How to Eat Better in the New Year

Note: This article is not meant as a substitute for proper medical advice. Please consult with your medical practitioner before making any major changes to your diet or using any type of remedy, herbal or otherwise.

By Robert Luby, MD

“You are what you eat” is a phrase that has become the basis of many New Year’s resolutions to eat a healthy diet.  When examined more closely however, it is only the case that “you are what you eat” if you fully digest and absorb that which you consume.  In other words “You are what you assimilate.”  What you are able to digest, absorb, and assimilate depends greatly on how you eat.  Therefore, the claim which will be made in this article is that “You are HOW you eat.”

The digestion, absorption, and assimilation of nutrients is highly dependent upon the nervous system, specifically the parasympathetic branch of the involuntary nervous system (PSNS).  The involuntary nervous system operates in an oscillatory fashion with either the sympathetic or parasympathetic function being predominant depending on the situation.  For example, during times of emotional stress or the need for physical exertion, the sympathetic nervous system will predominate.  When the stressful period has passed, the PSNS takes the reins to allow such important functions as sleep, immune function, detoxification, and tissue repair to occur. 

Enhancing the optimal function of the PSNS is the target of many mind-body modalities and relaxation techniques such as meditation, guided imagery, hypnosis, yoga, breathing exercises, and the like.  Therefore the extent to which an individual engages in these activities will also improve digestion and nutrient assimilation.  This is probably especially the case when the PSNS-enhancing relaxation technique is performed prior to eating.  It is also the basis for the common wisdom to set aside all tasks and sit while eating, optimally taking a few moments to express gratitude prior to commencing the meal.  Dimmed lights, a quiet atmosphere, and friendly company also have the potential to enhance the PSNS, thereby improving nutrient digestion and assimilation.

Moving on to a more biochemical and anatomical perspective, there are four phases of digestion: cephalic, oral, gastric, and intestinal.  Nutrient assimilation will be greatly affected by how well each of these phases functions.  It should be noted at the outset however, that each of these phases may function optimally only when the PSNS is the predominant modality of the nervous system.  What follows is a primer on how to improve the function of each phase, and therefore to improve your nutritional status.

Cephalic Phase
The mere sight, smell, and texture of foods can stimulate certain regions of the brain to begin the process of digestive enzyme release in the stomach.  This phenomenon is mediated by the vagus nerve, which is, you guessed it, the main nerve of the PSNS.  These organoleptic qualities of food are able to exert their maximal effect on digestion when time is taken to prepare the food in a pleasant atmosphere.  Therefore, it is not inconceivable to extend our previous maxim to “You are how you prepare your food.”

Oral Phase
Enzymes in the stomach and intestine are much more effective at digesting small food particles than large ones.  Therefore, chewing becomes an important determinant in the effectiveness of nutrient assimilation.  It is important to chew slowly and thoroughly, thus spawning the digestically-correct quip “Drink your foods.”  Saliva, as a liquid, is best able to transform solid foods to into a slurry prior to the act of swallowing when care is taken to chew mindfully.  Saliva, as an agent of digestion, contains enzymes capable of digesting not only carbohydrates, but fats as well.  Thus, thorough oral mastication can ensure that the stomach receives food in a partly digested state.  To coin new phrases of nutrient assimilation wisdom:  “You are how you chew” and its correlation, “Be in a slurry, not a hurry.”

Gastric Phase
As previously mentioned, digestive enzyme release in the stomach is initiated by signals from the brain via the vagus nerve (PSNS) in response to experiencing the sensory qualities of food.  The presence of food in the stomach is a further stimulation of enzyme release.  Optimizing the gastric phase of digestion also involves stomach motility, or the churning action of the stomach.  This, in turn, is optimized by being in a relaxed state while eating to promote the action of the PSNS. 

For individuals who release suboptimal gastric digestive enzymes, it is likely important to limit the amount of liquids consumed with meals.  Liquid ingestion acts to dilute the concentration of digestive enzymes and it is conceivable that this could impair nutrient absorption.  On the other hand, the ingestion of organic acids such as vinegar and lemon juice shortly before or at the start of a meal may enhance digestion in the gastric phase.  Suboptimal gastric enzyme release can also be the result of antacid medications.  While they may relieve the symptoms of heartburn and stomach upset, they do nothing to reverse the foundational causes of these conditions, and it is well established that they impair nutrient digestion.

Special consideration may also be given to the order of food ingestion.  Of the three macronutrients carbohydrate, fat, and protein, it is the last which is the most difficult to digest.  Therefore, choosing to eat the protein-rich food at the start of a meal will allow it to be in the stomach at a time when the concentration of digestive enzymes is highest, and allows for the most time for complete digestion.  Postponing the ingestion of carbohydrates to later in the meal has the added benefit of blunting the rise ofblood sugar levels after a meal.

Intestinal Phase
Intestinal function is silenced during sympathetic nervous system stimulation and enhanced when the PSNS is predominant.  This is yet another way in which optimal nutrient digestion, absorption, and assimilation depends on the emotional and physical state of the individual. 

The intestinal phase of digestion is also dependent on enzymes from the pancreas and gall bladder, but more importantly on chemicals released by the easily damaged components of the intestinal lining.  Therefore, whatever damages the intestinal lining may impair nutrient assimilation.  The list of such substances is growing and includes not only the obvious culprits of alcohol, aspirin, and ibuprofen (and similar pain medications), but also emotional stress, sugar, and many processed foods and artificial food additives.

It is not too late to consider making a New Year’s resolution to improve your health.  Yes, there is no doubt about the verity of the adage “You are what you eat” and I don’t expect to see “You are how you chew” or any of my other adaptations on bumper stickers any time soon.  But even without changing what you eat, you may improve your nutritional status by remembering to be mindful of how you eat.