Spring is here. Do you know the top wild vegetables?

When spring comes, many people start to miss wild vegetables. Some people eat wild vegetables for the taste they remember, while others think that "wild" vegetables are natural and may be healthier than those in supermarkets. Is this true?

Today, let’s talk about one of the top wild vegetables - Purslane.

Figure 1: Common purslane flowers (copyright image from the gallery, reprinting may cause copyright disputes)

0 1What nutrients does Purslane contain?

The nutritional value of purslane is mainly reflected in two aspects.

First, purslane is a dark-colored vegetable .

Literally speaking, "dark vegetables" are vegetables with darker colors, such as dark green, orange, and purple. Nutritionists have found that these dark vegetables are usually rich in antioxidant plant compounds , such as anthocyanins, lycopene, and carotene . These compounds can protect cells and prevent and delay aging.

Figure 2: Various vegetables (copyright image from the gallery, reprinting may lead to copyright disputes)

According to the recommendation of the Chinese Nutrition Society, each person should eat at least 300 grams of fresh vegetables every day , of which dark vegetables should account for more than half . However, a large-scale survey in China shows that people generally do not consume enough dark vegetables, only about 60% of the recommended amount. Therefore, eating some fresh purslane will enrich the variety of dark vegetables you consume and make your diet more balanced .

Second, purslane is high in n-3 fatty acids .

The so-called "essential fatty acids" are fatty acids that the human body cannot fully satisfy and must obtain from food . Essential fatty acids are divided into two categories: linoleic acid and alpha-linolenic acid (ALA). From the perspective of chemical structure, each has its own characteristics: linoleic acid is an n-6 fatty acid, and ALA is an n-3 fatty acid; EPA and DHA, which frequently appear in infant and toddler advertisements, are derivatives of ALA after carbon chain extension and desaturation .

The latest version of the "Dietary Reference Intake of Nutrients for Chinese Residents" points out that insufficient essential amino acids may cause growth retardation and neurological and visual diseases . A 2016 study showed that the ratio of n-6 to n-3 fatty acids in the diet affects lipid metabolism , which in turn affects the risk of cardiovascular disease . Many adults have dyslipidemia, which, to some extent, is caused by the imbalance of n-6 and n-3 fatty acid intake in their daily diet. Therefore, the World Health Organization recommends that the ratio of linoleic acid to α-linolenic acid in the diet should be less than 10:1 ; considering the domestic situation, Chinese scholars suggest that this ratio should be 4~6:1 .

As shown in Table 1, people of different ages have different requirements for n-3 polyunsaturated fatty acids.

Table 1: Recommended intake of n-3 polyunsaturated fatty acids for Chinese residents, source: "Dietary Nutrient Reference Intake for Chinese Residents"

What about the actual intake? In 2022, a large-scale survey jointly conducted by the State Administration of Grain and Material Reserves and the Chinese Center for Disease Control and Prevention showed that the ratio of n-6 to n-3 fatty acids in the diet of urban residents was 8.6:1, and that of rural residents was 7.9:1. In other words, n-6 fatty acids should be appropriately reduced and n-3 fatty acids should be increased . So where do we get n-3 fatty acids? Generally speaking, ALA is mainly found in vegetable oils and fats . Vegetable oils and fats are not low in calories, and eating too much is also a problem. In contrast, purslane is very special: first, it is a vegetable with very low calories; second, the "Provisional Table of n-3 Fatty Acids and Other Fat Components in Specific Foods" issued by the U.S. Department of Agriculture shows that wild purslane is the richest in n-3 fatty acids among all the vegetables tested ; moreover, purslane is easy to cook, can be mixed, fried, and made into stuffing. It may sometimes be more convenient to use it to supplement ALA.

0 2Other nutritional components of purslane

In addition to the nutritional ingredients mentioned above, scholars have also isolated some other ingredients from purslane, such as flavonoids, terpenes, sterols, alkaloids, etc. Scholars from Huazhong University of Science and Technology found that the total flavonoid content in the whole plant of purslane was 7.67%; in 2023, research by foreign scholars showed that terpenes in purslane accounted for 81.2% of the total volatile substances; research by Hu Benquan and others showed that the total alkaloid content in purslane from different origins was between 0.059% and 0.090%. In theory, after these substances enter the human body, they can play a series of roles, such as anti-inflammatory, antibacterial, hypoglycemic, and lipid-lowering . Among them, the most notable is the hypoglycemic effect . For example, a 2011 study showed that taking 5 grams of purslane seeds twice a day each time had a similar effect on blood sugar as the "chief" hypoglycemic drug metformin.

Figure 3: Blood glucose monitoring (copyright image from the gallery, reprinting may lead to copyright disputes)

Of course, the current research on purslane is still in its early stages, and the relevant research on humans is not sufficient, and the results are not consistent. If you want to scientifically control blood sugar, you should follow the advice of the National Health Commission: use medication on time and change your lifestyle comprehensively .

Conclusion

The Dietary Guidelines for Chinese Residents mentions that there are three principles for choosing vegetables: first, time, try to choose seasonal and fresh ones; second, color, buy more dark vegetables; third, variety, change more. Purslane undoubtedly meets these conditions, so why not give it a try in spring?

References

[1] Chinese Nutrition Society. Dietary Guidelines for Chinese Residents [M/OL]. People's Medical Publishing House, 2022 [2023-07-20]. https://book.douban.com/subject/35885945/.

[2]LIN YAN. Dark Green Leafy Vegetables[EB/OL]//USDA. (2023-11-09)[2024-02-05]. https://www.ars.usda.gov/plains-area/gfnd/gfhnrc/docs/news-articles/2013/dark-green-leafy-vegetables/.

[3] Chinese Nutrition Society. "Scientific Research Report on Dietary Guidelines for Chinese Residents (2021)" [J/OL]. Acta Nutrimenta Sinica, 2021, 43(2): 102. DOI:10.13325/j.cnki.acta.nutr.sin.2021.02.001.

[4] Chinese Nutrition Society. Dietary Reference Intakes for Chinese Residents 2023 Edition [M/OL]. People's Medical Publishing House, 2023 [2024-02-24]. https://book.douban.com/subject/36581765/.

[5] Pang Shaojie, Jia Shanshan, Fang Wei, et al. Dietary fatty acid intake and food sources of Chinese residents aged 18-59 years [J/OL]. Acta Nutrimenta Sinica, 2022, 44(4): 366-370,376. DOI:10.13325/j.cnki.acta.nutr.sin.2022.04.005.

[6] Lei Hongwei, Lu Fuer, Xu Lijun, et al. Determination of total flavonoids in Portulaca oleracea by UV spectrophotometry[J]. Journal of Integrated Traditional Chinese and Western Medicine, 2010, 2(3): 126-128.

[7]EL-SAYED MI K. Effects of Portulaca oleracea L. seeds in treatment of type-2 diabetes mellitus patients as adjunctive and alternative therapy[J/OL]. Journal of Ethnopharmacology, 2011, 137(1): 643-651. DOI:10.1016/j.jep.2011.06.020.

[8]ZHOU YX, XIN HL, RAHMAN K, et al. Portulaca oleracea L.: A Review of Phytochemistry and Pharmacological Effects[J/OL]. BioMed Research International, 2015, 2015: 925631. DOI:10.1155/2015/925631.

[9] Li Yaochen, Fan Zipei, Yang Jing, et al. Research progress on functional components and bioactivities of wild vegetables[J]. Journal of Zhejiang A&F University, 2022, 39(4): 913-922.

[10] AL-QUWAIE DA, ALLOHIBI A, ALJADANI M, et al. Characterization of Portulaca oleracea Whole Plant: Evaluating Antioxidant, Anticancer, Antibacterial, and Antiviral Activities and Application as Quality Enhancer in Yogurt[J/OL]. Molecules, 2023, 28(15): 5859. DOI:10.3390/molecules28155859.

[11] YANG L, SONG Z, CAO W, et al. Effects of diets with different n-6/n-3 fatty acids on cardiovascular risk factors in mice fed high-fat diets[J]. Wei Sheng Yan Jiu = Journal of Hygiene Research, 2016, 45(3): 436-441.

[12] Liang Xiao, Li Yanan, Wang Zhina, et al. Research progress on the material basis and pharmacological activity of Portulaca oleracea[J/OL]. Journal of Liaoning University (Natural Science Edition), 2023, 50(4): 373-384. DOI:10.16197/j.cnki.lnunse.2023.04.005.

[13]EBRAHIMIAN Z, RAZAVI BM, MOUSAVI SHAEGH SA, et al. Effects of Portulaca oleracea L. (purslane) on the metabolic syndrome: A review[J/OL]. Iranian Journal of Basic Medical Sciences, 2022, 25(11): 1275-1285. DOI:10.22038/IJBMS.2022.63264.13967.

[14] Dietary Guidelines for Adults with Diabetes (2023 Edition) [J/OL]. General Practice Clinical and Education, 2023, 21(5): 388-391. DOI:10.13558/j.cnki.issn1672-3686.2023.005.002.

Author: Zhao Yanchang, a popular science author

Reviewer: Tian Weina, Associate Professor of Beijing Institute of Food Science and Registered Nutritionist of Chinese Nutrition Society

Produced by: Science Popularization China

Produced by: China Science and Technology Press Co., Ltd., China Science and Technology Publishing House (Beijing) Digital Media Co., Ltd.