by Jason Fung
ANIMAL PROTEIN AND PLANT PROTEIN: A SIDE-BY-SIDE COMPARISON
Variation in the amount and type of protein consumed affects biological processes that are linked to health, aging, and disease. Finding the optimal amount of protein can yield big benefits, helping us to live longer and to experience fewer of the diseases and less of the frailty of aging. Too little protein causes disease. Too much protein causes disease. What’s the right amount?
The Recommended Daily Allowance (RDA) set by the Institute of Medicine of the National Academy of Sciences to meet the minimal requirements of healthy adults is 0.8 gram per kilogram per day.1 But the nitrogen balance method of determining protein requirements that they used is subject to large errors,2 and some researchers believe the RDA has been significantly underestimated. They think the RDA should be 40 to 50 percent higher, at 1.2 grams per kilogram of body weight as a safe population-wide recommendation. (That’s 84 grams of protein per day for an adult who weighs 70 kilograms [154 pounds].)
The RDA is only an average, and protein requirements vary greatly depending on whether a person is a child, an adult, elderly, pregnant, an athlete, in ill health or frail, obese, or is losing or gaining weight (or desiring to do so). The official dietary recommendations are intended to prevent deficiency rather than to suggest optimal protein intake for longevity, which is understandable given that knowledge of how protein affects longevity is relatively new.
Our food is composed of three main macronutrients: fats, carbohydrates, and protein. Fats and carbohydrates are chiefly sources of energy, although there are a small number of essential fatty acids, whereas there is no such thing as an essential carbohydrate. Protein is different. Its primary function is for growth and maintenance rather than providing energy. Thus, the chief difference in protein requirements reflects the need for growth. In adults, there is little need for growth, except if you are trying to build muscle. An adult’s liver, lungs, and kidney do not need to get any larger. In an infant, though, all organs and muscles need to grow, which means that an infant has a much higher protein requirement for its body weight. The infant must grow from less than 10 pounds to more than 100 pounds, and that growth requires more protein. Also, a person who has a higher lean mass—the entire body excluding fat tissue and water—has a higher protein requirement. However, there is an upper limit of protein use. You can’t gain muscle only by eating lots of protein; otherwise, we’d all look like bodybuilders just from eating more protein.
Severe protein deficiency is rare in developed countries, but the amount that prevents deficiency and the optimal amount are not the same. If a person consumes less than the minimal amount of protein, loss of lean mass (especially muscle) and decreased antioxidant capacity could result.3 Whereas most people in the Western world already consume this higher amount of protein (about 70 percent coming from animal sources and 30 percent coming from plant sources4), some do not, notably among the elderly. In hospitals, older people with protein malnutrition are often admitted; they’re referred to as “tea and toasters.” These frail, elderly people had difficulty cooking, so they would eat mostly tea and toast, which contain very little protein.
Protein for Growth and Development
People in a life stage when growth and development is a priority, such as pregnant women, infants, children, and adolescents, should eat more protein. Estimated protein requirements vary with the rate of growth of infants over the first year of life, ranging from an estimated 2 grams per kilogram of body weight at the age of one to two months to about 1.3 grams per kilogram at six months of age and then to about 1.0 gram per kilogram at one year.5 The protein content of human milk, as well as its ratio of casein to whey proteins, changes during that time; evolution has optimized milk to suit the infant’s needs. The American Academy of Pediatrics recommends exclusive breastfeeding for the first six months of life; after that time, breastfeeding may continue as the child begins to eat other foods, to one year or longer.6
As a child ages, the protein requirement slowly declines; by ten years of age, a safe level of protein is about 0.9 gram per kilogram, which is a level only slightly higher than for an adult. In early pregnancy, a woman’s protein requirement is estimated to be about 1.2 grams per kilogram; in late pregnancy, her requirement is about 1.5 grams.7
Protein for the Elderly
Protein requirements for the elderly are different than for other adults. They have increased protein needs because they cannot use protein with the same efficiency as younger adults. Failure to meet those increased needs can result in loss of muscle and other lean mass, lower antioxidant capacity, and lower immune function, all of which play a role in increased risks of illness and frailty.
Losing skeletal muscle (sarcopenia) with age affects health in many ways. Muscle acts as a “metabolic sink” by taking up nutrients and contributing to overall insulin sensitivity. Sarcopenia is a major cause of falls and bone fractures, and it can leave an elderly person unable to perform normal activities of daily living, such as getting out of a chair unassisted, which may lead to placement in a nursing home.
Sarcopenia is most commonly due to lack of activity. The adage “use it or lose it” is applicable. Prolonged bed rest, such as during hospitalization or major illness, results in a large loss of muscle mass. One study of healthy elderly patients found an astounding loss of 1 kilogram of muscle even while subjects were consuming adequate protein.8 Sedentary behavior, although not as extreme as bed rest, also contributes to sarcopenia. For this reason, strength training, especially when combined with extra or different types of protein, can be a boon for the elderly.
Also, anabolic resistance contributes to sarcopenia. Skeletal muscle undergoes a normal cycle of turnover—muscle breakdown balanced by protein synthesis. Anabolic resistance increases with age, and muscle protein synthesis in response to dietary protein decreases; the result is a decline in muscle mass. Lack of exercise, inflammation, and oxidative stress also can contribute to anabolic resistance.
Increased dietary protein can overcome anabolic resistance to help maintain muscle.9 A consensus statement from a group of experts, the PROT-AGE Study Group, made the following statements and recommendations:
• To maintain and regrow muscle, older people require more protein than younger people; older people should consume an average of 1.0 to 1.2 grams per kilogram of body weight daily.
• The amount of protein at one meal that increases muscle growth (i.e., that overcomes anabolic resistance) is higher in older people, at about 25 to 30 grams of protein per meal, equivalent to about 2.5 to 2.8 grams of leucine per meal.
• When possible, older individuals should perform endurance exercise 30 minutes a day and resistance exercise (strength training) 10 to 15 minutes or more, two or three times per week, if it is safe and tolerable for the individual.
• Protein supplementation, such as a whey drink, especially before or right after exercise, might help older people regain muscle. Whey has been shown to be more effective for muscle growth than casein. Bodybuilders are well known to ingest protein immediately before or after strength training to increase muscle growth, and exercise physiologists have studied this practice extensively. It works.
• Most older people with an acute or chronic disease (except kidney disease) need even more protein, in the range of 1.2 to 1.5 grams per kilogram of body weight daily.
• Older people with severe illness or injury or who have marked malnutrition might need as much as 2.0 grams per kilogram of body weight daily.
Eating one high-protein meal (known as “protein pulse feeding”) is more effective than distributing the protein equally over the day. Omega-3 fatty acid supplementation also augments the increase in muscle growth caused by dietary protein; regular supplementation with fish oil or other supplements that contain omega-3 fatty acids can help older people retain and regain muscle.10
Hospitalization, which sometimes involves forced immobility, often results in weight loss, particularly in undernourished
patients. An estimated 40 percent of hospital patients are malnourished, as defined by a body mass index of less than 20.11 This malnourishment puts them at risk of infections, and hospital-acquired infections are an increasing problem. The CDC estimated that in 2011, more than 720,000 cases of hospital-acquired infection occurred, which is about 1 in 25 people.12
Extra dietary protein can help this situation. In a geriatric population, provision of 8 grams a day of essential amino acids cut the infection rate by about 30 percent, while also increasing hemoglobin and improving other health markers.13 Trauma patients who received a formula containing whey protein also had a much lower incidence of infections.14 As for muscle, providing essential amino acids ameliorates muscle loss during bed rest.15
Protein for Athletes
Building muscle requires protein16 but also salt. During metabolism, stomach acid (hydrochloric acid) and pepsin break down dietary protein into peptide fragments and free amino acids. The amino acids pass into the small intestine, where absorption occurs. Antacids and medications that block stomach acid, such as commonly prescribed proton pump inhibitors, prevent normal digestion of proteins. Low-salt diets also reduce stomach acid by reducing the availability of chloride. Eating too many refined foods, especially with reduced stomach acid, might also lead to overgrowth of bacteria in the small intestine, known as small intestinal bacterial overgrowth (SIBO), which might impair protein absorption.
Low-salt diets also promote muscle insulin resistance, which can reduce muscle growth and cause overtraining syndrome (exercising in excess of the body’s ability to recover), muscle cramps, and muscle spasms that reduce your ability to exercise.17
You need to muscle-up by salting-up, especially before exercise. Dr. DiNicolantonio’s previous book, The Salt Fix, provides the precise salt intake dosing that you should use before exercise.
After the intestine has absorbed amino acids, the gut and liver use approximately half the amino acids. Known as “first pass” clearance, this means about 50 percent of the protein you consume isn’t even available for muscle growth. Importantly, branched-chain amino acids (BCAAs) are metabolized less by the liver, so they may be especially beneficial for muscle growth because of increased availability.18
Once the amino acids hit your systemic circulation, only about 10 percent goes toward skeletal muscle protein synthesis. The rest is used for energy (gluconeogenesis) or as building blocks for proteins and neurotransmitters throughout the body.19 Muscle protein synthesis begins about 30 minutes after amino acid absorption and peaks at around 2 hours. Increased blood amino acids stimulate muscle growth, but only up to a certain point.
Maximum muscle protein synthesis occurs with a protein intake of 0.24 gram per kilogram of body mass per meal in younger males (generally 50 years old or younger) and 0.40 gram per kilogram in older adults due to anabolic resistance.20 Muscle protein synthesis varies depending on the type and intensity of exercise. If you’re trying to build muscle, then eating 20 grams of protein every three hours might be appropriate for you because that schedule optimizes muscle protein synthesis throughout the day. A general rule is that young men generally can get maximal protein synthesis per meal if they consume 20 to 30 grams of protein; older adults need around 40 grams.21
Fig. 6.1: The 30 rule and the 40 rule
Eating more protein (40 grams versus 20 grams) can stimulate more muscle growth, but the benefits are marginal.22 Indeed, most athletes can satisfy their protein requirements by consuming around 30 grams of protein at each meal (0.24 to 0.30 gram per kilogram). However, pre-sleep doses of protein may need to be higher than 30 grams to maximize overnight skeletal muscle anabolism.23 To summarize, younger adults use the “30 rule”: consume 30 grams of protein per meal at least 3 hours apart and 30 grams of protein before going to sleep. Older adults should use the “40 rule”: consume 40 grams of protein per meal 3 hours apart and 40 grams of protein before going to sleep. Most adults should have an overall daily protein intake between 1.6 and 2.2 grams per kilogram for optimizing muscle mass growth with resistance exercise.24 A good general rule prescribes 1 gram of protein for every 1 pound of body weight (equal to 2.2 grams of protein per kilogram).
Athletes need about double the amount of protein for optimal performance (1.6 to 1.8 grams per kilogram per day) that sedentary people need (0.8 gram per kilogram per day).25 However, the amount varies widely depending on many interacting factors, like energy and carbohydrate intake; type, intensity, and duration of exercise; dietary protein quality; training history; gender; age; and timing of protein consumption. One size does not fit all. Lean athletes who are resistance-trained may need upward of 3 grams per kilogram per day of protein to prevent muscle losses during energy restriction.26
Athletes often are encouraged to drink sugary sports drinks. Glucose stimulates insulin secretion, which encourages muscle growth. However, this requires only around 5 IU/mL of insulin; higher doses do not enhance this effect.27 In other words, you don’t need sugar to build muscle. Most normal diets have sugar levels many times higher than what is needed.
Athletes should consume glycine as a supplement powder or capsule or as hydrolyzed collagen protein in addition to consuming protein from traditional sources. The body needs around 15 grams of glycine per day to meet both collagen and noncollagen synthesis requirements. However, the typical American diet provides only around 1.5 to 3 grams of glycine per day. The body can synthesize small amounts of glycine (around 3 grams per day), but the shortfall is still approximately 10 grams of glycine daily for almost everyone.28 Dr. DiNicolantonio’s research has shown that glycine taken at doses of 5 grams three times a day can benefit those with metabolic syndrome by reducing oxidative stress and systolic blood pressure.29
PRACTICAL RECOMMENDATIONS FOR HIGH-PERFORMANCE ATHLETES
• Aim to eat approximately 0.4 gram per kilogram of body mass of protein per meal.
• Space protein-containing meals three to five hours apart.
• Ingest around 30 to 40 grams of protein one to three hours before going to sleep to offset the effects of the overnight fast.
• When you’re performing resistance exercise, eat 1.6 to 2.2 grams of protein per kilogram per day distributed among three to four meals.
• Consider taking glycine supplements.30
RECOMMENDATIONS FOR ATHLETES IN ENERGY RESTRICTION
• Because daily protein requirements are greater for preserving lean body mass, consume around 2.3 to 3.1 grams per kilogram per day of protein. Those who are more overweight and exercise-naive should aim for the lower end of this range, whereas leaner resistance-trained individuals should aim for the higher end of this range.
• Perform resistance exercise during energy restriction to preserve lean body mass.
• Ensuring adequate protein intake helps appetite control during energy restriction.31
ENDURANCE ATHLETES
It would seem obvious that bodybuilders require more protein than other people. But oddly enough, they require only 1.05 grams of protein per kilogram of body weight (around 73.5 grams of protein per day for a 70-kilogram [154-pound] bodybuilder), which is only about 10 percent more than sedentary people require. Endurance athletes require far more protein; they need about 70 percent more (about 1.37 grams of protein per kilogram per day) than sedentary people. Less intensive endurance training may only require 0.97 gram of protein per kilogram per day. A safe level would be 1.6 grams of protein per kilogram per day for endurance athletes and 1.2 grams of protein per kilogram per day for bodybuilders.32 (See the “Protein Recommendations for Health and Activity Conditions” table at the end of the chapter for more specifics.) Bodybuilders often supplement with protein, but runners and other endurance athletes often do not, which puts them at risk of deficiency.
It’s important to note that these safe margins of intake are based on a diet that is approximately 50 percent carbohydrate. Increased workout intensity or a lower carbohydrate intake may necessitate higher levels of protein. A
dditionally, pregnant and lactating women and adolescent athletes likely require more protein.33
Overtraining—which is characterized by fatigue, infections, and poor athletic performance—often sets in for elite and Olympic-level athletes, and it might be due partially to inadequate protein intake.34 Researchers found that when fatigued athletes consumed an extra 20 to 30 grams of protein a day, blood amino acid patterns returned to normal, and many of them overcame their fatigue to resume regular training at their previous level.
To summarize:
• Protein requirements for athletes depend on many factors.
• Strength athletes need only a little more protein than sedentary people.
• Endurance athletes need much more protein than sedentary people (at least 1.6 grams of protein per kilogram per day).
• Inadequate protein intake during intense training may lead to overtraining syndrome.
Protein for Weight Loss
