Lettuce is a Green food. Green foods are safe to eat as a regular part of a diet.
Guideline related quotes related to Non-Starchy and Green throughout Geoff Bond's publications.
Eat at least 2 3/4 lbs of mixed salad and vegetables per day, consisting of "Green-Green” and “Green” foods. Of these, at least 3/4 lb should be mixed salad. Also include at least 5 cups of “Green-Green” leafy vegetables or 2 1/2 cups of other vegetables per week. ~Paleo in a Nutshell p.102
Specific references to Lettuce throughout Geoff Bond's publications.
It is quite easy really to achieve six servings by eating one big salad every day with all the usual ingredients we think of as salad vegetables: Tomatoes, lettuce, radish, cucumber, mushrooms, onions, and so forth. ~Paleo in a Nutshell p.48
Our evolutionary past designed our digestive systems to have high volumes of plant food passing through them. These non-starchy plant foods were, by nature, low-density: That is, they had few calories for their volume. A lettuce leaf, for example, is 95 percent water (the remaining 5 percent is a wonderful cornucopia of vital nutrients). In addition, plant food is rich in various plant fibers, the sort that our colons are designed to work with. The typical Western diet is the opposite: Energy-dense and low in fiber. ~Paleo in a Nutshell p.55
Oats, of all the grains, contain rather more soluble fiber than average, a quality that manufacturers promote as cholesterol-reducing and therefore hearthealthy. This, nevertheless, is not a valid argument: They are still glycemic, contain anti-nutrients and antigens, and are deficient in micronutrients. Oats are no alternative to proper plant food, like lettuce and avocado. ~Paleo in a Nutshell p.59
Conforming non-starchy, colored plant foods are foods that are low-glycemic, rich in micronutrients and fiber, and harmless with regard to anti-nutrients and antigens. Broadly, they include most salad foods, such as lettuce, onions, cucumber, radish, and mushrooms, and they also include colored vegetables, such as broccoli, green beans, bell peppers (sweet peppers), and Brussels sprouts. These are considered "Green-Green," "Green," and "Green-Amber." Under "Green-Green," we have separated out the vegetables that have the high concentrations of background micronutrients that our ancient ancestors delighted in. You can have unlimited consumption of these foods, and the ideal is up to two pounds (900 g) per day. ~Paleo in a Nutshell p.62
The idea of eating salad for breakfast does indeed run counter to our Western cultural programming, but it is something that many societies do, notably in Africa. A copious mixed salad with some avocado, tuna flakes, or shrimp makes a great start to the day. Again, make it a large portion— at least one pound per person. It is not really so much: One large tomato, one cucumber, some onion, and some lettuce leaves make 9 oz of plant food. Round it off with 3 oz of canned tuna, and you have a hearty breakfast. ~Paleo in a Nutshell p.87
The U.S. Department of Agriculture (USDA) does not subdivide its Vegetable Group: they classify french fries and ketchup as vegetables just like lettuce and broccoli. As this example shows, it does indeed make a difference just what kind of vegetable we are eating— not all "vegetables" conform to the type of plant food to which we are naturally adapted. ~Deadly Harvest p.54
The vegetables from above ground cover a huge range of plant parts: stems, such as asparagus from the Mediterranean and kohlrabi from Europe; buds, such as Brussels sprouts from Belgium; leafstalks, such as celery from the Mediterranean and rhubarb from Asia; leaves, such as Europe's cabbage, lettuce, and spinach; immature flowers, such as cauliflower from Europe, broccoli from Turkey, and artichoke from the western Mediterranean; immature fruits, such as eggplant from southern Asia and cucumber from northern India; mature "vegetable-fruits," such as tomato from Peru, avocado from Central America, and bell pepper from the Andes; edible bean pods, such as runner beans from tropical America; and edible fungi (mushrooms) from just about everywhere. Of course, today, these plants are grown all over the world, wherever farmers can produce them economically. ~Deadly Harvest p.56
In common parlance, starches are still called complex carbohydrates; however, a new category of "very complex carbohydrates" has been created for foods such as broccoli, lettuce, and so on, and these now inherit the mantle of "good" carbohydrates. ~Deadly Harvest p.98
Farmers grow lettuce hydroponically (the technique of growing plants with their roots not in soil but in nutrient-dosed water), only using nutrients that are essential to lettuce. Ordinary soils too might have reduced levels of micronutrients, either from intensive farming or just because they are made that way. Does it matter? W hen we say "reduced levels," that still means that there are enough nutrients. The main problem with the average Westerner is that he or she is only consuming about 12% of the ideal amount of plant food. Just by doubling consumption, this will double the intake of micronutrients and they will be a lot better for it. ~Deadly Harvest p.170