• High levels of antioxidants in the blood were associated with a lower risk of dementia.
  • Experts suggest eating foods rich in antioxidants, including dark leafy greens and orange fruits.
  • The researchers warn that more research is needed before knowing which amount of these antioxidants has the greatest impact on reducing the risk of dementia.

People with higher blood levels of certain antioxidants may be less likely to develop dementia in later life, a new study has found.

This adds to growing evidence that eating a wide variety of fruits and vegetables rich in these phytonutrients may have long-term benefits for the brain.

The researchers warn that more research is needed before knowing how many and which of these antioxidants have the greatest impact on reducing the risk of dementia.

“This study may indicate that only certain types of carotenoids may be effective in reducing dementia risk, and these may include lutein + zeaxanthin and beta-cryptoxanthin,” the study author said. May Beydoun, PhDepidemiologist at the National Institute on Aging at the National Institutes of Health in Baltimore.

However, “without evidence from randomized controlled trials, it is too early to advise people to change their diet,” she added.

The researchers used data on more than 7,200 participants from the third National Health and Nutrition Examination Survey (NHANES 1988-1994).

The people were between the ages of 45 and 90 at their first study visit and were followed for an average of 16 to 17 years and up to 26 years.

All of the participants were dementia-free at the first visit, during which they had an interview, physical exam, and blood draw to measure antioxidant levels.

The researchers looked at how many people had been diagnosed with dementia during the follow-up period, including Alzheimer’s disease and other types.

People 65 or older at baseline with the highest blood levels of lutein and zeaxanthin had a lower risk of developing any type of dementia during the follow-up period compared to people with lower levels of these antioxidants. .

High levels of beta-cryptoxanthin, compared to lower levels, were linked to a lower risk of any type of dementia in those aged 45 to 64 and in those aged 65 or older at baseline.

These specific antioxidants are a type known as carotenoids, which give fruits and vegetables their yellow, orange and red color.

Lutein and zeaxanthin are found in high amounts in dark green vegetables like kale, spinach, and broccoli. Beta-cryptoxanthin is abundant in fruits like oranges, papaya, peaches, and tangerines.

The apparent protective effect of these antioxidants was somewhat reduced when the researchers took into account other factors such as income, education and physical activity. This suggests that these other factors also shape the risk of developing dementia.

No clear link was observed between dementia risk and lycopene, alpha-carotene, beta-carotene, or vitamins A, C, or E.

The study was published online May 4 in Neurologythe medical journal of the American Academy of Neurology.

Some previous studies have found a link between a higher dietary intake of carotenoids or flavonols and a reduced risk of Alzheimer’s dementia. Other studieshowever, have been less conclusive.

Flavonols are found in a wide variety of fruits and vegetables, as well as some teas.

The different results between the studies could be due to the way they are conducted, the differences between the people included in the study, the types of foods they typically eat, as well as several other factors.

Additionally, many studies simply measure antioxidant levels based on the foods people eat. This forces people to track their diet for a period of time or try to remember what they ate during that time.

In contrast, the current study measured antioxidant levels in the blood sample, which provides a more accurate picture of these nutrients, at least for this specific time.

One limitation of the study is that the researchers only assessed antioxidant levels once. Ideally, researchers would monitor people at multiple points in their lives to see if there is a change.

However, Dr. Thomas M. Holland of the Rush Institute for Healthy Aging said that “people’s diets tend to be quite stable over time…unless someone has a major life event” prompting him to change his diet.

This event could be as small as their doctor telling them they have high blood pressure or something more serious like a heart attack or stroke.

In addition to blood antioxidant levels, Beydoun and his colleagues also looked at the participants’ diet quality, which was based on their recollection of what they had eaten over a 24-hour period.

Beydoun said they expect diet quality to be directly related to most — but not all — antioxidant levels measured by a blood test.

This is especially true for carotenoids and vitamin C, she said, as well as when the Diet Quality Index places a heavy emphasis on fruit and vegetable consumption.

In addition, Beydoun said, “other external factors may influence these [antioxidant] levels, including other lifestyle factors such as smoking tobacco, drinking alcoholic beverages, and following a high-fat diet.

Like most previous research, the new study is an observational study, so it cannot prove the link between antioxidant levels and dementia risk.

For this, randomized clinical trials will be needed, such as with a specific diet or antioxidant supplements. Researchers would then follow people over time to see how many participants developed dementia.

More studies are also needed to determine how much food people need to eat each day to achieve antioxidant levels that support brain health.

“There’s still a lot to understand about how these nutrients enter the body and then how they’re used,” Holland said, including how nutrients can support brain health.

Until researchers answer some of those questions, Holland said studies on specific diets show the benefits of the diet for the brain.

He mentions the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet, which was developed by Rush nutritional epidemiologist Martha Clare Morris, ScD, and colleagues.

This diet is similar to the plant-heavy Mediterranean diet, with an emphasis on antioxidant-rich berries and leafy green vegetables.

A randomized controlled trial published this year found that this diet improved mental performance and brain structure in healthy obese women.

“[The Neurology] study, as well as these other studies, [found brain-related benefits of consuming] leafy greens, especially dark leafy greens — kale, arugula, spinach, romaine lettuce,” Holland said.

“These are nutrient dense,” he added. “These are, as some would say, power foods that really should be eaten one serving a day.”