November 19, 2010 |
I was doing my diet for more traditional reasons: I was short of cash. I needed whatever I could scrape up to keep the utilities turned on. So the garden needed to provide the food. And not just vegetables, either. Staple foods. I'm both highly allergic to wheat as well as gluten intolerant. And I'm sensitive enough so that I can't eat other grains that are milled on the same mills as wheat, which includes nearly all the corn, oats, and other grains that would be gluten-free otherwise. Grains milled on dedicated mills are a specialty item, and are expensive. So the cheap foods so widespread in our culture are not available to me. I need to be able to grow my own staples. And the staple food it is easiest to provide from a garden here in maritime Oregon, as well as much of the rest of the temperate world, isn't grain or beans. It's potatoes. Good thing, too! There is no food I would rather mostly survive on for serious periods of time than the potato.
Potatoes are unique compared with other roots and tubers because they are an excellent source of protein as well as carbohydrate. Potatoes can be thought of as being honorary grains. Since a bite of wheat might kill me from anaphylactic shock before the ambulance arrived, I tend to look at it the other way round. Potatoes are the standard. I view grains as honorary potatoes. Potatoes and grains are comparable as sources of protein. A boiling type of potato, for example, with 2.1 grams of protein per 100 grams fresh weight, has 10.4 percent protein per unit dry weight. Brown rice with 7.5 percent protein in the bin, has 9.6 percent protein per unit dry weight. (Many people don't realize potatoes are a high-protein food because they are used to seeing numbers that compare the levels of protein in wet potatoes with those of dry grain.) Pasta varieties of wheat have protein amounts comparable to those of rice and potatoes. Bread varieties of wheat have higher protein contents. But grain protein is low in the essential amino acid lysine, so is not as usable to fill our protein (actually essential amino acid) needs as is the same amount of potato protein. In addition, we don't absorb wheat proteins as well as those of rice or potatoes. Taking these factors into account, the potato is about as good a source of protein as the higher-protein grains, and is superior to lower-protein grains such as rice or standard commercial hybrid corn. Of annual crops, only beans are better sources of protein.
If I am eating nothing but 2,000 calories per day of potatoes, for example, which is about 5.8 pounds of potatoes (taking boiling potatoes as the standard), I would get 55 grams of protein. The RDA for protein for adult women, adult men, and pregnant or lactating women is 46 grams, 56 grams, and 71 grams per day respectively. However, RDAs are set at somewhat above the needs of the average person so as to cover most of the population, including those with above average protein needs. This means that 55 grams of protein per day would be adequate for many but not all people. Those for whom the protein was a bit short would not be very short. A little milk or an occasional egg or bit of cheese, meat, or fish along with the spuds would be all that was needed.