Fats

The second primary nutrient is fat. Like carbohydrates, fats provide energy (nine calories per gram). However, fats also serve a variety of other functions in the body. These functions include (1) offering protection for the other tissues (i.e. the major organs of the body), (2) allowing insulation from the cold, (3) storing the fat-soluble vitamins, and (4) comprising the major structural component of cell walls.

Fats can be classified as (1) saturated, (2) poly-unsaturated or (3) mono-unsaturated. The saturation of each type of fat is based on the number of hydrogen ions attached to the fat molecule. Saturated fats have the most hydrogen ions attached, the poly-unsaturated fats have less, and the mono-unsaturated fats have the least hydrogen ions.

Saturated fats are the least healthy of the three types of fats and are characterized by remaining solid at room temperature. Common examples include lard and butter. Even though this type of fat is the least healthy, it is still required by the body in small amounts and therefore should not be totally eliminated from the diet.

Poly-unsaturated fat is healthier than saturated fat and is characterized by being semi-solid at room temperature. Many of today’s margarines and butter alternatives are made with poly-unsaturated fats and thus require refrigeration.

Mono-unsaturated fat is the healthiest of the fats and remains liquid at room temperature. Examples of mono-unsaturated fats include most natural oils, such as olive oil.

Food items that contain mono-unsaturated fats but have been hydrogenated (meaning that hydrogen ions have been added) are less healthy than non-hydrogenated fats. One must be careful to read the ingredients of each food eaten to watch for mono-unsaturated fats that have been hydrogenated called partially hydrogenated oils.

Shortly, food labels in the US will also list these “transfats” in the food item which will help us avoid this potentially unhealthy type of “hydrogenated” fat.

Experts recommend that distance runners obtain 20 to 30 percent of their daily calories from fats. In addition, approximately one-third of one’s fat calories should come from each type of fat (saturated, poly-unsaturated and mono-unsaturated).

All excess fat in the diet will be stored as adipose (fat) tissue, which increases “dead” body weight and decreases performance. Examples of foods containing significant amounts of fats are lard, butter, meats, some dairy products and most varieties of oils.

Fats should be avoided prior to a race or hard workout. Fats are slow to empty from the stomach and may cause cramps, due to the decreased blood flow to the stomach which occurs during running.

Protein

The third primary nutrient is protein. Experts can’t agree but the ranges recommended are from 10 to 30 percent of their daily calories from protein for runners. The average American eats two to three times the protein requirement each day but finicky runners (and those who break down easy from hard training) may need to focus on their protein intake.

Proteins are composed of small substances called amino acids. They function as the major component of every structure in the body and also provide four calories of energy per gram, though you hope that you don’t regularly have to ‘burn’ protein for energy.

As a result of training and racing, our muscles and tendons experience small tears or micro-traumas which are repaired by the protein in our diet. This fact is why we even see a renewed focus on adding some protein to the traditionally carbohydrate-loaded recovery drinks. Some athletes even find that supplementing with protein powder aids their recovery. Excessive protein in the diet places great strain on the kidneys so there’s no need to eat like a body builder. Meats, beans and nuts are common examples of foods which contain significant amounts of protein.

脂肪

第二种主要营养素是脂肪。和碳水化合物一样，脂肪也能提供能量（每克9卡），但是脂肪同时在体能还有其他功能。这些功能包括（1）为组织（比如身体的主要器官）提供保护；（2）隔离寒冷；（3）储存脂溶性维生素；（4）细胞壁的主要结构组成物。

脂肪可以分为（1）饱和脂肪酸（2）多不饱和脂肪酸（3）单不饱和脂肪酸。每种脂肪酸的饱和程度是基于脂肪分子上的氢原子数量而划分的。饱和脂肪酸上的氢原子最多，多不饱和脂肪酸要少一些，而单不饱和脂肪酸的氢原子最少。饱和脂肪酸是三种脂肪中最不健康的，在室温下保持固态，包括猪油和黄油。尽管这种脂肪最不健康，身体依然需要少量，因此不能从饮食中完全去除。

多不饱和脂肪酸比不饱和脂肪酸要健康一些，在室温下保持半固态。现在许多人造奶油和黄油都是用多不饱和脂肪酸做的，因此需要冷冻保藏。

单不饱和脂肪酸是最健康的脂肪，在室温下保持液态。常见的包括植物油如橄榄油。

那些包含单不饱和脂肪酸但是被氢化（添加氢原子）的食物比没有氢化的要不健康。每种食物的成分都必须认真看看，是不是氢化的单不饱和脂肪酸，也就是所谓的部分氢化油。

最近，美国食品标签上同时列出了“反式脂肪酸”，这有助于帮助我们避免可能存在的不健康的氢化脂肪。

专拣建议在长跑选手每日摄取的热量中应当有20-30%来自脂肪。同时来自每种脂肪（饱和、多不饱和和单不饱和）的热量应该大致各占1/3。

饮食中额外的脂肪都将储存为脂肪组织，也就是为增加身体的死重量，降低跑步水平。含有很多脂肪的食物包括猪油、奶油、肉、一些乳制品和绝大多数各种油。

在比赛或强度训练前要避免摄入脂肪。脂肪很难从胃中排空，这会在跑步中由于流向胃的血液减少而导致胃痉挛。
蛋白质

第三种主要营养素是蛋白质。专家推荐跑步者每日摄取的热量应当有10-30%来自蛋白质。美国人每天平均摄入的蛋白质超过需要的2-3倍，但是讲究的跑步者（以及那些很容易在强度训练中放弃的跑步者）需要注意他们摄入的蛋白质量。

蛋白质是由氨基酸小分子组成的，他们是身体中所有器官的主要组成物质，同时每克可以提供4卡的热量，即使你并不希望依靠燃烧蛋白质来获得能量。

在训练和比赛之后，我们的肌肉和肌腱会出现小疲劳或微创伤，这就需要我们饮食中的蛋白质。这就是为何我们发现在传统的以碳水化合物为基础的恢复性饮料中又开始强调加入蛋白质。一些运动员甚至发现补充蛋白粉可以有助于他们恢复。饮食中过量的蛋白质会对肾产生很大的压力，因此不必摄入像在身体发育阶段那样多的蛋白质。肉、豆类和坚果是常见的富含蛋白质的