Lower MS Risk in People With High Vitamin D Levels When Young

People with high levels of free vitamin D in circulation before the age of 20 have a lower risk of developing multiple sclerosis (MS) later in life, a new study suggests.

A significantly lower risk was also observed among people who, at ages 30–39, had elevated levels of a vitamin D carrier protein, called vitamin D-binding protein.

The study, “Free Vitamin D₃ Index and Vitamin D-binding protein in multiple sclerosis – a presymptomatic case-control study,” was published in the European Journal of Neurology.

Evidence indicates that people with high vitamin D levels have a lower risk of developing MS. The benefits of this vitamin are also evident among MS patients —  those with higher vitamin D have less inflammation and reduced clinical activity.

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The major circulating form of vitamin D is called 25-hydroxyvitamin D3, or 25(OH)D3, and its availability to cells is largely controlled by its main carrier protein in the blood, vitamin D-binding protein (DBP).

It’s believed that DBP binds to 85% of circulating 25(OH)D3, while about 15% of this vitamin binds to another protein called albumin, and less than 0.1% is free.

While the free portion is what’s usually available to cells, some cells can take up the vitamin D form that is bound to DBP. Thus, a real estimate of the free availability of the active form of vitamin D should be assessed in relation to DBP levels.

DBP itself also has many other functions, including the ability to modulate the immune system, suggesting it could also have an impact in MS, alone and combined with vitamin D.

To determine if vitamin D and DBP levels were associated with the risk of developing MS, a team led by researchers at the Umeå University, Sweden measured the levels of free 25[OH]D3 in blood samples obtained from 660 people who went on to develop relapsing-remitting MS later in life.

These levels were reported as a free vitamin D3 index, essentially a ratio of total 25[OH]D3 and total DBP.

All samples were donated before age 40 and prior to MS symptom onset. Overall the median age at sample collection was 25, and the median age at which MS symptoms became evident was 33.4. For comparison, researchers examined blood samples from 660 people without MS, matched to patients for sex, date of blood sampling, and date of birth.

The results showed that, among younger patients (below age 20), the free vitamin D3 index was lower for MS patients compared with controls. A trend showed that the higher the vitamin D3 index was, the lower the MS risk later in life.

No differences were seen in other age groups.

The median concentration of DBP showed no significant differences between MS and controls. However, statistical analysis showed that elevated DBP levels were associated with a significantly lower MS risk, with older patients (ages 30–39) showing the most reduced risk. The results remained significant even after adjusting for 25[OH]D3  levels.

Overall, these findings suggest that “high levels of free 25(OH)D3 at young age are associated with a reduced risk of developing MS later in life,” the researchers wrote.

Also, elevated DBP levels were linked with a lower risk for developing MS, which “may indicate an independent role of DBP in MS aetiology [cause],” the study concluded.