Whole grains are good for your heart. How do you know if you’re eating enough?

Christopher Dilts/Bloomberg Creative/Getty Images

The secret is out: Eating whole grains is good for you.

Extensive research in the past two decades has shown that a diet rich in whole grains is associated with lower risks of heart disease, high blood pressure, high cholesterol and type 2 diabetes and helps people maintain a healthy weight .

In a new analysis, researchers reviewed dozens of studies to drill down on how whole grains contribute to cardiovascular and metabolic health at a molecular level — and how much you have to eat to make a difference.

The results, published Tuesday in the European Heart Journal , suggest that the benefits start at about 90 grams, or three servings, per day — about as much as you’d get from two slices of whole wheat bread and a bowl of oatmeal. Eating four to six servings per day is even more powerful, according to the study.

The researchers found evidence that people who ate three to six servings of whole grains for a prescribed period of time — as little as two weeks and up to two years — had slightly improved levels of about a dozen markers of health, including total cholesterol, LDL (low-density lipoprotein or “bad”) cholesterol, blood pressure, body weight and waist circumference, all of which are associated with a greater risk of cardiovascular disease. Though the effects were small, taken together, the findings back up what large population studies have found, said Dagfinn Aune, a coauthor on the meta-analysis.

Therefore, there is “likely a causal effect” from eating whole grains, and “this may translate into a reduced risk of cardiovascular disease,” Aune, a research fellow in the department of epidemiology and biostatistics at the Imperial College London’s School of Public Health, concluded.

But that doesn’t mean you can add two pieces of whole wheat toast to your morning bacon and eggs and expect to improve your heart health.

Doctors recommend choosing whole grains over products made with refined grains for heart health.

Whole grain foods — such as oatmeal, brown rice, whole wheat bread, farro, popcorn and quinoa — include all the parts of a grain as it exists in nature. Refined grains (think white rice and anything made with white flour) are processed to remove the less palatable parts, which are also where most of the fiber and other nutrients are found.

Get to know farro and other superfood whole grains

Eating whole grain food is important, but a single dietary swap is not going to prevent heart disease, Alice Lichtenstein, a professor at the Friedman School of Nutrition Science and Policy at Tufts University in Medford, Massachusetts, told CNN.

“If you eat a cinnamon bun made of whole grain, as opposed to a cinnamon bun made with refined grain, I’m not sure you’re going to see a benefit,” said Lichtenstein, who was not involved in the new meta-analysis.

And just adding more carbs to your diet to achieve a whole grain target could lead to weight gain, she added.

Most people in the United States don’t eat the two to four servings of whole grains a day suggested in the federal government’s latest Dietary Guidelines for Americans . A serving could be a single slice of whole wheat bread, or half a cup of cooked oats, brown rice or quinoa.

The American Heart Association recommends eating foods made with whole grains, but it doesn’t specify a target amount to aim for each day. That’s because there’s no one amount that’s clearly most effective or that is right for every person’s body, genetics and lifestyle, said Lichtenstein, who was lead author of the nonprofit’s dietary guidelines published in March. Rather than nail down a magic-bullet number of any particular good-for-you food, “we’re trying to keep the focus on the dietary pattern.”

In addition to whole grains, the guidelines emphasize eating a variety of vegetables and fruits and limiting saturated fat, added sugar and salt, ultraprocessed foods and alcohol.

If it helps to have a goal in mind, replacing three servings of refined grains with whole grains every day could be a good place to start.

“My suggestion is as items run out in the pantry, replace them with whole grain versions,” Lichtenstein said.

That’s not always as easy as it sounds, she warned. Dark brown breads and products labeled as “multigrain” or “made with whole grain” may be predominantly made up of refined flour.

“Turn the package over and look at the ingredient list,” she said. “The first ingredient should be a whole grain.” If it’s not, she advised, leave it on the shelf.

Get inspired by a weekly roundup on living well, made simple. Sign up for CNN’s Life, But Better newsletter for information and tools designed to improve your well-being.

Christopher Dilts/Bloomberg Creative/Getty Images

秘密已经揭晓：吃全谷物对你有好处。

过去二十年的大量研究表明，富含全谷物的饮食与降低心脏病、高血压、高胆固醇和 2 型糖尿病的风险有关，并有助于人们保持健康的体重。

在一项新的分析中，研究人员回顾了数十项研究，深入探讨了全谷物如何在分子水平上促进心血管和代谢健康，以及你需要吃多少才能产生效果。

周二发表在《欧洲心脏杂志》上的研究结果表明，每天摄入约90克（相当于三份）全麦面包即可获益——这大约相当于两片全麦面包和一碗燕麦片的营养成分。研究还发现，每天食用四到六份全麦面包效果更佳。

研究人员发现，在规定的时间内（最短两周，最长两年），每天食用三到六份全谷物的人，其十几种健康指标略有改善，包括总胆固醇、低密度脂蛋白胆固醇（LDL，即“坏”胆固醇）、血压、体重和腰围，所有这些指标都与心血管疾病风险增加有关。该荟萃分析的合著者达格芬·奥恩表示，虽然这些改善幅度较小，但综合来看，这些发现与大型人群研究的结果相符。

因此，食用全谷物“很可能具有因果效应”，并且“这可能转化为降低患心血管疾病的风险”，伦敦帝国理工学院公共卫生学院流行病学和生物统计学系的研究员奥恩总结道。

但这并不意味着你可以在早晨的培根鸡蛋中加入两片全麦吐司，就期望改善心脏健康。

为了心脏健康，医生建议选择全谷物食品，而不是精制谷物制品。

全谷物食品——例如燕麦片、糙米、全麦面包、法罗小麦、爆米花和藜麦——保留了谷物天然存在的全部成分。精制谷物（例如白米和任何用白面粉制成的食品）经过加工，去除了口感较差的部分，而这些部分恰恰是膳食纤维和其他营养物质的主要来源。

了解法罗小麦和其他超级食品全谷物

马萨诸塞州梅德福市塔夫茨大学弗里德曼营养科学与政策学院的教授爱丽丝·利希滕斯坦告诉 CNN，食用全谷物食品很重要，但仅仅改变一种饮食习惯并不能预防心脏病。

“如果你吃的是用全麦面粉做的肉桂卷，而不是用精制面粉做的肉桂卷，我不确定你会看到什么好处，”利希滕斯坦说道，他没有参与这项新的荟萃分析。

她补充说，仅仅为了达到全谷物摄入目标而在饮食中增加碳水化合物的摄入量可能会导致体重增加。

美国大多数人都没有达到联邦政府最新发布的《美国膳食指南》建议的每天摄入两到四份全谷物的标准。一份全谷物可以是一片全麦面包，也可以是半杯煮熟的燕麦片、糙米或藜麦。

美国心脏协会建议食用全谷物食品，但并未具体规定每日摄入量目标。该协会膳食指南的主要作者利希滕斯坦表示，这是因为没有一个特定的摄入量是绝对最有效或最适合每个人的，无论其体质、基因还是生活方式如何。该指南于今年3月发布。与其设定某种特定有益健康食物的“神奇”摄入量，我们更倾向于关注膳食模式。

除了全谷物外，该指南还强调食用各种蔬菜和水果，并限制饱和脂肪、添加糖和盐、超加工食品和酒精的摄入。

如果设定一个目标会有帮助，那么每天用全谷物代替三份精制谷物可能是一个不错的开始。

“我的建议是，当食品柜里的某些东西用完时，用全谷物版本代替，”利希滕斯坦说。

她警告说，这并不总是像听起来那么容易。深棕色的面包和标有“多谷物”或“全谷物制成”的产品可能主要由精制面粉制成。

“把包装翻过来，看看配料表，”她说。“第一种配料应该是全谷物。” 如果不是，她建议，就别买了。

每周精选健康生活小贴士，助您轻松享受美好生活。订阅 CNN 的“生活更美好”电子报，获取提升幸福感的资讯和实用工具。