They don't call protein one of "the building blocks of life" for nothing. This macronutrient makes up the major component of all our cells and provides the essential amino acids that keep our bodies up and running. Problem is, some of us aren't getting as much of it as we should be.
人们将蛋白质称作"生命的基石"之一并不是毫无来由的。这一常量营养素是人体所有细胞的主要成分，提供人体所需的氨基酸（保持身体正常运转）。问题是，有些人摄入的蛋白质还不够。

A true protein deficiency is very rare in the United States-though it can be seen in people who have anorexia, cancer, or, in the case of severe malnutrition, undiagnosed Crohn's disease-but sometimes, vegans or people who follow a raw food diet could find themselves running a little low, says Leslie Bonci, a nutritionist, owner of Active Eating Advice, and nutrition consultant for the Kansas City Chiefs.
在美国，真正缺乏蛋白质的案例十分罕见--尽管厌食症、癌症或严重营养不良、未确诊的克罗恩病的患者会发生这一情况--但有时候，素食者或生吃食物的人群也会发现自己摄入的蛋白质含量较低，Active Eating Advice的所有者、Kansas City Chiefs的营养顾问莱斯利·邦思营养师说道。

"We have all these plant-based foods in the marketplace, but [in terms of protein], they're not all created equal," Bonci explains. Take milk, for example: One cup of 1% cow's milk contains about 8.5 grams of protein, while a cup of almond milk only contains just 1 gram.
"市场上有很多植物性食物，但就蛋白质而言，它们的成分并不均等，"邦思解释道。以牛奶为例：一杯1%浓度的牛奶含有约8.5克蛋白质，而一杯杏仁奶仅含1克。

1. You're prone to stress fractures
1. 你很容易患应力性骨折

Your bones need more than just a healthy dose of calcium-they also need enough protein, too. That was the conclusion from a 2018 research review from some of the world's leading osteoporosis foundations, which found that eating a protein-rich diet can help protect your bones.
健康的骨骼不仅需要摄入足量的钙元素--而且还需要足量的蛋白质。一些世界领先的骨质疏松症基金会于2018年写了一篇研究综述，综述发现了如是结论，吃富含蛋白质的饮食有助于保护骨骼。

When we aren't getting enough protein to fuel our organs and brain, our bodies borrow from other areas, including the storages in our skeletal muscle tissue, says Bonci. Without the support of strong skeletal muscle tissue, our bones are more susceptible to injures like fractures.
当我们没有摄入足够多的蛋白质来为器官和大脑供给能量时，我们的身体会从其它地方借用蛋白质，包括骨骼肌组织中存储的蛋白质，邦思说道。失去强有力的骨骼肌组织的支撑，我们的骨骼就更易受到骨折等伤害

2. Your hair and nails look brittle
2. 你的头发和指甲看上去很脆弱

Because protein is an essential part of your hair and nails, your nails can feel softer and your hair can become more brittle over time, says Bonci. "The hair can lose some of its luster, and may not be quite as thick as it used to be," she explains. "It may also start to split."
因为蛋白质是头发和指甲的重要组成部分，所以随着时间的推移，你的指甲会变软、头发也会更脆弱，邦思说道。"头发会渐渐失去光泽，可能也不如以前那般浓密，"她解释道。"可能会开始分叉。"

After a few months of not eating enough protein, you may also experience some hair loss, according to the American Academy of Dermatology.
连续几个月没有摄入足够的蛋白质之后，你可能会开始脱发，美国皮肤病学会表示。