There is a lot of information available about nutrients. Unfortunately, a lot of it is presented in a bewildering fashion and seems to contradict other sources.
Below, we try to simplify the chaos and give you some basic information about nutrients and what, exactly, composes the food you eat. First, some basic vocab and principles underlying our guidelines:
Macronutrient refers to the three main nutrients that compose foods: fat, carbohydrates, and protein.
Micronutrients are the rest of the components of food: vitamins, minerals, water, and fiber.
There are no inherently good or bad foods. It is not reasonable to cut out an entire food category (such as fat or carbs). Humans have, and always will, rely on the three macronutrients for sustenance. In each category, there is a continuum of food choices, from not-so-healthy to more healthy and beneficial.
The big picture is what counts. What you eat over the course of a week, a month, and even a year is more important than what you eat at a single meal.
Fat – This much-maligned nutrient is actually a very important part of one’s daily food intake. Many people all but eliminated it from their diets in the 1980s and 90s because it has the most calories per gram of any of the macronutrients (9, compared to 4 calories per gram for both carbs and protein). In other words, fat is energy dense because it has more than twice as many calories as the same weight of carbs or protein (this is why we store excess energy as fat). Reduced fat, low fat, and fat free foods proliferated from the late 80s on, but people often unconsciously interpreted this as license to eat unlimited quantities of food as long as it was fat free, which often meant people ate more calories than they otherwise would have.
But, FEAR NOT FAT! Despite its bad reputation, your brain and body need this nutrient, which provides cushioning to internal organs and aids in the absorption of various vitamins. There are various types of fats. Fats can be saturated or unsaturated, the latter being more desirable than the former. Go for a high ratio of monounsaturated fats to polyunsaturated fats (good sources include olive oil, avocados, and nuts like cashews and walnuts). One group of polyunsaturated fats are an exception to this guideline, however: omega 3 and 6 fatty acids are especially important for healthy brain functioning (good sources include seafood such as salmon and mussels, and flax seeds or flax seed oil).
You have probably heard of trans-fatty acids, which are thought to be at least as harmful, if not more so, than saturated fats. Although these are not included on nutrition labels (food manufacturers will be required to provide this information beginning in 2006), their presence in packaged food (and they are virtually EVRYWHERE) is indicated by the phrase “partially hydrogenated” or “hydrogenated” oil on ingredient labels, and are also present in fried foods. Because they are technically unsaturated fats, they are currently included in this total on food labels.
The Bottom Line – Eat fat! Anywhere from 20% to 30% of calories consumed throughout the day should come from fat (for example, on a 2000 calorie a day diet, this equates to 44 to 67 grams of fat per day). Also, humans do not not need to consume any saturated fat, a major contributor to heart disease; keep it under 20 grams a day.
Carbohydrates – Since the advent of agriculture, carbohydrates (grains, breads, and vegetables) have historically been the major component of the human diet because they are the most efficient fuel for the body. They are composed of chains of individual sugar molecules, and provide readily available energy to the body’s cells, which primarily use the sugar molecule glucose as a source of cellular energy. About 55 to 60% of calories should come from carbs (for example, on a 2000 calorie diet, you should aim for about 275-300 grams of carbohydrates per day).
As with fats, some carbohydrates are more beneficial for you than others. Complex carbs are found primarily in whole grain products and vegetables. Simple or refined carbohydrates are in those foods whose grains have been stripped of their bran and/or germ layers, and have been broken down into smaller parts from the long chains they once were. This distinction is important because, although the body eventually converts all food needed for energy into glucose, it takes longer to do so for complex carbs, resulting in a slower rise in blood sugar and a longer period of digestion. In other words, you will feel fuller longer, and will miss out on the rapid rise and fall in blood sugar that accompanies eating large amounts of refined carbs.
As of late, low carbohydrate diets have replaced their low fat counterparts, evident by the explosion of available foods that fit into these diets that was seen with regard to fat. You can buy “low carb,” “no net carbs”, and “carb-free” foods of every type, including those that have always fallen in this category (e.g., meat, nuts) and some that are rather surprising (e.g., cereal, bread). In fact, the Food and Drug Administration (FDA) has not yet caught up with thise trend. While there are specific guidelines a food must meet to be labeled low fat, no comparable regulations exist with regard to the carbohydrate content of foods. Basically, anything can potentially be labeled low carb. Often, manufacturers say some item has a certain amount of “net carbs.” They calculate by subtracting the number of carbs that do not have a measurable impact on blood sugar from the total, including fiber. This is also unregulated by the FDA, and the effect that a particular food will have on blood sugar depends on what else you have eaten and what you eat with that food, not to mention individual body chemistry.
The Bottom Line – Carbohydrates are an important part of eating nutritiously, and are not expendable. Go for whole grains and products without bleached flour (if the label says only “wheat flour,” this does not mean it is a whole grain), and don’t cut out fruits or vegetables – they have valuable vitamins, minerals, and antioxidants.
Proteins – Proteins are composed of chains of amino acids. Sources of protein include animal products (flesh as well as eggs and dairy) and vegetable sources (nuts, seeds, and legumes). Most Americans eat a sufficient amount of protein on a daily basis (10-20% of calories, about 50-100 g on a 2000 calorie per day diet), and do not have to adjust the amount eaten (too much protein, a feature of low carb diets such as Atkins, places a lot of stress on the liver and kidneys).
Nevertheless, the type of protein eaten is worth addressing. Dietary saturated fat is a main cause of heart disease, and is abundant in many animal protein sources and dairy products. In red meats, the fat is “marbled” throughout the tissue, and cannot be trimmed. Opt for leaner cuts of meat and low fat dairy products to minimize your intake of this non-essential nutrient. Additionally, animal products and by-products are the only sources of cholesterol (your body has the ability to produce a sufficient amount of cholesterol), so reducing these can help lower high cholesterol.
The Bottom Line – In general, Americans consume enough protein to meet the body’s needs. Stick to lean animal (e.g., chicken, turkey) and vegetarian (e.g., soy products, legumes) sources.