短语讲解：
1. A new study casts doubt on the merits of reducing salt in our diet
.
cast doubt on使人对…产生怀疑
例句：She cast doubt on this news.
她对这消息有所怀疑。
2. Graudal mathematically combined the results of 167 previous studies to come up with his results.
come up with (针对问题等)想出;提供
例句：He came up with good ideas for the product promotion.
他想出一个推广产品的好方法。
3. Even a modest reduction for people with high blood pressure is probably a good thing, but the study also found that people on a low-sodium diet had higher levels of cholesterol, which is associated with an increased risk of heart disease.
associate with与…交往, 联系
例句：The doctor was associated in the child's mind with injections and pains.
在孩子的心里, 医生总是使他联想到打针与疼痛。
4. It might be more helpful to look directly for a link between salt consumption and heart disease or death, but Graudal says very few studies have tried to do that.
look for寻找
例句：She is looking for her lost child.
她正在寻找失去的孩子。
5. "It would be very difficult to make a randomized, a big randomized study and keep people on special diets for many years," he explains.
keep on继续
例句：They kept on working after dark.
天黑了他们还继续工作。
