Nutrition and Strength
What do you do if you want to gain muscle strength? Most likely you head to the gym and start lifting weights. Exercising muscles to increase strength is important, but what about eating to develop strength? If you think this type of eating is just for bodybuilders or powerlifters, you're wrong. Since we all have muscles and use them every day, strength concerns each of us.
Primer on Nutrition
Food is our body's fuel. We measure food energy in calories, or the amount of energy needed to increase the temperature of 1 kilogram of water by 1Â°C. Calories in food are provided by three macronutrients: carbohydrate, protein, and fat. In addition to supplying the energy our body needs to function, each macronutrient also provides raw materials for building the body's tissues (bones, muscles, organs, blood, hormones, enzymes, etc) and regulating all the activities of the body.
Protein's Role in the Body
Although protein can supply energy, that's not its primary job. Instead, it’s required to build, maintain, and repair muscles and other body tissues. All macronutrients are made of carbon, hydrogen, and oxygen, but protein also contains nitrogen. The building blocks of protein are amino acids linked in chains-similar to a chain of pearls-in an almost unlimited variety of sequences. It's these different sequences of amino acids that give each protein its individual characteristics. Our body contains an estimated 50,000 different types of proteins, and each protein has a very specific function.
There are two types of amino acids: essential and nonessential. In the nutrition world, essential means that the substance must be provided by foods in the diet. Therefore, essential amino acids must come from our foods, while the body can make nonessential amino acids from fragments of carbohydrate, fat, and nitrogen.
Think of the body as a factory assembly line. If you're making cars in the factory, you need all the components of the car to put an entire car together. If one part is missing, the assembly line stops. The same thing happens when our bodies make proteins. The liver can produce nonessential amino acids if necessary, but if an essential amino acid is missing, production stops. We need to provide our bodies with an adequate amount of essential proteins on a daily basis for the processes of synthesis and repair to continue as needed.
The body constantly makes new proteins and breaks down old proteins to reassemble them into something different in a process called protein turnover. Excess nitrogen from broken-down protein is excreted in the urine, feces, and sweat. We can measure nitrogen output and compare that to the amount of nitrogen taken in from foods in the diet. When both are equal, a person is in zero nitrogen balance, or a state of general health. If more nitrogen is excreted than is consumed, a person is in negative nitrogen balance. People who are starving, malnourished, or suffering from severe stresses such as burns, infections, or major trauma are often in negative nitrogen balance and are unable to build enough protein to satisfy the body's needs. At the opposite end of the spectrum, those in positive nitrogen balance are taking in more nitrogen than they excrete and are able to add blood, bone, skin, and muscle cells to their bodies. Pregnant women and bodybuilders have a positive nitrogen balance.
How Much Protein Do We Need?
In 2005, the Institute of Medicine published dietary reference intakes (DRIs) for several nutrients, including protein. The DRIs are based on the concept that there is a range of protein intakes necessary for good health when calorie intake is sufficient to meet the body's energy needs. The current suggested protein intake for healthy adult men and women is 0.4 grams protein per pound of body weight, meaning that a 130-pound woman needs 52 grams of protein per day. Most adults get plenty of protein, with the median adult daily intake at 55 to 100 grams per day.
Just because the majority of adults regularly consumes adequate amounts of protein doesn't mean that all people are meeting their protein needs.
Increasing muscle size
Say you want to build stronger, more muscular arms, or you want to be able to bench press a certain amount of weight. For muscles to increase in size, two conditions must be met: The body has to make new muscle proteins, and you need to be in positive nitrogen balance. Instead of 0.4 grams of protein per pound of body weight, aim for 0.7 to 0.8 grams protein per pound of body weight to increase muscle mass. According to the American College of Sports Medicine, doubling protein intake is necessary to create and sustain more muscle mass.
Don't believe everything you read in bodybuilding magazines. Their articles often encourage excessive amounts of protein as the yellow brick road to increased muscle size. Just because we consume a large amount of protein doesn't mean that it's used to build larger muscles. If we regularly exceed our body's capacity for protein use, two things can happen. Either the excess protein is stored as body fat, or some of the excess is burned as energy. In both cases, nitrogen must be removed from the amino acids and excreted from the body. We're better off in the long run consuming more energy from carbohydrate, which doesn't require eliminating nitrogen, and keeping our protein intake at healthy levels.
Protein for endurance activity
Endurance athletes such as marathoners or cyclists are often trapped in a carbohydrate-focused world. Sure, carbohydrate is the primary fuel for exercising muscles, but protein also plays an important role. During endurance exercise, especially if energy intake is adequate, protein metabolism will slow down. Amino acids are also used for energy at a greater extent during long-distance aerobic activity. Both of these situations slightly increase protein intake needs for endurance activity to 0.5 to 0.6 grams of protein per pound of body weight per day. Just because endurance athletes aren't focused on building large muscles doesn't mean their protein needs aren't important.
More Than Protein
In his book Advanced Sports Nutrition, Dan Bernadot, PhD, RD, FACSM, highlights a common misunderstanding among strength athletes and others looking to increase their muscle mass: You've got to consider more than just protein. He points out that total calorie intake plays a crucial role in building muscles, and ignoring calories from carbohydrate and fat will cause even the best-laid plans to backfire.
Protein can only perform its muscle-building work when there are sufficient calories present to fuel every other function in the body. If calorie intake is too low, our bodies start to dismantle protein in body tissues to use the carbon portions for energy. To increase muscle mass, we have to make sure we're getting adequate energy as well as optimal amounts of protein.
What About Supplements?
Susan M. Kleiner, PhD, RD, FACN, CNS, lays out a no-nonsense approach to using supplements to increase strength in her book The Powerfood Nutrition Plan. Food comes first, and there isn't a whole lot of research on the huge amount of supplements heavily promoted in magazines and on the Internet.
The one supplement that does have good research behind it is creatine. Creatine helps replenish adenosine triphosphate stores, providing more energy for muscles to increase gains in muscle mass and strength. It's a well-researched sports supplement, with no long-term side effects. Kleiner recommends 5 grams of creatine per day, taken with a carbohydrate source such as fruit juice. Drink an extra 8 to 12 ounces of water as well, since creatine draws water into muscles.
In addition to creatine, Kleiner recommends using whey protein, especially after exercise. Whey protein is one of the components in milk. Whey protein is rapidly absorbed by the body and also is high in branched-chain amino acids, which make up almost one third of the amino acids in our muscles and are rapidly depleted when we exercise. Many protein shakes are formulated with additional whey, but you can get a similar effect by mixing plain whey protein with chocolate milk.
Aging is an Endurance Sport … Almost
If you've never heard of sarcopenia, it's high time you learn more about this condition. Sarcopenia is defined as the age-related loss of skeletal muscle mass, strength, and function. Skeletal muscles are the muscles that move your skeleton around-biceps and triceps in your arms, quadriceps and hamstrings in your legs, etc. Beginning in our 40s, we lose 3% to 5% of our muscles mass per decade. After the age of 50, we lose 1% to 2% of our muscle per year. The well-known Framingham Study showed that 40% of the female population aged 55 to 64, 45% of women aged 65 to 74, and 65% of women aged 75 to 84 were unable to lift 4.5 kilograms -that's a 10-pound bag of flour!
Losing muscle means we're not as strong, so carting a sack of groceries from the car into the house becomes more difficult, as does shoveling the sidewalk or going up and down stairs in the house. A lower amount of muscle also causes our body to burn fewer calories, because there's less muscle to support metabolism. Think of the lower amount of fuel it takes to power a compact car vs. an SUV, and you get the picture. If we need fewer calories but continue to eat the same amount of food, you know what happens: We gain weight. Typical age-related weight gain shows up in the spare tire around our middle. Not only does that mean we have to purchase new pants; it also increases our risk of developing type 2 diabetes and heart disease.
The decreased muscle mass seen in aging is also associated with decreases in bone density leading to osteoporosis, insulin sensitivity leading to diabetes, and aerobic capacity leading to cardiovascular disease. As we age, protein is more than building big biceps; it's our overall health, independence, and ability to fully live our lives.
What Causes Sarcopenia?
Aging in general is associated with a decline or slowing down of all body processes. We tend to make new skeletal muscle more slowly as we age, which causes a net loss in total muscle amounts. In addition, aging slows down muscle repair. We produce less testosterone, a hormone necessary for muscle synthesis. Growth hormone production slows by 14% per decade, leading to decreased amounts of muscles and increased amounts of fat.
You know how a hinge gets rusty over time if it's not regularly used? The same thing happens with our muscles. The more we sit on the couch and watch TV instead of getting outside and playing touch football or going for a walk, the more "rusty" our muscles become. Skeletal muscles especially need activity that overloads them, such as strength exercises at the gym using free weights or machines.
The USDA estimates that 25% of women aged 65 and older do not consume the recommended amount of protein. Add to that a reduced calorie intake from a desire to be thin, and many do not get adequate calories or protein to maintain muscle mass. The combination of decreased calorie and protein intake plus less hormones that create muscle and decreased amount of activity that uses muscles translates into sarcopenia and needing a helping hand to get out of the recliner because we've lost strength in our legs and core muscles.
Stop Age-Related Muscle Loss
The most effective and logical first step to slow age-related muscle loss is optimal nutrition, including both adequate calories and protein intake. While energy needs decrease because of loss of muscle mass, protein needs increase to preserve and even gain muscle mass. It's a viscious cycle that leads to less strength to perform daily activities, depressed immune system (antibodies are made of proteins) and decreased functions in the body (many hormones and enzymes are also made of proteins). Recent research suggests that adults older than the age of 51 need slightly more protein than their younger counterparts: 0.5 grams of protein per pound of body weight vs. 0.4 grams for younger adults.
Strength training will increase muscle strength and mass, which can improve daily function, as well as overall health and vitality. Exercises that overload all muscles of the body, from large muscles in the legs, chest, and back to the smaller muscles in the arms and calves, can promote increased strength in all these areas. Overloading muscles with resistance from weights, machines, or resistance exercise bands is the most effective method to increase muscle strength.
In her book Strong Women Stay Young, Miriam Nelson, PhD, outlines specific weight training programs to increase muscle mass as we age and avoid the effects of sarcopenia. In one of her studies, one half of a group of 40 postmenopausal, sedentary women lifted weights twice each week. The other half maintained their sedentary lifestyle. After one year, the sedentary women had even lower levels of muscle, and their bone mass had decreased as well. But the women who lifted weights twice each week gained bone density and scored at levels typical of women in late thirties on strength tests. Many even lost weight and dropped a dress size. The message: It IS possible to regain lost muscle from aging and a sedentary lifestyle if we adopt regular strength training.
Eat for Strength
In many ways, eating to increase strength incorporates the same healthy eating strategies you've heard before: Start your day with breakfast, eat regularly throughout the day, choose primarily whole foods that are less processed, and avoid foods high in saturated and trans fats. But eating to gain strength requires extra effort in these areas:
- Timing of meals and snacks. Eat a snack containing primarily carbohydrate with a small amount of protein 30 to 60 minutes before exercise to give muscles adequate fuel. An example is a turkey or peanut butter sandwich, or a 6-ounce container of yogurt.
- Refuel as soon as possible after exercise to provide the nutrients muscles crave to recover and build. Aim for approximately 20 grams of protein with 30 to 45 grams of carbohydrate, about the amount in many sports bars and protein shakes; or a ham, turkey, or roast beef sandwich with a glass of milk.
All of us have muscles, but it's what we do to preserve or even increase muscle strength that makes the difference in our health and lifestyle as we age. A combination of healthy eating habits and regular strength training will help us become a bodybuilder or pursue an active lifestyle through retirement. I aim to be one of the 80 year olds who regularly hikes, bikes, and gets up out of the chair on my own. How about you?
— Lynn Grieger, RD, CDE, cPT
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