雅思阅读 160: What the Science Actually Says About Sports Supplements（运动补剂的真相）

改编自 Nutrients / International Society of Sports Nutrition（2024–2026年）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://pmc.ncbi.nlm.nih.gov/articles/PMC10848936/

Reading Passage

A. Walk into any shop selling sports nutrition and the eye is immediately ambushed. Shelves sag with coloured powders, pills, gels and drinks, each label promising explosive power, instant recovery or an unstoppable engine. Most of what fills these shelves has one thing in common: a claim outrunning the evidence behind it. Athletes, trainers and coaches nonetheless spend enormous sums, because the margin between winning and losing can be a fraction of a second, and any edge that is legal feels worth chasing. Sorting the genuinely useful from the merely advertised is the job of a small branch of science — sports nutrition — which subjects each candidate to controlled trials and ranks them by how strong the proof is. The picture that emerges is less exciting than the marketing but more useful. A tiny number of substances have survived rigorous testing and can honestly be called performance-enhancing. The vast majority cannot, and an athlete who knows the difference is spending money where it actually matters rather than where it glitters. This matters for the wallet as much as the body: a jar of pills that does nothing is still expensive, and a supplement contaminated by an unlisted stimulant can even end a career through a failed drugs test.

B. At the top of the evidence list sits a substance whose fame is well deserved: creatine. It is, researchers consistently conclude, the most studied and best supported of all legal ergogenic aids. The body makes a little of it and obtains a little from meat, but supplementing it saturates the muscles' store of phosphocreatine — the chemical that replenishes the fuel, ATP, during the shortest, hardest efforts. This is why creatine helps precisely in activities measured in seconds: a sprint, a heavy lift, a repeated jump. Trials find improvements of one to five per cent in a single maximal effort, rising to five to fifteen per cent when the effort is repeated several times, with the largest effects in tasks lasting under thirty seconds. Dosed at three to five grams a day, it also modestly increases lean mass, and long-term use has so far shown a clean safety record in healthy people. For a weightlifter or a sprinter it is close to a no-brainer; for a marathon runner, running for hours, it offers little, because its benefits belong to the explosive, anaerobic end of the spectrum.

C. A close second, and the most widely used in the world, is caffeine. Long dismissed as a mere pick-me-up, it is now understood to work on the central nervous system by blocking receptors for adenosine, the chemical that builds up and signals fatigue. By dulling that signal, caffeine makes an effort feel easier, so an athlete can push harder before the brain calls a halt. Taken in a dose of three to six milligrams per kilogram of body weight, roughly half an hour to an hour before exercise, it reliably improves endurance time-trials by a modest two to four per cent — small, but decisive at the front of a race. The response, however, is far from uniform. A person's genes influence how fast they clear caffeine, and regular drinkers build a tolerance that blunts the effect, while doses above the optimum mainly bring jitteriness and sleeplessness without extra gain. Coaches now treat caffeine as a precise tool — a dose, a clock, and an awareness of the individual — rather than a generic boost.

D. Beyond the two giants, a handful of substances occupy a middle tier with narrower, honest roles. Beta-alanine, an amino acid, raises the level of carnosine in muscle and seems specifically to help efforts lasting one to four minutes — the grey zone between a sprint and a run — though it causes a harmless tingling that surprises first-timers. Dietary nitrate, found in beetroot juice, widens blood vessels and can make endurance effort a little more economical, though again the gain is modest and variable. Protein, finally, is not exotic but essential: after hard training, an adequate intake supports the repair that makes the body stronger. What trials have repeatedly failed to support is the long catalogue of expensive products that promise synergy, fat-burning or "activation". Combining creatine with caffeine, for instance, has produced mixed results, with several studies finding no extra benefit from taking both at once. The marketing rule of thumb — stack everything for maximum effect — runs directly against the evidence, which rewards choosing the few that fit the event and ignoring the rest.

E. The honest conclusion for an athlete is humble. Supplements, even the best, buy small gains measured in single percentages. The giant determinants of performance remain unglamorous: total training, sound technique, enough sleep, enough total energy and protein, and a diet of ordinary food. No powder compensates for those being wrong, and an athlete who supplements while under-sleeping has spent well and trained badly. Younger athletes, in particular, are targeted by advertising that implies a product is essential, when for them a balanced diet of ordinary food almost always supplies what a growing body needs, and supplements are rarely worth the cost until training volume is genuinely high. This is not an argument against the useful few but a warning against the industry's real product, which is hope. Creatine and caffeine, used correctly, are legitimate tools; the other hundred products on the shelf are mostly taxes on anxiety. A coach who knows the evidence can spend an athlete's budget well instead of hoping for alchemy. The most nutritional edge, in the end, is the one most athletes already know — train hard, eat real food, sleep, and let the two or three substances with actual evidence do their modest, honest work.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. A market where most claims outrun the evidence ii. The best-supported supplement of all: creatine iii. How caffeine quietly changes the brain's sense of effort iv. A long list of products that failed the trials v. The middle tier and the myth of "stacking" everything vi. The vitamin that replaces sleep entirely vii. A humble conclusion: supplements buy only a small edge

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. In which kind of activity does creatine help most? A. A multi-hour marathon. B. Short, explosive efforts such as sprints and heavy lifts. C. Long-distance swimming. D. Pure mental concentration.

6. How does caffeine mainly work? A. It directly supplies energy to the muscle. B. It blocks adenosine receptors, blunting the feeling of fatigue. C. It builds new muscle fibres. D. It slows the heart rate.

7. What effect does nitrate from beetroot juice have? A. It doubles sprint speed. B. It widens blood vessels and may make endurance effort slightly more economical. C. It has no effect at all. D. It causes permanent tingling.

8. What did studies find about taking creatine and caffeine together? A. It reliably doubles performance. B. Several found no extra benefit from combining them. C. It is always dangerous. D. It is required by anti-doping rules.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. Creatine improves repeated high-intensity efforts by roughly five to fifteen per cent in trials.
10. Caffeine taken at any dose always improves performance without side effects.
11. Regular caffeine drinkers can build a tolerance that blunts its effect.
12. Beta-alanine mainly helps efforts lasting more than two hours.
13. Most athletes who use supplements have already trained poorly.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

Creatine saturates the muscles' store of (14) __________, replenishing ATP during brief, hard efforts, whereas caffeine works centrally by blocking (15) __________ receptors.

答案与解析

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