The Digestion Dilemma
When nailing down nutrition and balancing athletic training programs, it is best to view our bodies in the most basic physical form: a colossal colony of cells, genes, and foreign strands of DNA. Genetic activity — turning genes on and off; locking them in with changes in environment — is part of our adaptability and dietary flexibility. How our genes are read and expressed is conditional upon what we are exposed to, including the food we put into our bodies.*
Our guts house trillions of bacteria and other microbes which work as a composite (termed microbiome) to help break down the food we eat. The flora and fauna of our gastrointestinal system–which scientists now consider to be an extra organ albeit non-human–can change rapidly with what we are putting into it. If you have a diet heavy in meat protein and cheese, your microbiome will adjust to break down the excess fat and will produce more bile to do so. If you are vegetarian, the bacteria will provide a more robust microbiome for breaking down fiber and different species of plants. Certain genes activate, different substances are secreted, new bacteria is introduced, and our bodies become more efficient at digesting specific foods within just 48 hours of consumption. Determining which diet (heavily plant based vs. near carnivorous) produces a healthier microbiome is another story and one which is just beginning to be tested in the laboratory, however, scientists do know that the typical Western diet of lots of meat, sugar, and fat create a profile that is less diverse and better at accumulating calories from energy-rich food. As people lose weight and shift to a lower calorie, whole-food diet, their guts develop a microbial profile associated with being svelte. Researchers have also found that obese people have more of a certain type of hydrogen-producing bacteria called Prevotellaceae in their intestines and that bacteria could be contributing to their obesity because of its efficiency, and thus the person’s digestives system doesn’t require as much energy to metabolize food.
Varying microbiomes and physiologies are chiefly responsibly for the unique ways our bodies extract calories from what we eat. Nutrition labels provide a general guideline but can be very inaccurate because they exclude this intricate system of digestion. If you have a gut that has adapted to simple sugars and sauteed goods, you will have less enzymes and bacteria that can dissolve plant fibers and you will assimilate less nutrients from, say, raw carrots than would a person who eats more fruits and vegetables. And depending on your ethnic background, the length of your intestine has an impact on how long your food will sit and be available to absorb nutrients. But not only does our “other organ” aid in digestion, heating and processing our food is what has allowed us to dramatically increase the number of calories derived. Raw food requires more energy to break down, so cooking it takes care of some of the expenditure for us and makes it more digestible. More nutrients enter circulation and have the potential for being stored as fat. Eating a piece of whole grain bread takes more energy (meaning less calories are taken in) than eating the same bread but toasted. Protein is a complex string of amino acids which demands more energy and enzymes to unravel than digesting a grain or fruit, so even though 1-ounce of lean meat typically contains around 50 calories on a nutrition label, you cannot be guaranteed you are taking in that much. The cost of digestion is simply too complicated to have a definite number.
So now we know that it’s nearly impossible to count calories but we also know that how much we digest is highly changeable depending on what we choose to eat and how it’s prepared. This adaptability also makes cycling diets throughout the year more interesting. As athletes, you can tailor what you eat to meet your work-load needs not just seasonally but weekly, or even daily. This can be tied into the debate over the Paleo-diet and Ketogenic diet. Is one better than the other? Are they better than other diets? How long should you stay with one should you choose to try it? The truth is that most of the fueling issue falls into a vast gray area. More research is needed to find out how sustainable and healthy certain diets are but as of right now we know that fruits and vegetables are healthy, most processed foods are not, and that genes express themselves differently depending on environment. Our bodies are machines and as our workouts and training changes, so must the types of food we eat, both directly after the workout and throughout the course of the week. So now is the season to play around with what works best for you. Whatever your diet you embark on, be prepared for a drop in energy in the first week as your microbiome adjusts and your body is shifting to work with what you are feeding it.
*It is a common misconception that any given gene is “for” a specific trait. Phenotypic characteristics are dependent upon what context a gene is in and what “community” of other genes is working with it. A gene that codes for one phenotype in one environment can be expressed very differently if that environment changes, which must mean that behavior and body performance alters as well.
Written by Tanya Acker (Davis)