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The Very Real Risks of Consuming Too Much Protein

Story at-a-glance -

  • Most Americans consume three to five times more protein than they need, along with excessive starchy carbs and not enough healthy fats
  • A more ideal protein intake is likely around one-half gram of protein per pound of lean body mass, which for most is 40 to 70 grams a day. Examples are given
  • Excess dietary protein can lead to elevated blood sugar, weight gain, kidney stress, leaching of bone minerals, and stimulating cancer cells
  • Restricting your protein to plant-only sources may create a sulfur deficiency and potentially accelerate age-related functional decline
  • Protein quality is as important as quantity; consuming a wide variety of high–quality, grass-fed animal- and organic plant-based whole foods is the best approach

By Dr. Mercola

With the popularity of "high-protein" diets, you might be tempted to believe you simply can't overeat protein. But the truth is that consuming excessive protein can actually be quite detrimental to your health. Eating more protein than your body needs can interfere with your health and fitness goals in a number of ways, including weight gain, extra body fat, stress on your kidneys,1 dehydration and leaching of important bone minerals.

Granted, your body needs protein. Protein and its array of amino acids are the primary building blocks for your muscles, bones and many hormones. You cannot live without it. As you age, and during pregnancy, consuming sufficient amounts of high-quality protein is especially important, as your ability to process protein declines with age, raising your protein requirements.

This is especially true for aging males. Protein helps preserve lean muscle that is typically lost with age. High-quality proteins from pasture raised animals are more easily used by your body than those from plants.2 That said, there is an upper limit to how much protein your body can actually use. On average, Americans consume anywhere from three to five times more protein than they need for optimal health, along with far too many carbohydrates and not enough healthy fats.

Meat consumption has risen dramatically in the US over the past century. Making matters worse, a large amount of this excess meat is typically poor quality, originating in concentrated animal feeding operations (CAFOs), where the animals are mistreated and fed an unnatural diet of genetically engineered grains instead of fresh grass. Your goal should be a diet with enough — but not too much — high-quality protein from a variety of plant and animal sources.

Excess Protein May Fuel Weight Gain, Yeast Overgrowth and Cancer

There are a number of reasons why I believe it's prudent to limit your protein intake. The first is that if you eat more protein than your body requires, it will simply convert most of those calories to sugar and then fat. Increased blood sugar levels can also feed pathogenic bacteria and yeast, such as Candida albicans (candidiasis), as well as fueling cancer cell growth.

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. When you reduce protein to just what your body needs, mTOR remains inhibited, which helps minimize your chances of cancer growth.

Additionally, when you consume too much protein, your body must remove more nitrogen waste products from your blood, which stresses your kidneys. Chronic dehydration can result, as was found in a study involving endurance athletes.3

Lowering Your Protein Intake May Extend Your Lifespan

New studies have brought some additional insights into the protein discussion, as it relates to your longevity. Many animal studies have established that calorie restriction leads to increased longevity, but the latest science suggests this phenomenon may actually result more from reduced protein intake — specifically, reduced intake of the amino acid methionine, which happens to be high in meats.4

Yet, other new research suggests it may be the balance of amino acids that is the key, especially with other amino acids like glycine that may actually help lower methionine levels. How can you use this information to your advantage?

Well, you can implement approaches like protein cycling in which you replicate ancestral patterns of going through feast and famine, which can help normalize your amino acid levels. That is one of the reasons why I am such a major fan of intermittent fasting. Bone broth may also be particularly useful as it is especially high in glycine.

How to Calculate Your Protein Requirements

Now that you can appreciate some of the many advantages of reigning in your protein consumption, how do you know exactly how much protein you actually need? Fortunately, there is a simple rule, and all you need to know is your lean body mass. You likely need about one-half gram of protein per pound of lean body mass.

For most people, this amounts to 40 to 70 grams of protein a day. Rarely does a person need more protein than this—the exception would be those who are aggressively exercising (or competing) and pregnant women, who should have about 25 percent more. Forty to 70 grams a day is in the general range of the CDC's protein recommendations for adults (46 grams a day for women, and 56 grams a day for men).

But the formula has the major advantage of taking into account your weight and body composition, which is more relevant than age and gender.5 This comes down to a protein serving that is about the size of a deck of cards. To estimate your protein requirements, first determine your lean body mass. Subtract your percent body fat from 100.

For example, if you have 20 percent body fat, then you have 80 percent lean body mass. Just multiply that percentage (in this case, 0.8) by your current weight to get your lean body mass in pounds or kilos. So, in the above example, if you weighed 160 pounds, 0.8 multiplied by 160 equals 128 pounds of lean body mass. Using the "one-half gram of protein" rule, you would need about 64 grams of protein per day.

Translating Ideal Protein Requirements Into Foods

Substantial amounts of protein can be found in meat, fish, eggs, dairy products, legumes, nuts, and seeds. Some vegetables also contain generous amounts of protein—for example, broccoli.6 Forty grams of protein is not a large amount of food — it's the equivalent of just two small hamburger patties, or one 6-ounce chicken breast.

To determine whether or not you're getting too much protein, simply calculate your body's requirement based on your lean body mass, as described above, and write down everything you eat for a few days.

Then, calculate the amount of daily protein you've consumed from all sources. Again, you're aiming for one-half gram of protein per pound of lean body mass. If you're currently averaging a lot more than what is optimal, 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 that food.

Red meat, pork, poultry, and seafood average 6 to 9 grams of protein per ounce.

An ideal amount for most people would be a 3-ounce serving of meat or seafood (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

Eating ONLY Plant-Based Foods May Lead to Deficits

In order to gain the greatest nutritional benefit from the proteins you eat, I recommend consuming a wide variety of high-quality proteins from both animal and plant whole food sources. Research consistently shows that nutritional deficits are extremely hard to avoid if you limit yourself to a strictly plant-based diet.

From the standpoint of ancestral nutrition, the hunting and foraging of our predecessors resulted in their consuming a much wider selection of foods than we do today, which means they received a much broader complement of nutrients, including proteins.

Research published in the journal Nutrition7 shows that people who eat a strictly plant-based diet may suffer from subclinical protein malnutrition. This puts one at risk for not getting enough dietary sulfur. Sulfur is derived almost exclusively from dietary protein, such as fish and high-quality (organic and/or grass-fed/pastured) beef and poultry. Meat and fish are considered "complete" as they contain all the sulfur-containing amino acids you need to produce new protein.

A new Japanese study shows that adequate intake of animal protein may lower your risk of age-related functional decline. Men who consumed higher levels of meat and fish had a 39 percent lower risk of mental and physical decline compared to those who ate the least animal protein.8

On the flip side, plant-based proteins may be helpful in reducing your blood pressure. A recent meta-analysis9 found that removing meat from the diet led to blood pressure reductions similar to losing 5 kilos of body weight. So... which is better — plant or animal? I believe the answer is neither — meaning, clinically speaking, most would be best served by consuming a variety of high-quality proteins in order to reap the benefits of both plant- and animal-based protein sources, as each offers its own particular health benefits.

How Much Protein Is Too Much for Your Body?

I've mentioned before that too much protein can be bad for your health. Ideally, you should consume only one-half gram of protein per pound of lean body mass. But what is the excess amount before protein can negatively impact you?

According to a study in ISRN Nutrition, which pegs the recommended dietary allowance (RDA) for protein in adults at 0.8 grams of protein per kilogram of body weight, going beyond the prescribed RDA, can actually be detrimental to your health. This can lead to several adverse effects, such as:10

  • Bone disorders
  • Kidney problems
  • Liver problems
  • Increased risk of coronary artery disease

Again, I encourage you to follow the calculations I mentioned earlier to help safeguard your health from the effects of excessive protein consumption. Ordinary people who are not doing high-energy activities only need a moderate amount of protein. If you're an athlete or a bodybuilder, you only have to increase the amount by 25 percent more for optimal muscle repair and recovery.

What Happens If You Eat Too Much Protein?

Published evidence indicates that excess protein can lead to adverse health effects. Several noteworthy examples include:

Weight gain: A study released by Clinical Nutrition notes that a high-protein diet can lead to excess body weight, which directly relates to an increase in total death risk, but not when protein is replaced by healthy fat.11

Weakened bones: According to The Journal of Nutrition, too much protein consumption can release a large amount of acid in body fluids. The kidneys excrete these acids, and your skeleton assists by acting as a buffer through active bone resorption. As a result, calcium loss occurs. Researchers went on to say that this can be mitigated by increasing intake of alkali-rich foods.12

This information is corroborated in another study, wherein researchers found that increasing protein intake led to an increase in urinary calcium.13

Increased risk of cancer: As mentioned before, too much protein can increase your risk of cancer. One study notes that high intake of red and processed meat is associated with an increased risk of colon cancer.14 Another study reports similar findings when consuming red meat, while conversely noting that fish and chicken (without skin) had lower risk.15

Kidney stones: According to the American Family Physician, low fluid intake along with excess protein (along with salt and oxalate) is a crucial risk factor for the development of kidney stones.16

Heart disease: A report from the American Heart Association notes that middle-aged men on a high-protein diet have a 33 percent higher risk of developing heart failure from all protein sources.17

Be Very Selective About Where Your Meat Comes From

The quality of the meat you eat is as important as the quantity. As a general rule, the only meat I recommend eating is grass-fed, pastured, 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 that from animals raised in concentrated animal feeding operations (CAFOs).

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 (GE) grains these animals typically consume.

Researchers are even suggesting that CAFO beef may be spreading slow-acting prion infection causing Alzheimer's disease. 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 U.S. 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 versus 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

Whey Protein

An excellent source of convenient, quick-to-prepare high-quality protein is whey protein. Whey protein is an excellent "fitness food" because it contains not only high-quality protein, but also extremely high amounts of leucine, which is particularly important for muscle growth and repair.

One of the reasons whey protein is so effective for exercise recovery is that it assimilates very quickly — it gets into your muscles within 10 to 15 minutes of swallowing it, just when they need it most. Whey is also excellent for your immune system, as it is rich in immunoglobulins, lactoferrin and other precursors for glutathione.

With regard to whey supplements, a word of caution is in order. Isolated amino acid supplements and branched-chain amino acid isolates (such as leucine and glutamine) are dangerous and potentially damaging to your health — so stay away from them. Many contain "putrid proteins," as well as the proteins in the wrong form (isomers) so they cannot be properly used by your body.

They also tend to be acid-processed and contain surfactants, artificial sweeteners, heavy metal contaminants (arsenic, cadmium, lead and mercury19), and a long list of chemical additives. Instead, look for a high-quality whole food whey supplement that is minimally processed, comes from organic, grass fed, non-hormone treated cows and is independently tested and verified for purity.

Seeds, Sprouts and Spirulina Are Other Great Protein Foods

A key factor in maximizing your nutrition is achieving the right balance of macronutrients—carbohydrates, proteins and fats. By far, most Westerners consume too much protein and carbohydrate, and not enough healthy fats. For a comprehensive guide, please refer to my Optimized Nutrition Plan, starting with Beginner Plan: Protein, and then progressing into Intermediate Plan: Protein. In addition to the foods already discussed, 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 fats20
  • Chia seeds: About 14 percent protein, providing about 4 grams per 3 tablespoons;21 also high in omega-3 fats (but most are ALA)
  • Spirulina: Seventy 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 improve 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: Forty 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