Healthy Living

ASK THE DOCTOR: Why do I become dizzy after a meal?

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Guests serve food during a recent event. Feeling dizzy is common among people who eat foods that are high in carbohydrates.

Guests serve food during a recent event. Feeling dizzy is common among people who eat foods that are high in carbohydrates. Photo by Stephen Wandera. 

By Vincent Karuhanga

Posted  Monday, February 10   2014 at  02:00

In Summary

Feeling dizzy after eating a heavy meal is a common occurrence and may not be related to health conditions. Ensuring you do not skip breakfast and eating small, regularly spaced-out meals is recommended.

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Dear Doctor: I enjoy eating my lunch with passion but when I do so, I become dizzy, drowsy and fail to attend to work in the afternoons. Should I avoid eating? What would be the consequence?
James Bond Balaaga

Dear James: It is wrongly and widely believed that feeling sleepy after a meal (postprandial somnolence) is caused by redistribution of blood flow from the brain to intestinal (mesenteric) blood, with resultant blood deficit in the brain, prompting it to compensate by being less active.

However, it is well-known that the brain takes preference to the digestive system when blood needs to be redistributed after a meal due to a requirement for more blood for digestion and absorption of food.

The same thing happens during exercise. When a large amount of blood is diverted to the muscles, the flow to the brain is maintained and a person does not feel drowsy during exercise. After especially a big meal, many people show lack of mental and physical energy, which manifests in drowsiness, lethargy and lack of motivation. This is largely harmless and can strike anyone who eats foods that are high in carbohydrates, fats or sugars, especially table sugar (sucrose).

Eating stimulates activity in certain parts of the nervous system called the parasympathetic nervous system (feed and breed or rest and digest), which tells the body to slow down and digest. The more food one consumes, the more the body is made to shift its focus and energy towards digestion and absorption.
When food is digested to produce simple sugar such as glucose (the simplest form of sugar, which the body uses for fuel), its entry into the blood system causes the body to produce insulin hormone from the pancreas to remove the sugar and take it for either storage or utilisation.

The increase in insulin also causes the brain to produce more serotonin and melatonin, two chemicals that can leave a person feeling groggy. Luckily, this sleepy sensation does not last long, and usually passes after about one hour.
The parasympathetic and the sympathetic nervous systems work automatically, that is why they are called autonomic nervous system. They work in an opposing manner so that after a meal, when the parasympathetic activity increases, the sympathetic one reduces.

The sympathetic system is often known as the fight or flight system which keeps us alert while the parasympathetic systems is considered the rest and digest or feed and breed system and not surprisingly on its own, its activation leads to a person becoming sleepy. What is happening to you is normal and will not cause you problems except if you drive or operate machinery when you are sleepy.

Dear Doctor: I had difficulty sleeping with my wife. When I went to see a nurse, she said I had high blood pressure and I am now on inderal and aldomet medication. Will I recover?
Reader

Dear Reader: Hypertension is a condition in which abnormally raised blood pressure principally causes problems to blood vessels, eyes, the heart, kidneys and brain. Erectile dysfunction or impotence may result from problems affecting blood vessels, including hypertension and if not controlled overtime, may harden vessels denying them dilatation that makes blood rush into the penis to cause an erection.

Hypertension is sometimes associated with diseases such as diabetes that are known to lead to erection problems due to damaging blood vessels and nerves. Therefore, impotence may be a symptom of another condition that may also be causing hypertension.

Medications including those for hypertension such as aldomet and inderal can also lead to impotence. Lowering pressure from any anti-hypertensive drug will make it difficult for blood to rush into the penis to cause an erection.
Impotence can also result from perpetual anxiety that surrounds any illness, but especially hypertension as a person may be preoccupied with fear of having a stroke and death, and not having enough time to think about sex.

Erectile dysfunction (impotence) sometimes can be a clue to undiagnosed and uncontrolled high blood pressure, and to avoid the problem, you will need to first control your pressure with drugs that may not risk you impotence.

Dear Doctor: Is it true that having sex or walking triggers labour? And since you said saunas do affect men’s reproductive system and prevent them from having babies, can I use this as a family planning method?
Jonas Ssabakaki

Dear Jonas: What triggers labour is still a mystery but it is likely that this involves an exchange of hormonal signals between the mother and baby. It is an open secret that many sengas in Uganda recommend sex to trigger labour or reduce fear of pain during delivery.

Medics have used synthetic substances called prostaglandins to kick start or induce labour and procure abortion. Semen also contains prostaglandins that theoretically should help soften and dilate the cervix hence starting labour.
Orgasms in women during sex are known to cause the uterus to contract, which may be assumed to jump start labour. Walking causes, gravity to lower the baby with pressure on the cervix helping dilate it and quicken delivery.

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