The study, which spanned for up to seven years, looked at data from over 13,000 older adults in Japan, which included their diet and brain health. During this time, the team examined their rate of consumption of citrus fruits and whether or not they have developed some form of cognitive impairment -- including dementia. The results were positive: Researchers found a direct link between frequent consumption of citrus fruits and improved memory and brain health. Among the adults who were part of the study, those who ate lemons, limes, and oranges daily had decreased their chances of developing dementia by at least 23 percent, compared to those who just ate it less than twice a week. In addition, those who did not regularly eat citrus fruits were at risk of experiencing age-related cognitive decline.
According to the researchers, the neuroprotective effect shown by those who regularly ate oranges and lemons can be traced to nobiletin, a brain-boosting flavonoid mainly found in the peels of various citrus fruits. Based on earlier studies on the compound, nobiletin has been found to slow down and even reverse the signs of age-related cognitive impairment and memory loss, based on animal studies.
This biological effect is another addition to the many health benefits of nobiletin, such as:
- Anti-inflammatory. Multiple studies have identified the anti-inflammatory properties of nobiletin and its metabolites. In particular, a study has shown that it can inhibit the expression of certain pro-inflammatory proteins. In a discrete study, researchers found that nobiletin is able to reduce inflammation in the airways of asthmatic rats, while another found that it can reduce the severity of UVB (ultraviolet-B) ray-induced inflammation.
- Anti-cancer. Research has shown that nobiletin contains anti-proliferation properties, that is, the ability to slow down the abnormal increase of cells. It has also shown promising results against certain cancers, based on cancer cell lines on the liver, stomach, colon, and prostate.
- Cholesterol reduction. Nobiletin can reduce blood cholesterol levels by preventing the formation of fat-loaded macrophages. These cells attach themselves to the artery walls, increasing the risk of atherosclerosis and other cardiovascular diseases.
"Some biological studies have indicated citrus may have preventive effects against cognitive impairment, but no study has examined the relation between citrus consumption and rates of dementia," the researchers concluded in their study. "Our findings suggest frequent consumption is linked with a lower risk of dementia." (Related: Emerging research shows that a natural citrus fruit extract can prevent cancer growth.)
Other food items for brain health
It's not just citrus fruits that are great for brain health. Here are some foods that are great with the tart fruits -- and offer an added layer of protection for the brain.
- Leafy greens. Spinach and other leafy greens are great sources of magnesium, which improve blood circulation to the brain.
- Blueberries. The antioxidants found in blueberries are known to protect the body against oxidative stress and toxic pollutants. These two, in particular, spell trouble for the brain, since they are linked to neurodegenerative diseases like dementia and Alzheimer's disease. Studies have also shown that blueberries improve learning ability, as well as motor skills.
- Avocado. The main ingredient in guacamole is also a key ingredient in brain health: It contains healthy fats that help regulate blood flow to the brain.
Of course, there are other fruits and vegetables that can help with boosting brain health. The key is to eat (and enjoy!) them on a regular basis.
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