January 22, 2019
Interviewer Mike Roberts, Ph.D.: Austin, thanks for taking the time. You’ve done some stunningly brilliant research on the interaction between sodium intake and hypertension. So, my questions below are largely meant to highlight this topic.
[AR] Hi Mike, thanks for the kind words and for featuring me on Auburn KINEversity!
Q1: I’ve always heard that eating too much sodium from processed foods, cured meats, or simply dousing food with table salt will lead to hypertension. Is there truth to that or is it more complicated in the sense that I, for example, may experience this phenomenon whereas you wouldn’t?
[AR] Yes, this is a bit of a complicated issue. Salt sensitivity of blood pressure refers to the blood pressure changes that are responsive to changes in dietary salt intake. In other words, a person is salt sensitive if their blood pressure increases when they consume a high amount of dietary salt or decreases when they reduce the salt in their diet. If there is no change in blood pressure with increased salt intake, an individual is considered salt resistant. Although, this does not mean salt intake is harmless in these individuals. Even if your resting blood pressure doesn’t change with increased sodium consumption, it can still affect your blood vessel health, brain, or kidneys.
Not everyone is salt sensitive (in fact most people are not), but it can affect people with or without high blood pressure and certain groups are more likely to be salt sensitive such as the elderly, African Americans, and individuals who already have conditions such as hypertension or kidney disease. So while our individual blood pressure responses to changes in dietary salt can vary quite a bit, large scale studies show that reducing salt is an effective strategy to reduce the population’s blood pressure, especially in those with high blood pressure.
Q2: Let’s say I’m a person who is “salt-sensitive.” If I were more physically active would this reduce the effects that dietary salts had on my blood pressure? Additionally, if exercise can help these outcomes, does the mode of exercise matter (e.g., weight training versus cardiovascular training)?
[AR] There isn’t enough research to directly answer these questions yet, but one study found that high levels of physical activity were protective against salt sensitivity. Another study found six months of aerobic exercise training significantly reduced the occurrence of salt sensitivity of blood pressure in middle aged to older adults with high blood pressure.
Unfortunately, it has not been determined if resistance training is protective, at least to my knowledge. There is some thought that the sweating during exercise is protective against high salt diets, because it is another way our bodies can get rid of excess sodium. If this is the case, then it would seem likely resistance exercise could be helpful, but studies will have to be completed to confirm this.
Q3: In relation to the questions above, you’ve also examined the influence of race and have found some interesting results. What have been the highlights of that research?
[AR] Yes, our research group recently published a paper demonstrating that response to a short term salt load, black individuals may have (1) impaired ability to get rid of excess sodium, and (2) that for any given increase in levels of blood sodium they are more likely to demonstrate an larger increase in blood pressure. These findings seem to support large scale studies that black individuals and Asian individuals are more likely to be salt sensitive and provide some insight into why that might be.
Q4: Switching gears a bit, you performed work examining vascular function in sedentary/obese versus active/leaner individuals. This is a multi-part question, but: a) what does having good vascular function mean, and why is it so important?, and b) vascular function is seemingly impaired in sedentary/obese individuals, so can increasing physical activity improve this outcome?
[AR] Vascular function is essentially how us science nerds say blood vessel health. We all want our blood vessels to dilate (expand) and constrict (get smaller) appropriately so that we can effectively deliver blood to the various parts of our body. When our blood vessels cannot dilate appropriately to allow blood flow and increases our risk for heart disease, which is the number one cause of death in the United States for both men and women.
Obesity is associated with heart disease and a host of other diseases such as type 2 diabetes and Alzheimer’s disease. Not surprisingly, several studies have shown individuals who are afflicted with obesity have impaired blood vessel function. On a positive note, regular physical activity and exercise can improve blood vessel health in overweight and obese adults. Some of the benefits include improving blood sugar and cholesterol and improving the ability of the blood vessels to dilate appropriately.
Q5: With regard to vascular function research in exercise physiology, what are some of the current “hot” areas or themes that are slated to be at the forefront of the field in the near future?
[AR] A long-standing question in the field is “Can you out-exercise a bad diet?” More studies are starting to come out demonstrating that regular exercise may protect our blood vessels against dietary offenders such as high-fat, high-sugar meals. I am currently working on a study that seeks to determine if regular physical activity protects our cardiovascular system against negative changes that result from dietary salt before changes in resting blood pressure. In fact, Dr. Stu Phillips who was recently interviewed here just published an article on out-running bad diets. My take is that while exercise may protect us against a poor diet to some extent, we should try to do a good job with both!
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