By Chiara Townley

Fact checked by Jasmin Collier

A new study on the effects of vitamin D found that too much may lead to slower reaction times and increase the risk of falling among older people.

Vitamin D is an essential vitamin that helps build and maintain healthy bones and teeth. Without this, our bodies cannot absorb calcium, which is the main component of bone.

Vitamin D may also protect against cancer and diabetes.

Our bodies synthesize vitamin D when sunlight reaches the skin.

The amount of vitamin D that our skin produces depends on several factors, including where we live, season, and skin pigmentation. During winter, vitamin D production may decrease or be completely absent.

We can also get vitamin D from salmon, sardines, canned tuna, oysters, and shrimp. People who are vegetarian can obtain this vitamin by consuming egg yolks, mushrooms, and fortified food products such as soy milk, cereal, and oatmeal.

Vitamin D in older adults

It may be harder for some older adults to absorb vitamin D because they may not get regular sun exposure. In this case, taking a vitamin supplement or a multivitamin that contains vitamin D may help boost bone health and improve memory.

Studies have linked vitamin D deficiency to conditions such as dementia, depression, diabetes, autism, and schizophrenia.

As we age, it is crucial to ensure that our bodies get the right amount of vitamin D, because the risk of cognitive impairment and dementia may increase.

According to the National Institutes of Health (NIH), the recommended daily amount of vitamin Dis:

• infants 0–12 months: 400 international units (IU)
• children 1–18 years: 600 IU
• adults to age 70: 600 IU
• adults over 70: 800 IU
• pregnant or lactating women: 600 IU

While it is crucial to take vitamin D, excessive exposure can also pose risks. A study led by Rutgers University found that older women who are overweight or obese who took more than three times the recommended daily dose of vitamin D had slower reaction times.

Slower reaction times may increase fall risk

The Centers for Disease Control and Prevention (CDC) estimate that more than 1 in 4 adults aged 65 and older will fall each year. This equates to 29 million falls, 3 million visits to the emergency room, 800,000 hospitalizations, and 28,000 deaths.

These falls also have an impact on Medicare, resulting in more than $31 billion in costs.

Recently, scientists at Rutgers University in New Brunswick, NJ, conducted a study looking at risk factors for falls. They published their results in The Journals of Gerontology: Series A.

They analyzed the effects of vitamin D on three groups of women aged 50–70 in a randomized controlled trial:

• The first group took the recommended daily dose of 600 IU.
• The second group took 2,000 IU.
• The third took 4,000 IU.

The results showed an improvement in memory and learning in the groups that took more than the recommended daily dose. However, the same groups also experienced a slowdown in reaction times.

“The slower reaction time may have other negative outcomes such as potentially increasing the risk of falling and fractures,” says senior study author Sue Shapses.

Shapses believes that the team’s findings indicate a slower reaction time may be the reason behind the increased risk of falls.

According to the scientists, taking 4,000 IU of vitamin D per day might not be a problem for young people, but it could compromise older adults’ ability to walk or catch balance to avoid a fall.

More studies are needed to determine whether slower reaction times are linked to an increase in the risk of falls and injuries.

Examining different doses of vitamin D supplementation in people of different ages and different races over a longer period could be the next step to investigate the issue further.