Welcome to Part 5 of our “Primer on Protein” series, in which we are digging into nutrition as the base of the pyramid and unpacking CrossFit’s nutrition prescription: “Eat meat and vegetables, nuts and seeds, some fruit, little starch, and no sugar.” The first two words — eat meat — are used as a simple placeholder for animal foods in general (beef, pork, chicken, fish, eggs, dairy, etc.), in which the primary macronutrient is protein.
Most of the protein you eat is not burned for energy but goes toward building all your tissues, hormones, neurotransmitters, immune cells, etc. Every bit of you is built out of something you ate. In this six-part series, we are exploring the under-appreciated but vital role of the structural elements of the diet and all the weird and wonderful ways the body uses dietary protein to support good health.
So far, we have explored how the food we eat relates to skeletal muscle mass in Part 1, bone density in Part 2, mental health in Part 3, and joints and connective tissue in Part 4. In Part 5, we will examine how protein from our food supports the body’s antioxidant system.
Free Radicals
To make energy for high-intensity exercise or simply stay alive, our biology combines the fats or carbohydrates from our diet with the air we breathe in a process called aerobic respiration that occurs in our cells’ mitochondria. These little powerhouses (hundreds or even thousands per cell) crank out ATP, known as the energy currency of the cell, which allows our muscles to contract and do work. However, turning food into energy can be messy work.
Reactive Oxygen Species (ROS), also known as free radicals, are produced as byproducts of normal cellular metabolism and are a group of highly reactive molecules containing oxygen. They go by names like Superoxide Anion (O₂⁻), Hydrogen Peroxide (H₂O₂), and Hydroxyl Radical (OH·). Radical indeed.
A state known as oxidative stress occurs when there is an imbalance between the production of ROS and the body’s ability to neutralize them into non-harmful molecules. Excess ROS left floating about causes severe damage to our cells by initiating lipid peroxidation, DNA strand breaks, and protein oxidation. Although we think of oxygen as the life-giving stuff of clean air, it’s actually quite toxic. Reacting with oxygen is what causes metal to rust, walnuts to go rancid, and apples to turn brown. For people, if nothing else gets us first, we will eventually die from the accumulated damage caused by exposure to oxygen.
In athletes, some ROS are actually beneficial for signaling the repair adaptations to exercise. When the balance tips toward oxidative stress, this impairs recovery, hinders performance, and increases the risk of injury. Over time, the damage from unchecked free radicals leads to chronic inflammation, aging our bodies inside and out, and accelerating the development of chronic diseases such as cancer, cardiovascular disease, and neurodegenerative conditions like Parkinson’s and Alzheimer’s. There’s even a new word for this now: Inflammaging.
Think of ROS like a bunch of hyperactive toddlers running loose in a fine china shop. They’re small, but they’re everywhere — knocking over vases, chipping plates, and causing all kinds of chaos. Antioxidants are the responsible adults you need to stop those kids from smashing up everything in sight and leaving a trail of destruction in their wake. The antioxidants are there to calm those free radical kids down, guide them out of the shop, and keep things from getting totally wrecked.
Antioxidants
The term “antioxidant” is a buzzword in food and supplement marketing. While many people associate this term with fruits and vegetables, the human body has a complex, built-in antioxidant defense system that relies heavily on certain amino acids derived from protein-rich foods in our diet to function properly.
Glutathione: The Most Responsible Adult in the Room
The body’s multi-layered antioxidant defense system includes enzymatic and non-enzymatic components. While vitamins like C and E found in veggies, fruit, and nuts, play a part in this defense, the star of the body’s antioxidant system is glutathione, often referred to as the “master antioxidant.”
Glutathione works directly on free radicals by donating an electron and turning these rogue molecules into water or other less reactive substances. It also regenerates other antioxidants, such as vitamins C and E, and allows them to help with neutralizing free radicals as well.
Glutathione is a tripeptide made from three amino acids: glutamine, cysteine, and glycine. These amino acids come from dietary protein sources like meat, eggs, fish, and dairy. A diet rich in these whole-food protein sources supplies the necessary amino acids for glutathione synthesis, supporting the master antioxidant system. Diets that lack these nutritious foods leave the body ill-equipped to keep free radicals under control.
In healthy adults, glutathione synthesis decreases as dietary protein decreases, and the bare minimum RDA for protein of 0.8g per kg of body weight per day is not enough to sustain the body’s antioxidant system. An intake at least 25% higher than the RDA is needed to support glutathione production. In older adults, a higher protein diet, particularly with a higher intake of the amino acid cysteine, increases glutathione production, which lowers mortality and improves frailty. Getting enough protein in the diet literally slows the aging process.
Melatonin: Not just for sleep
ROS being a natural byproduct of making energy, the mitochondria are both the primary source and target of oxidative damage. With a delicate double membrane and their own independent set of DNA, mitochondria are particularly vulnerable to these rogue molecules. Damaged mitochondrial function is an intense area of cutting-edge research and has been linked to everything from cancer to schizophrenia to elusive conditions like Chronic Fatigue Syndrome. In CrossFit athletes, it should come as no surprise that healthy, robust mitochondria are required for cardio-respiratory endurance, muscle function, and all aspects of increasing work capacity across broad time and modal domains.
Interestingly, melatonin — generally known for regulating sleep — is the primary antioxidant within the mitochondria. Melatonin directly neutralizes several types of ROS, including hydroxyl radicals and hydrogen peroxide, which are particularly harmful to mitochondrial function. Also, melatonin enhances the activity of other antioxidant enzymes that go by fun names like superoxide dismutase, catalase, and glutathione peroxidase.
Melatonin is so essential that it is considered the master regulator of “quality control” for the mitochondria, initiating damaged organelles’ repair or elimination (mitophagy). Low melatonin is considered a biomarker for aging, poor cognition, and psychiatric disorders, while healthy levels are neuroprotective. Melatonin also augments the effectiveness of all traditional cancer treatments, an effect in line with the theory of cancer as a mitochondrial metabolic disease.
As we learned in Part 3 of this series, melatonin is produced from the amino acid tryptophan (with the feel-good chemical serotonin as the intermediary step). Tryptophan is an essential amino acid, meaning we must get it from our diets. Normally a “rare” amino acid, animal-based protein sources, such as turkey, chicken, eggs, and dairy, are rich in tryptophan, making them ideal for supporting melatonin production. However, the signal to start this production is controlled by darkness, so it should be noted that minimizing light exposure in the evening (put your phone away!) and maintaining a dark bedroom environment are necessary for healthy melatonin levels.
The CrossFit nutrition prescription to “eat meats and vegetables, nuts and seeds, some fruit, little starch, and no sugar” is about more than building muscle and doing more thrusters. It prioritizes protein-rich foods, which supply the building blocks needed to control free radicals — the unruly toddlers of metabolism. With amino acids from meat, fish, eggs, and dairy, your body can produce the powerhouse antioxidants glutathione and melatonin, the much-needed responsible adults in the room, to protect your cells from damage. This helps slow aging, reduce inflammation, promote recovery, reduce injury, and improve your Fran time.
About the Author
Jocelyn Rylee (CF-L4) and her husband David founded CrossFit BRIO in 2008, starting in a modest 1500 sq ft space and focusing on personal training. Her dedication to excellence has also earned her a position on CrossFit LLC’s Level 1 Seminar Staff, a role that allows her to share her passion and expertise with aspiring coaches. Jocelyn holds specialties in Endurance, Gymnastics, Competition, and Weightlifting and is also a certified Strength and Conditioning Specialist through the NSCA. As a Level 2 Olympic Weightlifting Coach and a Level 3 referee, she has been deeply involved in the sport, even serving as a board member of the Saskatchewan Weightlifting Association for five years. Her achievements include being Saskatchewan’s top-ranked female Olympic Weightlifter from 2012 to 2015, during which she held provincial records in the Snatch, Clean & Jerk, and Total in her weight class. With an MS in Human Nutrition, Jocelyn loves sharing her knowledge on nutrition and performance through her blog and Instagram as “The Keto Athlete,” where she delves into the science of nutrition and its impact on athletic performance.
The Primer on Protein: Part 5 - Antioxidants