Statins are pharmacological interventions that have been shown to reduce dyslipidemia, inflammation, and improve vascular endothelial function (VEF) (Ballard et al., 2013). Interestingly, carbohydrate restricted diets (CRDs) have also been shown to improve blood biomarkers, similar to statins (Ballard et al., 2013). However, the authors noted that no research explored the potential additive benefits of statins and CRDs as a combined therapy (Ballard et al., 2013). Thus, Ballard et al. (2013) investigated the aforementioned question by implementing an experimental research design comparing baseline biomarkers of statin users with a concurrent statin and CRD intervention, over a six-week period. Results indicated that participants’ biomarkers, compared to baseline intakes, improved significantly; systolic and diastolic blood pressure decreased after three and six weeks, and peak forearm blood flow increased after six weeks (Ballard et al., 2013). Finally, serum triglycerides, insulin, soluble E-Selectin, and intracellular adhesion molecule decreased at week three, and were maintained at week six (Ballard et al., 2013). In the following sections, I would like to look more deeply into the research methods of Ballard et al. (2013), as a means of determining the quality and applicability of the authors’ findings.
Ballard et al. (2013) recruited thirteen interested participants (13 males, 8 females) for the experiment. Independent variables included carbohydrate restriction (<50gr/day), while dependent variables included blood pressure, peak forearm blood flow, serum triglycerides, insulin, soluble E-Selectin, and intracellular adhesion molecule (Ballard et al., 2013). Extraneous variables for each participant were controlled before (beginning four weeks prior to the intervention), and during (six weeks), the intervention by: encouraging and tracking physician recommended daily doses of statins, refraining from consumption of lipid-lowering supplements, and maintaining consistent use of other medications as prescribed by a physician (Ballard et al., 2013). Other strategies to control extraneous variables included: screening participants for stable weight (±2.2kg) at least two months before, and during, the intervention, habitual diet regimens of at least forty percent carbohydrates per day (pre-intervention), no gastrointestinal disease, no renal insufficiencies, was a non-smoker, sedentary to recreationally active, and was post-menopausal for at least two years (Ballard et al., 2013). Controlling the aforementioned variables helped maximize the likelihood that the outcomes from the intervention to be (i.e., validity) from the intervention (i.e., carbohydrate restriction) rather than an inconsistency or unintended manipulation of the extraneous variables.
The CRD intervention (independent variable) was closely monitored by a Registered Dietician. Specifically, each participant was expected to track food intake including: weighing each food, recording the date and time of consumption, brand name, serving size, and carbohydrate content (Ballard et al., 2013). Additionally, a five day food record was required prior to the intervention (T0), and during the intervention, at weeks one (T1), three (T3), and six (T6) (Ballard et al., 2013). Finally, each participant fasted for twelve hours prior to T0, T1, T3, and T6 avoiding caffeine, alcohol, and exercise during this period (Ballard et al., 2013). As a means of maintaining compliance of the aforementioned guidelines, the Registered Dietician met with each participant on a weekly basis to help review the food logs, as well as helping with food recommendations to maintain weight to within ±2.2kg of pre-intervention bodyweight (Ballard et al., 2013). Additionally, the Registered Dietician helped each participant decrease total calories from carbohydrates by approximately 420 kcal compared to baseline (Ballard et al., 2013). All of the aforementioned interventions helped minimize the opportunities for participants to deviate from the recommended protocols (i.e., maintaining target bodyweight, maintaining daily statin use, and consuming <50gr carbohydrate/day) thereby improving the repeatability or reliability of test measures by minimizing dietary and statin inconsistencies. Moreover, maintaining this consistency also upheld the validity of the experiment, in that the results were most likely due to the intervention, as all extraneous variables were controlled.
Testing of flow-mediated dilation was performed using high frequency ultrasonic imaging. Protocols to measure each participant were consistent; baseline brachial artery diameter was recorded for 30 heartbeats. The tester proceeded to inflate the cuff to 200 mm hg for 5 minutes. Measurements were taken immediately after the cuff pressure was released for 300 heartbeats. Additionally, the same tester was used for each of the participants, and had to demonstrate reproducibility of diameter measurements of 1.2% and 1.6% for resting and peak diameters, respectively (Ballard et al., 2013). In this way, inter-rater reliability was diminished, and intra-rater reliability was improved.
Blood collection and analysis were conducted at T0, T3, and T6. Each participant was instructed to rest comfortably for ten minutes in the supine position. After the resting period, 10 ml of blood was collected from the forearm arm vein. Additionally, every sample from each participant was sent to the same laboratory (Quest Diagnostics) for determination of serum lipid and glucose concentrations (Ballard et al., 2013). Analysis of fasting plasma glucose and insulin were measured using analytic equipment from the same company brand each time, and completed to the manufacturer’s instructions (Ballard et al., 2013). This method helped improve validity by decreasing the chances of conflicting results that could have occurred, had the authors chosen to use multiple blood analysis companies and assessment techniques.
In conclusion, the findings indicated statistically significant improvements in biomarkers: decreases in resting blood pressure, serum triglycerides, serum insulin, soluble E-Selectin, intracellular adhesion molecule, and increases in peak forearm blood flow (Ballard et al., 2013). Additionally, the results from the study of Ballard et al. (2013) are applicable to my field as several clients are on statins to control their dyslipidemia. Moreover, the age ranges (59.2 ± 9.5) found in the experiment of Ballard et al. (2013) closely match those of my personal training and post-rehabilitation clientele, and developing an experiment that explores the outcomes of combined therapies (i.e., statin + CRDs) serves as a safe and complimentary protocol for my clients. Finally, the favorable effects recorded from the combined therapy might help encourage my clients to pursue such an intervention, providing an opportunity for enhanced health, wellness, and longevity.
References
Ballard, K. D., Quann, E. E., Kupchak, B. R., Volk, B. M., Kawiecki, D. M., Fernendez, M.L., …. Volek, J. S. (2013). Dietary carbohydrate restriction improves insulin sensitivity, blood pressure, microvascular function, and cellular adhesion in individuals taking statins. Nutrition Research, 33(11), 905-912.
-Michael McIsaac