The Starch Solution (15 page)

Proteins are built from 20 amino acids that are connected into chains in varying sequences. It’s a bit like the way all of our words in a dictionary are made up of combinations formed from the 26 letters in our alphabet. Plants and microorganisms are able to synthesize all 20 of these amino acids. Humans can synthesize only 12 of them, which we call
non-essential
because we needn’t rely on food to get them already formed. The eight remaining amino acids are called
essential
because we must get them from the foods we eat.

When we eat, our stomach acids and intestinal enzymes break the protein molecules back down into individual amino acids. The body absorbs these amino acids into the bloodstream, and then reassembles them to form new proteins. These newly formed proteins help us to maintain the shape of our cells, to create enzymes for biochemical reactions, to produce the hormones that signal messages between our cells, and to perform other life-sustaining activities.

Because they are such a rich source of complete proteins, plants alone meet the entire protein and amino acid needs of the Earth’s largest animals, including elephants, hippopotamuses, giraffes, and cows, all of which are vegetarian. If plants can satisfy the demands of these enormous mammals, wouldn’t you think they could easily meet our own protein needs? Indeed, they can and they do.

The misconception that protein from animal foods is of superior quality to that found in plants dates back to 1914, when Lafayette B. Mendel and Thomas B. Osborne published studies on the protein requirements of laboratory rats; specifically, the effects of animal versus vegetable protein sources on growth.
⁸

Mendel and Osborne found that rats grew faster and larger from eating protein derived from animal sources than from vegetable sources. These and other animal experiments led to the classification of meat, eggs, and dairy foods as superior, or “Class A,” protein sources. Vegetable proteins were relegated to inferior, or “Class B,” status. Subsequent researchers suspected that the vegetable foods used in the study contained insufficient amounts of some of the amino acids essential to the growth of rats.

Studies in the early 1940s by Dr. William Rose of the University of Illinois found that 10 amino acids were essential to a rat’s diet.
⁹
The removal of any one of these essential amino acids from the rats’ food led to profound nutritive failure, accompanied by a rapid decline in
weight, loss of appetite, and eventual death. Feeding the rats meat, poultry, eggs, and/or milk prevented this decline. Based on these early experiments with rats, the amino acid pattern found in animal foods was considered the gold standard.

Subsequent research affirmed what should have been obvious: Even though animal products supply the ideal protein pattern for rats, that does not mean the same is true for humans.
¹⁰
In fact, the dietary needs of humans and rats are quite different. One important difference is our relative rates of growth: Rats grow very rapidly, reaching their full adult size after just 6 months; humans take about 17 years to fully mature. Rapid growth requires high concentrations of nutrients, including protein and amino acids. Comparing the breast milk of these two species makes the differing nutritional needs crystal clear: Rat breast milk is 10 times higher in protein concentration than human breast milk.
^11
,
12
Their rapid growth, with baby rats doubling in size in just 4½ days compared to the 6 months required for a human infant, underscores the rat’s need for that high-protein support.

In 1942, Dr. Rose turned his attention to people, studying amino acid requirements in healthy, male graduate students using essentially the same methodology he had used with the rats.
¹³
The students were fed a diet of cornstarch, sucrose, butterfat, corn oil, inorganic salts, and known vitamins. Their only protein came from mixtures of highly purified amino acids. They also received a large brown “candy” made of concentrated liver extract to provide any missing vitamins. The candy was sweetened with sugar and flavored with peppermint oil for a “never-to-be-forgotten taste.”

Dr. Rose tested the students’ need for each individual amino acid by removing one at a time from the diet. When an essential amino acid was given in insufficient quantity for approximately 2 days, all subjects
complained bitterly of similar symptoms: nervous irritability, extreme fatigue, and a profound loss of appetite. The subjects were unable to continue the amino acid—deficient diets for more than a few days at a time.

Dr. Rose found that only eight of the 10 amino acids essential to rats were also essential to these young men. The other two amino acids essential to rats were
non-essential
to humans because we can synthesize them ourselves. Dr. Rose also identified the minimum required level for each of the eight essential amino acids. Because he found small amounts of variation in individual needs among his subjects, he included a large margin of safety in his final conclusions on minimum amino acid requirements: For each amino acid, he took the highest recorded level of need in any subject, then doubled that amount for a “recommended requirement,” described as a “definitely safe intake.”

Even Dr. Rose’s inflated amino acid levels are easily met by a diet consisting of any single grain, legume, or starchy vegetable. Rice or potatoes alone supply all of the protein and amino acids both adults and children need. All unrefined starches and green, yellow, and orange vegetables, it turns out, are perfectly calibrated by natural design to meet our protein needs, so long as we eat enough of them to satisfy our energy (caloric) requirements. These foods perfectly support peak human nutrition, as they have done for eons.