Essential Nutrients

So we know thr are 6 essential nutrients - carbohydrates, lipids, proteins, vitamins, minerals and water.  What you may not know about carbohydrates is that they essentially break down to be sugars - Glucose. Sugars or Glucose are what the body uses for energy. All the carbohydrates we ingest are derived from plant sources. So there are complex carbohydrates which derive starches as we know as bread, cereal, flour, pasta, nuts, rice and potato. And there are simple carbohydrates which are simple sugars in carbonated drinks, candy, fruit, young immature vegetables. And we cant forget fibre - polysaccarides provide in the form of Cellulose, found in most vegetables, we cant digest it but it is necessary to facilitate defecation - thats right - the poop shoot. Then there is soluble fibre, found in pectin in apples, in citrus fruits, and this reduces blood cholesterol.
So if you get your apple or 2 a day, you are reducing your blood cholesterol.
There is a misconception that athletes need to eat large amounts of protein to improve performance and maintain muscle mass.
But actually a diet rich in complex carbohydrates is much more effective in sustaining intense muscle activity, because excess sugars or Glycogen from the carbs is stored in muscles.
Alot of athletes practice glycogen loading or 'carbo loading'. which tricks the muscles into storing more glycogen. they eat a diet of 75% carbs for 3 - 4 days before an event while decreasing activity. It has been shown that it improves performance and endurance.
Human Anatomy & physiology, Marieb & Hoen, 8th Ed