242 girls aged 5-12 Vitamin D levels were measured by  researchers from the University of Michigan School of Public Health.  They found that those who were Vitamin D deficient were twice as likely to begin menstruation  as the ones whose D levels were highest. during the study period . (That would explain why I was younger than all my friends when I started my periods and early menopause!)

Among the vitamin-D-deficient girls, 57 percent started their period during the study, compared to 23 percent with adequate vitamin D. However, researchers defined adequate vitamin D as =30 ng/mL, which is actually still a deficiency state! For optimal health, vitamin D levels should be a minimum of 50 ng/mL, which means the number of vitamin-D-deficient girls with early puberty was probably much higher than the study reported.

Research presented last year at the San Antonio Breast Cancer Symposium found that more than half of women with breast cancer have low vitamin D levels, which is really a significant finding.

New research shows that low levels of sunlight, coupled with glandular fever, (better known as mononucleosis)  could increase your risk of developing multiple sclerosis (MS). This could be one reason that MS tends to be more common away from the equator.

The study suggested that low levels of sunlight could affect how your body responds to infection. Vitamin D deficiency could be another possible link.

BBC News reports:

"The researchers found that by just analyzing sunlight, they could explain 61 percent of the variation in the number of MS cases across England. However when they combined the effect of sunlight and glandular fever, 72 percent of the variation in MS cases could be explained."

"The researchers found that by just analyzing sunlight, they could explain 61 percent of the variation in the number of MS cases across England. However when they combined the effect of sunlight and glandular fever, ( mononucleosis.72 percent of the variation in MS cases could be explained."

Vitamin D Deficiency and Viral Exposure Can Explain the Vast Majority of MS Cases:

A large number of studies have confirmed that your risk of MS increases the farther away you live from the equator. In fact, a lack of sunlight was identified as a risk factor for MS as early as 1922. Within the United States, your risk of developing MS roughly doubles if you spend your childhood—up to the age of 15—in northern states than if you live in the south.

Another previously established risk factor is the Epstein-Barr Virus (EBV), which causes glandular fever. Eleven years ago, German researchers demonstrated the association between EBV and MS, showing that in contrast to control populations, 100 percent of MS patients had antibodies against EBV. The authors suggested that EBV might play an indirect role in MS as an activator of the underlying disease process.

In the most recent study, published in the journal Neurology last month, researchers assessed the relationship between ultraviolet B radiation (UVB) and Epstein-Barr virus (EBV) exposure in British MS patients.

Using English national Hospital Episode Statistics, they obtained the prevalence of MS and infectious mononucleosis (caused by the Epstein-Barr virus) during the seven-year period from 1998 to 2005. The UVB intensity data was collected from the US National Aeronautics and Space Administration.

After evaluating the relationships between these three variables: MS prevalence, Epstein-Barr virus prevalence, and UVB intensity, they found that UVB exposure alone could explain 61 percent of the variations of MS cases across England. When they combined UVB exposure and incidence of glandular fever, 72 percent of the variations could be explained.

The authors of the study made this conclusion:

"UVB exposure and infectious mononucleosis (IM) together can explain a substantial proportion of the variance of MS. The effect of UVB on generating vitamin D seems the most likely candidate for explaining its relationship with MS. There is a pressing need to investigate the role of vitamin D and EBV and how they might interact to influence MS risk to identify potential prevention strategies."

http://www.ncbi.nlm.nih.gov/pubmed/21502600 

http://www.ncbi.nlm.nih.gov/pubmed/16502434 Mono.

http://www.ncbi.nlm.nih.gov/pubmed/17713752

http://www.ncbi.nlm.nih.gov/pubmed/20031348