Nutrition has become a tricky subject. It shouldn't be so hard to figure out what to eat; after all, the birds and bees hardly seem to give any thought at all to their diet. But then, they haven't had the foresight to invent politics or financial interests—both of which intrude too often in the interpretation of research results on the human side of things. This spawns so many different and even opposing ideas about nutrition that we begin to feel like Dr. Doolittle's two-headed llama, the "push-me-pull-you."
The first concern in any discussion is for all parties to synchronize their understanding of the terms being used. Of course, everyone knows what "food" is, so it hardly seems necessary to bother with that one. But one never knows what interesting thoughts may be sparked while perusing a dictionary, so we looked it up anyway. Here's what one online dictionary had to say:
1. Any substance that can be metabolized by an organism to give energy and build tissue.
2. Any solid substance (as opposed to liquid) that is used as a source of nourishment; "food and drink."
3. Anything that provides mental stimulus for thinking.
Obviously that third definition refers to the old catchphrase, "food for thought." And let's take that a little more literally than we usually do, because it's true that food—the right kinds of food—can nourish the brain as well as the body. But what is the right kind of food?
Fortunately, it's not as complicated as it may seem. Ideally, a nutritious diet provides all the nutrients essential for the normal functioning of the body. We know what these nutrients are, and the minimum essential needs of our bodies, so it should be easy to decide what to eat, right? Except that now we have so many foods available to us that have deviated so far from their roots that there is very little nutrition left in them. Unfortunately, these are often the foods that are most attractive and appealing to our palates, so we gain weight and become susceptible to diseases, and we look for gurus who will solve these problems for us without requiring us to give up our chosen food vices. Some of these gurus tell us we can keep eating our favourite "fatty" foods if we give up the carbs. Others tell us we can continue to enjoy our empty, white carbs if we'll just go low-fat. Still others invent "fun" theories to interest people in new diet fads like personality diets, blood-type diets, and diets based on the length of the little finger on your left hand.
But in fact, unless we have a serious malfunction in our bodily processes, we all need essentially the same building blocks for health and growth. These fall into the following six basic categories: proteins, carbohydrates, fats, vitamins, minerals, and water. In order to get these six nutrients in the amounts that keep us healthy and trim, we have no alternative but to eat foods that are as nutrient-dense as possible, and as close to their natural state as possible. For example—the closer a carbohydrate is to its original form, the more complex it is. That means the body has to work harder to turn it into energy, and produces more beneficial enzymes as it does so. This is true of the carbohydrates in fruits and vegetables as well as grains, of course. The more whole and fresh the vegetable, fruit or grain, the more of its vitamins, minerals and fiber will still be viable. Conversely, the farther our foods from their natural state, the larger the servings that are required to get the nutrients we need, and we end up gaining weight from all the empty calories—sometimes even without getting many nutrients at all.
Even though it sounds overly-simplistic, good nutrition really is almost that easy to understand. Despite the fact that there is much to read about enzymes, co-enzymes, antioxidants, lipids, and all the other necessary components of good health, understanding their roles shouldn't make the big picture any more complicated. If the basic six categories mentioned above are provided to the body in the right balance from good-quality sources, the other components will be where they need to be, when they need to be there.
But what is that balance? We'll concentrate on balancing high-quality proteins, carbs and fats, since other nutrients will often follow in their wake if you get these right—at least if you're lucky enough to live in the Western world where culinary variety is almost obscenely abundant compared to other cultures. For these three core nutrients, decades of nutritional studies consistently suggest the following guidelines: About 10-15 % of our total calories should come from protein (some will extend this to 35%). Of course, crucial to the math is the fact that a gram of protein is equal to about 4 calories. Next, consider that 45-65% of our calories should come from complex carbohydrates (a gram of carbohydrate is also equal to about 4 calories). Please note that the important distinction is that little word, "complex." There is huge nutritional difference between complex carbohydrates and "empty refined carbs." This is where the language of politics enters the arena to confuse us in the grocery store (or in "low carb" diets) where terms such as "whole wheat" and "whole grain" lose much of their meaning in the hands of those who create "legal" definitions for them.
Of course, carbohydrates are not only in grains, although whole grains are a rich source while also making other important and unique contributions to good health. But we also get some of our carbohydrates from dairy products, nuts, meats, and of course—fruits and vegetables, which are a particularly important part of a balanced diet. Besides providing complex carbohydrates, most fruits and vegetables are also dense in essential vitamins and other nutrients the human body needs in order to survive and thrive. Some of these are fat-soluble vitamins (A, D, E, and K), while others are water-soluble. Interestingly, the fat-soluble vitamins are stored in the body's fatty tissues and liver, and are toxic in high doses. Megadoses of A or D in particular can lead to very serious health problems, so these are not vitamins that need to be replenished every day, particularly in Western diets. Overconsumption is a more relevant concern in our society. The water-soluble vitamins, on the other hand, are destroyed more easily in cooking and storage and the body does not store these—rather they are eliminated from the body in urine, so they must be replenished on a regular basis.
Knowing the difference between these two types of vitamins sheds a little light on why some fat is essential and also introduces the idea that there may be other reasons besides aesthetic ones that excessive amounts of stored fat would pose health risks.
Most people do realize that it isn't healthy to entirely eliminate fats and that too much fat—even from quality sources—can do us equal harm. But the actual numbers may be surprising. Nutrition researchers find that we really need only 15 - 20% of our calories to come from fat, although some people's bodies can metabolize up to 35% if they are the right kinds of fats from high-quality sources, which is why the USDA recommendation ranges from 20-35%. Anything beyond that, however,our bodies will just store. Ever wonder what fat is stored as? Exactly. Fat. At least it's comforting to know that excess carbs have to be converted to fat to be stored. Fat is already, well . . . essentially, fat. Unfortunately, a full discussion of the body's metabolism of this fascinating and essential nutrient is not possible here. Suffice it to say that as important as this nutrient is, it does not take as much as one might think in order for it to perform its functions.
The 15-35% recommendation for fat intake may seem paltry, but the fact is that 1 gram of fat has more calories than any other nutrient. And while there is no need to obsess about calories if the overall diet is balanced, it is nevertheless important to consider them occasionally. There is a whopping 9 calories in every gram of fat—more than twice the calories of proteins or carbohydrates. Most food packaging lists fat in grams, which means a little math is required when determining the percentage of calories. For instance, let's say you have a single-serving size of a popular brand of tortilla chips, and you propose to eat them as a "healthy" snack. The total calories for the little bag of chips is 140. The total fat is 8 grams. Eight!! A tiny little number compared to 140! "Fabulous," you think, "what a great, low-fat snack!" Think again. Take that 8 grams of fat, and multiply it by the 9 calories that are in each gram. Even with my minimal math skills, I get 72 calories. What percentage of 140 is 72? Well, if you double 72, you get 144, so you're really in the 50% fat ballpark, aren't you? Ironically, both a "low-fat" diet and a "low-carb" diet would (wisely) ban that bag of chips.
A high-quality protein provides the amino acids that the human body needs but is unable to produce on its own. The body processes these essential amino acids in particular ratios, so a protein is "limited" by the amino acid that occurs in the smallest proportion. There are three "limiting" amino acids, so-called because they are more difficult to find in food than the others. Even if a protein contains a high proportion of some amino acids, the body will be unable to take advantage of their bounty beyond what can be offset by the limiting one.
Most people recognize that meats are generally rich (some would say "complete") sources of protein: they tend to contain all of the essential amino acids in sufficient proportions. What may be less well-known is that other foods can be eaten in combinations that can supply the body with all of the essential amino acids every bit as well as, and sometimes even better than, meat. The general rule of thumb is to combine legumes (such as beans or peanuts) with nuts (or seeds), or to combine legumes with whole grains. These complementary foods should be consumed at least within the same day if not in the same meal. However, it is unlikely this concept needs to be obsessed over. Thanks to the abundant variety of foods available to most in the West, any vegetarian diet containing a variety of foods is likely to provide all the necessary amino acids over the course of a day. A peanut-butter sandwich, for instance, fulfills this requirement, as does a bowl of split-pea soup eaten with a handful of whole-grain crackers.
Unfortunately there are also drawbacks to the abundance our society experiences. The prevalance of obesity is of growing concern in almost all Western nations, and there is much debate over the reasons behind our growing behinds. However, there is little doubt that one area that gets us into trouble relates to those little hidden calories that we hardly think about. A nutrition professor once told our class, "It's not so much the food that is bad, it's the company it keeps." What did she mean? Well, the example she used was potatoes, but once you get the idea you can apply it to anything. Are potatoes bad for you? Absolutely not—not at all. There are loads of nutrients in potatoes, and not just in the skin. The skin is a wonderful source of fiber, but the potato itself, white though it is, is a great source of potassium (as much as a banana), vitamin C (almost half the daily recommendation), and trace amounts of essential minerals. And a whole, good sized potato is only 100 calories. Okay, so if potatoes are so good for you, what's the problem? As my professor said, it's the company it keeps. If you can find healthy toppings to use (with appropriate restraint) on your potato, enjoy it guiltlessly. But how many restaurants have you been in where you are offered the following toppings: butter (or margarine), sour cream, cheddar cheese, bacon—and in some cases, as much of all of them in combination as you can pile on?
Not that some of these toppings can't be healthful when used in moderation, of course: one topping, let's say, in restrained amounts on a potato instead of the whole company of them. But even if you're topping your potato with a good, raw butter (not, margarine, please!) maybe you won't want to order the deep-fried breaded chicken patty that's smothered in pseudo-cheese to go alongside it. (And do restaurants really think in this day and age that it's appetizing to use the words "smothered in cheese" as liberally as they do on their menus?)
At any rate, here are some interesting tidbits (or titbits for my UK readers) that you may find interesting about "the company" our food "keeps."
Butter: 1 "pat" of butter (1 1/4 inches square, 1/3 inch thick) has 25 calories, is entirely fat. (all 25 calories) and may have only trace nutrients unless you're lucky enough to be in a restaurant that uses raw, organic butter. Now a question: Knowing the size of a pat of butter (not much larger or thicker than a 50-cent piece), can any of us truthfully say we have ever put only one on our baked potato? Isn't it usually more in the neighborhood of 4 pats . . . probably 100 calories, all entirely fat? Okay, let's go on.
Cheddar cheese: 1 cubic inch is about 70 calories, out of which 54 calories are fat.
Sour cream: 1 level tablespoon has 25 calories, all of which is fat. Have you ever put just one level tablespoon of sour cream on your baked potato? More commonly we put three servings of at least two of the above on our otherwise nutritious potato. We have now turned a 100-calorie, nutrient-dense food into a 300 calorie or more side dish, the nutrients of which are now diluted down to about 1/3 of the total calories (though we may have added some beneficial calcium, vitamin A and phosphorous on the off-chance it's real sour cream and real cheese we've been offered).
With all of these considerations, lets go back now and look at the dictionary definition of "food."
1. Any substance that can be metabolized by an organism to give energy and build tissue. [Our "overdressed" potato is now higher in empty calories than in usable substances that can be metabolized to build tissue...though it's giving us more energy than we can use, so we will have to store the excess as fat.]
2. Any solid substance (as opposed to liquid) that is used as a source of nourishment; "food and drink". [Again, the nutritional value has been sorely diluted.]
3. Anything that provides mental stimulus for thinking. [In this area we may be doing all right. At least in the event our potato has provided an adequate illustration.]
If we subjected everything we ate to this definition of "food," would we be surprised at the conclusion that in most Western nations we are actually undernourished and yet overfed?
This thought is particularly ironic considering that we live in an age when diet books virtually fly off the shelves of bookstores and we collect factoids about nutrition far more avidly than did our ancestors. The rub is that we also tend to focus on tiny pieces of the nutrition picture. As each new diet fad enters the scene, we are asked to focus independently on fats, carbs, or proteins. We may even focus on individual foods. There have been grapefruit diets, egg diets, cabbage soup diets. We may latch on to one fabulous food as a single health panacaea: if everyone only drank green tea, raw whole milk, or pulverized animal horns, all health problems would be solved. Green tea and raw milk (well, and perhaps animal horns) certainly offer their share of health benefits, but of and by themselves none could be said to form the sole foundation of the "ideal" nutritious diet, if there is such a thing. The human body is capable of great flexibility as long as it gets certain essentials, and there are a variety of sources that can provide these essentials.
Perhaps it's human nature to look for a single "easy button." Even so, perhaps the easiest button is the one on the wide-angle lens rather than the zoom. Could the secret to good nutrition be so simple as eating a balanced diet that includes a variety of healthy foods that are as close to their original form as possible?
It's food for thought, anyway.
1 Dolezal, R. (1985). Eat Better, Live Better: A Commonsense Guide to Nutrition and Good Health (1st ed.). New York: RDA. 2 Guthrie, H. A. (1988). Introductory Nutrition (7th ed.). London: Mosby: Elsevier.
3 Taylor, S. (2008). Advances in Food and Nutrition Research. London: Academic Press.