The physiological impact of stress
Originally published on 27/02/15
Those butterflies you feel before a big match are caused by a lack of blood in your stomach. Pre-match nerves and anxiety are part and parcel of a tennis player’s life. Whatever level you play at, you’ll no doubt have felt that nervous tension in the pit of your stomach on match day. Some players are able to channel the excitement, while for others it can be severely debilitating.
Understanding how your body reacts in stressful situations can help you deal with anxiety. Your on-court performance should improve, too. Our stress response is controlled by the hormones adrenaline and cortisol. The fight-or-flight mechanism helps ensure we have the energy to combat the stress of a situation, by signalling the need to break down glycogen stores or initiate the conversion of fat or protein to produce energy, where glycogen isn’t available.
For some the stress is defined as ‘eustress’ which is an excitement or euphoric state accompanied by a ‘seize the day’ attitude, while for others it is ‘distress’ – the heightened anxiety that can knock a player off their game, often seen in the early stages of a match.
However, stress can also impact on digestion and can have serious consequences. When our body sends blood to our muscles, it reduces the blood flow to other organs, and our digestive function and immune response are two systems that are considered less important during times of stress. When stress impacts on digestion it can not only cause unwelcome symptoms, but also affect the body’s ability to absorb nutrients effectively.
Production of cortisol reduces the secretion of hydrochloric acid, the main component of stomach acid. Not only is this the first line of defence for destroying any food-borne bacteria or pathogens, but it is needed in order to release digestive enzymes which start the job of breaking down food into the molecules that will later be absorbed in the intestines. It is also needed to help absorb specific nutrients in the stomach and to produce the carrier molecule that allows us to absorb vitamin B12 from our food – one of the main catalysts in energy production within the body.
If pathogenic bacteria reach the small intestines they can affect the balance of microflora (naturally-occurring bacteria found in the gut), which in turn can reduce the barrier protection to the gut wall – already compromised due to the down-regulation of the immune system. We carry around 80% of our immune antibodies in and around the digestive tract because this is actually our biggest interface with ‘the outside world’.
Cortisol slows down our immune function, so the antibodies that normally protect the gut and surrounding tissue from harmful bodies are reduced, leaving us more susceptible to gut-derived toxins and bacteria, which can cause bloating, cramping, pain and diarrhoea. Worse still, the lack of gut defence could lead to the development of food intolerances, which can result in symptoms such as fatigue, muscle or joint pain, or brain fog.
Similarly, if the gut flora is disturbed and digestive enzymes are not being produced appropriately, the body will struggle to absorb the nutrients from even the most perfect diet, leaving you depleted in energy and recovery nutrients. So in order to avoid nasty symptoms such as stomach cramps and diarrhoea, there are two areas to address. Firstly, managing the release of the hormone cortisol on match day is more of a psychological issue than a nutritional one. However, managing cortisol levels the rest of the time will help diminish the effects on an ongoing basis. After all, it is not just tennis that can stress us out: busy jobs, home and family life and exam stress will all elicit the same reaction.
Skipping meals means the body has to release cortisol to break down stored energy, so eating three good meals and two snacks per day can help reduce demand. Eating a high-sugar diet will cause energy dips that will see more pressure being put on cortisol release, so stick to low GI food choices: instead of processed foods, refined sugars and saturated fats choose whole-grains, plenty of fruit and vegetables and lean protein in the form of chicken, turkey or fish. And avoid stimulants such as alcohol and caffeine – so coffee, tea and caffeinated soft drinks are out!
The second area to consider is ensuring that gut function is restored to normal. You can stimulate stomach acid production by starting the day with a cup of hot water and lemon, taking a spoonful of apple cider vinegar before each meal, and including bitter foods like radishes, artichokes, beetroot, lemon, garlic, ginger, turmeric and dark green or red leaves. Beneficial gut bacteria thrive on fibre, whereas pathogenic bacteria like to feed on sugar, so eating plenty of fruit and vegetables and cutting out sugary foods will help to rebalance your gut flora.
If you still experience digestive disturbance you may need some specialist advice from a nutritional therapist or sports dietician who can organise tests to understand the complete picture and help restore your gut to better health.