Question

Derrick is a 35-year old African American advertising executive with a very hectic schedule. He’s fairly active, has a BMI of 23, and is in generally good health. However, at his annual physical, his doctor discovered that Derrick has high blood pressure. Derrick assures his doctor that he eats well and can’t understand why his numbers are so high. Derrick’s doctor recommends that he limit his salt intake and eat more whole foods rather than packaged products. Derrick takes his doctor’s advice to heart and takes the time to prepare some of his favorite meals. He takes a ham and cheese on rye sandwich to work instead of ordering Chinese food with his coworkers, even though it means giving up his favorite dish, General Tso’s Chicken. For dinner he has smoked trout with mashed potatoes and steamed broccoli rather than his usual frozen dinners that have about 650mg of sodium. He no longer salts his food at the table. Derrick even replaces his usual snack of salted peanuts with dry cereal, his favorite being Corn Flakes. His bedtime snack is now a pudding cup instead of chips or salty, buttery popcorn. Derrick sips on water or 100% fruit juice during the day, but he rarely drinks milk.

After a month on his new diet, Derrick returns to his doctor, confident that his numbers are down. To his surprise, his blood pressure remains unchanged! “I don’t understand! I don’t put salt on anything and I’m eating whole foods!” he laments to his doctor.

Question 1: Explain how sodium is a contributing factor to Derrick’s hypertension, detailing the role(s) that sodium plays in the body that affect blood pressure. You will need to defend your answer using specific facts, data, and other information drawn from the textbook and at least one other supplemental source.

Answer 1

Hypertension or high blood pressure is a lifestyle disease that is being reported in increasing numbers all over the world. There are many causes for hypertension. These causes range from stress at work, mental tension, lack of physical activity, drugs(medicines) and obviously the diet and many other factors. A diet in high salt content can increase the blood pressure.

Blood should have a normal fluid content to keep the pressure at balance. Whenever there is an increase or persistent increase in blood fluid levels, the blood pressure is also increased accordingly. Whenever the osmolarity of blood fluid increases, there occurs a decreased potential to take up the water from blood by the kidneys (due to reversal of or lowering of magnitude of concentration gradient), leading to increased volume of blood fluid. This causes the blood pressure to increase.

(Note:- blood pressure is the pressure exerted by the artery walls on the flowing blood. This pressure increases as the amount of fluid is increased or as the diametre of artery is decreased.)

So, a high salt intake causes water to be retained in blood causing high blood pressure.

Water balance is the key to normal blood pressure. The intake of water is stimulated by behavioural stimulus like thirst. The excretion of water is regulated by the kidneys along with hormones like ADH (Anti diuretic hormone, also called as vasopressin as it can increase blood pressure). As said earlier, whenever sodium level increases, the reabsorption of water in the kidneys is decreased or arrested. This triggers release of elevated amounts of the hormone ADH. ADH can directly increase blood pressure(Vasopressin - another name of ADH for this reason). Release of ADH is triggered by increase in blood osmolarity(increase in solutes in blood). Another situation is that when blood sodium level increases, it has to be absorbed by the distal parts of the kidney. This is stimulated by Renin-angiotensin mechanism. The hormone angiotensin II upon activation causes stimulation of Aldosterone release. Aldosterone causes increased sodium uptake by distal parts of the renal tubules with a corresponding release of water to blood stream, causing increase of blood fluid. This also causes increased blood pressure.

As far as Derrickk is concerned, since he is an African American, his genetics may be designed in such a way that he has hypertension. This could be a possible reason for high blood pressure even after keeping his diet on check. Also, the food that he had viz. Cheese, corn flakes etc has a good amount of sodium in it. He used fruit juices and water, which also can increase blood fluid volume, particularly thd fruit juice that increase both fluid volume and electrolyte content. He doesn't consume much milk. This coupled with his dietary sodium(cheese, corn flakes etc) can lead to high blood pressure.

Also, he didn't quit his favourite food like Chicken, chips etc with happiness. Although he wanted to be healthy, he always craved for his favorite food that was put away from him for a long time. This could make imbalances inbrelease of adrenaline and nor adrenaline.

If more clarification is needed, please text in comments box.