Final answer:
The reference quantity of food in a database is always per 100 grams, which provides a consistent basis for comparing the nutrient content of different foods. The serving size on food labels indicates the recommended amount to consume, while calories are a unit of energy measurement.
Step-by-step explanation:
When referring to the reference quantity of food in a database, it is typically measured per 100 grams. This standardization allows for a consistent comparison across different foods and nutrient content analyses. On nutrition labels, you'll often find the serving size indicated, which tells you the recommended amount of food to consume to intake the nutritional content listed. Additionally, labels will generally show nutritional information such as calories and macronutrient content both in terms of per serving and as a percentage of daily values based on a 2,000-kilocalorie diet. While the serving size can vary between products, the 100-gram reference is a universal standard for nutritional databases.
It is important to understand the different units used to measure food quantity and nutrient content. For instance, calories are a unit of energy and are equivalent to one kilocalorie (kcal), which is the amount of energy needed to raise 1 kilogram of water by 1 degree Celsius. Similarly, when discussing nutrient or food mass, the gram is commonly used because it is a practical unit of measurement for the quantities typically consumed or used in nutritional studies, as opposed to kilograms, which are too large for these purposes.