Iceberg lettuce comes in at the bottom of the list due to its low nutrient density compared to other lettuces and leafy greens. It contains very low amounts of important vitamins and minerals such as vitamins A, C and K and has less fiber and antioxidants than its dark-leaf counterparts. Iceberg lettuce’s light green, almost white color indicates a lower concentration of phytonutrients and beneficial compounds. Although it helps hydrate due to its high water content (approximately 96 percent), its nutritional value is limited compared to more nutrient-dense leafy greens such as romaine or cilantro.
The healthiest way to eat salad
Like romaine lettuce, iceberg lettuce is not often cooked or heated. It is best used raw in salads, sandwiches and other fresh dishes to maintain a crisp texture. Do not cook lettuce, as heat can cause it to wilt and lose its nutrients, especially its water-soluble vitamins and delicate antioxidants.
Vegetables and vitamins
Although we only need them in tiny doses, vitamins are vital for the proper functioning of our bodies. They boost our immune system, keep our bones strong and keep our skin healthy. Our bodies cannot produce them on their own, so we must get them from food.
“Vegetables are an important source of essential vitamins, especially vitamins A, C, K, folate and E,” explains Dr. Maria Traka, Head of the Food and Nutrition Department at the Quadram Institute. For example, vitamin A helps us see things in dim light, while vitamin K promotes blood clotting so wounds can heal.
Unfortunately, taking a multivitamin isn’t a quick fix if you don’t eat enough vegetables. “Getting nutrients from whole foods maximizes nutrient absorption and minimizes the risk of overdose,” which can be toxic, she explains. Over long periods of time, 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 compounds such as polyphenols, carotenoids and phytochemicals” that are not found in supplements, notes Dr. Traka. “Studies suggest that these reduce the risk of many diseases, including cancer, cardiovascular disease, degenerative eye disease and osteoporosis.”
Vegetables and fiber
Dietary fiber is a carbohydrate found in plants. “It pushes other substances through the intestines, promoting regular bowel movements, improving intestinal motility and can relieve constipation,” explains Dr. Traka.
It fills us up, which can prevent overeating and weight gain, improves our blood sugar control, which can protect against type 2 diabetes, and nourishes our gut microbiome, which has a positive impact on our gut health, she notes. Fiber has also been shown to protect against inflammation, cardiovascular disease, and colon cancer, Dr. Traka adds.
Per 100g, peas (6g), sweet potatoes (4g), Brussels sprouts (3.9g) and broccoli (2.6g) are among the vegetables richest in fibre.
Vegetables and carbohydrates
Hearty, carbohydrate-rich vegetables are often demonized because they contain more calories than leafy greens and salad vegetables. However, potatoes, sweet potatoes, carrots, parsnips and sweetcorn are still nutritious. They are starchy foods that are rich in fiber and vitamins.
“They offer unique benefits that low-carb vegetables may not,” explains Dr. Traka. “They provide a quick and sustained source of energy. The fiber content of these vegetables promotes satiety, supports weight control, and helps regulate digestion and blood sugar levels.”
Cooking vegetables
Fresh vegetables are of course full of nutrients, but frozen vegetables can be just as nutritious, or in some cases even more so.
For example, studies suggest that frozen kale contains more antioxidants, while frozen broccoli contains more B vitamins. This is because vegetables are frozen at their peak, preserving their high nutritional value. However, frozen vegetables can lose some vitamins when cooked because they release more water when cooked.
When it comes to canned foods, the picture is mixed. “Some water-soluble vitamins, such as B vitamins and vitamin C, can be lost during the canning process or leached into the surrounding liquid,” explains Dr. Traka. “You should also check the label and choose canned vegetables that have no added salt or sugar.”
As for cooking, root vegetables drizzled with honey and roasted in the oven for an hour are obviously delicious. Unfortunately, minimal cooking is generally better because it means no nutrients are lost, explains Dr. Traka.
“Lightly steamed is better than boiled, as cooking vegetables in lots of water causes B vitamins and vitamin C to leach into the water,” she says. When frying or roasting, avoid dipping vegetables in oil or butter, as this adds unnecessary calories, she says.
The science of plant-based nutrition was published on June 27 by DK
