Vegan for Life - Jack Norris [10]
Peer Review
Scientific journals make sure that studies are credible and worth publishing by having them reviewed by other researchers qualified to do so. The reviewers can recommend that the study be published or not, based on what they think of the study design and other factors.
Who Paid for the Study?
Most nutrition research is funded by the government, but some is paid for by industry. It probably doesn’t matter as much as you might think.
The results are what they are and the sponsoring party can’t change them. The only real advantage is that they get a peek at the data before it is published; that way their PR department can be ready to issue a press release.
In conclusion, we can make educated statements about vegan nutrition only by looking at what most of the studies say (rather than drawing conclusions from individual studies) and by focusing on the studies that are likely to yield the most reliable information. It’s also important that studies are published in peer-reviewed journals.
CHAPTER 2
PROTEIN FROM PLANTS
Nutrition researchers declared more than thirty years ago that plant foods can provide adequate protein.1 But “where do you get your protein?” is a question that most vegans have heard more times than they can count. Many of the questions about protein in plant-based diets stem from confusion over what it means for proteins to be “complete.”
COMPLETE AND INCOMPLETE PROTEINS
Proteins are made of chains of twenty different amino acids. Some amino acids can be made by the body (generally from other amino acids) and therefore we don’t need a dietary source of them. Others—the essential amino acids (EAAs)—must be supplied by the diet.
Proteins in the human body tend to have a consistent ratio of EAAs. Because the percentage of EAAs in animal products and soybeans are a close match to those in the human body, proteins from these foods are considered “complete.” Plant foods like grains, beans and nuts have a lower percentage of at least one essential amino acid, making them “incomplete.” For example, beans (other than soybeans) are low in the EAA methionine, and grains are low in lysine. But when grains and beans are consumed together, their amino acid profiles complement each other and produce a mix that is “complete” and therefore a good match to the body’s needs.
In the early 1970s, the idea that vegetarian meals should contain these specific complementary pairings was popularized in Diet for a Small Planet by Frances Moore Lappé.2 Today we know that the theory about what happens when protein foods are combined in this way wasn’t wrong; it just turned out to be unnecessary. Newer research has shown that the body maintains its own storage supply of the essential amino acids.3 We need to keep replenishing that storage with all of the amino acids, and so it’s important to eat a variety of plant foods. But the old idea that certain combinations of plant foods—the complementary pairings—must be consumed together isn’t true.
While fruit is extremely low in protein, and oils don’t provide any, all other plant foods contain protein. One common misconception is that plant foods are completely without one or more amino acids. That’s not true. All plant sources of protein contain at least some of every essential amino acid. In fact, you could get enough protein and all of the essential amino acids by eating just one type of food like pinto beans. You’d need to eat a lot of them, though—about four cups per day. That’s not practical, partly because it would be boring, but also because all those beans are likely to displace foods that are needed to satisfy other nutrient requirements. So eating a variety of protein sources makes better nutritional sense.
PROTEIN RDA FOR VEGANS
Protein needs are calculated on the basis of healthy (or “ideal”) body weight—that is, what a person with a healthy amount of body fat weighs. Scientists use the metric system, so U.S. protein needs are determined using your healthy weight in kilograms.
The protein