Question

Keith is a college student. He is extremely busy studying and working part-time. Keith sleeps in late and therefore does not take time for breakfast. He rushes off to class. At lunch he has time for only French fries. When he gets home from school, he eats canned corn (only corn, nothing else) and washes it down with water. Then, he goes to work, only to start the same routine the next day.
When Keith is confronted about his poor diet, he responds, "The French fries are a good source of carbohydrates. Since they are fried in oil, I get my daily requirement of fat. At supper time, I eat corn and it has a lot of amino acids in it."

You, a medical student, suggest that Keith see a doctor. Keith complies and makes an appointment with a doctor. The doctor's report looks like this: Keith is pale and underweight, his urine and blood pH are low, and the ketones in the urine and blood are high. The Na+ concentration in the blood is low. Keith seems to have possible nerve problems.

The doctor explains that Keith is pale due to anemic conditions brought on by the poor diet. With a poor protein diet, Keith's erythrocytes may not be making adequate hemoglobin. Because his diet is very low in carbohydrates, his body is metabolizing fat, which is causing the weight loss. By products of fat metabolism are ketones, which are acidic. This accounts for the increase in ketones in the urine and the blood and a drop in the pH. A drop in blood pH will inhibit the small intestine from putting Na+ into the bloodstream. Sodium ions are necessary for proper nerve function. In short, Keith needs to begin eating well-balanced meals.

1. Why is corn considered to be an incomplete protein?
2. How are ketones formed?
3. How are sodium ions involved in the nervous system?
4. How does this scenario relate to fad diets?

Answer 1

1. Incomplete proteins are proteins that lack one or more amino acids. In order to make up for this loss, we are supposed to make combinations in the diet. For example, cereals lack lysine whereas legumes lack methionine. So it good to take both beans and legumes as part of the regular balanced diet. In the case of corn, it lacks the entire lysine and tryptophan. In corn, niacin or vitamin B3 is present as an indigestible complex. Due to the low levels of niacin, there are higher chances for pellagra.

2.

• Ketone bodies are basically energy sources. Mainly produced in the hepatocytes of the liver.
• During fasting, ketone bodies have been mainly utilized the brain as it requires glucose.
• High levels of Acetyl CoA is needed for the synthesis of Ketone bodies. Acetyl CoA can be produced as a result of β- oxidation of fatty acids or due to reduced activity of the pyruvate dehydrogenase.
• Through mitochondrial HMG-CoA, we are able to observe the formation of Acetoacetate, Acetone, and β-hydroxybutyrate which all are ketone bodies. Acetone is exhaled, and that can be measured to observe ketone activity in the body.
• Ketones are water-soluble molecules.

3. The membranes in the neuron have sodium-potassium pumps. These pumps are vital for nerve signaling. Sodium ions are involved in the rising phase of the action potential. The neurons have a negative charge and hence they pump out the sodium ions and pull in the potassium ions for the action potential. So when the sodium is hasn't in our diet, these pumps don't function properly and as a result, nerve impulses shall not be sent, as the pump shall reach the resting potential, and hence the nervous system will be shut down.

4. Fad diets are generally diets that promise someone immediate weight loss. They may help you shed a few pounds but they are not a healthy decision in the long run. Unprocessed, commonly cooked forms of potato-like boiled or mashed potatoes, corn on the cob, etc tend to have higher nutritional value, and maybe we can make claims of receiving our share of nutrients. Too much of anything is good for nothing. And also you can't keep eating foods deficient in certain nutrients, without taking them along with foods that can make up for the lack. So when consumed in large amounts, it is possible that sugar levels spike and there is unhealthy weight gain or weight loss.