Vegan for Life - Jack Norris [5]
9. Plant proteins are missing some essential amino acids.
10. Vegans need to consume only 5 to 6 percent of their calories as protein.
CHAPTER 1
UNDERSTANDING VEGAN NUTRIENT NEEDS
Nutrition science was born in the early 1800s with the discovery of protein, carbohydrates, and fats. But long before that, humans knew a lot—strictly through trial and error—about food and health without actually understanding what the protective factors in foods were.
The first documented nutrition experiment was performed in 1747 by Dr. James Lind, a ship’s doctor with the British Royal Navy. At the time, being a sailor was a dangerous occupation, not just because of storms and piracy, but because as many as half of all sailors who set out on long voyages died from scurvy. Theorizing that it had something to do with the lack of fruits and vegetables on board, Lind fed different diets to a small group of sailors and noted that those who consumed lemons and limes didn’t get scurvy.
While the navy made good use of the information, ordering all British ships to carry limes, the reason that these foods were protective wasn’t known for another two hundred years when researchers discovered vitamin C. (And while Lind got all the credit for discovering the cure for scurvy, Chinese sailors had been growing greens on their ships to ward off scurvy since at least the fifth century.)
As early as 1916, well before the discovery of many vitamins, nutritionists were recommending intake of certain “protective foods.” The first RDAs were read over the radio to Americans in 1941 and have been updated and expanded a number of times since then.
Today, recommendations for individual nutrients are set by the Food and Nutrition Board (FNB) of the National Institute of Medicine. While these are official recommendations, the science behind them is sometimes still not entirely settled. In some cases, there isn’t enough research for anything more than an educated guess. And actual individual requirements are affected by lifestyle, overall diet, and genetics, which means that it’s impossible to pin down the exact nutrient requirements of any one person.
The recommendations are set at levels that are believed to meet the needs of the vast majority of Americans. Therefore, for any given nutrient, many Americans will need less than the recommended amount while others might need more. There can be exceptions, though. For example, many experts believe that current recommendations for vitamin D are far too low. And the debate about calcium recommendations is ongoing. We’re also starting to hear questions from world experts about protein requirements; some think that they may fall short of actual needs.1
VEGANS AND THE RDAS
The dietary recommendations are aimed at omnivores and, in a few cases, nutrient needs might be higher for vegetarians and vegans. Protein requirements are believed to be slightly higher because plant protein isn’t digested quite as well as protein from animals. It’s a small difference and it’s easily satisfied with vegan diets as long as calorie needs are met and your diet includes high-protein plant foods. Zinc needs may also be higher, and it’s possible that some vegans have intakes that are less than optimal.
The situation for iron is a little more controversial. We’ll see that vegans have higher requirements but how much higher is a subject of some debate. We’ve included the FNB recommendations for iron in the chart below, but we don’t think that vegans should worry too much about getting this much iron. We’ll talk much more about this issue in Chapter 6.
NUTRIENT INTAKE OF VEGANS: HOW DOES IT COMPARE TO RECOMMENDATIONS?
There isn’t much available information about nutrient intakes of vegans, but a few studies show that vegans are likely to consume more of certain nutrients—vitamin C, thiamin, riboflavin, niacin, vitamin B6, folate, and sometimes iron—than omnivores.2 In contrast, many vegans have intakes of calcium and zinc that are lower than the recommendations. In the chart on pages 4 and 5, we’ve compared