Sunday, September 16, 2012

Vitamin D research update

Vitamin D and Parkinson'sA study from Finland suggested that higher vitamin D status provides protection against Parkinson's disease. People with the highest vitamin D levels (above 20 ng/mL) had a 65% lower risk of developing Parkinson disease than those with the lowest vitamin D levels (below 10 ng/mL).  

 Vitamin D and Alzheimer's
A study in France among women 75 years of age and older found those with higher intakes of vitamin D from their diets least likely to develop Alzheimer’s disease over a seven-year study period.43 Women consuming more than 3,108 IU of vitamin per week (444 IU per day) were 77% less likely to develop Alzheimer’s disease than those with lower vitamin D intake. There was, however, no association between vitamin D intake and the risk of developing other types of dementia. The study excluded women who had taken vitamin D supplements.

Vitamin D and Rheumatoid Arthritis
Low levels of vitamin D are also associated with a higher risk in women of developing rheumatoid arthritis. There is conflicting evidence about whether vitamin D helps reduce the overall risk of dying from cancer, although studies have consistently shown that higher vitamin D serum levels were associated with decreased risk of death from gastrointestinal cancers.

Vitamin D and Diabetes
Vitamin D appears to reduce the risk of insulin resistance in obese individuals. Obesity itself is a major risk factor for insulin resistance, but too little vitamin D may increase the risk. A study found that obese individuals with vitamin D blood levels below 20 ng/mL were 12 times more likely to be insulin resistant than obese individuals with sufficient levels of vitamin D.41 The researchers suggest that insulin resistance in obese individuals may be reduced by making improvements in vitamin D levels.

Having insulin resistance increases the risk of type 2 diabetes. So it is not surprising that a review of studies found that daily vitamin D intake over 500 IU decreased the risk of type 2 diabetes by 13% compared with intake of less than 200 IU. Similarly, individuals with vitamin D levels over 25 ng/mL had a 43% lower risk of developing type 2 diabetes compared to those with levels under 14 ng/mL. However, vitamin D supplementation has not been shown to affect glucose tolerance among people with established type 2 diabetes.23

There is preliminary evidence that giving vitamin D supplements to infants might decrease the risk of type 1 diabetes later in life.

23 Mitri, et al, Vitamin D and type 2 diabetes: a systematic review, Eur J Clin Nutr, 2011, 1-11

41 Kabadi  Joint Effects of Obesity and Vitamin D Insufficiency on Insulin Resistance and Type 2 Diabetes: Results from the NHANES 2001-2006. ,  2012

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