Nutritionist shares 5 tips to minimise nutrient loss when cooking

Is blanching or stir-frying vegetables healthier? While blanching can cause significant loss of heat-sensitive nutrients like Vitamin C, a nutritionist points out that one type of vegetable is actually better boiled for health. By following 5 simple techniques, you can retain more nutrients when blanching vegetables. Additionally, steaming vegetables, which has become popular in recent years, can retain nearly 100% of Vitamin C, making it the most nutritious cooking method. However, one type of vegetable is not suitable for steaming and could potentially affect your health.

Which Cooking Method is Least Nutritious? One Method Retains Nearly 100% Vitamin C

Registered Dietitian Gloria Tse from "Nutri Life" compared several vegetable cooking methods on social media, including steaming, stir-frying, boiling, and microwaving. Which method retains the most Vitamin C, and which loses the most nutrients?

1. Boiling/Blanching: The least recommended method is boiling. Studies have found that boiling vegetables for just 5 minutes can cause a 33-38% loss of Vitamin C, along with some loss of B vitamins, folate, potassium, and antioxidants. This significantly weakens the vegetable's ability to reduce water retention, maintain immunity, and provide antioxidant effects.
2. Stir-frying: Quick stir-frying causes about a 24% loss of Vitamin C but retains more folate and potassium. A small amount of oil also helps the body absorb fat-soluble vitamins like beta-carotene.
3. Microwaving: Microwaving vegetables causes only about a 16% loss of Vitamin C. The advantage is using minimal water and the shortest cooking time to cook the vegetables, thereby reducing nutrient loss.
4. Steaming: The most recommended method is steaming. Steaming vegetables for 5 minutes retains nearly 100% of Vitamin C, as well as more folate and antioxidants, helping the body fight aging. However, steaming can sometimes make the "grassy" taste more pronounced.

5 Tips for Boiling Vegetables to Reduce Nutrient Loss: Adding Oil Aids Nutrient Absorption

Although boiling vegetables causes the most nutrient loss, Tse admits that she also boils vegetables because it's convenient, quick, reduces oil use, and is low in calories. Boiling also has the benefit of reducing oxalic acid. Oxalic acid can hinder the absorption of calcium and iron from meals and also gives vegetables a bitter, grassy taste.

She shares 5 tips to minimize nutrient loss when boiling vegetables:

1. Don't Cut Too Small: The finer you cut the vegetables, the more surface area is exposed to water, leading to greater loss of water-soluble vitamins and potassium.
2. Shorten Soaking Time: When washing vegetables, soak them for only 5-10 minutes and rinse under running water. Use your hands or a cloth to rub the vegetables, which helps wash away pesticides and dirt faster.
3. Use Less Water: When boiling, use just enough water to barely cover the vegetables. The less water in contact with the vegetables, the less nutrient loss.
4. Add a Little Oil: Add 1-2 teaspoons of oil to the boiling water. This makes the vegetables smoother and greener, and also aids in the absorption of fat-soluble vitamins like beta-carotene.
5. Shorten Boiling Time: Wait until the water is boiling before adding the vegetables, and cover the pot while cooking to help them cook faster. The shorter the blanching time, the better; try to cook for only 2-5 minutes.

Which Vegetables are Suitable for Boiling, Stir-frying, or Steaming?

Tse emphasizes that different vegetables have different optimal cooking methods. For example, she tends to boil high-oxalate spinach, while others are better suited for steaming or quick stir-frying.

1. Orange-Red Vegetables:
   • Examples: Carrots, tomatoes, pumpkin, red and yellow bell peppers
   • Best Cooking Method: Quick stir-fry with a little oil
2. High Vitamin C, Low Oxalate Vegetables:
   • Examples: Broccoli, Chinese kale (Gai Lan), Choy Sum
   • Best Cooking Method: Steam, quick stir-fry with a little oil
3. High Oxalate Vegetables:
   • Examples: Spinach, amaranth leaves, watercress
   • Best Cooking Method: Blanch or cook in garlic broth