Have we Gone Overboard on Protein?
Have we Gone Overboard on Protein?
What does the Science Say?
*Reader’s note: Much of the content of this article is drawn from the Physician’s Committee for Responsible Medicine. Their website, http://www.pcrm.org/ is an excellent resource for anyone interested in the science of healthy eating.
We all need to eat to live, so let’s look at just what food is from a nutritional standpoint. Food consists of macronutrients and micronutrients. Micronutrients are a massive topic; one best left for another article, but basically this class of nutrients consists of vitamins, minerals and phytonutrients. Today’s discussion will focus on ‘macronutrients’, protein in particular.
There are three classes of macronutrients:
- fats, and
You need to consume all three of these nutrients; there is no question about that. However, a perpetual debated exists around the amount of each macronutrient that we need for health and survival. From a survival point of view we must consume food for fuel, but also to acquire the raw materials necessary for our metabolic needs, such as growth, tissue repair, to support our immune system, and many other important functions. Let us first look at food as fuel.
Metabolism 101 (A really basic view of energy conversion)
From an energy point of view, the entire body runs exclusively on adenosine triphosphate (ATP), which is manufactured from glucose (a carbohydrate). Carbohydrates eventually get broken down into glucose for their stored energy. Fats, on the other hand are essentially a dense energy storage vehicles. They are highly concentrated energy. (A little goes a long way). Fats can be burned when blood sugar (glucose) is low, but the conversion involves many steps. The body is just like us; it is a bit lazy and would prefer to burn carbohydrates. Of the three macronutrients, carbohydrates create the least by-products (carbon dioxide and water) when compared to protein or fats. As well, this is the simplest and easiest energy pathway of the three macronutrients.
It is worth noting that when the body has an excess of nutrients, it often stores the excess energy as fats, a process known as lypogenesis. It might be a big word, but every one of us knows something about the effects of this process, and we are all trying to keep lypogenesis to a minimum.
Proteins, on the other hand, serve primarily as building blocks for tissue repair. They can be converted to ATP for body energy as well, but a lot of nitrogen is created in the process (which the body will eventually convert to urine) and as well, ketoacids are created. As you might guess, acids create several problems for the body, one of which is blood pH levels. Blood pH is regulated to stay within the narrow range of 7.35 to 7.45, making it slightly basic, as opposed to acidic. If the blood is acidic the body dips into its calcium reserves (our muscles and bones) and adds the calcium to our blood to adjust the pH. For anyone concerned about osteoporosis, this should be setting off some alarm bells. We will revisit this topic later.
Diets, Diets, Diets!
There are literally hundreds of diets out there, with many of them being promoted by people with excellent medical credentials. You hear low-carb, high-carb, vegetarian, vegan, Paleolithic, South Beach, Atkins and hundreds more. To whom should we listen? Everybody has a different agenda, and a vested interest in what they promote. I searched for years for the best diet to achieve not only ideal body weight, but also for optimum health. I am still perfecting my personal diet and will continue to tweak it till I die, but no matter what diet you choose, it has to leave you satiated, satisfied, it has to taste good or else you will go off of it, it must help you maintain a healthy weight, and it must in fact be healthy aka good for your body’s long-term health. Much more could be said about diets, but for the sake of the topic I will keep this short.
Let me say in the interest of transparency that I follow a plant-based dietary pattern. What convinced me to follow this path was not just the ethical, the environmental, and the sustainability arguments (as strong as they might be); it was the persuasive health argument. I work as a regulated health professional and my food choices have to make nutritional sense to me, so before I made the change to this lifestyle I needed to see medical proof that I was making the right choice following a plant-based diet. As it turns out, this eating pattern supplies more than enough protein (roughly 70% more than is required for human needs), and interestingly enough it is probably the least expensive diet out there!
What is Protein, and What Does it Do?
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 nine essential amino acids, which cannot be produced by the body, must be obtained from the diet. A variety of grains, legumes, and vegetables can provide all of the essential amino acids that 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 acids1. As long as the diet contains a variety of grains, legumes, and vegetables, protein needs are easily met.
The Recommended Dietary Allowance (RDA) for protein for the average, sedentary adult is 0.8 grams per kilogram of body weight.
Our Protein Requirements
With the traditional Western diet, the average American consumes about 70% more protein than needed (whether omnivorous or vegetarian). Additionally, the main sources of protein consumed by Americans tend to be from 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 0.8 grams per kilogram of body weight2. 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. An 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 is 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, such as:
Osteoporosis. High protein intake is known to encourage urinary calcium losses. 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.6-8
Long-term high intake of meat, particularly red meat, is associated with significantly increased risk of colorectal cancer. In 2007, 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.9
The American Academy of Family Physicians notes that high animal protein intake is in part 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.10
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.11 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 (From the Physician’s Committee for Responsible Medicine)
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 five or more servings of grains each day. This may include 1⁄2 cup of hot cereal, 1 ounce of dry cereal, or one slice of bread. Each serving contains roughly 3 grams of protein.
- Aim for three 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 ounces of tofu or tempeh, 8 ounces of soy milk, and 1 ounce 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.
An excellent book that delves deeply into on this topic is Proteinaholic by Dr. Garth Davis.
*Legal Disclaimer:This site does not provide medical advice. Content is provided for informational purposes only. Always check with your primary care physician before making changes to your dietary regime.
1. Craig WJ, Mangels AR. Position of the American Dietetic Association: vegetarian diets. J Am Diet Assoc. 2009;109:1266-1282.
2. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients) (2002); Food and Nutrition Board (FNB), Institute of Medicine (IOM) (www.nap.edu/books/0309085373.html)
3. World Cancer Research Fund. Food, Nutrition and the Prevention of Cancer: A Global Perspective. American Institute for Cancer Research. Washington, D.C.: 2007.
4. Ornish D, Brown SE, Scherwitz LW. Can lifestyle changes reverse coronary heart disease? Lancet. 1990;336:129-133.
5. Rodriguez NR, Dimarco NM, Langley S. Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: nutrition and athletic performance. J Am Diet Assoc. 2009;109:509-527.
6. Butler LM, Sinha R, Millikan RC, et al. Heterocyclic amines, meat intake, and association with colon cancer in a population-based study. Am J Epidemiol. 2003;157:434-445.
7. Sinha R. An epidemiologic approach to studying heterocyclic amines. Mutat Res. 2002;506:197.
8. Zheng W, Lee SA. Well-done meat intake, heterocyclic amine exposure, and cancer risk. Nutr and Cancer. 2009;61:437-446.
9. Knight EL, Stampfer MJ, Hankinson SE, Spiegelman D, Curhan GC. The impact of protein intake on renal function decline in women with normal renal function or mild renal insufficiency. Ann Int Med. 2003;138:460-467.
10. Romero V, Akpinar H, Assimos DG. Kidney stones: A global picture of prevalence, incidence, and associated risk factors. Rev Urol. 2010;12:e86–e96.
11. Nestel PJ, Shige H, Pomeroy S, Cehun M, Chin-Dusting J. Post-prandial remnant lipids impair arterial compliance. J Am Coll Cardiol. 2001;37:1929-1935.