【英语生活】低钠高钾 健康生活

A new study suggests that in addition to cutting the amount of sodium in their diets to improve heart health, Americans should also increase consumption of a key mineral found in many fruits and vegetables: potassium.

The study, lead by researchers at the Centers for Disease Control and Prevention, looked at more than 12,000 adults who participated in a federal nutrition study. It tracked their diets and followed them for nearly 15 years to observe rates of cardiovascular disease, heart attacks and death. The study was published in this week's Archives of Internal Medicine.

Sodium, a key component of salt, has been shown to raise blood pressure, which in turn raises the risk of heart disease, but studies have shown inconsistent results as to whether high-sodium diets actually boost the risk of heart-related problems. Potassium has been found to offset sodium's impact on blood pressure.

The study, which looked at sodium and potassium intake, found that higher sodium intake was associated with a higher risk of premature death from any cause, while higher potassium intake was associated with a lower risk of dying prematurely. Looking at heart-related deaths alone, sodium itself wasn't associated with an increased risk, but researchers said higher potassium intakes were linked with lower heart-related death rates.

Researchers then looked at what is called the sodium-potassium ratio. A high sodium-potassium ratio means a person consumes more sodium relative to potassium. Sodium-potassium ratios could be improved by either lowering sodium intake or raising potassium intake, or both.

The study found that people with the highest ratios were more than twice as likely to die from a heart attack compared with those with the lowest ratios. They also were 46% more likely to die from a heart-related death compared with those with the lowest ratios. (Looking at all causes of death, people with high ratios saw a 46% higher risk.)

'When you have a more imbalanced diet, you are more at risk,' says Elena Kuklina, an epidemiologist at the CDC's division for heart disease and stroke prevention.

An easy way for people to improve their sodium-potassium ratios is to eat more fruits and vegetables, researchers said. About 80% of the sodium consumed by Americans comes from processed or restaurant foods, making it harder to lower sodium intake than it is to raise potassium intake.

The most recent U.S. dietary guidelines, released earlier this year, recommend adults consume 4,700 milligrams of potassium a day.

Foods high in potassium include potatoes, spinach, bananas, prune juice, plain yogurt and fish. People with chronic kidney disease may need to limit potassium intake. The guidelines called on Americans to reduce their daily sodium intake to less than 2,300 milligrams, or about a teaspoon of salt. For people who are 51 and older, African-American or have hypertension, diabetes, or chronic kidney disease, recommendations call for no more than 1,500 milligrams a day. The average American adult consumes 3,400 milligrams of sodium a day.

一项新的研究显示，想让心脏变得更健康，除了要减少饮食中钠的摄入之外，还应该增加一种重要矿物质的摄入，这就是许多果蔬中都含有的钾元素。

Associated Press香蕉，一种钾的来源这项由美国疾病控制与预防中心(Centers for Disease Control and Prevention)主导的研究对超过1.2万名参与一项联邦营养学研究项目的成年人进行了研究。它对参与者的饮食情况予以记录，对他们跟踪研究了近15年时间，以此观察心血管疾病和心脏病的发生概率以及受访者的死亡概率。该研究结果最近已刊登在《内科学档案》(Archives of Internal Medicine)杂志上。

钠是盐的重要成分，有迹象表明它会使血压升高，进而增加心脏病发作的风险，但至于高钠饮食是否真的会增加心脏相关疾病发作的风险，各种研究结果却是说法不一。有研究发现，钾可以抵消钠对血压带来的影响。

前述新研究在对钠和钾的摄入情况进行观察后发现，较高的钠摄入量与任何原因导致的过早死亡风险偏高均有关联，而较高的钾摄入量则与过早死亡风险降低有关联。仅以与心脏病有关的死亡情况为例，钠本身与死亡风险的上升并没有关系，但研究人员说，较高含量的钾摄入却是与心脏病有关的死亡率比较低有关联。

然后，研究者对钠-钾比例进行了研究。钠-钾比例高说明一个人摄入的钠相对于钾来说要更多。改善钠-钾比可以通过减少钠的摄入或是增加钾的摄入来实现，或是两种方法双管齐下。

该研究发现，钠-钾比最高的人群，他们因心脏病去世的可能性是钠-钾比最低人群的两倍还不止。相比后者，他们死于心脏相关疾病的可能性也要高出46%。（对所有死亡原因进行分析后发现，拥有较高钠-钾比的人的死亡概率要高出46%。）

美国疾病控制与预防中心下属心脏病及中风预防部门的流行病学家库克丽娜(Elena Kuklina)说，当你的饮食变得不均衡时，风险也随之增加了。

研究人员说，降低钠-钾比的一个简单方法是多吃水果和蔬菜。美国人摄入的约80%的钠都来自加工食品或是餐厅饭菜，因此相对于增加钾的摄入量来说，减少钠摄入量的难度就要更大一些。

今年早些时候公布的最新版本美国饮食指导建议成人每天摄入4,700毫克的钾。

富含钾的食物包括土豆、菠菜、香蕉、西梅汁、原味酸奶以及鱼。患有慢性肾病的人可能需要对钾的摄入量有所限制。这份饮食指导建议美国人将他们每日的钠摄入量减少到2,300毫克以下，也就是大概一茶勺的盐。对于51岁以上人群、非洲裔美国人和高血压、糖尿病以及慢性肾病患者，则建议将每天的钠摄入量控制在1,500毫克以内。目前，普通美国成年人每日的钠摄入量为3,400毫克。