In order to understand the effects of nutrients in apples on brain nerves and cognition, the research team of the German Center for Neurodegenerative Diseases used mice to conduct experiments and study the responses of their stem cells. The results confirmed that the nutrients in apples can stimulate the proliferation of brain neurons, which helps strengthen brain learning and memory, and prevent Alzheimer’s and various dementias; however, similar benefits only occur in Rats that eat the peel and pulp, and those that drink apple juice do not enjoy the aforementioned benefits.
Related research results have been published in the “Stem Cell Report” in February 2021. A large amount of literature confirms the health benefits of plant compounds in fruits. Among them, flavonoids are the nutrients rich in fruits and vegetables, and they help to adjust the molecular signal transmission path, and then affect brain cognition.
Existing studies have confirmed that resveratrol (a kind of flavonoids, found in red wine and red grape skins) can help adult hippocampal neuroproliferation. However, in these studies, there are a large number of potential active compounds that may work together, and whether resveratrol really helps central nervous system function and has a positive effect on learning and memory is questioned.
As the saying goes, “An apple a day keeps the doctor away.” As a fruit that is widely consumed worldwide, whether apples contain nutrients that maintain or promote hippocampal neuroproliferation has aroused the interest of the research team. The research team selected quercetin (Quercetin, which is also a kind of flavonoid) and dihydroxybenzoic acid (DHBA), which are the most abundant in apples, and observed the effects of these two nutrients on the brain neurons of mice.
It was found that the brain stem cells of mice that ingest quercetin or DHBA will proliferate more neurons and protect the cells from death, which makes the brain more capable of learning and memory. Interestingly, only the peel and pulp are rich in nerve-promoting compounds. In view of the huge consumption of fruit juice, the research team also studied whether the whole apple juice affects the brain nerves of mice.
In order to avoid the intake of fructose, which would increase the calories and possibly affect the results of the experiment, one group of mice drank sugar water with the same calorie, and the other group was given normal drinking water. After feeding apple juice for 3 weeks, the research team asked the mice to try to find underwater escape channels in the circular pool. This experiment can test the ability of nerves to perform spatial navigation and cognitive flexibility.
However, the performance of the mice that drank apple juice had no effect at all. The research team analyzed that this may be because the concentration of quercetin in apple juice is too low to allow nerve hyperplasia.
The research team concluded that apples are rich in quercetin, which not only promotes the survival and differentiation of hippocampal precursor cells, but also promotes endogenous antioxidants. In addition, the 3,5-dihydroxybenzoic acid in apples increases the proliferation and neurogenesis of precursor cells and helps to increase the proliferation and neurogenesis of precursor cells. However, these benefits are limited to those who consume apples rather than juice.
