has suggested that some diseases may be associated with low levels of vitamin D, but whether the disease or the low vitamin D levels come first is not known.

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Filed under: Health • Vitamins

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