Vitamin B12 may help to protect people against Alzheimer’s disease, a small study suggests. But other studies in this area have had mixed results. Some have found a link between B12 and Alzheimer’s risk. Others have not.
The new study included 271 Finns. They were 65 to 79 years old at the start of the study. At that time, they did not have Alzheimer’s or other dementia. Researchers gave people blood tests. They measured levels of homocysteine, one of the building blocks of proteins. People with high homocysteine levels have a greater risk of stroke. They also measured the active form of B12, which lowers homocysteine levels. During the next 7 years, 17 people developed Alzheimer’s disease. People with higher levels of homocysteine also were more likely to develop Alzheimer’s. But people with higher B12 levels were less likely to develop it. The study appeared in the journal Neurology. HealthDay News wrote about it October 18.
By Mary Pickett, M.D.
Harvard Medical School
What Is the Doctor’s Reaction?
Are you getting enough vitamin B12 to keep your memory from failing? A Finnish study tracked the health of older adults for 7 years. In that time, 6% of the group showed the beginning signs of dementia. This was not unexpected, since the people in the study were 65 to 79 years old when the study began.
People were given blood tests during the first year of the study. They showed lower vitamin B12 levels in the people who later developed dementia.
Doctors have known for decades that being deficient in vitamin B12 can cause a loss of memory and thinking skills. When people complain to a doctor about memory loss, a measure of B12 is one of the first blood tests checked.
This study was pretty small. It included fewer than 300 patients, and only 17 developed dementia. But the study suggests that even mild deficiency in B12 could contribute to risk for dementia. This study reminds us that B12 can be checked well before memory symptoms begin. And B12 can be given if the level is low. Why don’t we check this test more often?
Now that is a good question. It is very common for elderly patients to have a low level of vitamin B12. The main reason is that B12 becomes harder to absorb from the intestine for some elderly people.
About 3% of the population have very low levels — the kind that catch your doctor’s eye. Some experts think that more than one-third of adults have low B12 levels. They believe the “normal” range that is used to interpret the lab test today was not set fairly. People who have B12 at the low end of the normal range might still need supplements.
B12 deficiency can cause memory loss. It also can cause anemia, numbness or tingling, walking problems and weakness.
Vegetarians are at particularly high risk for B12 deficiency. That’s because B12 is found mainly in meat, fish, eggs and dairy products. Other groups at high risk include:
- The elderly
- People who have had gastric bypass surgery for obesity
- People who take antacid medicines for the stomach on a regular basis
What Changes Can I Make Now?
Vitamin B12 deserves more attention, and doctors should test its level in more people.
Ask your doctor to check your B12 level if you have taken antacid medicines for longer than 3 or 4 years. In fact, ask your doctor if you still need to take the medicines! Many people stay on these medicines for longer than is needed. Side effects such as bone thinning can occur from long-term use.
You should also have your B12 level checked if you have numbness or weakness that has not been explained.
Vitamin B12 is a pretty harmless vitamin. However, supplements are not necessary for people who don’t have low levels. Taking B12 supplements has not been proven to prevent dementia, and no expert group has recommended this.
How can you lower your risk for dementia?
Try exercise. A nicely designed study looked at future dementia risk in people ages 39 through 64. Those who exercised at least twice a week in mid-life cut their risk of later dementia in half. Obesity and diabetes also have been linked with increased dementia risk.
It also helps to be intellectually and socially active. These life strategies do appear to work.
Other ideas for prevention are not recommended. Some research has looked at the possibility that statin drugs or nonsteroidal anti-inflammatory drugs (NSAIDS) might help to prevent dementia. NSAIDs include aspirin, ibuprofen and naproxen.
But experts say you should take NSAIDS or statins only if you have another reason to use them. Do not take them to prevent dementia. They have not been proven to protect against dementia, and they have potential harms.
Taking estrogen after menopause has been linked to a higher risk of Alzheimer’s disease. Avoid estrogen after menopause unless it is truly needed to treat symptoms. Stop it after a few years of use.
People with a strong family history of Alzheimer’s disease may choose to take vitamin E. The suggested dose is 400 to 800 international units per day. There is some evidence that vitamin E may offer some protection, but its benefit is still unproven.
What Can I Expect Looking to the Future?
The cause of Alzheimer’s disease remains a mystery. Scientists will keep working to find which conditions increase dementia risk. This may eventually allow us to understand the biology of dementia, and its triggers.
October 19, 2010, News Review From Harvard Medical School — Vitamin B12 May Lower Alzheimer’s Risk
