This window is what you see first on starting Gnutrition:

List of foods eaten in a day, to calculate total intake
Views a particular recipe.
Analyses a Single Food
The Single Food screen is good place to start. By clicking in the ``single banana'' icon, this screen in displayed:

Gnutrition can only analyse the foods present in its database. Press the ``Search'' button, to show the search window:

In this example, I searched by the word ``apple'' The database produces dozens of options for this word, such as ``Babyfood, fruit, applesauce, strained'', or ``Pie, apple, prepared from recipe'' This are displayed in a tree format, with the first word forming the header, the second the sub-header, etc. You must explore the tree to find the one you what, cicking on the little pluses, explodes the sub-hierarchy of foods. In this example, I have selected ``Apples, raw, with skin'':

In the ``Search'' window, ``Nutrient Search'' can be selected:

Foods are selected by their nutrient content. ``Content'' can be assessed by grams (weight), or calories (energy).
You can maximise nutrients, selecting foods rich in those nutrients, or minimise nutrients, selecting foods low in that nutrient.
The ``constraint'' refers to a weighting given to each nutrient in computing its score. So nutrient with a constraint of 3 will be three times as important in calculating the score, as one with a constraint of 1.
The minimised nutrients have a negative constraint, as they subtract from the score. The search gives the foods with the highest score by this method.
The foods are displayed in a tree as for the ``Search by Name'' box.
When you have found the food you what, press the ``OK'' button, and you will return to the main screen with your food selected:

To understand what all these mean, refer to the Nutrient Notes