A recent study found that vitamin D status was inversely related to physical capacity before cardiac rehabilitation among patients with heart disease. In addition, the researchers discovered that vitamin D deficiency was associated with less improvement in physical capacity for patients after cardiac rehabilitation.
Modifiable risk factors for heart disease include the following:
- Poor diet
- Physical inactivity
Heart disease patients often enroll in cardiac rehabilitation to assist in recovery from heart attacks and heart surgery. The program consists of regular physical activity, counseling and education with the purpose of improving the modifiable risk factors mentioned above, thereby, reducing the risk of future heart problems.
Longitudinal studies have repeatedly found an inverse relationship between vitamin D levels and heart disease, suggesting low vitamin D status may be a risk factor for heart disease. Research also suggests that vitamin D plays a role in physical performance by aiding in oxygen consumption, reducing muscle inflammation and increasing muscle force.
Since physical fitness is an easily measured indicator of health improvement and a modifiable risk factor associated with heart disease, researchers conducted a study to determine the relationship between vitamin D status and physical fitness in patients undergoing cardiac rehabilitation.
The researchers assessed the vitamin D status in a retrospective cohort of 131 patients who underwent cardiac rehabilitation at the Rangueil Hospital in Toulouse, France. Physical fitness was evaluated with the six-minute walk distance (6MWD) and the maximal power (Pmax). 6MWD is the measurement of the distance an individual is able to walk over a total of six minutes on a hard, flat surface. Pmax was evaluated using a stationary bike beginning at a 20 W resistance and increasing by 10 W every minute until maximum performance. Pmax and 6MWD were measured at the beginning and end of cardiac rehabilitation. Here is what the researchers discovered:
- A total of 37% of all patients were considered vitamin D deficient, as defined by vitamin D levels less than 20 ng/ml.
- At baseline, vitamin D deficient patients had lower initial 6MWD and Pmax than vitamin D sufficient patients (p = 0.006).
- The improvement in 6MWD and Pmax after cardiac rehabilitation was significantly lower in vitamin D deficient patients compared to vitamin D sufficient patients (p = 0.048 and 0.000001 respectively).
The researchers concluded,
“Our study suggests that vitamin D deficiency may be associated with decreased physical fitness and a lesser response to physical training in heart failure patients undergoing [cardiac rehabilitation].”
The retrospective observational study design limits the findings, allowing the study to only prove association and not causation. Furthermore, the researchers did not adjust the findings for outdoor physical activity, which may contribute to the significant relationship between vitamin D status and physical capacity. The researchers called for future studies to investigate the effects of vitamin D supplementation during cardiac rehabilitation.
Tovey, A. & Cannell, JJ. New study finds vitamin D status may be inversely associated with physical capacity for patients undergoing cardiac rehabilitation. The Vitamin D Council Blog & Newsletter, 2016.