July 13, 2022
Taking measures to assure you have adequate levels of vitamin D may help to keep the brain in good working order, according to a new report. The study found that people with low levels of the vitamin had reduced brain volumes and were at increased risk of both dementia and stroke. Alzheimer’s disease is the most common form of dementia.
“Vitamin D is a hormone precursor that is increasingly recognized for widespread effects, including on brain health, but until now it has been very difficult to examine what would happen if we were able to prevent vitamin D deficiency,” said the study’s senior investigator, Elina Hypponen, a professor at the University of South Australia. “Our study is the first to examine the effect of very low levels of vitamin D on the risks of dementia and stroke, using robust genetic analyses among a large population.” The findings were published in the American Journal of Clinical Nutrition.
For the study, researchers analyzed data from 294,514 British men and women in the UK Biobank, a robust storehouse of medical information. They found that people with the lowest vitamin D levels, below 25 nanomoles per liter of blood, had a 54 percent higher risk of developing dementia than those who had healthy vitamin D levels of 50 nanomoles or higher. Dementia could have been prevented in many of those with low vitamin D levels if they had taken supplements or other measures to boost their levels of vitamin D into the normal range, the researchers predicted.
The study showed only an association and cannot prove a direct cause-and-effect between low vitamin D levels and dementia. Due to the complex nature of Alzheimer’s disease, it is extremely difficult in general to establish causality, but the researchers here used a genetic technique called Mendelian randomization that aims to identify the underlying causes of a particular illness, in this case dementia.
Earlier studies have likewise suggested that low levels of vitamin D may increase the risk of Alzheimer’s disease in older people. One study from 2015, for example, found that memory skills declined two to three times faster in those with low blood levels of vitamin D compared to those with adequate levels of the vitamin.
The findings underscore the importance of identifying vitamin D deficiency in older men and women. Your doctor can check your levels during a routine blood test.
Vitamin D is sometimes called the sunshine vitamin because it is produced in the skin upon exposure to sunlight. One way to raise blood levels of the vitamin is to spend at least 15 to 20 minutes in the sun each day.
People living in northern latitudes, however, may be particularly prone to vitamin D deficiency during the winter months, when sunlight levels are low. Certain ethnic groups are also particularly prone to vitamin D deficiency, including African-Americans and Hispanics, who are less able to absorb sunlight through the skin.
Vitamin D has long been known for its bone-strengthening properties. That’s one reason it is added to milk. But a growing number of studies point to additional benefits, like lowering the risk of diabetes and certain cancers.
In addition to fortified drinks like milk, soy milk and some juices, the vitamin is also found in oily fish like salmon, mackerel, bluefish, catfish, sardines and tuna, as well as cod liver oil and fish oils. Fish oils have also been linked to a lower risk of Alzheimer’s disease.
Some experts recommend that people in their 60s and older discuss taking a daily vitamin D supplement with their physician. But don’t take too much. The vitamin is stored in fat, and excessive levels can build up and cause side effects ranging from digestive problems and headaches to irregular heartbeats and extreme fatigue.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Shreeya S. Navale, Anwar Mulugeta, Ang Zhou, et al: “Vitamin D and brain health: an observational and Mendelian randomization study.” The American Journal of Clinical Nutrition, April 22, 2022