When you think of "walnuts", what do you think of? Many people may have two words in their minds -- "replenish the brain"!
What is the nutrition of walnuts? Can eating more walnuts really "nourish the brain"? Let's talk about it in detail today.
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Insist on eating walnuts for 6 months,
The brain has really changed!
In April 2023, a 6-month randomized controlled nutrition intervention trial was published in the well-known medical journal The Lancet, which gave us a preliminary answer to the question of "whether eating walnuts can replenish the brain".
The study included 942 middle school students aged 11~16 years, and 771 adolescents were included in the analysis and randomized after screening - the control group did not receive any form of intervention; the experimental group received a sachet containing 30g of walnut kernels per day, about 3~4 walnuts, and ate 1 bag per day for 6 months.
After observation, the researchers found that 133 people had good compliance, ate walnuts for > 100 days (not necessarily every day), and the red blood cell α-linolenic acid status of these adolescents was slightly higher, and their attention was enhanced, which significantly improved the behavior of some adolescents with symptoms of attention deficit hyperactivity disorder, which was manifested in paying more attention to the teacher in the classroom and increasing fluid intelligence-related functions, such as perception, memory, calculation speed, reasoning ability, etc.
In this way, for teenagers who insist on eating walnuts for 6 months and have good compliance, walnuts do play a role in "tonifying the brain". Researchers also believe that eating walnuts regularly (more than 3 servings per week, about 10 walnuts) may lead to improvements in sustained attention, fluid intelligence, and ADHD symptoms, although there is no significant effect on neurodevelopment in healthy adolescents.
Research aside, walnuts do contain a lot of nutrients that the brain needs, such as protein, which is a building block, carbohydrates that fuel the brain, and the polyunsaturated fatty acid α-linolenic acid, which is converted into DHA in the body and contributes to brain health.
But I should remind you that although the above research shows that eating walnuts for a long time is somewhat useful for "brain supplementation", don't expect to improve your IQ by eating walnuts!
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What are the nutrients of walnuts?
Walnuts, also known as walnuts, are widely cultivated in the mainland, and as of 2020, the planting area of walnuts in the mainland ranks first in the world, which shows how popular walnuts are in the mainland. It can be used as a work of art, can play with walnuts, and can be eaten, killing three birds with one stone! To say that the nutritional value of walnuts is really good, it has the reputation of "longevity fruit" and "treasure of health".
protein
Walnuts have a protein content of 14.9g/100g, which is not very good among nuts, but it is still rich in amino acids. Studies have shown that walnut protein contains 18 kinds of amino acids, of which 8 are essential amino acids, accounting for 26.98%~30.38% of the total amino acids, which is conducive to growth and development.
unsaturated fatty acid
The fat content of walnuts was as high as 58.8g/100g, mainly polyunsaturated fatty acids, accounting for about 76.2% of the total fatty acids, and linolenic acid and linoleic acid accounted for 12.2% and 64% of the total fatty acids, respectively. The α linolenic acid content in walnuts is not as high as that of flaxseeds, but it is much higher than other nuts. This ingredient can be converted into DHA in the body, which is beneficial for brain and retinal health, but the conversion rate is generally low.
Vitamin E
Walnuts have a more prominent vitamin E content among nuts, up to 43.2mg/100g, which is nearly 1.2 times that of hazelnuts. Vitamin E has strong antioxidant properties and is also an essential nutrient for fertility maintenance, as well as maintaining normal immune function.
Antioxidants
Walnuts are rich in antioxidants, including total phenols and flavonoids. Phenolic substances and flavonoids were analyzed on the seed coat of fresh walnuts, and it was found that the content of phenolic substances was the highest in gallic acid, the lowest content in ferulic acid, and the highest content of flavonoids in rutin.
And most of the antioxidants are on the seed coat of walnut fruits, which have antioxidant properties, which can help our body fight inflammation and remove excess free radicals. However, the seed coat of walnut fruit has a high level of astringency, so it has an obvious astringency. If acceptable, it is best to eat it with the skin.
In addition, we have to remind everyone: walnuts ≠ pecans.
The walnut we usually talk about is a nut of the genus Juglans, and the pecan is not a "walnut in the mountains", it is also called a small walnut, which is a member of the genus Hickory. Pecans are much smaller than walnuts and have a thicker skin and lower edible parts, with 43% of walnuts and only 24% of pecans.
Source: iPlant
In terms of nutrition, the difference between the two is not small, compared with walnuts with higher content of linolenic acid, dietary fiber, potassium and selenium, and pecans with higher content of protein, vitamin E and magnesium.
Note: Pecan linolenic acid data is cooked pecans Source: Made by the author
Walnuts in addition to "brain supplement"
What are the benefits for the body?
Walnuts are so nutritious, don't just think about whether you can "nourish your brain" when you eat them, eating walnuts often has a lot of other benefits for the body!
Improves blood lipids
A 2018 analysis of 26 clinical trials involving 1059 participants found that a diet supplemented with walnuts significantly reduced plasma triglyceride (TG) levels by 5.52%, LDL cholesterol (bad cholesterol) by 3.73%, and total cholesterol by 3.25% compared to a control group that did not eat walnuts every day.
The decrease in these indicators is of great significance for the prevention of hyperlipidemia, and can also further reduce the risk of atherosclerosis and cardiovascular disease.
A meta-analysis of 13 intervention trials involving the United States, Germany, Iran, the United Kingdom, Spain, and the Chinese population in 2022 explored the effect of walnut intake on blood lipid levels. The study found that walnut intake was significantly associated with improvements in serum triglycerides, total cholesterol, and bad cholesterol levels.
In the study, the consumption of walnuts in healthy people was 15~64g per day, while for people with overweight, obesity and dyslipidemia comorbidities, the consumption of walnuts was 30~99g per day.
Prevent diabetes
A study in the American Journal of Clinical Nutrition mentions that a high consumption of nuts, especially walnuts, has been linked to a lower risk of diabetes, as well as a lower risk of obesity. Therefore, it is possible to stick to regular (about 1 time a day) nuts as part of a healthy diet to prevent obesity and type 2 diabetes.
May promote sleep
Melatonin is a hormone secreted by the pineal gland of the brain, which can naturally induce sleep, but due to physical or work reasons, many people's melatonin secretion has been affected, resulting in difficulty in falling asleep.
Walnuts are melatonin-rich foods, and some studies have found that the amount of melatonin in the blood of animals can be 4 times higher after feeding them walnuts. People who don't sleep well usually eat walnuts, which may help with sleep, so you might as well give it a try.
Relieves anxiety
Among nuts, walnuts have an excellent content of α-linolenic acid. Studies have shown that α-linolenic acid has neuroprotective effects, which can reduce anxiety symptoms, relieve emotional tension, and reduce stress.
4 tips for eating walnuts
Although eating walnuts is good for health, it is important to choose the most correct way to eat them. Here are 4 tips for eating walnuts healthily, be sure to check them out!
Choose plain walnuts
Now there are many walnut flavors on the market, such as sweet amber walnut kernels, salty salt and pepper walnut kernels, this kind of walnut kernels are generally high in sugar or salt, and eating them often is not good for health, which will increase the risk of dental caries, obesity, hypertension and other diseases.
The most recommended ones are plain walnuts or whole shelled walnuts.
It is best eaten with the skin on
Under normal circumstances, the surface of walnut kernels has dark brown walnut skin, the taste is a little bitter, many people do not like to eat, and there are also peeled walnuts on the market, which are white and clean. If you want to get more of the antioxidants in walnuts, eat them with the skin.
Pay attention to how you save it
Walnut kernels are rich in polyunsaturated fatty acids, which are easy to oxidize rancidity and have a hala taste. Therefore, it is recommended to buy less each time and keep it sealed and refrigerated. If you can buy the shelled one, it is better to store it in a cool and dry place, and eat it freshly opened. Don't eat moldy walnuts!
Keep the amount under control
Although eating nuts regularly can help prevent obesity, you should not eat too much. The "Dietary Guidelines for Chinese Residents" recommends eating 50~70g of nuts per week, with an average of 10g per day, which is equivalent to 1 large paper walnut or 2~3 pecans. If you eat too much, then appropriately reduce the amount of cooking oil, or use walnuts to replace part of pork and beef, so as to achieve polyunsaturated fatty acids to partially replace saturated fatty acid intake, which can reduce the risk of coronary heart disease.
The weight of 1 paper walnut is about 9g, source: provided by the author
Eating walnuts every day will make your blood lipid levels healthier, your weight maintenance better, your mood less anxious, your stress gradually reduced, and it may also make you more focused, better memory, and stronger reasoning skills.
Let's start eating walnuts!
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Planning and production
This article is a work of popular science China-Star Project
Produced by丨Popular Science of China
Producer丨China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd
Author丨Xue Qingxin is a registered dietitian
Audit丨Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center
Planning丨Lin Lin