Two months ago, I didn't much feel like eating a green salad for lunch or dinner. Now, I'm craving one. Perhaps it's the warmer weather that's making me choose salad greens over sautéed kale or roasted Brussels sprouts, my go-to veggies in the winter.
If you think I'm taking a nutritional hit by eating lettuce instead of cooked greens, think again. Sure, kale and spinach are often heralded as "super foods," but they're not the only nutrient-packed greens on the block.
Eating a healthy salad is an easy way to up your vitamin and mineral intake.
A small bowl of greens, for example, can deliver plenty of vitamins A and K, folate and potassium along with disease-fighting antioxidants. All that for fewer than 20 calories.
Robust health and nutritional benefits
Numerous studies have found that eating plenty of leafy-green vegetables, especially salad greens, slows cognitive decline in older adults. Folate, vitamins E and K, beta-carotene and other phytochemicals in greens are thought to help preserve brain functioning.
Leafy greens are a staple in the MIND diet, a brain-friendly eating plan associated with a lower risk of Alzheimer's disease. (MIND stands for Mediterranean-DASH Intervention for Neurodegenerative Delay; the diet was developed by researchers from the Rush University Medical Center in Chicago.)
A steady intake of leafy greens is also thought to help protect against heart disease, stroke, hip fracture and certain cancers.
Some leafy greens, including spinach and romaine lettuce, are outstanding sources of lutein, a phytochemical that guards against cataract and macular degeneration.
Even your gut may benefit from eating more salad.
It turns out, our good gut bacteria extract a sulfur-containing sugar in green vegetables, called SQ for short, to fuel their growth.
'Head-to-head' comparison
Not all lettuces, though, are created equal. Some types pack a healthy dose of nutrients and phytochemicals across the board, while others fall short in certain areas.
In general, you can count on darker green lettuces to deliver a stronger nutritional punch than lighter-coloured greens. That's because leaves of loosely packed lettuces (e.g., romaine, red and green leaf, butterhead) absorb more light than enclosed heads of lettuce (e.g., iceberg, endive) and, as a result, are able to synthesize more nutrients.
Not surprisingly, then, romaine lettuce earns top score for overall nutrient content. Two cups (a decent-sized side salad that's equivalent to two vegetable servings) supplies one-third of a day's worth of folate, 4.9 miligrams of beta-carotene, 2.2 mg of lutein and 96 micrograms of bone-building vitamin K.
There are no official daily requirements for beta-carotene and lutein. However, experts speculate that a daily intake of 3 to 6 mg of beta-carotene and 6 to 15 mg of lutein is needed to guard against disease.
Despite its pale-green colour, butterhead lettuce (a.k.a. bibb or Boston lettuce) is a close second, delivering, per serving, more folate, calcium, iron, potassium and 20 per cent more vitamin K than green-leaf and red-leaf lettuces. (Butterhead is also a great choice for lettuce wraps filled with stir-fried chicken or shrimp.)
Even so, red- and green-leaf lettuces are still excellent sources of beta-carotene and vitamin K.
Coming in last place is iceberg, often referred to as the "polyester" of lettuces. Yet, it's not without nutritional benefits, so don't feel guilty if you prefer it.
Two cups of iceberg lettuce provide potassium, folate (twice as much as red leaf lettuce, in fact) and 30 per cent of the daily vitamin K requirement for men (39 per cent for women). Its pale leaves lack, however, beta-carotene and lutein.
Beyond regular lettuce
There are other greens that deserve a place in your salad bowl, too. Spinach is an exceptional source of lutein (7.3 mg in two cups, raw) and vitamin K (290 mcg).
Tossing chopped kale, Swiss chard, watercress and/or dandelion greens with your usual lettuce will boost your salad's vitamin K, beta-carotene, lutein and flavonoid content.
Baby greens, pre-washed and bite-sized, are a salad base. A few studies even suggest that baby spinach may have higher amounts of vitamins C and K and certain phytochemicals than mature spinach leaves. (The difference, though, likely has more to do with growing, harvest and storage conditions.)
Don't go fat-free
Many nutrients and phytochemicals in leafy greens, including vitamin K, beta-carotene and lutein, are fat soluble, meaning they need a little fat to be absorbed from your gut. So, dressing your salad with a fat-free dressing or lemon juice only can rob you of these beneficial compounds.
One study from Iowa State University found that people who ate their salad with fat-free dressing absorbed almost no beta-carotene and lutein. When salad was served with reduced-fat dressing, more of these antioxidants were absorbed.
Using a full-fat dressing led to an even higher antioxidant absorption.
Plus, many vegetable oils (e.g., grapeseed, sunflower, safflower, olive) are good sources of vitamin E, an antioxidant nutrient thought to help maintain the integrity of brain-cell membranes.
To prevent dousing your greens with too many calories and, in some cases, too much sodium, limit your portion size of dressing to one or two tablespoons.
Final word: variety
A salad made with the right lettuce (or a mix of greens), other chopped, raw vegetables and a healthy vinaigrette is very nutritious. But don't eat salad at the exclusion of other vegetables.
For a wider range of vitamins, minerals and phytochemicals, include a variety of vegetables in your diet. Aim to eat two (or more) different coloured vegetables at lunch and at dinner.
Choose from green vegetables (e.g., lettuce, spinach, broccoli, green peppers), red and orange vegetables (e.g., carrots, sweet potato, squash, red peppers), purple ones (e.g., eggplant, beets, red cabbage) and white vegetables (e.g., cauliflower, mushrooms, onions).
Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto.