Nutrient Timing: Post-Exercise Window of Opportunity

article by Carson McQuarrie

Nutrition is the most beneficial ergogenic aid an endurance athlete can incorporate into their training. Whether carbohydrates, protein, or fats are ingested benefits experienced from these ‘macronutrients’ act to serve you by potentially increasing athletic performance and recovery. For most, time spent away from our sport far exceeds the time spent exercising so there’s more to gain from post-workout nutrition if we blend science with practicality. It’s been conceptualized the world over that immediately after a workout is the most important period for athletes to obtain nutrition for optimal recovery. This post will cover nutrient guidelines for what endurance athletes should consume to set their bodies’ processes for recovery up for success. 

Carbohydrates

As the saying goes carbohydrates are king for endurance athletes. While ketones (a breakdown of fat) have gotten some hype in recent news there’s a scientific consensus that carbohydrates are our bodies most optimal source of energy to fuel exercise and daily activities. Carbohydrates act to support recovery by increasing nutrient and water absorption, nervous system function for contracting muscles, replenishing depleted muscle glycogen stores, and maintain blood sugar levels between meals to maintain proper mental and muscular function. 

A process of carbohydrate metabolism called aerobic glycolysis is carried out to breakdown stored energy (glycogen) into glucose which can be absorbed into red blood cells that’s converted into adenosine triphosphate (ATP) which the body then uses for energy. Our bodies can hold roughly 450 (1,800 Kcalories) grams of carbohydrates in its stored form between the muscles, liver, and circulating blood. 450 grams of carbohydrates will become depleted, depending upon exercise intensity and size of individual glycogen stores, between 1.5 and 2 hours of intense aerobic exercise and thus post-workout replenishment is crucial. 

Post-Exercise Nutrition Window

Immediately proceeding exercise our bodies are most receptive to healthful nutrition, particularly carbohydrates, perhaps due to an evolutionary adaption because carbohydrates are our red blood cells’ and our brain’s only source for energy, except ketones in a state of starvation. Each macronutrient is metabolized at a different rate, however, in the time immediately following exercise (1-4 hrs) provides a more beneficial window for our bodies to absorb any nutrient at a faster rate. Assuming hydration levels are addressed first, carbohydrate intake is the second most important nutrient to focus on during this window of opportunity. 

The two most important factors regarding carbohydrates are the quantity and type of carbohydrate consumed. Because our bodies can digest, absorb, and utilize carbohydrates more readily we want to give it the simplest form of carbohydrates which are coincidentally called simple carbohydrates. Simple carbohydrates also have a higher glycemic index (GI), so looking for healthful foods with a glycemic index of 70 or higher is ideal. The second consideration, quantity, is important because this will, in turn, affect how much to consume of other macronutrients. In each of the 4 hours following exercise 1.2 grams (.035oz) per kg (2.2 lbs) of body weight of carbohydrates is optimal for recovery. An example of this would be a 75 kg (165 lb) athlete ingesting 90 grams (3.17 oz) of carbohydrates immediately following exercise and an additional 90 grams (3.17 oz) in each of the following 4 hours. 

Protein

Protein is probably the most asked or talked about nutrient among all sports and culture. Endurance athletes commonly have protein needs equivalent to strength-based athletes. However, most athletes as a whole often become too concerned with how much protein they’re getting resulting in overlooking the importance of carbohydrates and some downsides of getting too much protein. Protein, when consumed in appropriate amounts and of optimal quality, serves to aid recovery by promoting muscle damage repair, regulating fluid and blood pH balance, increases satiety, and are an integral part in many bodily compounds and processes.

In protein metabolism, ingested protein from food is broken down in the stomach into smaller protein molecules (polypeptides) and broken down further into individual amino acids. Amino acids are small enough to be absorbed through the intestines where they get carried to the liver for two processes of protein synthesis called transamination and deamination. In transamination, a process of growth, nitrogen is taken from an amino acid and used to build upon another where the body needs repair and growth. In deamination, a process of ‘excess’ protein, the amino portion of the amino acid molecule is taken and stored as fat or in small amounts burned as fuel such as during endurance exercise. Excess amino acids are also converted to ammonia and excreted through the urine as urea.  The effects of excess protein which are hard on the body raise considerations for optimal post-workout intake. 

Post-Exercise Nutrition Window

We also know that protein is not digested, absorbed, or utilized at the same rate as carbohydrates which affect consideration of intake post-exercise. The body has a lower limit of protein it can utilize at once so an important solution to optimize protein synthesis is consuming some protein immediately after exercise and small frequent amounts throughout the day. Virtually all foods have protein in them, even fruits, and all have a complete amino acid profile so know you don’t necessarily need to think of high protein foods. 

It’s accepted 1.2 – 1.4g/kg/day (.04 – .05oz/lb/day) is optimal protein intake for endurance athletes however in the 1 hour proceeding exercise I recommend 10 – 25 grams (.35 – .7 oz) or 2 – 2.5g/kg (.07 – .09 oz/lb), followed by returning to the previous recommended intake throughout the day. An example of this would be a 75 kg (165 lb) athlete ingesting 12.5 – 15.5 grams (.44 – .54 oz) in the proceeding hour and smaller amounts throughout the day. An example of an optimized post-exercise meal is 1 cup of pineapple, 1 cup of prunes, 2 cups of apricots, and an open face sandwich of whole-grain bread with 1 medium tomato (sliced) and ½ cup of spinach with some salt and pepper and you consumed an abundance of carbohydrates (105 grams), 20 grams of fiber, as well as an optimal 14 grams of protein ideal for a 75 kg (165lb) adult athlete. 

Fats

Fat hasn’t gotten much attention in sports compared to its macronutrient counterparts which have led endurance athletes to be unmindful of the subtle yet crucial role of fat in their diet. Fat in the diet serves to act as transporters for fat-soluble vitamins (A, D, E, & K), building blocks of hormones, source of essential fatty acids (EFAs) and increases satiety. Fat provides the body with fuel during low-intensity exercise, however, because fat is over twice as calorically dense as protein or carbohydrates (9 calories compared to 4 of protein and carbohydrates) athletes can find themselves very quickly consuming too much, even of high-quality sources. While ‘everything in moderation’ is key to maintaining optimal health and longevity, this applies strongly to fats for endurance athletes whose performance stand to gain by not letting their fat intake reduce total carbohydrate intake to below 60% – 70% of daily calories consumed. 

When fat is ingested it’s broken down by a cholesterol-based compound called bile secreted by the liver into the small intestine. It gets emulsified and absorbed into the bloodstream to get utilized by various organs and cells. Bile which emulsifies dietary fat is comprised of 50% cholesterol. This is partly why dietary fat intake is more strongly associated with blood cholesterol levels than dietary cholesterol. Too much cholesterol in our bodies, either through ingestion or natural production within our body to breakdown fat has a causal effect of chronic cardiovascular degenerative diseases such as heart disease and stroke. 

Post-Exercise Nutrition Window

There is no reason to think that increasing fat positively affects endurance performance unless it’s to obtain adequate calories or obtain the small amounts needed for essential bodily functions. So, there’s no set fat requirement immediate post-workout. Regarding total fat intake the adult acceptable macronutrient distribution range (AMDR) is 20% – 35%, however scientific literature indicates there’s no benefit for athletes to ingest more than 25% even if the athlete requires 4000+ calories/day. Energy-dense foods low in fat include complex carbohydrates such as potatoes, wild rice, and black beans. Simple carbohydrate energy-dense foods include dates, bananas, dried fruit, pineapple, and other tropical fruits. 

Conclusion

Humans all evolve throughout our lifetime of being athletes. Many of us were raised to speak, think, act, an even eat a certain way. Similar to how we learn to behave in a business setting as we grow older and more mature, we serve our bodies best to learn that perhaps the way we ate being sedentary or at least not as elite at a younger age is different than what our bodies perform best on. It’s difficult to unlearn what we’ve been raised to eat, often as a way of life. The guidance of a nutrition professional can help simplify the complex and support the changes your body will go through at a comfortable transition towards optimal performance and health. American and Canadian adult men and woman have a minimum daily fiber requirement of 38grams/day and 28grams/day respectively. A recent study published in the American Society of Microbiology showed that those eating 30 or more types of whole plant foods had greater microbiome diversity than those eating 10 or less, or more animal-based foods. When we have someone who’s knowledgeable and experienced we can trust we begin to understand through practice how a varied diet comprised of whole foods from nature can adequately and optimally serve our bodies day-to-day and athletic functions. 

References

Bernardot, D 2012, Advanced Sports Nutrition: Fine-tune your Food and Fluid intake for Optimal Training and Performance, 2nd edn, Human Kinetics, Champaign, IL.

Davis, B, Melina, V & Berry, R 2010, Becoming Raw: The Essential Guide to Raw Vegan Diets, Book Publishing Company, Summertown, TN.  

Kim, MS, Hwang, SS, Park, EJ & Bae, JW 2013, ‘Strict vegetarian diet improves the risk factors associated with metabolic diseases by modulating gut microbiota and reducing intestinal inflammation’, Environ Microbiol Rep, vol. 5, no. 5, pp.765-75, https://www.ncbi.nlm.nih.gov/pubmed/24115628 

NutrionFacts.org 2017, Microbiome: We Are What They Eat, https://nutritionfacts.org/video/microbiome-we-are-what-they-eat/

Wong JM 2014, ‘Gut microbiota and cardiometabolic outcomes: influence of dietary patterns and their associated components’, The American Journal of Clinical Nutrition, vol. 100, no. 1, pp. 369S-77S, https://academic.oup.com/ajcn/article/100/suppl_1/369S/4576479.

Thomas Endurance Coaching’s (TEC) Carson McQuarrie is a dedicated athlete and coach who specializes in ultra-distance cycling and nutrition. For more information on Carson’s coaching services, or to schedule a coaching consultation with him click HERE. 

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