by Iceberg lettuce is ranked at the bottom because of its low nutrient density compared to other types of lettuce and leaf. It provides very small amounts of essential vitamins and minerals, such as vitamins A, C, and K, and is lower in fiber and antioxidants than its darker-leafed counterparts. The light green, almost white color of iceberg lettuce indicates a lower concentration of phytonutrients and beneficial compounds. Although it adds hydration due to its high water content (about 96 percent), its nutritional benefits are limited compared to more nutrient-dense greens such as romaine or collard greens.
The healthiest way to eat lettuce
Like romaine, iceberg lettuce is rarely cooked or exposed to heat. It is best used raw in salads, sandwiches and other fresh dishes to provide a crispy texture. Avoid cooking lettuce, because heat can cause it to wilt and lose its nutritional content, especially its water-soluble vitamins and sensitive antioxidants.
Vegetables and vitamins
Although we only need them in small doses, vitamins are essential to keep our bodies working properly. They boost our immune system, strengthen our bones and keep our skin healthy. Our bodies cannot make them, so we must get them from our diet.
“Vegetables are great sources of essential vitamins, especially vitamins A, C, K, folate and E,” explains Dr Maria Traka, head of food and nutrition at the Quadram Institute. For example, vitamin A helps us see things in dim light, and vitamin K helps blood clot so that wounds can heal.
Unfortunately, popping a multi-vitamin isn’t necessarily a quick fix if you’re not eating enough vegetables. “Getting nutrients from whole foods maximizes nutrient absorption and reduces the risk of over-intake,” she explains. Over long periods, very high doses of vitamin A can weaken our bones, too much vitamin D can damage the kidneys and heart, and excessive amounts of iron can be fatal.
“In addition, vegetables contain other beneficial components such as polyphenols, carotenoids and phytochemicals,” which are not present in supplements, according to Dr. Traka. “Studies show that these reduce the risk of many diseases, including cancer, cardiovascular disease, degenerative eye diseases and osteoporosis.”
Vegetables and fiber
Fiber is a carbohydrate found in plants. “It acts to push other materials through the intestine, so it promotes regular bowel movements, improves gut motility and can relieve constipation,” explains Dr. Traka.
It helps fill us up, which can help prevent overeating and weight gain, it improves our blood sugar control, so it can protect against Type 2 diabetes, and it nourishes our gut microbiome , so it’s beneficial to our gut health, she notes. Fiber has also been shown to protect against inflammation, cardiovascular disease and bowel cancer, says Dr. Traka.
Per 100g, peas (6g), sweet potato (4g), Brussels sprouts (3.9g) and broccoli (2.6g) are among the vegetables richest in fibre.
Vegetables and carbs
Hearty carbohydrate vegetables are often demonized because they are higher in calories than leafy greens and salad vegetables. However, potatoes, sweet potatoes, carrots, parsnips and sweet corn are still nutritious. They are starchy foods full of fiber and vitamins.
“They offer unique benefits that low-carb vegetables cannot provide,” explains Dr. Traka. “They provide a quick and sustainable source of energy. The fiber content in these vegetables promotes satiety, aids weight management and helps regulate digestion and blood sugar levels.”
Cooking vegetables
Fresh vegetables are, of course, packed with nutrients, but frozen can be just as nutritious or, in some cases, better.
For example, studies suggest that frozen kale has more antioxidants, and frozen broccoli has more B vitamins. This is because vegetables are frozen at their peak, giving them high nutritional value. However, frozen vegetables can lose some vitamins during cooking, as they release more water during cooking.
The picture is mixed for canned goods. “Some water-soluble vitamins such as B vitamins and vitamin C can be lost in the canal process or leached into the surrounding fluid,” explains Dr. Traka. “Also, check the label and choose canned vegetables that have no added salt or sugar.”
When it comes to cooking, it is clear that root vegetables are drizzled with honey and roasted in the oven for a delicious hour. Unfortunately, minimal cooking is generally better, because it prevents nutrients from being lost, explains Dr. Traka.
“Lightly steamed is better than boiled, because boiling vegetables in a lot of water leaches B vitamins and vitamin C into the water,” she says. When frying or roasting, avoid dousing vegetables in oil or butter as it adds unnecessary calories, she says.
The Science of Plant-Based Nutrition published by DK on 27 June
