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Adding a few servings of whole grains linked to slower memory decline in Black people
Black people who eat more foods with whole grains, including some breads and cereals, quinoa, and popcorn, may have a slower rate of memory decline compared to Black people who eat fewer whole grain foods, according to a study published in the November 22, 2023, online issue of Neurology®, the medical journal of the American Academy of Neurology. The researchers did not see a similar trend in white participants.
The study does not prove that eating more whole grains slows memory decline; it only shows an association.
The study found that among Black people, those who ate the most whole grains had lower levels of memory decline—equivalent to being 8.5 years younger than those who ate small amounts of whole grains.
“With Alzheimer’s disease and dementia affecting millions of Americans, finding ways to prevent the disease is a high public health priority,” said study author Xiaoran Liu, PhD, MSc, of Rush University in Chicago. “It’s exciting to see that people could potentially lower their risk of dementia by increasing their diet of whole grains by a couple of servings a day.”
The study involved 3,326 people with an average age of 75 without dementia. Of all participants, 1,999 people, or 60%, were Black. They were followed for an average of six years.
They filled out a questionnaire every three years on how often they ate whole grains. They also completed cognitive and memory tests every three years, including recalling lists of words, remembering numbers and putting them in the correct order.
Participants were then divided into five groups based on the amount of whole grains they had in their diet. The lowest group consumed less than half a serving per day, and the highest group consumed 2.7 servings per day. The Dietary Guidelines for Americans recommend at least three servings of whole grain foods daily. One serving of whole grains is equivalent to an ounce of food, such as one slice of bread, a half cup of cooked pasta or rice, an ounce of crackers or a cup of dry cereal.
Researchers found that a higher proportion of Black participants had more than one serving per day of whole grains than white participants, with 67% and 38%, respectively.
To determine rates of cognitive decline, researchers used an overall global cognition score summarizing four cognitive tests and examined their change over time.
After adjusting for factors that could affect the rate of cognitive decline, such as age, sex, education and smoking, researchers found that the global cognitive score of Black people who had the highest intake of whole grains, or more than three servings a day, declined at a rate of 0.2 standard deviation units per decade more slowly than Black people who had the lowest intake, or less than one serving per day.
“These results could help medical professionals make tailored diet recommendations,” Liu added. “More large studies are needed to validate our findings and to further investigate the effect of whole grains on cognition in different racial groups.”
A limitation of the study is that the food frequency questionnaire was self-reported, so people may not accurately remember what they ate.
The study was supported by the Alzheimer's Association and the National Institutes of Health.
注释：
quinoa: n
表示" [植]藜麦"，如：Quinoa brings a lot to the table. 藜麦给我们提供很多营养。
deviation: n
表示"偏离；出轨；背弃"，means "a variation that deviates from the standard or norm;"，如：The deviation is reduced to one millimetre. 偏差减为一毫米。There was little deviation from his usual routine. 他没有什么反常的举动。
中文简要说明：
一份美国研究显示，每天多吃包括爆米花在内的全谷类食物，或能降低罹患失智症的风险。
综合《纽约邮报》（New York Post）、英国《每日邮报》（Daily Mail）、美国神经学会（American Academy of Neurology）新闻稿，美国芝加哥鲁希大学（Rush University）的研究发现，每天吃一包爆米花的人，罹患失智症的可能性较低，这份研究已于22日获《神经学》（Neurology）期刊发表。
研究人员持续追踪、观察3326名平均年龄为75岁、没有失智症的长者达6年，邀请他们每3年填写一次问卷，描述自己的饮食，受试者也每3年定期接受认知、记忆测验。受试者中多达60％为非裔。
研究根据问卷中有关全谷类摄取的份量，将受试者分为5组，从每天吃不到半份，到每天全谷类摄取量多达2.7份。研究中的全谷类包含面包、麦片、藜麦及爆米花。
研究人员发现，非裔受试者摄取更多全谷类，每天摄取超过1份全谷类的受试者占67％，相较之下白人受试者仅占38％。
在调整年纪、性别、教育程度、是否抽烟等因素后，研究人员发现，每天吃超过3份全谷类的非裔受试者，认知功能下降的速率较吃得最少的非裔受试者还慢。认知能力下降是失智症的早期征兆。
值得注意的是，研究人员仅在非裔受试者身上看到这样的结果，推测白人受试者样本数太少，或是本身摄取的全谷类含量就不多，因此没有看到相同趋势。
研究人员目前仍不清楚为何摄取全谷类能降低失智风险，推测可能和调节血糖，或促进肠道健康有关，如此能降低发炎、及对血管造成的伤害，而发炎及血管损伤可能会增加失智风险。此外，摄取较多全谷类的民众，本身可能有较健康的生活型态，例如有较充足的睡眠及运动量，都有助于降低失智风险。
不过这份研究仍属于观察性研究，非常仰赖受试者的问卷响应，只能描绘摄取全谷类与罹患失智风险的关联，无法证明两者之间的因果关系。
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