A randomized, double-blind, controlled study was conducted to determine whether the consumption of leafy vegetables by preschool children would enhance their serum vitamin A concentration to acceptable levels.

The importance of these findings in alleviating and/or controlling vitamin A deficiency in developing countries is discussed.

Preschool children in Saboba, northern Ghana, were randomly assigned to five feeding groups, differing essentially in the amount of fat and beta-carotene, fed once per day, 7 days per week, for 3 months.

The consumption of dark green, leafy vegetables (with fat- 10 g/100 g) significantly enhanced serum retinol; consequently, the percentage of children with adequate retinol status increased from after feeding.

Dark green leafy vegetables are good sources of many vitamins and minerals your body needs to stay healthy, such as vitamins A, C, and K, folate, iron and calcium. They are also great sources of fiber. Research suggests that the nutrients found in dark green vegetables may prevent certain types of cancers and promote heart health. It is recommended that teenage girls eat 3 cups of dark green vegetables per week, or about ½ a cup every day.

Dark Green Leafy Vegetables

Dark green vegetables are also high in fat-soluble vitamins such as vitamins A, K, D, and E. These vitamins require a little bit of dietary fat in order for the body to absorb them. When you eat dark green vegetables, make sure to add a teaspoon of dietary fat, such as flax oil, olive or sunflower oil, avocado or seeds and nuts to make sure your body absorbs all of the vitamins you eat.

• Arugula has a peppery taste and is rich in vitamins A, C, and calcium. Arugula can be eaten raw in salads or added to stir-fry, soups, and pasta sauces.
• Broccoli has both soft florets and crunchy stalks, and is rich in vitamins A, C, and K, folate, and fiber. Broccoli can be eaten raw or steamed, sautéed or added to a casserole.
• Collard Greens have a mild flavor and are rich in vitamins A, C and K, folate, fiber, and calcium. The best way to prepare them is to boil them briefly and then add to a soup or stir-fry. You can also eat collard greens as a side dish. Just add your favorite seasoning and enjoy!
• Dandelion Greens have a bitter, tangy flavor and are rich in vitamin A and calcium. They are best when steamed or eaten raw in salad. (very detoxifying!)
  
• Kale has a slightly bitter, cabbage-like flavor and is rich in vitamins A, C and K. Kale is tasty when added to soups, smoothies, stir-fries, and sauces.
• Mustard Greens have a peppery or spicy flavor and are rich in vitamins A, C, and K, folate, and calcium. They are delicious when eaten raw in salads or in stir-fries and soups.
• Romaine Lettuce is a nutrient rich lettuce that is high is vitamins A, C, and K, and folate. It is best when eaten raw in salads, sandwiches or wraps.
  
• Spinach has a sweet flavor and is rich in vitamins A and K, folate, and iron. Spinach tastes great eaten raw in salads or smoothies, or steamed.
• Swiss Chard tastes similar to spinach and is rich in vitamins A, C, and K, potassium and iron. It is best stir-fried or eaten raw in salads.

find the full article here at pub med