By Andrew Yang
Eating “superfoods” has become a modern-day health trend. Ms. Li Wanping, a nutritionist at Taiwan Shu-Tian Clinic, said that dark-green vegetables are cheap and nutritious superfoods. They are rich in fiber, trace minerals, such as iron, calcium, and magnesium, and phytochemicals, such as folic acid and beta carotene. In addition to helping with detoxification, bowel motility, and antioxidation, dark-green vegetables can also improve symptoms of cancer and cardiovascular diseases.
Vegetable fiber is a low-calorie substance and forever an indispensable nutrient for the human body. There are three main functions of fiber.
- Detoxification: From its passage through the mouth, vegetable fiber passes through the esophagus, stomach, small intestine, and finally, the large intestine. On its way, toxins are excreted alongside the fiber, reducing the incidence of oral, esophageal, and gastroesophageal cancers, reducing gastric acid, and clearing other issues.
- Helps move the bowels: Fiber can increase intestinal peristalsis and metabolism, increase stool bulk, and help with bowel movements.
- Increases intestinal probiotic bacteria: Fiber is the food for probiotic bacteria in the intestine, so increasing it can cultivate more good intestinal bacteria.
Ms. Li said the dark vegetables considered superfoods include sweet potato leaves, bird’s nest fern (Asplenium nidus), spinach, broccoli, and red amaranth (Amaranthus tricolor L.). It is recommended to pick one of these vegetables every day. These five are considered superfoods because there are more than 3 grams of fiber for every 100 grams of each of them.
In addition to being high in fiber, these superfoods contain a variety of different phytochemicals and trace minerals too.
- Lutein: Modern-day people use many “3C” (computer, communications, consumer electronics) products, which are harmful to the eyes. Supplementing lutein can help reduce wet macular degeneration. Usually, a daily supplement of 6 milligrams of lutein is considered normal, equivalent to 33 grams (1.2 ounces) of spinach intake, about one-third of a 100-gram (3.5 ounces) measuring rice cup stuffed with cooked spinach.
- Beta carotene: Beta carotene can be converted into vitamin A inside the human body. Increased vitamin A intake can help improve eye issues like dry eyes or excessive tearing. The beta carotene in carrots, oranges, and pumpkins will cause the skin to turn yellowish if consumed for prolonged periods, but there is no such worry if it’s obtained from dark vegetables.
- Folic acid: All dark vegetables contain folic acid. Folic acid is an essential nutrient for mothers-to-be and an important nutrient in preventing cancer and cardiovascular diseases.
- Iron: Bird’s nest leaves and spinach are vegetables with high iron content.
Some people may worry that dark-green vegetables such as spinach, lettuce, or celery are also rich in nitrates, and excessive intake will adversely affect the human body. Ms. Li said that after the nitrate passes through the gastrointestinal tract, all the nitrates will be reduced to nitric oxide. Nitric oxide can help dilate blood vessels so blood flows smoothly, which helps to lower blood pressure and intraocular pressure.
Glaucoma patients usually suffer two conditions: One is high intraocular pressure, and the other is low blood pressure resulting in relatively high intraocular pressure. So if you want to increase blood circulation in the eyes, eating more dark-green vegetables can widen the blood vessels, increase blood flow, and thus reduce intraocular pressure. Ms. Li cited the case of one patient whose eyes were always dry, and she didn’t like taking health supplements. The patient was advised to eat 300 grams (10.6 ounces) of dark-green vegetables daily. After three months, her dry eyes improved, and she also lost weight.
High-Calcium Green Food
Many dark-green plants such as spinach, water spinach, Okinawa spinach (Gynura bicolor), and red amaranth have a high calcium content. But dark-green vegetables usually contain oxalic and kojic acid, both of which affect calcium absorption. Therefore, Ms. Li recommends cooking them with boiling water to dissolve 80 percent to 90 percent of the acids so they won’t go into your body. On the other hand, cruciferous vegetables are safe to eat because of their low folic acid content.
Animal calcium is easier to absorb than plant calcium. For example, milk contains lactoferrin, which can help with calcium absorption. There are two ways to increase calcium absorption from green vegetables. One is to cook them with small, dried fish, whitebait, or high-protein food such as bean curd (tofu). An alternative way is to eat fruits containing plenty of vitamin C after meals, such as Taiwanese orange, tangerine, and regular oranges, which can help the absorption of calcium from dark vegetables.
Red amaranth is a superfood for iron supplementation. Ms. Li said that 100 grams (3.5 ounces) of red amaranth contain 11.8 milligrams of iron, and the plant-based absorption rate is 5 percent—an absorption of 0.59 milligram. Compared with 100 grams (3.5 ounces) of beef steak containing 2 milligrams of iron, and an animal absorption rate of 25 percent, achieving an absorption of 0.5 milligram, the absorption from red amaranth is even slightly better than beef steak’s.
Nutritionist’s 2 Favorite Vegetables
Sweet potato leaves and Gracilaria seaweed are Ms. Li’s first choices for dark-colored vegetables. In addition to the phytochemicals mentioned above, another thing she likes most is they are free from pesticide pollution. Ms. Li said that once a farmer patient in her clinic refused to eat the hospital’s provided vegetables. It turned out the patient was worried about the excessive use of pesticides in growing vegetables, but he had no such safety concerns about sweet potato leaves and Gracilaria seaweed because they are not treated with pesticides.