How Much Protein Do You Really Need?
A) The marketing is enticing: Get stronger muscles and healthier bodies with minimal effort by adding protein powder to your morning shake or juice drink. Or grab a protein bar at lunch or for a quick snack. Today, you can find protein supplements everywhere-online, at the pharmacy grocery store, or health food store. They come in powders, pills, and bars. With more than $12 billion in sales this year, the industry is booming and, according to the market research company, Grand View Research, is on track to sell billions more by 2025. But do we really need all this supplemental protein? It depends. There are pros, cons and some ho-hums to consider.
B) For starters, protein is critical for every cell in our body. It helps build nails, hair, bones, and muscles. It can also help you feel fuller longer than eating foods without protein. And, unlike nutrients that are found only in a few foods, protein is pretty much ubiquitous. “The typical American diet is a lot higher in protein than a lot of us think,” says registered dietitian Angela Pipitone with Johns Hopkins McKusick-Nathans Institute of Genetic Medicine. She says it's in foods many of us expect, such as beef, chicken, and other types of meat and dairy. But it's also in foods that may not come immediately to mind like vegetables, fruit, beans and grains.
C) The U.S. government’s recommended daily allowance (RDA) for the average adult is 50 to 60 grams of protein a day. This may sound like a lot, but Pipitone says: “We get bits of protein here and there and that really adds up throughout the day.” Take, for example, breakfast. If you ate two eggs topped with a little bit of cheese and an orange on the side, you already have 22 grams of protein. Each egg gives you 7 grams; the cheese gives you around 6 grams and the orange - about 2 grams. add a lunch of chicken, rice, and broccoli, and you are already over the recommended 50 grams. “You can get enough protein and meet the RDA before you even get to dinner,” says Pipitone.
D) So if it’s so easy to get your protein in food, why add more in the form of powders, snack bars or a boost at your local juice bar? No need to, says Pipitone because, in fact, most of us already get enough protein in our diet. “Whole foods are always the best option rather than adding supplements,” she says, noting the FDA does not regulate supplements as stringently as foods or drugs, so there could be less protein, more sugar, and some additives you wouldn’t expect, such as caffeine and even steroids.
E) If you are considering a supplement, read the list of ingredients, she says although this is not always foolproof. “I’ve seen very expensive protein supplements that claim to be high quality but they might not really be beneficial for the average healthy adult,” she says. “It could just be a waste of money.”
F) But there are certain situations that do warrant extra protein. “Anytime you’re in an anabolic state or building muscle,” Pipitone says, such as if you’re an extreme endurance athlete, training for a marathon, or you’re a body builder. If you’re moderately exercising for 150 minutes a week, as the Centers for disease control and Prevention recommends, or less than that, you’re probably not an extreme athlete. Extreme athletes expend lots of energy breaking down and repairing and building muscles. Protein can give them the edge they need to speed along that process.
G) Vegans can benefit from protein supplements since they do not eat animal-based protein sources like meat, dairy, or eggs. And, for someone always on-the-go who may not have time for a meal, a protein snack bar can be a good option for occasional meal replacement. Also, individuals recovering from surgery or an injury can also benefit from extra protein. So, too, can older people. At around age 60, “muscles really start to break down,” says Kathryn Starr, an aging researcher at Duke university School of Medicine, “and because of that, in addition to the fact that as we get older our body's ability to break down protein is reduced, the protein needs of an older adult actually increases.”
H) In fact, along with her colleague Connie Bales, Starr recently conducted a small study that found that adding extra protein foods to the diet of obese older individuals who were trying to lose weight strengthened their muscles. Participants in the study were separated into two groups—one group was asked to eat 30 grams of protein per meal in the form of whole foods. That meant they were eating 90 grams of protein a day. The other group—the control group—was put on a typical low-calorie diet with about 50 to 60 grams of protein a day.
I) After six months, researchers found the high protein group had significantly improved their muscle function —almost twice as much as the control group. “They were able to walk faster, had improved balance, and were also able to get up out of a chair faster than the control group,” Starr says. All 67 participants were over 60 years of age, and both groups lost about the same amount of weight. Starr is now looking into whether high-protein diets also improve the quality of the muscle itself in seniors. She's using CT scans to measure muscle size and fat, and comparing seniors on a high-protein diet to those on regular diets. She says her findings should be available in a couple of months.
J) In the meantime, 70-year-old Corliss Keith, who was in the high protein group in Starr’s latest study, says she feels a big difference. “I feel excellent,” she says, “I feel like I have a different body, I have more energy, I'm stronger.” She says she is able to take Zumba exercise classes three times a week, work out on the treadmill and take long, brisk walks. Keith also lost more than 15 pounds. “I'm a fashionable person, so now I'm back in my three-inch heels,” she says.
K) As people age, researcher Starr says muscle strength is key to helping them stay strong and continue living on their own in their own home. “I feel very much alive now,” says Keith, “I feel like I could stay by myself until I'm 100.”
L) But can people overdo protein? Pipitone says you do have to be careful. Too much protein can cause nausea, cramps, headaches, fatigue, and bloating. Dehydration is also a risk when you eat too much protein. Pipitone says if you increase protein, you also have to increase your fluid intake. “I always tell people to make sure they're drinking enough fluids,” which for the average person is 60 to 70 ounces a day, which translates into eight 8-ounce glasses of water or liquid per day.
M) There have been some indications that extra protein makes the kidneys work harder which could be problematic for individuals with a history of kidney disease and for them, the supplements may increase the risk of kidney stones, she says.
N) Bottom Line: if you think you need more protein in your diet, consider these questions: Are you are an extreme athlete; are you recovering from injury or surgery; or are you are 60 years or older? If so, adding high protein foods like eggs and meat products to your diet can be beneficial. And, if you're not sure, it is always a good idea to check with your primary care provide.
36. It is quite easy for one to take in the recommended amount of protein.
37. Pipitone claims that healthy adults need not spend money on protein supplements.
38. The protein supplement business is found to be thriving.
39. Protein can speed the repairing of damaged muscles.
40. Protein supplements may overburden some internal organ, thus leading to its malfunctioning.
41. Older adults need to take in more protein to keep their muscles strong.
42. Protein is found in more foods than people might realize.
43. Additional protein was found to help strengthen the muscles of overweight seniors seeking weight loss.
44. Pipitone believes that whole foods provide the best source of protein.
45. People are advised to drink more liquid when they take in more protein.
答案解析：
36. 由题干中的关键词“take in the recommended amount of protein”定位到C段。C段提到通过早餐和午餐的搭配，在还没吃晚餐时就能达到美国政府推荐的每日蛋白质摄入量，这表明一个人很容易摄入推荐量的蛋白质，所以选C。
37. 由题干中的关键词“Pipitone”“healthy adults”“spend money on protein supplements”定位到E段。E段中Pipitone说看到很贵的蛋白质补充剂声称高质量，但对普通健康成年人可能没好处，就是浪费钱，即健康成年人不必在蛋白质补充剂上花钱，所以选E。
38. 由题干中的关键词“Protein supplement business”“thriving”定位到A段。A段提到蛋白质补充剂行业今年销售额超过120亿美元，且到2025年还会大幅增长，说明蛋白质补充剂生意蓬勃发展，所以选A。
39. 由题干中的关键词“Protein”“speed the repairing of damaged muscles”定位到F段。F段提到极端耐力运动员等处于合成代谢状态或增肌的人，蛋白质能给他们提供加速肌肉分解、修复和构建过程所需的助力，即蛋白质能加速受损肌肉的修复，所以选F。
40. 由题干中的关键词“Protein supplements”“overburden some internal organ”“malfunctioning”定位到M段。M段提到有迹象表明额外蛋白质会让肾脏工作更努力，对有肾脏疾病史的人来说可能是个问题，补充剂可能增加肾结石风险，即蛋白质补充剂可能使一些内脏器官负担过重，导致其功能障碍，所以选M。
41. 由题干中的关键词“Older adults”“take in more protein”“keep their muscles strong”定位到G段。G段提到60岁左右肌肉开始分解，老年人对蛋白质的需求实际上增加了，即老年人需要摄入更多蛋白质来保持肌肉强壮，所以选G。
42. 由题干中的关键词“Protein”“more foods than people might realize”定位到B段。B段提到蛋白质几乎无处不在，不仅在牛肉、鸡肉等食物中，也在蔬菜、水果等可能不会立刻想到的食物中，即蛋白质存在于比人们想象的更多的食物中，所以选B。
43. 由题干中的关键词“Additional protein”“strengthen the muscles of overweight seniors seeking weight loss”定位到H段和I段。H段和I段描述了给试图减肥的超重老年人饮食中添加额外蛋白质食物的研究，发现高蛋白组肌肉功能有显著改善，即额外蛋白质有助于增强试图减肥的超重老年人的肌肉，所以选H。
44. 由题干中的关键词“Pipitone”“whole foods”“the best source of protein”定位到D段。D段中Pipitone说全食物总是最好的选择，而不是添加补充剂，即Pipitone认为全食物是蛋白质的最佳来源，所以选D。
45. 由题干中的关键词“drink more liquid”“take in more protein”定位到L段。L段提到Pipitone说如果增加蛋白质摄入，也必须增加液体摄入，即建议人们在摄入更多蛋白质时多喝水，所以选L。
