But the earlier research did not distinguish between two different forms of the vitamin.“Preformed”vitamin A, known as retinol, is found mainly in liver and dairy products like milk, cheese, butter and eggs.But vitamin A is also made in the body from carotene, which is abundant in a variety of vegetables and fruits, including carrots, spinach, squash, tomatoes, sweet potatoes and apples.
In the Western Electric study, Shekelle and his colleagues found little correlation between the incidence of lung cancer and the consumption of foods containing preformed vitamin A.But when they examined the data on carotene ntake, they discovered a significant relationship.Among the 488 men who had the lowest level of carotene consumption, there were fourteen cases of lung cancer; in a group of the same size that ate the most carotene, only two cases developed.The apparent protective effect of carotene held up even for longtime smokers - but to a lesser degree.
Further studies will be necessary before the link between lung cancer and carotene can be firmly established.In the meantime, researchers warn against taking large number of vitamin A pills, because the tablets contain a form of the chemical that can be extremely toxic in high doses.Instead, they advise a well-balanced diet that includes foods rich in carotene.For a smoker, a half-cup of carrots every day might possibly make the difference between life and death.
1.What does“malignancy”in the text refer to?A.Cancer.B.Sickness.C.Vitamins.D.Disease.
2.Dr.Richard Shekelle.
A.is leading the nutrition study.
B.works in a Chicago medical center.
C.has been studying the links between food and cancer.
D.all of the above.
3.Why did Dr.Shekelle think the correlation between vitamin A and lung cancer protection was logical?A.Vitamin A causes lung cancer.
B.Vitamin A cures lung cancer.
C.Vitamin A is necessary for the growth of the tissue lining the lungs.
D.Vitamin A is a molecule that prevents smoke from being inhaled.
4.Among the groups studied, who had the most cases of lung cancer?A.Those with the lowest level of carotene intake.
B.Those with the highest level of carotene intake.
C.Those who ate only foods containing carotene.
D.Those with the lowest intake of carrots.
Living in an unfamiliar country
Leaving home to live in an unfamiliar country will bring a few surprises and can be stressful but it may help to understand that it is perfectly normal.Some of the differences include:
The Weather
The weather in the UK is very unpredictable and changeable.Differences between the seasons may not be as extreme as in some countries and although London is warmer than many other parts of the UK it can get very cold,particularly between November and February (below 0 ℃/ 32 ℉).
The temperature often seems lower than it is because it can be very windy and wet, and the air is often damp.Autumn temperatures are around 12～20 ℃ (54～68 ℉).Summer is around 20～30 ℃ (54～86 ℉).It rains all year round.
The sky is often grey and it may take you some time to adapt to this.You can check the latest weather report for London at the Met Office website.
The Weather
The weather in the UK is very unpredictable and changeable.Differences between the seasons may not be as extreme as in some countries and although London is warmer than many other parts of the UK it can get very cold,particularly between November and February (below 0 ℃/ 32 ℉).
The temperature often seems lower than it is because it can be very windy and wet, and the air is often damp.Autumn temperatures are around 12～20 ℃ (54～68 ℉).Summer is around 20～30 ℃ (54～86 ℉).It rains all year round.
The sky is often grey and it may take you some time to adapt to this.You can check the latest weather report for London at the Met Office website.
Food
British food has in recent time improved considerably, particularly in London.This trend can be seen in the ever-expanding range of foods available in large supermarkets, high profile chefs becoming celebrities and the growing number of restaurants.London is the largest and most ethnically diverse city in Europe with a population of just under 8 million people.The vast array of food and restaurants available in London reflects this diversity.
The types of cuisines available range from African,Eastern European，Mexican,Russian, Scandinavian, Vietnamese and many more.And of course it is possible to go for the more traditionally English such as roast beef and Yorkshire pudding, fish and chips and afternoon tea.It is particularly easy to find food and ingredients for cooking from China, Japan and India in many parts of London.When you get here, speak to students from your country to find out where they buy supplies.
Language
If English is your second language, you may have learned a lot from books and English classes.Even students with a high level of English find the regional accents and colloquialisms in English very difficult.Practice English as much as possible before you get here.Listen to an English-speaking radio (for example,the BBC World Service),watch films and speak to native English speakers in your country if you can.You can also learn online at the British Council.
Social Behaviour
Smoking: Smoking is banned in many public places and on public transport in the UK.All college sites at the University are non-smoking.The place where people smoke most is in pubs.Most cafes and restaurants have non-smoking areas.