- It must be supplied by food, because the body cannot create it in sufficient quantities
- If the nutrient is missing, it results in a deficiency disease
- When added back to the diet, the disease corrects
- Explanation exists as to why the abnormalities occurred when the substance was missing.
## Phytochemicals
Phytochemicals are substances in plants that *may* have healthful benefits. Examples of phytochemicals include:
- Caffeine
- Beta-carotene
- Nicotine
## Calories
In nutrition, the term Calorie typically refers to a kilocalorie, or 1000 calories, where a calorie is the amount of energy needed to heat up one gram of water one degree Celsius.
| Nutrients | The life sustaining substances found in food. Necessary for growth, maintenance, and repair. |
| Nutrition | The study of how nutrients affect our body. |
| Diet | A person's usual pattern of food choices. Everyone has a diet, and you don't begin and end diets, you just make changes to your existing diet. |
| Lipid | Fat |
| Organic | An organic substance contains *carbon*, and can be degraded. |
| Essential nutrient | A nutrient is considered *essential* if it *must* be supplied by food, because the body cannot create it in sufficient quantities. If an essential nutrient is missing, it results in a *deficiency disease*. |