Scientists have revealed just how dangerous energy drinks can be, and can cause a sudden heart attack in some cases. While we all probably assumed that the large amounts of caffeine contained in these drinks probably weren’t great for our health, a study has now explored how another common ingredient could be dangerous.

Guarana, a plant containing caffeine, is commonly used in energy drinks and can often lead to unexpected reactions when combined with other ingredients. In the case of energy drinks, guarana is often combined with ginseng(西洋参) or taurine(硫磺酸) to improve flavouring.

A study explained the risk of sudden cardiac(心脏的) events in young people after consuming such drinks. They wrote: “It seems clear that energy drinks might lead to critical events relating to the heart and blood vessels in the young population, even some of which are unable to recover.” The scientists wrote that such drinks can lead to fatal events, with heart attacks often occurring without warning.

A 2021 Australian study, published in the Nutrition Journal, surveyed 8942 students aged from 12 to 17 years old. Of the sample, they found that eight percent of students reported drinking energy drinks at least once a week, while one in four students had consumed energy drinks at least once. 

While a study of a 21-year-old UK man was published in BMJ Case Reports in 2021, who had unexpectedly been experiencing kidney failure(肾衰竭). The report stated: “There was no significant past medical history and he had no family history of heart attacks.” However, the man had explained he had been drinking four 500 ML energy drinks a day for approximately two years—with each drink containing 160 mg of caffeine. The study added: “Given the history of long-term energy drink consumption, lack of significant past medical or family history, cardiac imaging(心脏影像) findings and improvement with ceasing intake, energy drink-caused cardiotoxicity(心脏毒性) was felt to be the most likely cause.”

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1.Why is guarana used in energy drinks?

A To improve people’s health.

B To find out a new ingredient.

C To make drinks taste better.

D To test the unexpected reactions.

解析：选C。C细节理解题。根据第二段最后一句“In the case of energy drinks, guarana is often combined with ginseng or taurine to improve flavouring.”可知，功能饮料中使用guarana是想让饮料的口味更好。故选C。

2.Which feature of cardiac events is NOT mentioned in Paragraph 3?

A They can be irreversible.

B They can cause death.

C They give no warning signals.

D They widely occur in certain areas.

解析：选D。D细节理解题。根据第三段内容可知，突发心脏疾病有三个特点：有些心脏疾病不可逆转(even some of which are unable to recover)；引发死亡(such drinks can lead to fatal events)；发生之前通常毫无预警(heart attacks often occurring without warning)。只有D项“它们在某些区域广泛发生”没提到。故选D。

3.Why did the writer mention the example of a 21-year-old UK man?

A To show the potential dangers of energy drinks.

B To advise people to focus on past family history.

C To ask people to stop their own bad habits.

D To experience the kidney failure when young.

解析：选A。A推理判断题。 根据最后一段的“energy drink-caused cardiotoxicity was felt to be the most likely cause”可知，研究报告得出结论，这名21岁英国男子肾衰竭是由于摄入功能饮料，因此作者提及这个案例就是为了表明功能饮料的潜在危害。故选A。

4.What’s the main idea of the passage?

A Large amounts of caffeine are contained in drinks.

B Drinking energy drinks causes sudden heart attacks.

C People should pay more attention to cardiac health.

D Energy drinks are the most dangerous in our life.

解析：选B。B主旨大意题。根据全文内容可知，作者主要介绍了摄入功能饮料可能引发心脏病这一研究结果。故选B。