B Vitamins, Homocysteine and Parkinson’s disease
What are the B vitamins and what do they do?
Vitamin B1, B6, and B12 make up the major B vitamins important to our health.
Vitamin B1 or thiamin is involved in the production and use of glucose for energy. It is important for muscle, brain and heart health. Deficiencies are rare but can be seen with malnutrition and excessive alcohol use.
Vitamin B6 or piroxidine is involved in fat metabolism, red blood cell health, immune health and production of niacin (another vitamin). Of particular importance is the role that it plays in the production of amino acids and neurotransmitters such as GABA, serotonin, norepinephrine, and even dopamine. B6 deficiency can cause skin problems and neurologic symptoms such as depression, sleepiness and confusion. Toxic amounts can cause neuropathy with numbness or painful, burning feet or hands.
Vitamin B9 or folate is needed to produce new cells. Low folate levels during pregnancy can increase birth defects related to impaired fetal nerve cell development in utero. Folate can reduce levels of homocysteine (high levels can be associated with heart disease and stroke). Folate may reduce the risk of some cancers such as breast and colon cancer.
Vitamin B12 is needed to produce new cells and deficiencies are associated with anemia, blood cell abnormalities, peripheral nerve disease and cognitive changes. The elderly, people with pernicious anemia and strict vegetarians are at greater risk for deficiency.
B Vitamins and homocysteine
A deficiency in vitamin B6, folate or B12 can increase levels of the amino acid homocysteine. Homocysteine is also produced in the metabolism of levodopa and can be elevated by COMT inhibitors (entacapone, Comtan, Stalevo), medicines that are used to treat PD. Elevated levels of homocysteine may be toxic to nerve cells and are associated with blood clotting problems that can lead to stroke or coronary artery blockage (heart attack). In addition, recent research suggests that higher homocysteine levels can increase the risk of dementia and cognitive decline in PD. Despite these associations there is no evidence that shows that lowering homocysteine levels reduces the risk of dementia, stroke, or heart disease.
B Vitamins and brain health.
The B vitamins play a significant role and maintaining healthy cells include neurons found in the brain. Reduced levels of B vitamins have been linked to various brain conditions such as seizures, migraine, pain, dementia, Alzheimer’s and Parkinson’s disease.
Vitamin B12 plays an important role in cognitive health. Research suggests that low levels of vitamin B12 are associated with brain cell loss or brain atrophy in older patients without thinking problems. Low levels of B12 were also show to be associated with decline in cognitive function, and Alzheimer’s disease. Unfortunately treatment with vitamin B12 has not been shown to slow decline in AD.
An analysis evaluating whether the amount of vitamin B in your diet affects the risk of developing PD showed that people with higher intake of vitamin B6 had lower risk of developing PD compared to those with lower dietary intake (but not B1 or B12)[i]. However further analysis showed that this stronger in smokers over nonsmokers. Whether B6 is helpful once you are diagnosed with PD is not known.
The role of vitamin B and PD is further strengthened in yet another study in which blood levels were measured in 111 consecutive patients with PD[ii]. Patients treated with levodopa had lower levels of folate and B12 than other people with neurologic disease, PD patients with cognitive problems had lower B12 levels than those not cognitively impaired and folate was lower in people with depression. Inadequate folate levels may also affect treatment of depression as low folate levels are linked to poor efficacy with a common class of antidepressants called SSRIs.
What is the recommended dose?
B vitamins are included in most multiple vitamin products and sold separately as vitamin B complex. As always, aim to get your vitamins through the food you eat rather than relying on a vitamin as the sole source. This insures you get the fiber, healthy fats, and antioxidants necessary for optimal health.
Recommended daily allowance (RDA) for each B vitamin is listed below:
B1- 1.1 to 1.5mg/day depending on gender
B6 - 1.3 to 1.7mg/day depending on age and gender.
B9(Folate) - up to 1000mcg/d
B12 - 2.4 mcg/day although as much as 25- 50 mcg per day may be needed in elderly or people with absorption problems. Pernicious anemia is a unique condition in which vitamin B12 can not be absorbed from the stomach because intrinsic factor (needed for absorption) is missing. Intramuscular injections rather than pills are used for this condition.
How do I get more vitamin B in my diet?
Vitamin B1 is found in pork wheat and rye flour, kidney beans, and wheat germ.
Vitamin B6 is found in cheese, mild, eggs, beans/legumes, potatoes, fish, meat, flour, grains, carrots, and peas.
Vitamin B9 (folate) is found in fortified cereals and goods baked with fortified flour, leafy green vegetables, fruits such as bananas and melons, legumes, yeast, liver, and mushrooms.
Vitamin B12 is found in dairy products, meat, fish and shellfish.
Are there toxic effects, interactions with vitamin B?
Many medicines can interact with vitamin B6 such as MAO inhibitors (rasagiline and selegiline are examples used to treat PD), hydralazine, isoniazid, penicillamine and theophylline. High amounts of vitamin B6 can interfere with the absorption of the PD medicine carbidopa/levodopa so it is not recommended that you take more than 15 mg if you are on this medicine.
Vitamin B12 supplements should be avoided in Lebers or optic neuropathy. Vitamin B12 can cause a skin rash and unmask certain problems such as polycythemia vera (associated with high red blood cell count) and gout. Vitamin B12 requires stomach acid to assist in its absorption so antacids and medicines used for acid reflux and heartburn can reduce B12 levels. Ask you cardiologist or primary doctor about B vitamins if you have heart disease requiring angioplasty and/or artery stents, as studies suggest that B vitamins can increase re-blockage.
The information and dose outlined above does not apply to everyone so talk to your doctor before starting any supplement or vitamin.
[i] Neurology 2006. 67; 315.
Parkinsonism and Related Disorders 2008. 14:3212
Author: Monique Giroux, MD. Medical Director NWPF and Booth Gardner Parkinson's Care Center