In many articles on the site, I go into a rather great deal of detail on various aspects of human nutrition and the various nutrients that comprise it. But it’s easy when doing this to miss the basics, which are arguably far more important. For that reason I wanted to put together this guide to basic nutrition. And I intend to keep it basic. Where appropriate, I’ll point readers to other articles on the site (or my books) which discuss a given topic in more detail than I want to cover here.
Essential vs. Non-Essential Nutrients
The body has a requirement for somewhere around 60 nutrients on a daily basis for normal functioning or basic health. Please note that as nutritional science has progressed, it’s clear that many more nutrients contribute to optimal health even if they aren’t required for survival. Put differently, you can live without consuming them but you might be healthier or perform better as an athlete if you did eat them.
I should also mention that this list of 60 nutrients includes things such as air and water that, while they aren’t considered as nutrients per se, are usually not an issue. If you’re having issues obtaining adequate amounts of air or water, you have bigger problems to deal with.
Of more relevance to today’s article, nutritional science often groups nutrients into the categories of essential and nonessential (recently the terms indispensable and dispensable have come into vogue) which is what I’d like to discuss next. For quick summary, there are roughly 8 essential amino acids, the 2 essential fatty acids, a host of vitamins and minerals and a few others substances that are required on a daily basis. You might note that carbohydrates were not listed as an essential nutrient, a topic I’ll come back to below.
What Defines an Essential Nutrient?
So what is an essential nutrient as opposed to a non-essential nutrient? I’m actually going to answer that by explaining what a non-essential nutrient is first. Contrary to what it sounds like, the term non-essential (or dispensable) doesn’t mean that the nutrient isn’t essential for life. Rather, it’s not essential that the nutrient be obtained from the diet itself. That is, it is physiologically essential in that it is required for life. But it is not nutritional essential in that it must come from the diet.
Translating that into English, there are some nutrients (such as glucose, certain fatty acids and just over half of the amino acids) that can be made in the body from other sources. For example, many amino acids can be made in the body via metabolism from other amino acids. As well, glucose can be made in the body from a number of different substances. So while these nutrients are physiologically essential they are not nutritionally essential. That is they don’t have to come from the diet.
At the same time, there are nutrients that cannot be made by the body (the vitamins and minerals are examples, so are the essential fatty acids and roughly the other half of the amino acids) and are hence considered essential nutrients. That is, it is essential that they be obtained from the diet (generally on a daily basis).
In short, to be considered essential, a nutrient must several basic criteria:
- That nutrient is required for survival/the lack of that nutrient causes disease or poor growth
- That nutrient cannot be made in sufficient quantities (or at all) by the body
If a nutrient isn’t required to keep you alive, it’s not essential (even if consuming it improves health or what have you). If it’s required for life but the body can make sufficient amounts of it, it’s still not essential to get it from the diet; hence it is not an essential nutrient. Only when a given nutrient is both required for survival and can’t be made in the body in sufficient amounts is it an essential nutrient in terms of what I’m talking about here.
Although I want to keep this piece focused on the basics, I should probably mention one odd exception which is Vitamin D (currently getting a lot of press, and for good reason, in various places). Vitamins and minerals, generally, can’t be made in the body and must come from the diet. But while Vitamin D can be obtained from the diet (many foods are fortified with it), and is an essential nutrient, it is actually made by the body in response to sunlight hitting the skin.
The topic of essential nutrients can get even more complicated. For example, some nutrients are classified as conditionally essential. That is, under normal conditions, those nutrients are not essential. But under specific conditions, frequently pathologies or disease, they become conditional.
The word protein come from a Greek word meaning “the first” which is meant to signify its primary role in human nutrition. While you can survive rather extended periods without carbohydrate or fats in the diet, a long-term lack of protein intake leads to a loss of body tissue (muscle and organ protein), function and eventually death.
Whole dietary proteins are made up of smaller units called amino acids of which ~20 occur in the diet (there are many more that occur in the body). Of those 20 or so amino acids, roughly eight are considered essential meaning that they must come from the diet on a daily basis.
Under certain conditions, such as stress and trauma, some amino acids also become conditionally essential. Glutamine is perhaps the most commonly cited example with much higher amounts that can be made in the body being required under those kinds of conditions. There are other examples but few would be relevant outside of some very very specific situations (usually involving severe malnutrition or disease).
A primary distinction between protein and carbohydrate/fat is that only protein contains dietary nitrogen (which is technically an essential nutrient). Since humans can’t “fix” nitrogen from the air like plants, we have to obtain it from the diet. And that nitrogen is found in the individual amino acids that make up whole food proteins. Also, while there can be some interconversion of protein (more accurately, amino acids) to carbs or fat (this last one is very rare), neither carbs nor fat can be made into amino acids.
The Role of Dietary Protein in the Body
Proteins/amino acids have a number of crucial roles in the human body but most of them are structural (meaning the protein is used to build things). Many hormones are made of protein (some examples are IGF-1 and Growth Hormone), your organs, muscles, skin and hair all contain protein; protein has numerous other roles in the body as well.
Protein can also be used to produce energy in the body, usually by conversion to other nutrients (almost always glucose). For example, during long-term aerobic exercise, the breakdown of amino acids (specifically leucine) can provide 5-10% of the total energy generated. This value goes up when muscle glycogen is depleted.
Something to note is that, in contrast to carbohydrate (which is stored in both muscle and liver) and fat (which is stored on your butt and stomach), there is no real storage form of protein unless you count the relatively small amount floating around in the bloodstream and the protein that makes up your muscles and organs. But this isn’t a true storage form like for carbohydrates and fats since, in general, breaking down body protein is a bad thing (as I mentioned above).
Addendum: In recent years it’s become clear that the body can transiently store protein after a meal, usually as visceral (gut protein). This allows amino acids to be released into the body between meals.
Sources of Dietary Protein
In the diet, protein is found to some degree in almost all foods with the exception of pure fats like vegetable oils and such and some totally refined carbohydrates such as candy (e.g. jelly beans). Fruits and vegetables contain fairly small amounts of protein (perhaps a gram or two per serving) while beans and nuts can contain significant amounts of protein. But most people in modern society get their protein from animal based products: meat (red meat, chicken, fish), milk, cheeses, etc.
In terms of caloric content, protein has traditionally been assigned a value of 4 kilocalories/gram (~16.8 kj/g) but this is currently a topic of some debate. Because of how it is digested and assimilated in the body, at least one researcher is suggesting strongly that protein be given a lower caloric value (roughly 3.2 kcal/g or 13 kj/g) than the traditional value.
I covered a great deal of detail regarding different dietary proteins in my Guide to Dietary Protein and would refer readers there for more information.
The term carbohydrate refers to a number of different organic compounds ranging from simple sugars (e.g. glucose and fructose) to disaccharides (e.g. sucrose, lactose) all the way up to starches (long chains of individual carbohydrate molecules bound together). Because of its chemical structure, you will often see carbohydrate abbreviated as CHO (for carbon, hydrogen, oxygen).
I’d note that fiber is also classified as a dietary carbohydrate although it acts very differently within the body than the others. For the most part, fiber does not provide a major energy source to the body although the conversion of some fibers to short-chain fatty acids provides roughly 1.5-2 calories per gram to the body. Insoluble fibers, in contrast, cannot be broken down by the human gut and provide no calories. Fiber is discussed in detail elsewhere on the site.
The Role of Dietary Carbohydrate in the Body
In the body, carbohydrate’s role is primarily energetic, that is it provides energy (through breakdown) in various tissues of the body. Most tissues in the body can use glucose for fuel and, quite in fact, most will use glucose if it is available (they will switch to using fats or ketones if glucose is not available in sufficient amounts). A few tissues of the body such as the kidney and retina can only use glucose for fuel.
And while the above might suggest that dietary carbohydrates are essential, this isn’t the case. Recall from the discussion above that, to be considered essential a nutrient must not only be required by the body but cannot be made in sufficient quantities by the body. And, as I’ve also discussed elsewhere, the body is able to produce some carbohydrate from the breakdown of other nutrients, specifically about half of the amino acids, glycerol (the backbone of both dietary and body fat) and lactate.
In general this process (called gluconeogenesis which simply means the production of new glucose) is able to cover the body’s basic daily needs. As well, with low-carbohydrate diets, there is a whole body shift in fuel use from carbs to fats and ketones which reduces carbohydrate requirements. This is discussed to some degree in nearly all of my books but the greatest detail can be found in The Ketogenic Diet.
Carbohydrates can be stored within the body in the liver or muscle as glycogen (a long chain of glucose molecules bonded to each other) and is found in small amounts (~5-10 grams total) as free glucose in the bloodstream. Liver glycogen exists primarily to help maintain blood glucose levels.
In contrast, muscle glycogen within skeletal muscle exists to fuel activity in that specific muscles. Once carbohydrate is stored as glycogen within a muscle it can’t be released to be used elsewhere.
Carbohydrates as a Conditionally Essential Nutrient
I would finish by noting that high-intensity exercise tends to increase carbohydrate requirements beyond what the body can make putting carbohydrates into the conditionally essential category I discussed above (e.g. the body needs more than it can produce itself).
For those individuals who wish to perform high-intensity activity such as intensive weight training or even high intensity metabolic work, some amount of carbohydrates generally becomes required in the diet. For this reason, I would consider carbohydrates to be a conditionally essential nutrient. I discuss how many carbohydrates the body needs elsewhere on the site.
Sources of Dietary Carbohydrates
Dietary carbohydrates have traditionally been broken into various classifications. Some divide them into simple sugars and starches while others, typically in the athletic arena, use starchy and fibrous carbohydrates. This is mostly a division of convenience but is the one I will use.
Fibrous carbohydrates generally refers to vegetables which, with a few exceptions, tend to contain very small amounts of digestible carbohydrate while containing a lot of fiber. Pretty much any vegetable you care to name (with the handful of exceptions mentioned next) will fall into this category of carbohydrates and it’s often stated that you can eat these types of carbohydrates “without limit” due to their generally low caloric content. I’ll come back to this shortly.
Starchy carbohydrates are, more or less, everything else: breads, pasta, rice, and grains, basically any carbohydrate that contains a good bit of digestible carbohydrate. I should note that there are a few starchy vegetables such as carrots, peas, corn and potatoes: vegetables which contain larger amount of digestible carbohydrate and which need to be counted as starches in terms of real-world meal planning.
Fruits, while not technically a starch, are usually grouped with starches since they contain quite a bit of digestible carbohydrate (the majority of which are simple sugars). Some tend to consider fruits as more in the simple sugar category and I’d probably say they are their own category.
Explaining the caloric value of carbohydrates can be somewhat confusing. Starchy carbohydrates are generally assigned an average value of 4 calories per gram (16 kj/g) although this can vary slightly from food to food. As I mentioned above some fibers can provide energy to the body with estimated being 1.5-20 kcal/g (~6.3-8.4 kj/g). While this isn’t a large amount given most people’s average fiber intake, for people who are eating enormous amounts of vegetables (which don’t just contain fiber, mind you), the calories can start to add up.
While difficult, it is possible to consume such a massive amount of fibrous foods that the calorie count becomes significant. So the idea that fibrous carbs can be eaten “Without limit” is only true up to a point.
Dietary Fats and Cholesterol
I have looked at the topic of dietary fats and cholesterol in my Guide to Dietary Fats elsewhere on the site and I’d refer readers there for details. Here I want to take a briefer more streamlined look at the topic. This is supposed to be a Guide to Basic Nutrition, right?
Even though they are chemically and nutritionally distinct substances, dietary fat and cholesterol are so linked in the minds of most people that I’m going to discuss them together. As well, along with the never-ending debate over carbohydrates in the diet, the issue of dietary fats is one of almost constant debate in both nutritional sciences and among nutritional experts. I also won’t cover those debates here as I’ve discussed carbohydrate and fat controversies elsewhere on the site.
First let met get cholesterol out of the way since I don’t actually have a tremendous amount to say about it. Cholesterol plays a number of roles in the body not the least of which is involvement in the structure of cell membranes in the body. As well, cholesterol provides the “base” for the steroid hormones, testosterone, estrogen, progesterone and others are synthesized out of cholesterol in the body.
When most people hear the word “cholesterol”, they immediately think heart disease. Certainly, one aspect of cholesterol metabolism in the body is that it can cause atherosclerotic plaques (essentially the cholesterol builds up in arteries, potentially blocking blood flow). This tends to happen when that cholesterol oxidizes which has more to do with the rest of the diet and lifestyle.
Let me note that there are far more factors to heart disease than just cholesterol. It’s been the focus for decades but there is clearly more to it. Let me also note that the idea that cholesterol plays no role in this is as asinine as the idea that it was the only cause. It’s part of a multi-factorial disease.
This tends to be the source of much confusion about diet. The idea is that dietary cholesterol intake is a primary determinant of blood cholesterol levels. Generally this isn’t the case. There seems to be some percentage of people who are sensitive to dietary cholesterol intake but for the most part, it has little to no effect.
First and foremost, the liver usually makes more cholesterol than the average person eats in a day. More importantly, the body regulates cholesterol production based on intake. If you eat more cholesterol, your body make less. If you eat less cholesterol, your body makes more.
Rather, the big controller on blood cholesterol levels tends to be the intake of dietary fats, discussed next
Technically dietary fats are called triglyceride (TG) or triacylglycerol (TAG) if you want to be pretentious. This describes a chemical structure where a glycerol backbone is bound to three fatty acid molecules. Hence tri (“three”) glyceride (“glycerol”).
Arguably the primary role of dietary fats is energy production either by being burned immediately after eating or when stored body fat (which is also TG) is released into the bloodstream. For years, it was assumed that this was the only role of fat in the body.
This was especially true of stored body fat which was thought for decades to provide only a passive storage depot of energy. Rather it turns out that fat cells do much more in the body, producing hormones and such that affect myriad processes elsewhere in the body (a topic I’ve discussed at length on the site and in my books).
Fats are also found in the cell membranes of various tissues (and the type of fat stored there can affect various cellular processes). As well, the fats arachidonic acid (AA) and EPA/DH can be used to make eicosanoids, short-lived chemical messengers that affect numerous biological processes such as inflammation. Specific dietary fats can also affect gene expression in certain cells, impacting on things like fat storage and oxidation and many others.
From an energetic standpoint, fats are typically assigned a caloric value of 9 kilocalories/gram (~38 kj/g) although there are slight differences between specific fatty acids. For the most part, this is not worth worrying about as those differences will more or less cancel out.
There is also some evidence that certain types of fats are more easily stored as bodyfat or burned for energy although the differences are relatively small. Since I didn’t mention it above, I should note that dietary cholesterol does not provide energy to the body.
Dietary Fat Controversies
The biggest controversies regarding dietary fat usually revolve around the health effects of its consumption. It’s not unfair to say that, for many years now, dietary fat has been the whipping boy of the nutritional world (though carbohydrates are taking that role in recent years).
People will say that fat makes you fat, fat causes heart disease and cancer, fat is probably responsible for terrorism in the US and the decline in the family unit. You name it and the problem has probably been blamed on dietary fat by certain groups. At the other extreme are folks who argue that dietary fats have no health negatives, that they can be consumed effectively without limit or concern.
As with so many extremist stances, the truth is a little different and tends to lie somewhere in the middle.
In the past ten years or so, the issue of fat quality (i.e. type of fat) has become just as important as that of fat quantity (i.e. amount of fat). Simply put: all fats are not the same in terms of their effects on health. As well, whether a specific fat is good, bad or neutral in terms of health depends to a great degree on the context in which it’s eaten; this is a concept that neither extremist group can seem to wrap their heads around.
Whether the person is active or inactive, fat or lean, the rest of their diet, gaining or losing weight, and a host of others all contribute to the effect a given fat will have on the body. Once again I’d point you to a more detailed article I wrote on carbohydrate and fat controversies.
Types of Dietary Fats
Based on their chemical structure, dietary fats are divided into 3/4 different types. Each tends to have different effects on the body as well as being found in different types of foods.
Trans-Fatty Acids (TFAs)
Trans-fatty acids are a man-made fat made by bubbling hydrogen through vegetable oil to make it semisolid with a longer shelf-life; I’d note that there are naturally occurring trans-fatty acids found in foods as well. Margarine is probably the example most readers are familiar with although trans-fatty acids (also called partially hydrogenated vegetable oils) are commonly found in most processed foods (there is currently a big push for trans-fat free foods to be produced commercially).
Of the four types of fats, trans-fatty acids have the least amount of debate around them; their intake at even low levels tends to have exceedingly detrimental impacts on things like blood lipid levels and diabetes risk. Due to the high reliance on processed foods in the modern diet, trans-fatty acid intake is thought to be at least one part of the problems being seen in the modern world (note: there are certainly other contributors).
Saturated Fatty Acids (SFAs)
Saturated fats are found almost exclusively in animal products (two exceptions are coconut and palm kernel oil) and are solid at room temperature. Traditionally, the impact of saturated fats on blood lipid levels and heart disease risk has been thought to be universally negative but it turns out to be much more complicated than this.
While some saturated fats do reliably raise blood cholesterol levels (primarily due to an impact on liver metabolism), others are completely neutral. For any readers interested in the details of this topic, I’d recommend the journal article Saturated Fats: What Dietary Intake?
As well, as I mentioned above there is far more to heart disease risk than just blood cholesterol levels. And, as also noted above, the overall impact of any fat (including saturated fats) on health risk depends on the context of their intake. In one context (e.g. low fruit/vegetable/anti-oxidant intake, high stress, inactivity, high body fat, excessive total energy intake), a high saturated fat intake may be exceedigly harmful.
In a different context (e.g. high fruit/vegetable intake, low stress, high activity, low body fat, appropriate energy intake), they may have no effect. I hope that any of the pro-saturated fat folks reading this article will read this paragraph a couple of times before they leave me comments about how I’m anti-saturated fats.
I’d finish by noting that saturated fats are not an essential nutrient. They aren’t required for life and, even if they were, the body can produce them from other sources.
Monunsaturated Fatty Acids (MUFAs)
Monounsaturates are present in almost all foods which contain fat and are liquid at room temperature (quite in fact, the majority of fat in most “high-fat” foods is monounsaturated). Olive oil is arguably the most well-known of the monounsaturated fats and has received a great deal of attention as a relatively healthy fat.
Monounsaturates have a neutral, if not beneficial, effect on health and it’s thought that the high olive oil consumption among Mediterraneans is partly responsible for their robust health (there are ceertainly other factors involved here).
Like saturated fats, monounsaturated fats are not an essential nutrients, they may confer health benefits but they are not required for survival.
Polyunsaturated Fatty Acids (PUFAs)
Polyunsaturated fats are found primarily in vegetable oils and are liquid at room temperature. They are generally claimed to have a positive effect on human health although, as always, things are a little more complicated than that. Polyunsaturated fats come in two major “flavors”, referred to generally as omega-3 (aka w-3 or n-3) and omega-6 (aka w-6 or n-6) fatty acids.
The omega-3 fatty acids include a number of different fatty acids including the ‘parent’ fatty acid alpha-linoleic acid (ALA) found in things such as flax oil along with the fish oils (EPA and DHA). I would be surprised if anybody reading this hadn’t heard of the fish oils or their benefits. In sum, fish oils do just about everything, they decrease inflammation, help with depression (especially while dieting), decrease enzymes involved in fat storage and increase the levels of enzymes involved in fat burning.
I’d note that the conversion of ALA to EPA is fairly low and the further conversion to DHA is almost nil (it is slightly higher in women than men). For this reason, taking preformed fish oils is generally required to impact body levels of EPA/DHA to any great degree.
Similarly, the omega-6 fatty acids include a host of different fatty acids including linolenic acid (LA), found in many vegetable oils, along with things such as arichnidonic acid (AA) which are made from metabolism or LA within the body.
There has been some long standing controversy over w-6 and w-3 with excessive w-6/low w-3 intake thought to cause some health problems. LA/w-6 tends to be easy to obtain in the modern diet while ALA/w-3 sources are not. This give the modern diet a w-6/w-3 ratio of 20-25:1 when many think that a 1-4:1 ratio would be better. Some fringe groups believe that excessive w-6 rather than saturated fats are the cause of modern health problems. I’d refer readers to my Guide to Dietary Fats for more details on this topic.
I’d note that w-3 and w-6 fatty acids are the two essential fats as they are required for life and function but cannot be made by the body. Traditionally, linoleic acid and alpha-linolenic acid have been considered the actual essential fats but it may be that AA and DHA are the real essential fatty acids.
Everything Else: Fiber, Alcohol, Vitamins and Minerals
Let me wrap up this guide with a catch-all category to discuss, fiber, alcohol, vitamins and minerals.
I recently discussed fiber in some detail on the website and mentioned it briefly above but want to touch on it briefly here. While not an essential nutrient (e.g. you won’t die if you don’t eat it), fiber does play a number of important roles in human health in nutrition. If nothing else, high-fiber intakes tend to keep people full and, generally, high-fiber diets are associated with greater weight loss or at least less weight gain.
Fiber can be subdivided into a variety of different categories but, practically speaking, the main ones of importance are soluble and insoluble fiber. Soluble fibers mix in water and take up a lot of space in the stomach, it also holds food in the stomach longer: this tends to increase feelings of fullness. In contrast insoluble fibers don’t mix with water but help with bowel regularity and keep the colon healthy.
Both types of fiber appear to be important to human health and both are found in varying degrees in foods such as fruits and vegetables (grains have varying amounts of fiber depending on how processed they are).
Alcohol isn’t really a nutrient in that it provides nothing of actual nutritional value except for calories. Even there, alcohol intake doesn’t seem to scale with predicted weight gain although nobody is quite sure why this is the case. Some studies suggest that some alcohol calories go ‘missing’ but nobody can figure out where they are.
Alcohol also tends to impact on metabolism in a way that can promote fat gain. Certainly alcohol can have a place in any diet (with a large body of research suggesting that moderate alcohol intake has health benefits depending on the specifics) but excessive amounts can cause varying problems.
Vitamins and Minerals
Finally there are vitamins and minerals which serve innumerable roles in the body and which include a host of essential nutrients (again, can’t be made in the body, required for life). Minerals such as calcium are structural (e.g. bone) along with being involved in cellular signaling. Iron is involved, of course, in the formation of red blood cells, important for overall health and performance. Zinc is involved in immune system function and a host of other processes (including appetite regulation). Vitamins act as nutritional co-factors and are necessary for the body to function optimally.
Vitamins and minerals are found to some degree in all foods with amounts and types depending on the specific food. Fruits and vegetables tend to be nutritional powerhouses in this regards but some vitamins and minerals are optimally consumed in foods of animal origin. For example, iron in red meat is absorbed significantly better than iron in non-animal sources. The same holds for zinc and there is no naturally occurring non-animal food source of B12.
I’d note this works in reverse and other nutrients, magnesium being one, are found in greater amounts in non-animal sources foods on top of being absorbed more effectively from them. Basically, optimal human nutrition tends to require an intake of both animal AND non-animal foods.
In that context, I’d note that a class of nutrients called phytochemicals are only found in plant foods and there is currently a great deal of interest in the health benefits of these compounds. They aren’t essential by any stretch but may confer health benefits. Various anti-oxidant nutrients are also found in varying amounts in these foods and, while anti-oxidant supplementation has generally shown little to no real health benefits, diets high in food-based anti-oxidants have been found to confer many health benefits.
A Guide to Basic Nutrition
And that sums up what I consider the building blocks of basic nutrition. Here I looked at dietary protein, dietary carbohydrates, dietary fats and cholesterol along with fiber, alcohol, vitamins and minerals. Certainly there are other issues of importance, I didn’t cover things such as recommended intake levels for different situations.