By Jordan Feigenbaum MS, CSCS, HFS, USAW CC, Starting Strength Staff
Unless you’ve been living under a rock or living off the grid for some time, chances are you’ve at least heard about gluten and gluten-free diets. There is good reason for this as gluten and similar nutrients have been the subject of a flurry of recent research efforts and clinical observations. To begin, let’s talk about what gluten is and why we’re even bringing it up.
Gluten is a protein that’s found in all products containing wheat, barley, rye and other foods as a binding agent and even in some prescription drugs. Gluten generally increases elasticity of the dough and improves its texture to aid in palatability. It lets bread rise and maintain its shape as well.
Gluten is made up of what we call prolamin proteins. This essentially means that gluten is made of constituents rich in proline (prol-) and glutamine (-amin) and in wheat’s case, these prolamin proteins are gliadin and glutenin . The prolamin proteins in barley, rye, and corn are: hordein, secalin, and zein, respectively. Oats also contain a prolamin protein known as avenin, although this is a rather minor constituent in comparison to the others.
I will detail how these prolamin proteins interact with our bodies later on in this article, but for now we can say that these proteins resist being broken down in the small intestine by the usual proteases and peptidases . Proteases and peptidases are enzymes that help the body break down proteins from food we ingest for absorption in the small intestine. We can intuit that this might possibly be a bad thing as I’ll discuss later.
As mentioned before, gluten is a hot topic these days. Using the Google search engine and typing in “gluten free” results in over 82 million hits. Originally the topic of gluten intolerance or using a gluten free diet was limited to those suffering from celiac sprue disease. However, the number of those diagnosed with celiac disease has been increasing steadily in recent times, affecting approximately 1 in 133 Americans and countless undiagnosed people. It is important to understand that this disease commonly goes undiagnosed, for almost 11 years in most cases . The issue isn’t a lack of a formidable test to diagnose celiac or gluten intolerance, the test exists and it is very specific, however it is not very sensitive- or at least not as sensitive as some clinicians would prefer. At any rate we cannot deny that “gluten” and “gluten-free” are buzzwords in today’s health and fitness world.
Consider this, in 2003 there were approximately 135 “gluten-free” food products were introduced to the market and in 2008 alone there were 832 introduced. The growth in the gluten-free food sector has recently been estimated to be 15-25%. Then there’s the bevy of research coming out of the medical field.
A New England Journal of Medicine (NEJM) article catalogued 55 diseases associated with gluten intake including : osteoporosis, irritable bowel syndrome, anemia, cancer, fatigue, canker sores, rheumatoid arthritis, lupus, multiple sclerosis, numerous autoimmune diseases, anxiety, depression, schizophrenia, dementia, migraines, epilepsy, neuropathy, and autism . Government agencies associated with Celiac disease also report a decrease in symptoms for patients going on a gluten free diet with the following diseases: rheumatoid arthritis, Parkinson’s disease, neuromyelitis, Down’s syndrome, peripheral neuropathy, multiple sclerosis, seizures, ataxia and late-onset Freidreich ataxia, brain fog, osteoporosis, type 2 and type 1 diabetes mellitus, and anemia .
There are many reasons to believe that some people have become more intolerant of gluten as the generations go by. Celiac disease prevalence is increasing and reports of increasing sensitivity to gluten have also come to light. Plausible causes of this include the genetic manipulation of wheat and other grains, increased exposure to gluten, prolamin proteins in more and more food products at higher concentrations, and increased public knowledge of gluten intolerance or celiac itself.
While going gluten-free hasn’t been established as a weight-loss protocol in and of itself, anecdotal evidence disputes this with many people seeing weight loss as a nice byproduct of utilizing this diet. Some experts postulate that this is because without gluten in the diet overall calorie intake is decreased, while others claim it’s because gluten drives one to consume more palatable food. I tend to agree with this sentiment.
There is little certainty whether or not gluten is directly correlated to weight loss or gain, except in celiac patients that is. celiac patients often present with nutritional deficiencies stemming from malabsorbtion of digested food in the gut. When they switch to a gluten-free diet, however, their gut lining is repaired and they absorb more nutrients. So we could imagine that if a celiac patient ate a similar amount of food before and after the switch to a gluten free diet and now they are absorbing more nutrients than before, they might potentially gain some weight.
Interestingly enough, gliadin, which is found in gluten, exhibits what’s known as an insulin-mimetic effect. Gliadin mimics insulin’s effect on fat cells, that is, it attaches to the same receptor that insulin does on fat cells and causes it to incorporate glucose from the bloodstream into the tissue and store it as fat, just like insulin does. Insulin normally has a negative-feedback loop that keeps it in check. So when insulin levels rise more and more blood glucose is shuttled into the fat tissue and when blood sugar has been returned to a normal level insulin levels fall as the hormone (insulin) no longer interacts with its receptor. Gliadin, however, does not exhibit this negative-feedback loop and stays attached to the receptor and continues to exert its effect . Also gliadin interacts with digestive hormones such as cholecystokinin (CCK), which is involved in regulating appetite control. This gliadin exerts a negative effect essentially blocking appetite control and potentially causing storage of fat via its insulin-mimetic effect .
With all that out the way let’s delve in to what foods contain gluten, how gluten and prolamin proteins interact with the body, and what, if anything, we should do about it! Gluten, as mentioned before, is in all products made of wheat, processed with wheat, or anything that uses wheat, barley, rye, or modified food starch. These foods include:
-beers, breads, candies, cakes/pies, cereals, cookies, crackers, croutons, gravies, imitation meats, pastas, processed lunch meats, salad dressings, sauces (including soy sauce), self-basting poultry, soups, maybe oats during production, modified food starch, medications/vitamins may use gluten as a binding agent, play dough
Foods that don’t contain gluten include:
– corn, gluten-free flour, polenta, rice, tapioca, fresh meat, fruits, most dairy, potatoes, vegetables, wine/liquor/cider/spirits
When we take in any food it’s usually through the mouth (hopefully) and digestion, but not absorption, starts immediately. From the mouth the food is compacted into a bolus as it moves down the esophagus and to the stomach. In the stomach some digestion takes place but it and all the previous digestion pales in comparison to what is to come, digestion-wise, in the small intestine. After passing through the stomach the partially digested food enters the small intestine which is about 21 feet long and comprised of three different parts listed here from beginning to end: the duodenum, jejunum, and ileum.
Digestion primarily occurs in the duodenum, whereas absorption primarily occurs in the jejunum and ileum. We can think about the small intestine as a long tube with finger-like projections known as villi. The layer of cells covering the inside of this digestive tube are called enterocytes and these cells interact with any and all of the digested food particles including gluten and its components gliadin and glutenin. Enterocytes are sealed off between each other by what’s known as a tight junctions (zonula occludens), which is made up of three distinct proteins: cadherins, zonulins and occludins. We can generally think of the tight junctions in the gut as being impermeable or resisting the transmission of any molecule, substance, or compound between the cells. In a healthy person this would mean that absorption of nutrients happens directly across the enterocyte (transcellular) and not in between them (paracellular).
We already know that gliadin and gluttenin are not digested by the enzymes in the small intestine, via proteases and peptidases, and as such they interact with the enterocytes directly . When these prolamin proteins interact with enterocytes they cause a disruption of the tight junctions of the small intestine. They do this by binding to a zonulin receptor on the enterocyte which causes a release of zonulin, which was previously bound tightly, and a subsequent remodeling of the enterocyte’s structure and a loss of occludin. So we no longer have zonulin and occludin doing their job binding tightly to one another and we get an opening in the small intestinal wall, or permeability of the digestive tube .
Chronic exposure to gliadin from gluten or similar substances can cause a down-regulation in production of zonulin and occludin, which further increases small intestine permeability . This permeability allows molecules and substances to move freely into the body’s circulation or blood stream. Now these things are foreign and wherever these particles end up are recognized by the body’s immune system and this is bad news.
With this permeability other gliadin, glutenin, and prolamin proteins initiate an immune response, both the innate and cell-mediated immune cascade to be exact. The innate immune response causes the body’s inflammatory cells to be attracted to wherever these foreign materials end up. The innate immune response also ends up signaling inflammatory chemicals to be released to help destroy the invading foreigner. An enzyme called transglutaminase helps modify gliadin and gluttenin so that it more effectively stimulates the immune system . We could envision a situation where all this inflammation in remote areas that these foreign substances have relocated could cause some serious damage and it’s not hard to see why the New England Journal of Medicine has associated 55 diseases with gluten intake and reactions.
With a permeable gut due to faulty tight junction functioning we get antigenic materials into our circulation. Some clinicians refer to this as leaky-gut syndrome, although it’s not widely recognized in Western medicine. Gut permeability has been linked to allergy induced autism, nutritional deficiency, increased absorption of toxins, liver inflammation, infection, rheumatoid arthritis, asthma, multiple sclerosis, vasculitis, Crohn’s disease, colitis, Addison’s disease, lupus, thyroiditis, chronic fatigue syndrome, and fibromyalgia .
So what do we make of all this? The research and anecdotal evidence seems to suggest eliminating gluten and similar prolamin protein-rich foods from the diet is probably a good idea. Eliminating wheat products, barley, rye, and other potential trouble sources like corn and oats is not very difficult to do, just don’t eat the products and use grass-fed meats, wild-caught fish, vegetables, nuts, fruits, roots, tubers, and seeds to make up your diet. By committing to 30 days of this elimination diet you will be able to accurately assess what effect, if any, these foods have on you. Do you feel better, look better, perform better at the end of this period of time?
After the elimination period you can try and revisit one of the eliminated foods to see what happens. Does it make you feel sick, gassy, or bloated? If so, you might be better off without it. Essentially you are drawing a line in the sand and setting a baseline for your own nutrition. By establishing a “normal” level of digestive health you can tweak the parameters to fit your own goals. If fat loss is the goal avoiding the wheat products might be smart due to the insulin-mimetic effect, their potential hyperpalatability, as well as avoiding processed foods in general. If you are looking to put on some size then you should also think about optimizing your ability to absorb the foods you eat so perhaps taking in potentially noxious food stuffs isn’t a good idea. Hopefully you liked this article! Please share it with friends, family, and coworkers if you did!
2) Lammers KM, Lu R, Brownley J, et al. (July 2008). “Gliadin induces an increase in intestinal permeability and zonulin release by binding to the chemokine receptor CXCR3”. Gastroenterology 135 (1): 194–204.e3. doi:10.1053/j.gastro.2008.03.023. PMC 2653457. PMID 18485912.
8) S. Drago et. al Gliadin, zonulin and gut permeability: Effects on celiac and non-celiac intestingal mucosa and intestinal cell lines. Scandinavian Journal of Gastroenterology, 2005; 41: 408-419
What follows is both an excerpt from my upcoming e-book Practical Training Handbook and a Dynamic Fitness Coach preview. Head over to my other website and sign up for your free 1 week trial!
Muscles are made up of cells and each cell is between a few micrometers to a few centimeters in length. An actual muscle is comprised of thousands muscle cells that are organized at multiple different levels. The following picture is a good reference about this organization:
Fig. 1: Skeletal muscle organization. Many hundreds (if not thousands) of muscle cells make up each individual muscle fiber and a sheath of connective tissue called endomyosium surrounds each muscle fiber. A muscle fiber, or myofibril, is a series of repeated sarcomeres, which are the functional units of a muscle.
Fig. 2: A myofibril and sarcomere
Sarcomeres are overlapping thick and thin filaments that form cross bridges during muscle contraction. Without getting into too much detail here, we can simply state that each myofibril is a series of sarcomeres that contract simultaneously, thus shortening the muscle fiber as unit. When many myofibrils contract in unison, large-scale muscular movements can occur.
Muscle fibers (myofibrils) are grouped together as fascicles, which in Latin means, “little bundle of sticks.” Each muscle contains multiple fascicles that are each individually covered by another connective tissue sheath called perimysium. The entire muscle is additionally covered by yet another connective tissue sheath called epimysium, which blends into the muscle’s tendons at its origin and insertion. Muscular contractions are transmitted between the specific muscle’s origin and insertion, where the insertion is pulled, rotated, or otherwise moved towards the origin. In this manner, the origin remains relatively stable, whereas the insertion is the actively moving end of the contraction.
The skeletal muscle’s origin is the more proximal (closer to the axial skeleton-ribs, vertebrae, skull, etc.) connection to the skeleton and the insertion is more distal, or further away. Each skeletal muscle has its own innervation by a motor nerve, which receives signals from the central nervous system (CNS), i.e. the brain and spinal cord. A motor neuron, or nerve that provides innervation to a skeletal muscle, ends at what is known as a motor end plate (MEP). The motor end plate represents the junction of the CNS and the skeletal muscle, whereby through a series of events- excitatory or inhibitory signals are transmitted to the muscle fibers. The motor unit is the basic unit of the innervated skeletal muscle. It is defined as the motor nerve and all of the muscle fibers (myofibrils) that it innervates. Moreover, when the nerve sends an excitatory signal to the muscle (i.e. contract) then all of the muscle fibers of that motor unit contract. Similarly, all muscle fibers of a single motor unit are of the same type, i.e. either fast twitch or slow twitch.
Skeletal muscles are organized by what myosin heavy chain they possess and their oxidative phosphorylation ability of fuel (e.g. carbohydrates, fats, and protein metabolites). The two main categories are Type I (slow-twitch) and Type II (fast-twitch). There are many differences between these two types of fibers and in principal, we care pare the discrepancies down to the following three things: time to exhaustion, contraction strength, and size. Type I fibers, in general, take longer to fatigue, provide less strength when they contract (but can contract for long periods of time), and are small. These types of fibers are present in motor units, whose functions include maintaining posture, locomotion, and similar long-term tasks. Because they are resistant to fatigue, they must have high concentrations of mitochondria, which make energy for the muscle. They also are rich in capillaries and other vasculature, which allows them to remove metabolic byproducts that cause fatigue like hydrogen ions, for instance. Finally, these fibers tend to be smaller than their type-II counterparts, thus they are the first motor units to contract. Type II fibers come in a variety of flavors depending on the text used to describe them, but in general they are less resistant to fatigue, have the potential to generate high levels of force, and are larger than slow-twitch muscle fibers. Motor units are summoned to be active based on the needs of the muscular contractile force. That is, the higher the force, the more motor units are required to be active. Additionally, they are recruited from smallest to largest to produce the contraction and furthermore, as less and less force is needed the largest (read high threshold) motor units become less and less activated. So for a simple task like picking up a pencil off a desk, it is likely that only slow-twitch motor units are functioning, since there is a low force requirement for successful completion of this task. In a task like a limit squat or deadlift however, more motor units are required to complete this task, if it is possible to do so, and so the higher threshold motor units that are larger and more difficult to activate, must be summoned to contract. It would be appropriate to call slow-twitch muscle fibers “low threshold” and classify fast-twitch muscle fibers as “high threshold”. Imagine a muscle group like the quadriceps muscle. Whilst standing, walking, or kneeling there is certainly some low level activity by the low-threshold motor units, i.e. the slow-twitch (type I) fibers at all times to maintain posture, provide contraction for locomotive movements, and balance. Then during a squat, these motor units’ contractile strength are not sufficient to complete the task, thus other motor units of this muscle group must be called upon to help in providing contraction of the muscles during the movement. The heavier the weight or the quicker the movement requires incrementally more extensive motor unit recruitment. Thus, to effectively train more muscle, more motor units, and subsequently stress the muscle in a more complete fashion, there exists a certain intensity (weight and/or speed) that the load must represent of that individual’s particular ability.
This generalized distinction between the two main types of muscle fibers provides us with a framework for how muscles adapt to specific stressors we impart upon them during training. We will soon compare and contrast two different modalities of training, endurance exercise via running long distances and strength training via barbell exercise in order to showcase how the different fibers respond differently based on their own individual properties listed in Figure 3.
In summary, skeletal muscle fibers are organized at various different levels with the sarcomere representing the most basic unit of a fiber. Muscles receive nervous innervation from the CNS and are grouped together as motor units. Motor units can contain anywhere from 10-10,000+ muscle fibers, which is dependent on the amount of fine motor control necessary in the area. For instance, the motor units of the muscles of the hand are much smaller than those of the back or legs, as the back and legs do not require very fine movements, whereas the hands and fingers do. Motor units consist of only a single type of muscle fiber and each type of muscle fiber has specific properties that characterize its function in movement of the skeleton. Furthermore, muscles can either contract or relax from excitation or inhibition stemming from the nervous system. When they contract, they exert force between their origins and insertions to produce movement about the insertion. These movements are known as the actions of a muscle and they are only produced about the joint or series of joints that the muscle crosses. In short, if a muscle does not cross a joint it does not act upon that joint.
To complete this aerial overview of skeletal muscle anatomy and function we must briefly describe some anatomical terms so that all further explanations are clear. When we talk about anatomy, we do so with normal anatomical position in mind. Normal anatomical position looks like Figure 4.
Fig. 4-Standard anatomical position
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