We'll start this module with the basics of nutrition and diet required for basic human functioning as well as good health. Nutrition basics start with the idea of a balanced diet, which should provide the essential nutrients for daily human activities, growth and tissue repair, and overall health, that have been demonstrated by years of research on human nutritional needs. Figure 3.1.1 shows one recent attempt to summarize this scientifically grounded view of a balanced diet in an accessible way as a "healthy eating plate". You'll notice that the sections addressing diet throughout module 3 will refer back to the concept of balanced combinations of nutrients from different food sources that create this balanced diet. It is also important to state that nutritional theories and the concept of the optimal diet have been somewhat changing over decades and centuries, which may give us reason to be careful about the certainty with which we hold to nutrition beliefs. See "High-quality fats and shifting paradigms around fat in diets", further on in this module, on the changing attitudes from researchers towards different fat sources in human diets. Nevertheless, years of nutrition research up to the present have defined the requirements of a healthy diet that have been incorporated into the nutritional guidelines summarized in figure 3.1.1. and also published by the United States Department of Agriculture and other government agencies around the world.
Figure 3.1.1.: The Healthy Eating Plate concept for a balanced diet, which is focused on required foods in rough proportions shown on the plate, that will create needed amounts of energy sources, protein, fiber, and other important vitamin and mineral constituents for optimal human health. Note that adequate fluid intake, and some level of physical activity, are also important components of this balanced plate approach to human nutrition for health. Credit: Harvard School of Public Health; made available on Flickr (Creative Commons CC BY-NC-SA 2.0) by Steve Garfield and the Harvard School of Public Health. Copyright © 2011, Harvard University. For more information about The Healthy Eating Plate, please see The Nutrition Source, Department of Nutrition, Harvard School of Public Health, and Harvard Health Publications.
- Click for a text description of the Healthy Eating Plate image
Healthy Eating Plate: A plate divided into four sections: the left 1/2 of the plate shows 2/3 Vegetables and 1/3 fruits. The right 1/2 of the plate is 1/2 whole grains and 1/2 healthy protein. Outside the plate is healthy oils and water. Descriptions are as follows: Healthy oils: Use healthy oils (like olive and canola oil) for cooking, on salad, and at the table. Limit butter. Avoid trans fat. Vegetables: The more veggies - and the greater the variety - the better. Potatoes and french fries don't count. Fruits: Eat plenty of fruits of all colors. Water: Drink water, tea, or coffee (with little or no sugar). Limit milk/dairy (1-2 servings/day) and juice (1 small glass/day). Avoid sugary drinks. Whole grains: Eat whole grains (like brown rice, whole-wheat bread, and whole-grain pasta). Limit refined grains (like white rice and white bread). Healthy Protein: Choose fish, poultry, beans, and nuts; limit red meat; avoid bacon, cold cuts, and other processed meats.
What follows in the rest of module 3.1 is a summarized description of human nutritional requirements, intended to allow you to relate these to food systems as the source of human nutrition. Because of this, we will present both the requirements (e.g. vitamin A versus vitamin C versus amino acids) and also some major issues with particular nutrients that tend towards deficiency in many human populations and their related food systems. At the outset, we can already guide your learning by presenting an exceptionally simplified version of human nutrient needs that you will flesh out in the following pages. To a crude approximation, humans need the following components in their diets: energy, which in practice means carbohydrates, fats and protein seen in relation to their energetic content; "building blocks" of growth and maintenance, which is generally protein linked to higher-protein foods but occurring within both the protein and whole grain fraction of the healthy plate above; and promotion of health, proper development, and proper function,closely linked to vitamins and mineral intake. We'll delve into these elements of a balanced diet one by one in the following pages, and add a few details as well. An additional point that deserves mentioning now is the particular importance of proper nutrition for growth, mental development, and health promotion in children. Children are thus particularly vulnerable to nutrient deficiencies, and the consequences of deficiencies can be long-lived in their development into adulthood.