Stress, Health & Disease - Why Zebras Don't Get Ulcers (ch5)

Chapter 5: Ulcers, the Runs, and Hot Fudge Sundaes

Stress and food consumption

• During a stressor, appetite and energy storage are suppressed, and stored energy is mobilized.
• Post-stressor, appetite goes up.
• During a stressor both CRH* and glucocorticoids are released. CRH suppresses appetite (works fast) and glucocorticoids stimulate appetite (takes longer time).
• The appetite suppressing effects of CRH are stronger than the appetite-stimulating effects of glucocorticoids.
• If there are more glucocorticoids in the circulation and little CRH, then you have probably started the recovery period
• The changes in appetite depend on the type of stressor and the way people react to the stressor.
• Hyperphagia: abnormally increased appetite.
• Hypophagia: eating too little.
• Those who tend to secrete a lot of glucocorticoids are the most likely to be hyperphagic after stress.
• During stress, people who are normally restrained eaters (e.g.: dieters) tend to become more hyperphagic than others.        

Storing food

• Glucocorticoids increase the storage of ingested food.
• The fat can either make you apple shaped (having a waste bigger than hips) or pear shaped (having hips bigger than waist).
• When glucocorticoids stimulate fat deposition, they do it preferentially in the abdomen, promoting apple-shaped obesity.
• Those who develop apple shape are more at risk for metabolic and cardiovascular disease than those who develop a pear shape.
• For the same stressor, if you tend to secrete more glucocorticoids than most, not only are you going to have a bigger appetite post-stressor, you’re also going apple.
• By consuming more food, you bulk up on abdominal fat and you temporarily reduce stress, which makes it more difficult to fight obesity.

Bowel movements

• The role of the gastrointestinal (GI) tract – the esophagus, stomach, small intestines and large intestines – is to get food from your mouth to its digested form in your circulation
• Mammals spend 10 to 20% of their energy on digestion
• As digestion takes up so much energy, it stops during a stressor. It is also possible that your body wants to get rid of dead weight, like the excess baggage in your bowels.
• Organic GI disorder: the term used to describe a health condition in which there is an observable and measurable disease process, such as inflammation
• Functional GI disorder: a disorder in which the doctors can’t find what is wrong, but the there is a feeling of being unwell and it is sensitive to stress
• The most common functional GI disorder is irritable bowel syndrome (IBS), which involves abdominal pain that is relieved by symptoms such as diarrhea or constipation, passage of mucus, bloating, and abdominal distention.
• Major chronic stressors increase the risk of the first symptoms of IBS appearing, and worsen preexisting cases
• IBS patients tend to be less sensitive to skin pain and more sensitive to internal organs like the intestines
• The sympathetic nervous system is responsible for the increasingly large intestinal contractions during stress. People with IBS have overactive sympathetic nervous systems, and the pain of the gut can stimulate the sympathetic nervous system activation even further, making it a vicious cycle.
• Traumatic stress in early life greatly increases the risk of IBS in adulthood

Ulcers

• An ulcer is a hole  in the wall of an organ, and ulcers originating in the  stomach or in the organs immediately bordering it are called peptic ulcers
• The ulcers within the stomach are called gastric ulcers, those a bit higher up are called esophageal, and those at the border of the stomach and the intestine are duodenal (the most common peptic ulcers)
• There is a subtype of ulcers that forms rapidly (sometimes just few days) due to immensely stressful crisis. These ulcers are potentially life threatening
• For gradually emerging ulcers, a bacterium called Helicobacter pylori is responsible, next to stress, genes and environment

How does stress exacerbate the process of ulcer formation?

1. Acid Rebound

• There are foods that are more difficult to digest. For this, we need contractions and hydrochloric acid to pour into our stomach from the cells lining it.
• The stomach protects itself by layers of stomach wall with mucus coating it that buffers the acid.
• In a stressful period, there is less digestion and less acid, therefore the stomach decreases its protection (e.g.: by undersecreting mucus).
• After the stressful period, digestion comes back, however, the stomach is less protected. This can lead to the development of ulcers.

2. Decreased blood flow

• In response to  stress, your sympathetic nervous system diverts blood from the gut to more important places – like the exercising muscles.
• If your stressor is one that involves a dramatic decrease in blood flow to the gut, it begins to cause little infarcts – small strokes- in your stomach walls, because of lack of oxygen. You develop small lesions of dead tissue, which are the building blocks of ulcers.
• With decreased blood flow, less of the acid that accumulates is being flushed away.
• Running your cells on oxygen can sometimes produce an odd, dangerous class of compounds called oxygen radicals. These are usually disposed by another class of compounds (scavengers).
• During  periods of chronic stress, when blood flow to the gut decreases, your stomach can stop making those scavengers. The oxygen radicals then start killing cells in the stomach walls, leading to ulcers

3. Immune suppression

• Chronic stress suppresses immunity, and the lowered immune system equals more Heliobacters (a common cause of peptic ulcers)

4. Insufficient Amounts of Prostaglandins

• Micro-ulcers begin now and then in your gut. Normally your body can repair the damage by secreting prostaglandins, chemicals that aid the healing process.
• During stress, the synthesis of prostaglandins is inhibited by the actions of glucocorticoids.
• In this scenario, stress impairs your body’s ability to catch ulcers early and repair them.

5. Stress contractions

• Stress causes the stomach to initiate slow, rhythmic contractions (about one per minute); and for unknown reasons, these seem to add to ulcer risk.

*CRH: Corticotropin-releasing hormone

Resources: Sapolsky, R. Why zebras don’t get ulcers: The acclaimed guide to stress, stress-related diseases, and coping. New York (NY): Henry Holt and Company. 2004 3rd edition