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Do We Need To Eat Complementary Proteins All at One Time?
Scientists used to think that vegetarians, and especially vegans, would develop protein deficiency if they didn’t get eight or nine essential amino acids all together in proper amounts at every meal.
Frances Moore Lappé, author of the book ‘Diet For A Small Planet’, is well known for the theory of combining complementary proteins at each meal. In the 20th Anniversary Edition, she has altered her views in light of new knowledge about amino acid storage.
Whenever we eat, our body deposits amino acids into a storage bank, and then withdraws them whenever we need them. So, it’s no longer considered necessary to eat complementary proteins together at one sitting.
Protein Combining:
Each plant food has its own unique amino acid profile, from green leafy veggies to tubers, from barley to quinoa, from lentils to tofu, from macadamias to brazil nuts. By eating a variety of plant foods with 'incomplete proteins' throughout the day, we can easily get enough 'complete protein.' For lacto and ovo-lacto vegetarians, any food can be complemented by the high quality proteins in dairy products or eggs, but it isn't at all necessary to include animal foods to get enough protein in your diet.
In vegan protein combining, there are three broad categories: legumes, grains, nuts & seeds. These can be mixed and matched to get complete protein at any meal, or throughout the day. For instance, the amino acids in legumes (beans & lentils) are balanced by those in grains, nuts and seeds, and vice versa. Vegetables and fruits also contribute significant amounts of protein. A one cup serving of avocado, for example, has 3 grams of complete protein, and a medium potato with skin has 4 g.Vegans can't help getting all the essential amino acids, through eating different combinations of grains, legumes, nuts & seeds, vegetables & fruit several times a day.
Food combining for complete protein isn't a scientific system, where you have to keep track and analyze everything you eat. It's a natural traditional way of eating, which most human beings have eaten and thrived on, for thousands of years. Food is a sensual pleasure, and complete protein is a side benefit.
The chart below shows some examples of food combining for complete protein. While this chart is very limited, in reality the possibilities could fill several pages.
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The Building Blocks of Life
Protein is an important nutrient required for the building, maintenance, and repair of tissues in the body. Amino acids, the building blocks of protein, can be synthesized by the body or ingested from food. There are 20 different amino acids in the food we eat, but our body can only make 11 of them. The 9 essential amino acids, which cannot be produced by the body, must be obtained from the diet. A variety of grains, legumes, and vegetables can also provide all of the essential amino acids our bodies require. It was once thought that various plant foods had to be eaten together to get their full protein value, otherwise known as protein combining or protein complementing. We now know that intentional combining is not necessary to obtain all of the essential amino acids.1 As long as the diet contains a variety of grains, legumes, and vegetables, protein needs are easily met.
Protein Requirements
With the traditional Western diet, the average American consumes about double the protein her or his body needs. Additionally, the main sources of protein consumed tend to be animal products, which are also high in fat and saturated fat. Most individuals are surprised to learn that protein needs are actually much less than what they have been consuming. The Recommended Dietary Allowance (RDA) for protein for the average, sedentary adult is only 0.8 grams per kilogram of body weight.2
To find out your average individual need, simply perform the following calculation:
Body weight (in pounds) X 0.36 = recommended protein intake (in grams)
However, even this value has a large margin of safety, and the body’s true need is even lower for most people. Protein needs are increased for women who are pregnant or breastfeeding. In addition, needs are also higher for very active persons. As these groups require additional calories, increased protein needs can easily be met through larger intake of food consumed daily. Extra serving of legumes, tofu, meat substitutes, or other high protein sources can help meet needs that go beyond the current RDA.
The Problems with High-Protein Diets
High-protein diets for weight loss, disease prevention, and enhanced athletic performance have been greatly publicized over recent years. However, these diets are supported by little scientific research. Studies show that the healthiest diet is one that is high in carbohydrate, low in fat, and moderate in protein. Increased intake of whole grains, fruits, and vegetables are recommended for weight control and preventing diseases such as cancer3 and heart disease.4 High-carbohydrate, low-fat, moderate-protein diets are also recommended for optimal athletic performance.5 Contrary to the information on fad diets currently promoted by some popular books, a diet that is high in protein can actually contribute to disease and other health problems.
Osteoporosis. High protein intake is known to encourage urinary calcium losses and has been shown to increase risk of fracture in research studies.6,7 Plant-based diets, which provide adequate protein, can help protect against osteoporosis. Calcium-rich plant foods include leafy green vegetables, beans, and some nuts and seeds as well as fortified fruit juices, cereals, and non-dairy milks.
Cancer. Although fat is the dietary substance most often singled out for increasing one’s risk for cancer, animal protein also plays a role. Specifically, certain proteins present in meat, fish, and poultry, cooked at high temperatures, especially grilling and frying, have been found to produce compounds called heterocyclic amines. These substances have been linked to various cancers including those of the colon and breast.8-10
Long-term high intake of meat, particularly red meat, is associated with significantly increased risk of colorectal cancer. The 1997 report of the World Cancer Research Fund and American Institute for Cancer Research, Food, Nutrition, and the Prevention of Cancer, reported that, based on available evidence, diets high in red meat were considered probable contributors to colorectal cancer risk. In addition, high-protein diets are typically low in dietary fiber. Fiber appears to be protective against cancer.3 A diet rich in whole grains, fruits, and vegetables is important in decreasing cancer risk,3 not to mention adding more healthful sources of protein in the diet.
Impaired Kidney Function. When people eat too much protein, it releases nitrogen into the blood or is digested and metabolized. This places a strain on the kidneys, which must expel the waste through the urine. High-protein diets are associated with reduced kidney function. Over time, individuals who consume very large amounts of protein, particularly animal protein, risk permanent loss of kidney function. Harvard researchers reported recently that high-protein diets were associated with a significant decline in kidney function, based on observations in 1,624 women participating in the Nurses’ Health Study. The good news is that the damage was found only in those who already had reduced kidney function at the study’s outset. The bad news is that as many as one in four adults in the United States may already have reduced kidney function, suggesting that most people who have renal problems are unaware of that fact and do not realize that high-protein diets may put them at risk for further deterioration. The kidney-damaging effect was seen only with animal protein. Plant protein had no harmful effect.11
The American Academy of Family Physicians notes that high animal protein intake is largely responsible for the high prevalence of kidney stones in the United States and other developed countries and recommends protein restriction for the prevention of recurrent kidney stones.12
Heart Disease. Typical high-protein diets are extremely high in dietary cholesterol and saturated fat. The effect of such diets on blood cholesterol levels is a matter of ongoing research. However, such diets pose additional risks to the heart, including increased risk for heart problems immediately following a meal. Evidence indicates that meals high in saturated fat adversely affect the compliance of arteries, increasing the risk of heart attacks.13 Adequate protein can be consumed through a variety of plant products that are cholesterol-free and contain only small amounts of fat.
Weight Loss Sabotage. Many individuals see almost immediate weight loss as a result of following a high-protein diet. In fact, the weight loss is not a result of consuming more protein, but by simply consuming fewer calories. Over the long run, consumption of this type of diet is not practical as it can result in the aforementioned health problems. As with any temporary diet, weight gain is often seen when previous eating habits are resumed. To achieve permanent weight loss while promoting optimal health, the best strategy involves lifestyle changes including a low-fat diet of grains, legumes, fruits, and vegetables combined with regular physical activity.
Protein Checklist
High protein diets are unhealthy. However, adequate but not excess amounts of protein to maintain body tissues, including muscle, are still important and can be easily achieved on a vegetarian diet. If you are uncertain about the adequacy of protein in your diet, take inventory. Although all protein needs are individual, the following guidelines can help you to meet, but not exceed, your needs.
Aim for 5 or more servings of grains each day.This may include 1/2 cup of hot cereal, 1 oz. of dry cereal, or 1 slice of bread. Each serving contains roughly 3 grams of protein.
Aim for 3 or more servings of vegetables each day. This may include 1 cup of raw vegetables, 1/2 cup of cooked vegetables, or 1/2 cup of vegetable juice. Each serving contains about 2 grams of protein.
Aim for 2 to 3 servings of legumes each day. This may include 1/2 cup of cooked beans, 4 oz. of tofu or tempeh, 8 oz. of soymilk, and 1 oz. of nuts. Protein content can vary significantly, particularly with soy and rice milks, so be sure to check labels. Each serving may contain about 4 grams to 10 grams of protein. Meat analogues and substitutes are also great sources of protein that can be added to your daily diet.
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Should I be worried about getting enough protein on a vegetarian/vegan diet?
No, not as long as you're taking in enough calories. Official recommendations suggest that eating 8% of our daily energy as protein will provide an adequate amount. National and international recommendations for protein intake are based on animal sources of protein such as meat, cow's milk and eggs. Plant proteins may be less digestible because of intrinsic differences in the nature of the protein and the presence of other factors such as fibre, which may reduce protein digestibility by as much as 10%. Nevertheless, dietary studies show the adequacy of plant foods, as sole sources of protein as does the experience of healthy vegans of all ages.
The main protein foods in a vegan diet are the pulses (peas, beans and lentils), nuts, seeds and grains, all of which are relatively energy dense. As the average protein level in pulses is 27% of calories; in nuts and seeds 13%; and in grains 12%, it is easy to see that plant foods can supply the recommended amount of protein as long as the energy requirements are met.
The short answer is: "No, sufficient protein can be obtained by eating a variety of foods", but here is a longer explanation:
Protein is synthesized by the human body out of individual amino acids. The body breaks down food into individual amino acids and then reassembles the proteins it requires.
All amino acids must be present in the body to make proteins. Those that can be synthesized from other amino acids are called "unessential" amino acids. You can live on a diet deficient of these if you eat enough extra of the other amino acids to synthesize these. Those that cannot be synthesized from other amino acids are called "essential" amino acids and must be present in the diet.
Protein that contains all essential amino acids is called "complete" protein. Protein that contains some, but not all essential amino acids is called "incomplete" protein. It used to be believed that all amino acids must be eaten at the same time to form complete proteins.
We now know that incomplete proteins can be stored in the body for many days to be combined with other incomplete proteins. As long as all essential amino acids are in the diet, it does not matter if the proteins are complete or incomplete.
The amount of protein recorded on food labels only lists the complete proteins. A product may contain much higher amounts of incomplete protein that is not listed. Combining such products may increase the total amount of protein beyond the levels expected.
The 1989 revision of the FDA's RDA suggests a protein intake of 44-63 grams. Many scientists think this number is too high. Most scientists agree with this number.
Do I need to combine proteins on a vegetarian/vegan diet?
Frances Moore Lappe popularised the idea of protein combining in her book "Diet for a Small Planet" in the '70s, however in her revised edition: "Diet for a Small Planet 10th Anniversary Revised Edition" she has since renounced it.
The 1988 position paper of the American Dietetic Association emphasized that, because amino acids obtained from food can combine with amino acids made in the body it is not necessary to combine protein foods at each meal. Adequate amounts of amino acids will be obtained if a varied vegan diet - containing unrefined grains, legumes, seeds, nuts and vegetables - is eaten on a daily basis.
"Food combining" is another term for the Hay diet and has nothing to do with the concept of protein combining.
What non-meat products can I eat to get protein?
A similar question is answered by the Vegetarian Resource group (USA) at:
www.vrg.org/nutshell/faq.htm#protein
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Summary
It is very easy for a vegan diet to meet the recommendations for protein, as long as calorie intake is adequate. Strict protein combining is not necessary; it is more important to eat a varied diet throughout the day.
Some Americans are obsessed with protein. Vegans are bombarded with questions about where they get their protein. Athletes used to eat thick steaks before competition because they thought it would improve their performance. Protein supplements are sold at health food stores. This concern about protein is misplaced. Although protein is certainly an essential nutrient which plays many key roles in the way our bodies function, we do not need huge quantities of it. In reality, we need small amounts of protein. Only one calorie out of every ten we take in needs to come from protein 1. Athletes do not need much more protein than the general public 2. Protein supplements are expensive, unnecessary, and even harmful for some people.
How much protein do we need? The RDA recommends that we take in 0.8 grams of protein for every kilogram that we weigh (or about 0.36 grams of protein per pound that we weigh) 1. This recommendation includes a generous safety factor for most people. When we make a few adjustments to account for some plant proteins being digested somewhat differently from animal proteins and for the amino acid mix in some plant proteins, we arrive at a level of 1 gram of protein per kilogram body weight (0.45 grams of protein per pound that we weigh). Since vegans eat a variety of plant protein sources, somewhere between 0.8 and 1 gram of protein per kilogram would be a protein recommendation for vegans. If we do a few calculations we see that the protein recommendation for vegans amounts to close to 10% of calories coming from protein. [For example, a 79 kg vegan male aged 25 to 50 years could have an estimated calorie requirement of 2900 calories per day. His protein needs might be as high as 79 kg x 1 gram/kg = 79 grams of protein. 79 grams of protein x 4 calories/gram of protein = 316 calories from protein per day. 316 calories from protein divided by 2900 calories = 10.1% of calories from protein.] If we look at what vegans are eating, we find that between 10-12% of calories come from protein 3. This contrasts with the protein intake of non-vegetarians, which is close to 14-18% of calories.
So, in the United States it appears that vegan diets are commonly lower in protein than standard American diets. Remember, though, with protein, more (than the RDA) is not necessarily better. There do not appear to be health advantages to consuming a high protein diet. Diets that are high in protein may even increase the risk of osteoporosis 4 and kidney disease 5.
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It is very easy for a vegan diet to meet the recommendations for protein. Nearly all vegetables, beans, grains, nuts, and seeds contain some, and often much, protein. Fruits, sugars, fats, and alcohol do not provide much protein, so a diet based only on these foods would have a good chance of being too low in protein. However, not many vegans we know live on only bananas, hard candy, margarine, and beer. Vegans eating varied diets containing vegetables, beans, grains, nuts, and seeds rarely have any difficulty getting enough protein as long as their diet contains enough energy (calories) to maintain weight. [See the sections on Pregnancy, Lactation, and Infants and Children (pages 176-197 in Simply Vegan, 4th edition) for details about protein needs during these special times.]