Tuesday, September 18, 2012

Before You Reach For The Iceberg Lettuce - Select The Best Greens For Your Salad!

 Iceberg lettuce is crisp and delicious but not a nutritional star.

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Salad Greens
When I was a kid, we ate a salad with every meal. It was always the same - iceberg lettuce, tomatoes, vinegar and oil. There really wasn't much choice of salad greens in the super market back then. Today, of course, you can walk down an entire isle of salad green options - besides iceberg you may find romaine, butter lettuce, red leaf, green leaf, arugula, spinach and so on. And many are offered both organically or conventionally grown! So how are we to choose?

Taste preference is always a major factor. Arugula or rocket, has a slightly bittier or peppery taste. Lettuce has a more subtle flavor and often takes on the flavor of the salad dressing. Salad greens are also selected for their distinct textures. Romaine is crunchy while butter lettuce (also known as Boston or bibb lettuce), red leaf and green leaf have a more delicate texture. Salad greens also vary in their nutritional content.

Nutritional Comparison of Salad Greens
All salad greens are very low in calories (less than 10 calories per ounce), and have no saturated fat or cholesterol. They are also extremely low in sodium. Although they may not seem to be contain high amounts of vitamins and minerals, on a per calorie basis, they are very nutrient dense.  Here's how these salad greens differ in several beneficial nutrients:

Vitamin A
This fat-soluble, antioxidant vitamin is important for vision, growth and development, healthy skin and a strong immune system. If you have night blindness, dry skin or just want to boost up your immunity and want a salad green with the highest amount of vitamin A, your best choice would be romaine or spinach - just two ounces would provide your entire daily requirement. Red and green leaf lettuces are also a very good choice. Iceberg on the other hand only provides 3% of your daily requirement per ounce.

One ounce of Romaine lettuce is only 5 calories and provides:

2439 IU vitamin A
7 mg vitamin C
29 mcg vitamin K
38 mcg folate
9 mg calcium

Vitamin C
Vitamin C is also an antioxidant and supports a healthy immune system, teeth and gum health and the formation of collagen (that's what keeps our skin from sagging ladies!). It also enhances the absorption of iron. If you bruise easily or have other signs of capillary weakness, once again romaine and spinach are the best choices for their vitamin C content - two ounces provides about one quarter of your daily requirement. Since vitamin C is very heat sensitive, eating a big raw salad is a good way to get it. Make sure and include a sliced, raw, red bell pepper - one of the best sources of this vitamin (1 cup of sliced red bell pepper provides twice your daily requirement!)  

Butter lettuce is only 4 calories per ounce and provides:

927 IU vitamin A
only 1 mg vitamin C
29 mcg vitamin K
20 mcg folate
10 mg calcium

Vitamin K
Although most people aren't deficient in this important vitamin, some people are - like those suffering from Crohn's or other diseases that effect absorption in the digestive tract or those taking certain drugs that interfere with it. This fat-soluble vitamin is essential for the regulation of blood clotting and is also very important for bone health. Spinach has a high concentration of vitamin K (135 mcg/ounce), 1 ounce providing more than the daily requirement for a man (120 mcg/day) or a woman (90 mcg/day). Those of you on warfarin (Coumadin), a blood-thinning medication, may want to avoid foods this high in vitamin K. If that's the case, the other lettuces are better choices than spinach.

One ounce of Red Leaf lettuce has only 5 calories and provides:
2098 IU vitamin A
only 1 mg vitamin C
39 mcg vitamin K
10 mcg folate
9 mg calcium
Although red leaf lettuce, with its deep colors, looks more nutritious, green leaf lettuce is higher in vitamins C & K, folate, calcium and potassium. 
One ounce of Green Leaf lettuce has only 5 calories and provides:
2073 IU vitamin A
5 mg vitamin C
49 mcg vitamin K
11 mcg folate
10 mg calcium

Folate plays a key role in amino acid metabolism and DNA synthesis. It is essential during pregnancy in preventing neural tube defects. If it's folate that you are after, spinach is a good choice with each ounce providing 14% of the daily requirement with romaine coming in a close second (one ounce providing 10%). 

It's important to note that folate can mask vitamin B12 deficiency so raw food vegans, who eat lots of high folate foods and little or no B12-rich foods, can be B12 deficient for a dangerously long time without noticing it.

Arugula, or Rocket,  is 7 calories per ounce and provides:

664 IU vitamin A
4 mg vitamin C
30 mcg vitamin K
27 mcg folate
45 mg calcium

Calcium is the most abundant mineral in the body. It is important for bone and tooth development as well as muscle contraction and nerve transmission. Although salad greens aren't a huge source of calcium, the salad green with the most calcium is arugula. A 4 ounce arugula salad provides 180 mg of calcium. More important, it's an alkaline food which doesn't draw calcium from the body like dairy sources which are acidic and cause the body to draw calcium from your bones for neutralization.
Although spinach is fairy high in calcium, it is also high in oxalates which reduce the absorption and retention of this critical mineral. To reduce the oxalic content, it's best to eat spinach cooked.

Spinach is 6 calories per ounce and provides:
2625 IU vitamin A
8 mg vitamin C
135 mcg vitamin K
54 mcg folate
28 mg calcium

So How Does Iceberg Lettuce Stack Up?
This old favorite isn't completely devoid of all nutrients - it's just not nearly as high as others. 
It contains only 1/17th the vitamin A as romaine, 1/8th the vitamin C as spinach, 1/14th the vitamin K as green leaf lettuce, and 1/11th the calcium as arugula .

Iceberg lettuce is 4 calories per ounce and provides only:
141 IU vitamin A
1 mg vitamin C
7 mcg vitamin K
8 mcg folate
5 mg calcium

How they rank
Of course their ranking depends on the nutrient you are the most deficient in - but overall, for a raw salad, romaine and arugula are the best nutritionally.
Red and green leaf are next in line followed by butter leaf.
Although spinach is an excellent source of many key vitamins and minerals, it's better prepared cooked to lessened the effect of calcium robbing oxalates.
As you may have guessed, iceberg comes in dead last. 


Lynne said...

Wow, you summed up the nagging questions I have been having all summer and debating with some of my peers. Thanks, again Joanne.

Anonymous said...

Thank you, I have recently been looking for facts about this question for a while and yours is the best I have found so far.