Field Notes

Small Study Suggests Sugary Soda Linked to Reduced Kidney Blood Flow

Regular consumption of sugary soda sweetened with high-fructose corn syrup (HFCS) may reduce kidney blood flow, which could be linked to a greater risk of developing chronic kidney disease (CKD), according to a recently published study in the American Journal of Physiology-Renal Physiology. The study, chosen as an APSselect article for May, was conducted in two parts on 25 men and women.

Vascular resistance occurs when blood vessels constrict to impede the flow of blood in the kidneys. This can lead to increased blood pressure and reduced kidney function, among other complications.

Approximately 37 million people in the United States suffer from CKD, according to the National Kidney Foundation. The Foundation estimates CKD kills more people than breast cancer or prostate cancer. It’s considered to be an underrecognized public health crisis.

“Consumption of 500 mL of a commercially available soft drink sweetened with HFCS increased vascular resistance in the kidneys within 30 minutes,” the researchers wrote. “We also found that increases in segmental artery vascular resistance were exacerbated during the CPT (cold pressor test) compared with water consumption.”

In a follow-up study, the researchers also found changes in arterial blood flow inside the kidneys were brought on by HFCS, not due to the caffeine content or osmolality of the beverage. Increases in resistance in arteries inside the kidneys “were likely due to simultaneous increases in serum uric acid and copeptin. Collectively, our findings indicate that HFCS-sweetened soft drink consumption increased renal vasoconstrictor tone at rest and during sympathetic activation.”

— Source: American Physiological Society


Binge Eating Associated With Depressive Symptoms

Many people across the country have resorted to binge eating to cope with the coronavirus outbreak, but relying on unhealthful snacks is detrimental in the long run, according to Lina Begdache, PhD, an assistant professor of health and wellness at Binghamton University, State University of New York.

Begdache says binge eating mainly is caused by stress, which can alter the chemical in the brain that regulates mood, sleep, and appetite. While people can get a temporary feeling of happiness from unhealthful food, it tends to lead to feelings of depression.

“Binge eating during quarantine could be stress related or just due to boredom,” Begdache says. “Stress alters brain chemistry, namely levels of serotonin. The latter is a neurochemical that regulates mood, sleep, and appetite. By depressing serotonin levels, appetite regulation is disrupted and the brain craves food that stimulates serotonin biosynthesis.

“Although serotonin’s precursor is tryptophan, an amino acid that comes from protein, its transport to the brain is dependent on insulin, which is elevated after eating carbohydrates. Another important brain chemical lowered by stress is dopamine, which controls motivation, movement, learning, and focus. When dopamine levels decrease, individuals lose motivation to eat healthfully and exercise. After binge eating, people often feel ‘depressed’ about their bingeing.”

Begdache continues: “Mechanistically, eating food high in simple carbohydrates such as sweets temporarily elevates serotonin due to a fast increase in blood insulin. However, serotonin eventually crashes due to the sudden drop in insulin after a while, leading to a depressed mood. Unhealthful foods tend to be high in fat and also are devoid of several vitamins and minerals that support brain function and neurochemistry. Fat is a palatable nutrient, which means it activates receptors on the taste buds and stimulates the release of dopamine, the ‘motivation chemical.’ Dopamine activates the ‘pleasure centers’ in the brain, which learn that eating these types of food ‘brings pleasure’ and improves mood.

“However, the catch is that with binge eating, people are getting both the simple carbs and fat in unhealthful foods. The drop in insulin following the sharp rise after eating simple carbs will lead to an eventual drop in blood sugar, which will activate the stress response, as the body is seeking more carbohydrates to replenish blood sugar. This stress response causes dopamine to turn into the stress hormones catecholamines, such as epinephrine and norepinephrine, which promote stress-related eating. Consequently, to feel better, people resort to eating the ‘comfort food’ again and a vicious cycle of binge eating and low mood develops.

“Ultimately, eating healthfully provides your brain with the essential nutrients needed for optimal function. Eating healthfully means individuals are consuming complex carbohydrates and fiber, which control blood sugar and, hence, insulin levels. By keeping a steady blood insulin, not only do you control your stress response but you also preserve the key brain chemicals that support a positive mood.”

— Source: Binghamton University, State University of New York