I've been posed another question recently by a good friend, curious as to how a plant-based diet could possibly work since she'd heard that plants lack the essential amino acids necessary for the human body. She also asked about humans having a hard time absorbing fat-soluble vitamins from plants, and that she'd read that a lot of people, and men especially, can't absorb plant-based omega 3s.
I'm happy to report that these are all false. In fact, the myth of "Complimenting Proteins" and the lack of plant-based amino acids was debunked long ago. The originator of the topic, Frances Moore Lappe, retracted her statement multiple times in later editions of her book, Diet For A Small Planet.
In his article, "The Myth of Complimenting Proteins," Dr. Jeff Novick addresses this issue.
He examines where the concept of “essential amino acids” came from.
In 1952, William Rose and his colleagues completed research that determined the human requirements for the eight essential amino acids. They set the “minimum amino acid requirement” by making it equal to the greatest amount required by any single person in their study. To set the “recommended amino acid requirement,” they simply doubled the minimum requirements. This “recommended amino acid requirement” was considered a “definitely safe intake.”
Today, if you calculate the amount of each essential amino acid provided by unprocessed plant foods and compare these values with those determined by Rose, you will find that any single one, or combination, of these whole natural plant foods provides all of the essential amino acids. Furthermore, these whole natural plant foods provide not just the “minimum requirements” but provide amounts far greater than the “recommended requirements.”
Modern researchers know that it is virtually impossible to design a calorie-sufficient diet based on unprocessed whole natural plant foods that is deficient in any of the amino acids. (The only possible exception could be a diet based solely on fruit.)
For example, each of the following have plenty of the amino acids you need in a day:
1 Tbsp. ground flaxseeds (I actually put a handful of ground flax powder on my breakfast in the morning)
1/4 cup walnuts (I also include walnuts on my breakfast)
20 cups dark greens (So...don't JUST eat greens)
1 cup soybeans (Edamame in a hummus wrap with spinach and carrots is DIVINE!)
12 ounces firm tofu (Just make up a breakfast with tofu scramble and you're good to go!)
But what about the fact that humans simply can't digest plant-based vitamins and nutrients as well? AKA, fat-soluble vitamins like A,D, and K? Don't they stand between plant-eating humans and optimal health?
Let's take a closer look at each of these fat-soluble vitamins. I stole this info from The Vegan R.D.
Vitamin A: While it’s true that the preformed active type of this vitamin is found only in animal foods, plants are saturated in vitamin A precursors like beta-carotene. In fact, these compounds are important enough that the USDA measures vitamin A content of foods as “retinol activity equivalents (RAE),” which includes both preformed vitamin A and the compounds that the body turns into vitamin A.
There is no separate recommendation for animal-derived pre-formed vitamin A.
So where do you get it? You can meet your vitamin A requirement for the day by drinking just one-quarter cup of carrot juice or eating a cup of kale or spinach (my veggie sandwhich with baby kale fills my entire day's need for Vitamin A). Other foods that give you more than sufficient amounts of this fat-soluble vitamin are sweet potatoes, cantaloupe, and dark orange winter squashes, including pumpkin.
Vitamin D: This vitamin occurs naturally in only a few foods—fatty fish, eggs from chickens who were fed vitamin D, and mushrooms treated with ultraviolet light (I go mushrooms ALL the way--I love 'em in different dishes...or again, on my veggie "samits" I had today. Sorry, too much Ducky Dynasty today).
With such limited dietary options, we mere mortals wouldn’t have gotten very far through life if it weren't for the fact that we can make all the vitamin D we need when skin is exposed to sunlight. However, over the years as we've moved farther from the equator into colder climates, and taken jobs inside cubicle cages underneath life-draining florescent lights, we've taken to downing supplements or enriched foods.
Although people can get adequate vitamin D from fatty fish, most—omnivore or not—rely on fortified foods and sun exposure, two options that are as easily available to vegans as to omnivores.
Vitamin K: Best sources of this nutrient are leafy greens! One form of vitamin K, called vitamin K2 or menaquinone (try saying that five times fast), is found in animal products but in only one lone plant food—natto, a fermented soy product that isn’t a usual part of most western vegan diets. But, there's good news because there's no problem. Why? Because humans have no requirement for vitamin K2. We also have bacteria in our gut that produce this same form of vitamin K—so we’re covered either way (once more, a resounding YES! We have bacteria in our guts! It's necessary to our digestion!). Since vitamin K is essential for blood clotting we’d see some evidence of deficiency if vegans went around bleeding to death every time they got a cut (and I can tell you personally that my blood has NO problem clotting).
So how do you get enough of these fat-soluble vitamins? The best way to make sure you’re getting adequate amounts of the fat soluble vitamins is to eat plenty of leafy green and dark orange vegetables and to take a vitamin D supplement if you don’t get adequate sun exposure.
But...wait? If you're on a plant-based diet with low fat, doesn't that interfere with your body ABSORBING those fat-soluble vitamins efficiently?
Ah, but you're forgetting a few foods. When I talk about "plant-based" foods I'm not just talking about fruits and veggies, I'm also talking about nuts, seeds, avocados, soybeans, and olives.
As far as the Omega 3s go...I'm gonna need a WHOLE other post on that.