December 21, 2015 | 111,362 views
By Dr. Mercola
Protein is essential for your health as it's a structural component of enzymes, cellular receptors, signaling molecules, and a main building block for your muscles and bones.
Proteins also perform transport carrier functions, and the amino acid components of proteins serve as precursors for hormones and vitamins. But, when it comes to how much you need on a daily basis, there is a wide variety of opinions.
With advancing age, getting adequate amounts of high-quality protein is especially important, as your ability to process protein declines with age, as does the level of age-related muscle loss (sarcopenia), thereby raising your protein requirements.
That said, you'd be wise to monitor your intake to make sure you're not overdoing it. Americans consume the most meat per capita in the world — more than 175 pounds of pork, poultry, and beef per year,1 and evidence suggests this is far too much for optimal health.
Making matters worse, the vast majority of this meat comes from animals raised in concentrated animal feeding operations (CAFOs), the quality of which is significantly inferior to organically raised, pastured, or grass-fed and grass-finished meats.
CAFO meats are also associated with an increased risk for antibiotic-resistant disease, and may be a source of prion-like proteins associated with mad cow disease and Alzheimer's.
Adverse Consequences of Excessive Protein Intake
It's important to realize that there is an upper limit to how much protein your body can actually use. And, on the average, Americans consume anywhere from three to five times more protein than they need, along with far too many carbohydrates and insufficient amounts of healthy fats.
To understand why eating too much protein is a bad idea, consider the following:
- When you consume more protein than your body needs, your body must remove more nitrogen waste products from your blood, which stresses your kidneys.2 Chronic dehydration can result, as was found in a study involving endurance athletes.3
- Excessive protein can have a stimulating effect on an important biochemical pathway called the mammalian target of rapamycin (mTOR). This pathway has an important and significant role in many cancers. It's also a significant regulator of the aging process.
- Excessive protein also adversely impacts the GCN2 pathway, which like mTOR is involved in the aging process. As noted by health and nutrition blogger Dan Pardi,8 limiting protein beneficially inhibits this pro-aging pathway:
General Protein Recommendations
The Recommended Daily Allowance (RDA) established by the Institute of Medicine (IOM),10 is 0.80 grams of high-quality protein per kilo (kg) of body weight (0.36 grams of protein per pound [lb] of body weight), or about 46 grams of protein per day on average for sedentary women, and 56 grams for sedentary men.
That RDA has a built-in "safety buffer," which means most of us actually need even less than that for optimal health. Yet Americans eat on average about 100 grams of protein per day11 — about double, or more, the RDA.
Considering the fact that the majority of Americans are overweight or obese, I prefer using a more precise formula, calculating your protein requirement based on lean bodyweight (i.e. muscle weight) only.
For optimal health, I believe most adults need about 1 gram of protein per kilogram of lean body mass (not total body weight), or 0.5 gram of protein per pound of lean body mass.
How to Calculate Your Protein Requirement More Precisely
In this formula, you must first determine your lean body mass. To do that, subtract your percent body fat from 100. For example, if you have 30 percent body fat, then you have 70 percent lean body mass.
Then multiply that percentage (in this case, 0.7) by your current weight to get your lean body mass in pounds or kilos.
As an example, if you weigh 170 pounds; 0.7 multiplied by 170 equals 119 pounds of lean body mass. Using the "0.5 gram of protein" rule, you would need 59.5 or just under 60 grams of protein per day.
100 – % of body fat = % of lean mass X actual weight X 0.5 gm protein = total grams of protein recommended
Example: A 170 lb individual with 30% fat mass
100% total weight – 30% fat mass = 70 % lean mass
0.70 X 170 = 119 X 0.5 = 60 grams of protein recommended
For comparison, following the current US dietary guideline, which is based on total body weight, a 170 pound individual (regardless of their fat to muscle ratio) would need about 61 grams of protein per day. At first glance, these recommendations appear to be close enough to dissuade arguing.
The primary difference is that US guidelines do not take fat mass into account, which can vary wildly from one person to the next, even if they weigh the same.
For example, if this theoretical 170-pound person has a fat mass of only 15 percent, his protein requirement would be just over 72 grams. To use myself as an example, I weigh 173 pounds and have 10 percent body fat, which means my lean body weight is just under 156 pounds.
Using the above formula, my protein requirement is about 77 grams a day, although I typically don't go over 75 grams per day. I use MyFitnessPal to enter everything I eat and carefully calculate my protein requirement to the gram. You do not want to guess here, as it's simply too important. This is really the only nutrient you need to keep hard track of. Just be sure to enter the correct foods and amounts into the program, as the results will be inaccurate if you don't enter the correct details.
Protein Requirements Are Higher for Seniors, Pregnant Women, and Athletes
Certain individuals and life circumstances do raise your protein requirements. This includes seniors, pregnant women, and those who are aggressively exercising (or competing). As a general rule, these individuals need about 25 percent more protein.
Personally, even though I walk about 9 miles a day and work out for an additional hour a day, I still limit my protein to 75 grams per day. Some researchers12,13,14 argue that those over 50 may need to double the RDA of protein to prevent sarcopenia (age-related muscle loss), but based on everything we've already discussed, I would caution against arbitrarily increasing your protein intake if you're elderly.
Consider it only if you're currently eating far below the RDA. Your best bet, I believe, is to use the formula detailed above, to calculate your protein requirement based on muscle weight (lean weight), and then add 25 percent to that figure.
It's important to realize that protein in and of itself is not a magic solution against sarcopenia. You need strength training to actually build muscle and strengthen your bones. (If you have cancer, you'll want to be particularly cautious about stimulating the mTOR pathway with excessive protein).
In addition to exercise, the elderly may also benefit from increased leucine intake. The amino acid leucine signals your muscle to increase protein synthesis. In fact, leucine has been shown to stimulate your muscle protein synthesis even during times of food restriction or after prolonged physical hardship.
The highest concentrations of leucine are found in dairy products: particularly high-quality cheese and whey protein. Based on nitrogen-balance measurements, the requirement for leucine to maintain body protein is 1 to 3 grams daily, but to truly optimize its anabolic pathway, you may need as much as 8 to 16 grams daily. For more information and dietary recommendations to boost your leucine intake, please see this previous article that discusses how to prevent age-related muscle loss.
Translating Ideal Protein Requirements Into Foods
Substantial amounts of protein can be found in meat, fish, eggs, dairy products, legumes, and nuts. To determine whether you're getting too much protein, simply calculate your lean body mass as described above, then write down everything you're eating for a few days, and calculate the amount of daily protein from all sources.
Again, you're aiming for one-half gram of protein per pound of lean body mass, which would place most people in the range of 40 to 70 grams of protein per day. If you're currently averaging a lot more than that, adjust downward accordingly. You could use the chart below, or simply Google the food you want to know and you will quickly find the grams of protein in the food.
MyFitnessPal also has a comprehensive database of foods, just be careful to enter the correct food and portion as similar foods may have widely varying nutrient levels.
Red meat, pork, and poultry average 6 to 9 grams of protein per ounce. An ideal amount for most people would be a 3-ounce serving of meat (not 9- or 12-ounce steaks!), which will provide about 18 to 27 grams of protein
Eggs contain about 6 to 8 grams of protein per egg. So, an omelet made from two eggs would give you about 12 to 16 grams of protein. If you add cheese, you need to calculate that protein in as well (check the label of your cheese)
Seeds and nuts contain on average 4 to 8 grams of protein per quarter cup
Cooked beans average about 7 to 8 grams per half cup
Cooked grains average 5 to 7 grams per cup
Most vegetables contain about 1 to 2 grams of protein per ounce
Interestingly, while fish is typically considered a good source of protein, most fish contain only HALF of the protein found in beef and chicken. According to Dr. Longo,15 the reduced protein content in fish may actually be one reason why the Mediterranean diet is linked to life extension and reduced risk for chronic disease. In essence, those who eat more fish than red meat are automatically getting far less protein.
High-Protein Plant Foods
You can also get plenty of protein from plants. In addition to the foods listed above, a few others deserve special mention for their exceptional protein value:
- Hemp seeds (hemp hearts): About 33 percent protein, providing 11 grams per 3 tablespoons; also contain all 20 amino acids in an easily digestible form, and are loaded with omega-3 fats16
- Chia seeds: About 14 percent protein, providing about 4 grams per 3 tablespoons;17 also high in omega-3 fats (but most are ALA)
- Spirulina: 70 percent protein by weight; 6 grams of protein per 10 gram serving; contains 18 of the amino acids and all of the essentials, and is easily assimilated (avoid spirulina if allergic to iodine or seafood)
- Sprouts: The quality of the protein and the fiber content of beans, nuts, seeds, and grains improves when sprouted; sunflower sprouts provide some of the highest quality protein you can eat, along with abundant iron and chlorophyll; kamut, hemp, quinoa, and bean sprouts are also good sources
- Bee pollen: 40 percent protein and one of nature's most complete foods; you wouldn't eat a large amount of bee pollen at any one time, but it's an excellent addition for variety
Be Very Selective About Where Your Meat Comes From
The quality of the meat you eat is just as important as the quantity. As a general rule, the only meat I recommend eating is pastured, grass-fed, and grass-finished, ideally organically raised meats (and of course, the same goes for dairy and eggs.) Meat from pastured or grass-fed animals is FAR superior to factory farmed meats.
CAFO beef and poultry is likely to be contaminated with herbicides, pesticides, hormones, antibiotics, and other drugs, as well as GMOs from the genetically engineered grains these animals are typically fed. The routine practice of feeding herbivores meat and animal byproducts also increases the risk of CAFO meats to be contaminated with infectious proteins associated with Mad Cow and the human version of the disease, known as Variant Creutzfeldt-Jakob disease.
Research suggests this disease may actually be part of the Alzheimer's disease puzzle. The damage is identical to that seen in mad cow disease, except for the rate of speed with which the infection destroys your brain and causes death.
In 2009, a joint research project between the US Department of Agriculture (USDA) and Clemson University determined a total of 10 key areas where grass-fed is better for human health than grain-fed beef. In a side-by-side comparison, they determined that grass-fed beef was superior in the following ways:18
Higher in total omega-3s
A healthier ratio of omega-6 to omega-3 fatty acids (1.65 vs. 4.84)
Higher in CLA (cis-9 trans-11), a potential cancer fighter
Higher in vaccenic acid (which can be transformed into CLA)
Higher in the B-vitamins thiamin and riboflavin
Higher in the minerals calcium, magnesium, and potassium
Higher in vitamin E (alpha-tocopherol)
Higher in beta-carotene
Normalize Your Protein Intake to Optimize Your Health
Pinning down the ideal amount of protein can be tricky business, with plenty of variables adding to the confusion. However, a good starting point is to calculate your need based on your lean body weight. I believe it would be quite rare for someone to need more than 0.5 gram of protein per pound of lean body weight, taking into account the fact that pregnant women, athletes and seniors may need about 25 percent more on top of that.
I strongly encourage you to do a careful analysis of precisely how much protein you are eating every day. The results may surprise you, as I'm sure many are consuming more than 100 grams per day, and very few people would need that much.
You would have to be a 6-foot-4 inch, 225 pound athlete with 10 percent body fat to need that much. While higher protein may aid weight loss, the drawbacks are manifold, and can easily outweigh this benefit. Shifting over to higher quality protein sources is also important, as factory farmed animal foods come with drawbacks that go beyond the issue of protein.