Nutrition Beyond Weight Loss: Diet Impacts Neural, Immune, and Psychological Systems

By Dr. Sean M Wells, DPT, PT, OCS, ATC/L, CSCS, NSCA-CPT, CNPT, Cert-DN

The field of nutrition science continually expands. Once seen through only a metabolic and nutrient lens, nutrition science now interconnects with immunology, neurology, and psychology. How these fields of study interact are becoming amazingly complex but may help to shed light into various therapies and prevention for many common chronic conditions. How these various areas of clinical practice interact with nutrition makes it apparent that the practicing physical therapist needs to be aware of how foods interact with human physiology and biochemistry.

Immunonutrition

Nutrition certainly impacts immunology. From colds to rheumatic flares, diet can certainly mediate certain physiological processes that can drive or promote disease states. Nutrients play a vital role in disease prevention. Water helps to hydrate our eyes and mouth to prevent infections. Vitamin C helps to boost white blood cell count, which may help in the prevention of common colds; it also facilitates the absorption of iron and prevents rickets.

One major area of exploding research is the gut-microbiome. PTs should be aware of the billions of microbes that live in our gut and on our skin. These small bugs can interact with our bodies' ability to modulate the immune system (e.g. stimulate T or B cell aggregation), which can be seen in various rheumatoid arthritis (RA) and lupus studies. Fasting can positively impact patients with RA, while patients with lupus may benefit from diets low in sugar, high in omega 3 fatty acids, and rich in phenols.

In short, diet can help modify the gut biome, which can possibly mediate changes in disease state. All of these are solid reasons why a Doctor of Physical Therapy should be screening patients for potential nutrition-related issues. Diet is intricately connected with our immune systems, which can make or break our PT outcomes!

Neuronutrition

Our diet can impact our brain, nerves, and spinal cord. Don't think so? Try skipping your coffee today and see how your head feels...diet can and does modulate the nervous system in various ways.

Studies have shown that a poor, Western diet high in fat, sugar, and processed foods can mediate low-levels of chronic inflammation. Such inflammation has been linked with a phenomenon known as inflammaging, or advanced aging in flight of excessive inflammatory exposure. Inflammaging may explain how some individuals may present with cognitive decline, chronic tendon and joint pain, and cardiovascular disease. Such disease states are likely preventable and reversible, depending on the length of the condition and the applicable treatment methods.

It's not all bad news regarding diet and neurology. Diets rich in polyphenols from blueberries may help to improve balance in older adults, and may reduce the odds of Alzheimer's development by scavenging for free-radicals. Vitamin D, from the sun or supplementation, may help to increase muscle mass in older adults and help prevent some falls. Food can drive inflammation, mediate other physiological responses, as well as interact with the gut biome. The interaction with the gut biome and the brain is known as the gut-brain-axis, which we will discuss in depth in the next section.

Some of these findings have clear implications for neuro certified clinical PT specialists (NCS) and geriatric certified clinical PT specialists (GCS). Just as nutrition can modulate the immune system it can also directly impact the nervous system. PTs need to be educated on the interaction of food and nervous system.

Psychonutrition

Psychological disorders can alter the treatment response to physical therapy. As DPTs, how many clients have you seen successfully beat chronic pain when they are very depressed -- very few, right? In other cases, some of us have seen how psychological disorders can alter the posture (anxiety), reception of PT treatments (bipolar or memory issues), or pain response (depression). Psychological factors also dovetail in with social and economic factors, making it one powerful modifier to the response of physical therapy management. Diet does impact psychology and one popular nutrition term used for such study is psychonutrition.

How does nutrition factor into this? First, we understand more about how the gut talks to the brain (and vice versa). The gut-brain axis is a neural, endocrine, and immune system pathways that directly and indirectly communicate from the brain to the gut. Much of the "talking" is via neurotransmitters, short chain fatty acid production, and autonomic nervous system stimulation. The gut microbiome does much of the "talking" between the brain and gut, with the small gut bugs producing 90% of the body's serotonin in the gut vs the measly 10% the brain makes. WIth such a contribution of serotonin it's no wonder how diet can impact psychology! Food impacts the gut microbiome by shifting the type and amount of certain bacteria, fungi, or archaea, which all interact with our body in different ways. Probiotics have been studied for their mood and psychological impact, positively helping patients with depression, anxiety, and other mood disorders.

Second, diet directly modulates moods their various chemical and nutrients. Alcohol depressives the nervous system, which might either temporarily elevate or depress a person's mood. Chocolate studies have highlighted how certain compounds, like phenethylamine, may stimulate the release of dopamine, the feel-good neurotransmitter. In these cases, it's more clear how food directly impacts the psyche.

Physical therapists working with various patient populations will likely run into ways diet interacts with a patient's psyche. While some of the methods for modulating the psyche from food are very clear and direct, more research is needed to understand the complex interactions of the gut-brain axis. Regardless, the impact food has the psychology of a patient is one more facet that the DPT needs to be cognizant of.

Conclusions and PT Considerations

It's apparent that diet has intricate interactions with our immune, nervous, and psychological systems in a myriad of complex ways. Researchers are piecing apart, and looking for synergistic pathways, these interactions and systems in hopes of improving health and wellness. Physical therapists can also do their part by paying attention to patients' diet, screening for nutrition issues and substance abuse, and referring patients to dietary specialist (like RDs) for concomitant care when appropriate. Becoming more aware of nutrition science, taking nutrition continuing education courses, or enrolling in a nutrition certification program are also ways of staying current and offering best-practice. In the end, the future of PT may be one where a patient's gut biome is modulated with a probiotic strain while undergoing the "usual" exercise and education so commonly seen in PT practice. More to come!

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