Rau day, commonly known as 'green ginseng' in Japan, is a beloved summer vegetable in Vietnam that offers both refreshment and numerous health benefits. This affordable vegetable, typically sold for around 5,000 to 10,000 VND per bunch at local markets, is rich in essential nutrients, making it a staple in Vietnamese households during the hot summer months.

Rau day is packed with vitamins A, C, K, and various B vitamins, along with important minerals such as potassium and calcium. Notably, it contains a high iron content, with fresh rau day providing approximately 7.7 mg of iron per 100 grams. When cooked, the iron content decreases to about 3 mg per 100 grams, which is comparable to or even higher than that found in beef (approximately 2.4–2.6 mg per 100 grams). This high iron content supports blood production and overall health, making rau day a valuable addition to a balanced diet.

One unique characteristic of rau day is its mucilaginous texture when cooked, which some people may find off-putting. However, this mucilage aids in digestion due to its polysaccharides and soluble fiber content. The soluble fiber also helps manage cholesterol levels and promotes a feeling of fullness, making rau day a healthy choice for meals.

According to Bui Dac Sang, a traditional medicine practitioner in Hanoi, rau day has a sweet taste and a cooling property, making it effective for reducing heat in the body, alleviating skin irritations, and promoting detoxification through urination. During the hot summer months, dishes made with rau day can help cool the body and improve skin health.

Popular dishes featuring rau day include:

• Crab Soup with Rau Day: A national favorite during summer, this dish combines the sweetness of crab with the refreshing taste of rau day, creating a light and enjoyable soup.
• Shrimp Soup with Rau Day: This dish features fresh shrimp cooked with rau day, resulting in a naturally sweet and nutritious soup suitable for all ages.
• Minced Pork and Rau Day Soup: The combination of minced pork and the tenderness of rau day makes this dish both appealing and easy to eat.
• Stir-fried Rau Day with Garlic: Rau day can also be quickly stir-fried with garlic for a simple yet delicious side dish.

Rau day is easy to grow at home, thriving in sunny spots with minimal pests. To cultivate rau day, one can use foam boxes or small plots of land. Soaking the seeds in warm water for 12 to 24 hours before planting can enhance germination rates. Within about 40 days, the first harvest can be made by cutting the tops, allowing the plant to continue producing new shoots.

This affordable and nutritious vegetable is not only a culinary delight but also a health booster, making it a cherished ingredient in Vietnamese cuisine.