B Vitamins Do Not Protect Against Parkinson’s Disease, Long-Term Study Shows

About 1 million people in the United States have Parkinson’s disease, a progressive condition that affects the nervous system.[1] Typical symptoms include tremors (for example, in the hands or head), stiff muscles, slowed movement, impaired balance and changes in speech or writing.[2],[3]

The cause of Parkinson’s disease and to how prevent it are not known. However, because B vitamins such as B6 (pyridoxine), B9 (folate) and B12 (cobalamin) play an important role in the health of the nervous system,[4] use of these vitamins has been proposed as a means to lower the risk of developing Parkinson’s disease. A large, 30-year prospective observational study published in the May 2023 issue of Movement Disorders providesa partial answer. The study found thatthe long-term dietary and supplemental intake of these vitamins above thedaily recommended amount was notassociated with a lower risk of developing Parkinson’s disease.[5]

About Parkinson’s disease

Nerve cells in the brain called neurons produce the neurotransmitter dopamine, which acts as a messenger that helps to coordinate body movements.[6] In patients with Parkinson’s disease, the neurons in a part of the brain called the substantia nigra, which controls movement, are damaged or die and can no longer produce dopamine. Once the dopamine levels in the brain decrease, symptoms of Parkinson’s disease develop. At first, symptoms are often only barely noticeable and worsen gradually. Although medications can help to control some of these symptoms, they do not slow the progression of the disease.

Men and people 60 years of age or older are more likely to develop Parkinson’s disease.[7] Some genes and certain environmental factors, such as exposure to specific toxins, may slightly increase an individual’s risk of developing Parkinson’s disease.

B vitamins for Parkinson’s disease

People cannot produce B vitamins; they are obtained through the diet.[8] As B vitamins may help injured nerves to regrow and contribute to nerve functioning, supplementation has been suggested to offer protection against the development of Parkinson’s disease. Previous studies about the association between different B vitamins and the risk of developing Parkinson’s disease have had inconsistent results, either finding no link between these vitamins and the disease, or that a higher intake of some B vitamins may have a preventive effect.[9],[10]

The new study[11]

Researchers used data from two large cohorts of health professionals in the United States: the Nurses’ Health Study (all women) and the Health Professionals Follow-Up Study (all men). After excluding those for whom dietary or demographic data were missing or who had been diagnosed with Parkinson’s disease, 80,965 participants from the Nurses’ Health Study and 48,837 participants from the Health Professionals Follow-Up Study were included in the study.

The participants were followed for 30 years. The researchers collected information about vitamin intake (either through the diet or a supplement) and other demographic and lifestyle information through a food-frequency questionnaire at the beginning of the study and then every four years. The participants were divided into groups based on their B-vitamins intake and the results were adjusted to account for various factors, including body mass index, physical activity, smoking and alcohol intake.

Over 30 years, a total of 1,426 participants were diagnosed with Parkinson’s disease (739 men and 687 women). Overall, the researchers found no association between the cumulative average intake of B vitamins and the risk of Parkinson’s disease.

For the intake of each vitamin separately, the results were the clearest for folate, for which no link was found between total and supplemental intake and the risk of Parkinson’s disease, overall and in additional analyses. For vitamin B6, higher intake of this vitamin was associated with a lower risk of Parkinson’s disease, both for women and for those who obtained the vitamin through their diet, rather than as a supplement. For vitamin B12, the researchers observed a decreased risk of Parkinson’s disease risk in some analyses among individuals who took very high amounts (roughly 10 times the recommended daily allowance of this vitamin).

The study has several important limitations. For instance, the results are based on self-reported vitamin intake, which might not be accurate. Additionally, the absorption of B vitamins can be affected by several medical conditions and medications, and the blood levels of these vitamins among participants were not measured. The results also may not be generalizable to less-advantaged populations, as the study participants were mainly White, highly educated and well-nourished.

What You Can Do

Dietary supplements are not a replacement for a healthy diet and active lifestyle. Vitamins are present in many foods. Although vitamin B12 is only naturally present in foods of animal origin, such as fish, poultry, meat, dairy products and eggs, this vitamin can be included in the diet by consuming fortified foods, such as nutritional yeasts and some packaged foods, including breakfast cereals.[12] Important sources of vitamin B6 are also of animal origin, including fish and organ meats. Vitamin B6, however, can also be found in starchy vegetables, such as potatoes, and some non-citrus fruit such as bananas, mangos, pineapples, dates and figs.[13] Folate can be found in many vegetables, such as dark leafy greens, asparagus and Brussels sprouts. Folate is also present in fruit, nuts, grains, legumes and some animal products, including eggs, dairy, meat, poultry and seafood.[14]

Especially in the elderly, who are already at a higher risk of developing Parkinson’s disease, the ability to absorb adequate amounts of vitamin B12 can decrease this risk. For this reason, in their Dietary Guidelines for Americans, the U.S. Department of Agriculture encourages older adults to meet the daily recommended doses of this vitamin through dietary sources.[15]
 

References

[1] American Association of Neurological Surgeons. Parkinson’s disease. https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Parkinsons-Disease. Accessed September 1, 2023.

[2] Mayo Clinic. Parkinson’s disease. May 26, 2023. https://www.mayoclinic.org/diseases-conditions/parkinsons-disease/symptoms-causes/syc-20376055. Accessed September 1, 2023.

[3] National Institute of Aging. Parkinson’s disease: Causes, symptoms, and treatments. Updated April 14, 2022. https://www.nia.nih.gov/health/parkinsons-disease. Accessed September 1, 2023.

[4] Calderón‐Ospina CA, Nava‐Mesa MO. B Vitamins in the nervous system: Current knowledge of the biochemical modes of action and synergies of thiamine, pyridoxine, and cobalamin. CNS Neurosci Ther. 2020;26(1):5-13.

[5] Flores-Torres MH, Christine CW, Bjornevik K, et al. Long-Term intake of folate, vitamin B6, and vitamin B12 and the incidence of Parkinson's disease in a sample of U.S. women and men. Mov Disord. 2023;38(5):866-879.

[6] Mayo Clinic. Parkinson’s disease. May 26, 2023. https://www.mayoclinic.org/diseases-conditions/parkinsons-disease/symptoms-causes/syc-20376055. Accessed September 1, 2023.

[7] Mayo Clinic. Parkinson’s disease. May 26, 2023. https://www.mayoclinic.org/diseases-conditions/parkinsons-disease/symptoms-causes/syc-20376055. Accessed September 1, 2023.

[8] Calderón‐Ospina CA, Nava‐Mes, MO. B Vitamins in the nervous system: Current knowledge of the biochemical modes of action and synergies of thiamine, pyridoxine, and cobalamin. CNS Neurosci Ther. 2020;26(1):5-13.

[9] Murakami K, Miyake Y, Sasaki S, et al. Dietary intake of folate, vitamin B6, vitamin B12 and riboflavin and risk of Parkinson's disease: a case-control study in Japan. Br J Nutr. 2010;104(5):757-764.

[10] Shen L. Associations between B vitamins and Parkinson’s disease. Nutrients. 2015;7(9):7197-7208.

[11] Flores-Torres MH, Christine CW, Bjornevik K, et al. Long-Term intake of folate, vitamin B6, and vitamin B12 and the incidence of Parkinson's disease in a sample of U.S. women and men. Mov Disord. 2023;38(5):866-879.

[12] National Institutes of Health. Vitamin B12. Fact sheet for health professionals. Updated December 22, 2022. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/. Accessed September 1, 2023.

[13] National Institutes of Health. Vitamin B6. Fact sheet for health professionals. Updated June 16, 2023. https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/. Accessed September 1, 2023.

[14] National Institutes of Health. Folate. Fact sheet for health professionals. Updated November 30, 2022. https://ods.od.nih.gov/factsheets/Folate-HealthProfessional/. Accessed September 1, 2023.

[15] U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. December 2020. https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf. Accessed September 8, 2023.