The best sources of B12 are organ meats like liver and kidney, as well as beef, fish, shellfish, chicken, dairy products and eggs, Yourman says. Some breakfast cereals are also fortified with B12.

Most older adults don’t need a B12 supplement

Older adults should not take B12 supplements unless they have a documented deficiency, Yourman says — and only about 20 percent of adults over age 60 do, according to a report from the American Academy of Family Physicians.

What’s more, screening for a B12 deficiency — a simple blood test — should not even be considered unless you are exhibiting symptoms, such as signs of memory loss, mood changes or if you are on a strict vegan diet, says Dr. JoAnn Manson, chief of the division of preventive medicine at Brigham and Women’s Hospital in Boston and professor of medicine at Harvard Medical School.

Other symptoms of B12 deficiency include numbness in your hands and feet, sore mouth or tongue ulcers, vision problems, and loss of appetite or weight loss. If you are B12-deficient, your doctor will determine how much of the vitamin you need to take. 

Age-related changes can affect your B12 levels

Older adults can be susceptible to B12 deficiency because sometimes aging is concurrent with decreased absorption of the vitamin, Yourman says. Research from Tufts University finds that by age 75 or 80, around 40 percent of people have a diminished ability to absorb B12 from food. One reason: Changes in stomach acid can be part of aging, and you need hydrochloric acid in your stomach to absorb B12.

Older adults are also more likely to take medications that can interfere with B12 absorption, Manson says. For example, she says, it’s more common for people age 50-plus to take metformin, which is widely prescribed to lower blood sugar levels and manage type 2 diabetes. But metformin can also affect vitamin B12 absorption, she says.

Additionally, some older adults suffer from acid reflux disorders and take antacids to reduce the heartburn and indigestion. Prolonged use of these medications can limit B12 absorption, Manson says.

Another factor that can increase the risk of a B12 deficiency is a lack of a diverse diet, says Emily Peron, associate professor in the department of pharmacotherapy and outcomes science at Virginia Commonwealth University. Only animal foods have vitamin B12 naturally.

B12 and the Brain 

A vitamin B12 deficiency is typically one of the first things checked in someone who is experiencing unexplained cognitive impairment, Yourman says, since not getting enough of the essential vitamin can cause memory problems and confusion. Treating the deficiency can often reverse these symptoms. 

However, studies suggest that supplementing with B12 does not reduce the risk of developing dementia or Alzheimer’s disease in older adults, or slow its progression.

More clinical trials are needed to better understand the association between B12 and brain health.

It’s not just older adults who are more likely to have a B12 deficiency. If you’ve had a gastric bypass, have a history of Celiac disease or pancreatic deficiencies, or are on a vegan diet, you are also at risk, Yourman says.