Vitamin B12 Protective Against Parkinson's Disease?

A high baseline intake of vitamin B12 is linked to lower risk of developing Parkinson's disease (PD), new research suggests. "The results leave the door open for the possibility that vitamin B12 may have a beneficial effect in protecting against PD," lead author Mario H. Flores, PhD, a research fellow at Harvard T.H.

The findings were presented at the International Congress of Parkinson’s Disease and Movement Disorders (MDS) 2022.

B vitamins and PD

Previous preclinical studies have suggested that B vitamins protect against PD by reducing plasma homocysteine ​​levels and through other neuroprotective effects.

However, there have been two epidemiological studies of B vitamins in PD — and their results were inconsistent, Flores noted.

The new study included 80,965 women from the Nurses’ Health Study and 48,837 men from the Health Professionals Follow-Up Study. All completed food frequency questionnaires at baseline and every 4 years.

Researchers collected information on dietary, supplement, and total intakes of folate, vitamin B6, and vitamin B12 over a nearly 30-year period through 2012. They estimated hazard ratios and 95% CIs for PD according to quintiles of cumulative mean intake.

During follow-up, 495 women and 621 men were diagnosed with PD.

The researchers adjusted for potential confounders, including age, year, smoking status, physical activity, alcohol or caffeine intake, hormone use (in women), dairy and flavonoid intake, and Mediterranean diet score.

Analysis of cumulative mean total folate, B6, and B12 intake was not associated with PD risk. “The results of the primary analysis of cumulative intake were not significant for any of the vitamins we looked at,” Flores said.

The researchers also conducted secondary analyses, including an assessment of how the most recent intake of B vitamins was associated with PD risk. This analysis also did not find a significant relationship.

However, when examining baseline intake of vitamin B12, “we saw some suggestion of a possible inverse association with PD,” Flores said.

Among individuals with a higher total intake of vitamin B12, there was a lower risk of PD (pooled hazard ratio for top vs. bottom quintile, 0.74; 95% CI, 0.60-0.89; P for trend, .001). Intake from both diet and supplements contributed to this inverse relationship, the researchers noted.

Dietary sources of vitamin B12 include poultry, meat, fish, and dairy products; However, the main sources in this study were multivitamins/supplements and fortified foods such as whole grains, Flores said.

Many limitations

In an attempt to rule out risk for reverse causation, the researchers examined B12 intake at four delayed exposure periods: 8-, 12-, 16- and 20-year lags. They found a significant association between intake at 20-year lag time and the development of PD.

Overall, the study results provide support for a possible protective effect of early intake of vitamin B12 on the development of PD, Flores noted.

In addition to being involved in regulating homocysteine ​​levels, vitamin B12 may help regulate leucine-rich repeat kinase 2 (LRRK2), an enzyme involved in the pathogenesis of PD, he said.

However, the study did not examine how B12 deficiency might be related to the risk of PD, which is “something worth looking at in future studies,” Flores said.

He added that findings from single studies may not translate into recommendations for ideal vitamin B12 intake to prevent or delay PD onset, but the median intake in the highest quintile was associated with lower PD risk at study baseline of 18 µg/d. The dosage of a multivitamin can vary from 5 to 25 μg.

Flores said a limitation of the study was that it included US health care professionals, “most of whom have very good nutritional status.”

Also, assessment of vitamin B intake was self-reported, so there may be measurement error—and there may be an unmeasured confounding factor that could explain the associations.

Flores emphasized that the effect of B12 on PD risk was “very modest” and the results need to be confirmed in other studies “ideally looking at circulating levels of vitamin B12.”

Not ready to recommend

Commenting for Medscape Medical NewsMichael S. Okun, MD, medical advisor to the Parkinson’s Foundation and professor and director of the Norman Fixel Institute for Neurological Diseases at the University of Florida, Gainesville, noted that other recent studies have suggested that high-dose B12 may be preventive. Potential treatment in PD.

“Although the current study was a secondary objective, it was a potential benefit reported in the new study,” said Okun, who was not involved in the research.

However, the evidence is not yet strong enough to change prescribing habits, he said. “We do not recommend high-dose B12 to those at genetic risk for Parkinson’s or those who already have the disease,” Okun said.

He added that while many recent studies have questioned the beneficial effects of multivitamin combinations used to prevent neurological diseases, “the results showing a lack of protection against later-onset Parkinson’s disease were not surprising. [cumulative] Folate, B6, and B12 Intake in the Current Study”.

The study was supported by the NIH. Flores and Okun report no relevant financial relationships.

International Congress on Parkinson’s Disease and Movement Disorders (MDS) 2022. Abstract 39. Presented September 15, 2022.

medscape.com/viewarticle/98...

elondonbuzz.co.uk/is-vitami...