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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

Vitamin D levels of prison inmates: A problem?

A recent study published in PLOS ONE has found that low vitamin D levels are common among prison inmates.

Awareness of vitamin D levels among prisoners is important because most prison inmates are only allowed few hours of sun exposure each day. Yet, not many studies have examined the vitamin D status among prison inmates.

Researchers, led by senior author Dr. Benjamin Udoka Nwosu of the University of Massachusetts Medical School, recently looked at the vitamin D levels of 526 prison inmates in Massachusetts. They wanted to know what their average vitamin D levels were and what factors might be related to vitamin D levels.

The researchers found that 67% of the prison inmates were insufficient or deficient in vitamin D, meaning levels less than 30 ng/ml.

When looking at factors related to vitamin D levels, they found that prison inmates with darker skin types had significantly lower vitamin D levels when compared to those with lighter skin types.

Additionally, prison inmates who were under maximum security had significantly lower vitamin D levels compared to those in medium or minimum security facilities.

“In conclusion, this study shows that in a prison system with uniform nutritional guidelines, three principal factors determine inmates’ vitamin D status: skin pigmentation, seasons, and the security level of incarceration,” the researchers stated.

The researchers call for a prison health policy that includes maintaining healthy vitamin D levels, which could cut back on the costs of healthcare among inmates.


Nwosu, B. U. et al. The Vitamin D Status of Prison Inmates. PLOS One, 2014.

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4 Responses to Vitamin D levels of prison inmates: A problem?

  1. RodEverson says:

    Was there a breakdown of the percentage insufficient and the percentage deficient? And what are considered the cutoff points for each?

    I assume “insufficient” is under 30 ng/ml, but is “deficient” under, say, 15 ng/ml or ???

    The reason I ask is that I suspect a good percentage of the general population is under 30 ng/ml, but not many are under 15 ng/ml. It would be interesting to see the information broken down a bit more so that one could compare the prison population to the general population better. Is it known what percentage of the general population is found to be under 30 ng/ml, (vs. the 67% of the inmates)?

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  2. Jeff Nicklas says:


    Thanks for the question. The researchers defined vitamin D insufficiency as a level between 20 and 30 ng/ml. They defined deficiency as a vitamin D level below 20 ng/ml. With these cutoff points, 34% of the inmates were insufficient and 33% of them were deficient.

    Some scientists think that in the United States, around 75% of the population may have levels below 30 ng/ml. Let me know if you have any further questions or comments.

    Cheers, Jeff

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  3. So putting together the above 2 comments, it appears that the inmates actually had BETTER Vit. D levels, than the general population ?! (ie. a smaller percentage of them were insufficient).

    Also, allow me to ask the politically incorrect, but very relevant question: What percentage of the inmates is darker skinned, and what percentage of the general population is darker skinned?

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  4. Nessie2222 says:

    My husband is in prison in the state of Florida. In the southern states there are very large populations of African Americans in prison, sometimes as much as 70%. Although they are supposed to get several hours of sunlight each day, that is not necessarily true in all cases. They also are unable to “dress down” to get full sun exposure. They will not carry Vitamin D in the canteens and there are few if any foods the prisoners can buy that are fortified. Multivitamins are not very helpful. This is a very serious problem that is being ignored. These facilities have frequent outbreaks of influenza, bacterial infections and viral outbreaks. I was very pleased to read this report and hope that more can be done to remedy the situation.
    Thank you so much

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