New research has linked low levels of vitamin D with an elevated risk of cognitive decline and mental impairment. The study was conducted by Duke-NUS (a cooperative project between Duke University in North Carolina and the National University of Singapore), with elderly Chinese subjects. The researchers explain that a deficiency in vitamin D is most often caused by lack of exposure to sunlight. The nutrient is necessary to maintain healthy bones and muscles.

Other studies in Europe and North America have implicated low vitamin D leels with cognitive decline, as well as the long-known problems of cardiovascular and neurodegenerative diseases. News-Medical states:

Regardless of gender and extent of advanced age, individuals with lower vitamin D levels at the start of the study were approximately twice as likely to exhibit significant cognitive decline over time.

In addition, low vitamin D levels at baseline also increased the risk of future cognitive impairment by [two to three] times.

The researchers postulate that vitamin D provides protection against neuron damage and loss. They plan to conduct further studies to learn the mechanisms vitamin D uses to protect neurons, and the way in which optimizing vitamin D levels can protect against cognitive decline.

The availability of sunshine affects the vitamin D levels of people in different countries. In the United Kingdom, people ingest an average of 3 micrograms (120 IU) of vitamin D from food, and they are exposed to low levels of sunlight throughout the year. The result is a greater risk of bone-related disease. Elle UK says:

Women in particular should take note — history shows our bones degrade faster than our male counterparts.

When we hit menopause, the loss of bone density accelerates rapidly (up to 20 [percent] in just [seven] years), so keeping vitamin D levels topped up can only help to hedge our bets against calcium deficiency and irreversible bone loss later in life.

Public Health England (PHE) had previously recommended that “at risk” individuals and children under five years of age take vitamin D supplements. Now they have added a recommendation that all Britons take 10 micrograms (400 IU) daily as a supplement, although that amount is far below what is needed for health. Online British newspaper Health Spectator notes:

Citizens of other countries that lie far north of the equator are also at particular risk. In December of 2015, Scandinavians living in Oslo, Norway, had only six hours and four minutes of sunshine, from 9:00 in the morning until 3:12 in the afternoon. Residents of Edinburgh, Scotland, got only an hour more.