What Are Good Sources of Protein? – Micronutrient Content

As I move towards wrapping up this series this week, I need to discuss a couple of other topics of relevance to the question of what are good sources of protein.  A good bit of what’s been discussed in other sections was a bit on the theoretical/sciency end of things and I’m going to keep the next couple of topics a lot more applied.

Today I want to look at an issue that I don’t think is addressed as much as it could be when folks are looking at protein source; that topic is the presence (or absence) of other nutrients.  Outside of a few select groups (that often get a majority of their protein from isolated sources such as protein powders or amino acids), most people get their daily protein from whole food sources and whole foods contain other nutrients.  Some of those nutrients may be beneficial, some of them may be detrimental; all need to be considered when looking at protein sources and deciding which are good, bad, or neutral.

The major ‘extra’ nutrients I want to look at in this article are zinc, iron, B12, calcium. In the next part of this article series, I’ll take a look at the issue of dietary fat content, both in terms of good and bad fats.  This is simply to keep the length a bit more manageable.



Zinc is an essential mineral involved in an amazing number of processes in the body including immune system function, appetite (a lot of early research showed that zinc deficiency did weird things to appetite, zinc has been shown to regulate leptin levels as well) and hormone levels (zinc deficiency can reduce testosterone levels).   Since the body doesn’t store zinc, its intake is required on a daily basis.


What Are Good Sources of Protein? – Amino Acid Profile Part 3

In What Are Good Sources of Protein? – Amino Acid Profile Part 2, I looked a little bit at both the branched-chain amino acids (BCAAs) and glutamine before examining two distinct pathways by which exercise not only increases overall protein requirements but might impact on the specific amino acid profile needed by the body to support heavy training.

In the final part of this sub-series within the series, I want to look at the final way that training can potentially impact on specific amino acid requirements.  I’ll also touch on dieting at the very end.


Exercise and Amino Acid Requirements: Skeletal Muscle Adaptation

Although there are certainly other adaptations occurring to training (e.g. neural, cardiovascular), one of the primary places where adaptation to regular training occurs in skeletal muscle.  Both endurance training and heavy resistance training stimulate specific adaptations in skeletal muscle that work to improve performance in the long run.

Something to keep in mind is that resistance training and endurance training stimulate very different adaptations.  Resistance training generally causes an increase in the actual contractile tissue in skeletal muscle; in contrast, endurance training stimulates increases in mitochondria along with the enzymes responsible for energy production.

In premise this means that strength/power athletes (who typically engage in heavy resistance training) and endurance athletes might require different amounts of specific amino acids to support the specific  adaptations in those tissues.  Without going into a lot of detail, it simply doesn’t work that way.


What Are Good Sources of Protein? – Amino Acid Profile Part 2

In What are good sources of protein? – Amino Acid Profile Part 1, I examined the issue of amino acid profile, primarily as it relates to general health and wellness.  My basic conclusion, based on the research is that basically any high quality protein source (and this is eminently true in the modern world where people get plenty of protein from mixed sources along with lots of total calories) more than adequately meet the amino acid requirements of adult humans.

Today, I want to continue that by looking at some issues specific to athletes and those involved in heavy exercise training.  It’s fairly well established that athletes need more protein than sedentary individuals although there is still great argument over just how much is needed.

Two specific amino acids that tend to get focused on by athletes are the branched chain amino acids (BCAAs) and glutamine, I’ll give a quick primer on those before discussing any of the other specific issues.

There are a number of different ways by which by which exercise training might increase protein/amino acids requirements.  This includes the use of amino acids for energy directly during exercise, other pathways of interest (see below), and finally the actual adaptation to training.   I also want to touch briefly on the issue of dieting.

To keep this from getting too long, I’m only going to discuss energy use and the other pathways today.  Since it will be the longest part, on Thursday or Friday, I’ll look at the issue of the actual adaptations to training and how that might impact on specific amino acid requirements; I’ll also look at the issue of glutamine and BCAA supplementation in that regards.  I’ll discuss dieting then as well.

Again, I can’t really do these topics full justice in this article, it took me 225 pages to cover it all in The Protein Book and anybody who wants the full discussion (and all of my study references) should pick up that book.


What Are Good Sources of Protein? – Amino Acid Profile Part 1

Continuing from Wednesday’s article on What are good sources of protein? – Protein Quality, I want to talk a little bit about the amino acid profile of proteins and how that impacts on the answer to the question What are good sources of protein.

I’m going to actually divide this into two parts to keep it from getting too long.  In Part 1, I’ll discuss some basic concepts and look at how the amino acid profile of various proteins relates to supporting basic bodily function. In Part 2, which I’ll run on Monday, I’ll discuss the possibility that athletes have specific amino acid requirements above and beyond what’s necessary to support basic function.

What are Amino Acids?

Now, as I’ve mentioned but not gone into any great detail in this series, amino acids are simply the building blocks of protein.  Depending on which reference source you use, there are 18-22 different amino acids that occur in the human food supply.  Whole food proteins are simply long chains of these amino acids bonded together.  Typically whole food proteins are extremely long chains of amino acids, as I discussed in What are good sources of protein? – Digestibility, these long chains are cut into smaller and smaller chunks during digestion until only single amino acids and chains of 2-3 amino acids are actually absorbed.

I’d note that individual amino acids are often sold for either health or sports performance purposes.  Readers may be familiar with the amino acid L-tryptophan which is often sold as a sleep aid.  L-Tryptophan converts to serotonin in the brain which is involved in sleep.  Take L-tryptophan on an empty stomach and you get drowsy because of increased brain serotonin levels.

In the athletic realm, all kinds of products are available.  The branched-chain amino acids (BCAA) L-leucine, L-isoleucine and L-valine have been pushed for years to athletes; recently there has been a big push for isolated leucine for a number of reasons that I’ll touch on in Part 2.


What Are Good Sources of Protein? – Protein Quality

Having finished looked at the issue of speed of digestion in What are good sources of protein – Speed of Digestion Part 3, I want to move onto the next topic that I mentioned in the introduction: protein quality.  I’m going to keep this article as brief as possible, for reasons I’ll explain at the end of the article.  If you want or need more, you can pick up The Protein Book which has a detailed discussion of the issue.


What Does Protein Quality Mean?

Quoting directly from The Protein Book:

Protein quality refers, in a general sense, to how well or poorly the body will use a given protein.   More technically, protein quality refers to how well the essential amino acid (EAA) profile of a protein matches the requirements of the body; the digestibility of the protein and bioavailability of the amino acids (AAs) also play a role (1,2).

Essentially, protein quality simply refers to how well or how poorly a given protein is used by the body once it has been digested.  Clearly, any protein that escapes digestion (as discussed in What are good sources of protein? – Digestibility) can’t do anything in the body but that doesn’t mean that all of the protein that is digested automatically works the same in the body.

Repeating myself slightly, protein quality has to do with how well a given dietary protein is used by the body for all of the different purposes that protein is used for.  And the quality of the protein has to do with factors such as the amino acid profile of the protein (amino acids are just the building blocks of individual proteins) along with the speed of digestion issue I discussed in the last series of articles.  I’ll talk about amino acid profile a little bit in the next article of this series.