Blueberries • Dr. Sylvia Mandel – neuroscientist

Blueberries - health properties

In recent years, Israelis have been enjoying the presence of a variety of fresh berries such as raspberries, cranberries, blueberries and their friends in markets and food chains, which used to be a pleasure reserved for cold European countries and the United States and Canada. However, recently there has been a sharp increase in the cultivation of berries in the world in general and in the Israeli market due to the growing demand for these delicious and healthy fruits, as well as due to a special attraction for raspberries and blueberries among leading confectioners and chefs. Among all berries, blueberries receive unique attention from scientists and nutritionists due to their health properties and nutritional values.

Blueberries belong to the berry family that grow in temperate regions with cold winters. The origin of the blueberry bush (Cyanococcus) is in North America, where it is currently the leading blueberry producer in the world. Blueberries grow on bushes and have a purple-dark blue hue. Their peak season is in the summer months of June-July. Many studies in the world testify to a long list of health properties among them: prevention of inflammatory processes such as in the case of arthritis and cardiovascular diseases and prevention of deposition of fats in the walls of blood vessels (atherosclerosis). Nutrition experts note the ability of blueberries to prevent the development of malignant diseases of the digestive tract, strengthen eyesight, slow down the aging process and even reduce the damage of diabetes.

Studies have shown that daily consumption of blueberries reduces the chance of developing type 2 diabetes, a phenomenon attributed among other things to reducing insulin resistance, improving blood flow and reducing oxidative damage.
The wide-ranging health benefit of blueberries probably lies in its extremely high nutritional values, the main ones of which are: copper, potassium, manganese, magnesium, vitamin C, vitamin K, and a variety of dietary fibers. They also contain pterostilbene), which is produced by the plant to defend itself against the attack of pathogens such as bacteria or fungi) which helps maintain blood sugar levels by encouraging the creation of insulin and also lowers fats and cholesterol in the blood.

Blueberries contain sugar, but their caloric content is relatively low for a fruit, 57 calories per hundred grams, and the glycemic index is low-medium (meaning they don't spike blood sugar), which makes them an excellent replacement for a last meal. Beyond that, the ingredient in blueberries that most attracts researchers' interest is a purple-blue pigment known as anthocyanin found in the skin of the fruit (blueberries are one of the only foods in the world that are naturally blue in color). Anthocyanin belongs to the flavonoid family which are phytochemicals ("phyto" in Greek means plant) very powerful as antioxidants and in preventing inflammatory processes. Flavonoids are compounds found in plants that generally have strong antioxidant and anti-inflammatory properties.

Blueberries contribute to improving memory

Experts believe that stressful situations and inflammation contribute to cognitive impairment and that increased consumption of flavonoids may reduce the harmful effects. The positive effects of flavonoids on the nervous system, especially of anthocyanidins (anthocyanin to which sugars are attached), have been extensively demonstrated in animal models of aging and Alzheimer's disease. Prof. Jim Joseph (deceased) and his team of researchers from "Tufts" University, Boston in the USA are considered pioneers in this field as they showed for the first time that blueberries can improve memory in old animals. Not only that, but they did more and found that treating old rats with dried blueberry extract also has direct effects on the brain, including an increase in brain flexibility and neural communication and the growth of new nerve cells (neurons), a process called neurogenesis.

Other research groups have confirmed and expanded the above findings and today the prevailing opinion in the scientific community is that blueberries have additional properties beyond anti-oxidative capacity, including an anti-inflammatory effect and the activation of genes and proteins that encourage neurogenesis (the creation of new neurons) in the hippocampus area. Why is this important? The hippocampus is involved in forming and maintaining Short- and long-term memory is known to shrink with age as well as with ongoing stress. It is also the first structure to be damaged in dementia and Alzheimer's, along with the prefrontal cortex. Given that the hippocampus is critical for memory formation and learning, the generation of new neurons in this area may explain the improvement in cognition in animals. treated with blueberry extract.

Human studies

The experiments on animals paved the way for clinical experiments on humans, and indeed during the last two decades we are witnessing an increasing amount of research with the aim of evaluating the effect of blueberries on memory and cognitive performance. In a broad review published in the scientific journal Journals of Gerontology: BIOLOGICAL SCIENCES in 2019, epidemiological, prospective, preclinical and clinical trials were included that tested the effect of eating blueberries on the cognitive state in humans. Blueberry treatment forms included fresh fruit, juice, powder, extract and smoothie.

The largest study included in this review used data from 16,010 women from "The Nurses' Health Study" (The Nurses' Health Study) which followed cognition and dietary intake for 20 years. The study began in 1976 when the nurses were aged 30-55 and were asked to fill out a questionnaire every four years about the foods they consumed and their dietary habits. Between 1995 and 2001, the subjects were contacted when they were over 70 years old and had no history of stroke, in order to participate in a telephone study that assessed cognitive function using six tests. The results were combined into one global score and a separate score for verbal memory, and an assessment of flavonoid consumption (including blueberries) was also determined. The findings showed, after correction for intervening factors (such as age, physical activity, depression, etc.), that increased consumption of blueberries and strawberries delayed cognitive aging by about 2.5 years.

In two randomized and double-blind clinical studies with a small number of participants aged 60-80, a small cognitive benefit was recorded, especially in the area of ​​verbal function and memory. Two other randomized, double-blind studies examined brain activation using functional magnetic resonance imaging (fMRI) after blueberry supplementation. In one of them, fMRI findings were analyzed before and after giving 24 grams per day (about 1 cup of whole blueberries) of blueberry powder or a placebo to 21 adults with mild cognitive impairment for 16 weeks. Despite an increase in brain activity during a working memory test, no significant improvement in task performance was observed. Similarly, in the second study in healthy adults over the age of 65, the performance of the cognitive test showed no significant difference between the blueberry and placebo groups after 12 weeks.

It should be noted that the studies have several limitations arising from several factors such as the difference in the tasks to be performed by the participants between the studies, as well as the integration of tests that test certain aspects of the behavior compared to those that test one cognitive domain. In addition, the doses of anthocyanin ranged from 1.35 to 460 mg in chronic studies and from 143 to 253 mg in acute studies in which the duration of administration was short. The difference that may arise from the material production processes between the experiments must also be taken into account. Currently, the picture is incomplete, as there is a lack of studies examining the effects of blueberries on children, teenagers, young adults, or middle-aged adults. Acute effects were only diagnosed in children while chronic effects were only tested in adults.

In an overall view, it can be concluded from the data that blueberries have a moderate positive effect on some aspects of cognition throughout certain ages, especially in the area of ​​verbal function and verbal memory. The largest study reviewed in the Nurses' Health Study, although not randomized or placebo-controlled, showed a delay in cognitive aging (of 2.5 years) after many years of follow-up. In conclusion, additional studies with a higher number of participants and for a longer period of time are required in order to substantiate the findings.

Conclusions and insights for the future

Many experts in the field of nutrition and aging around the world recommend eating blueberries as an integral part of the daily diet. Based on the studies, the recommended dose is one cup per day (equivalent to 24 grams of blueberries). It should be noted that the researchers' recommendation is to eat blueberries whole and not as a supplement, since the various nutritional components may have synergistic effects that are only noticeable when combined. Everything seems to be important, each compound helps carry other compounds to different places in the body, and once you start isolating them, the sum of the parts is less than the whole. Food for thought indeed...