We found a significant reduction in the risk of cardiovascular disease following counselling about nutritional and physical activity provided by naturopathic doctors. The baseline-adjusted prevalence of metabolic syndrome was reduced by 16.9% over the course of 1 year in comparison to enhanced usual care alone. This implies that 1 in 6 individuals receiving additional naturopathic care benefit, in comparison to those who do not, by not developing metabolic syndrome over the course of 1 year. In addition, the baseline-adjusted relative 10-year cardiovascular risk decreased by 3.1 percentage points for the group who received naturopathic care. These findings translate into about 3 fewer people out of 100 with intermediate risk who receive naturopathic care experiencing a serious cardiovascular event (e.g., stroke, heart attack or death) during the next 10 years compared with those who receive usual care.
The results of our study are consistent with those from other pragmatic trials that have studied lifestyle programs for the prevention of metabolic disease. The Diabetes Prevention Program successfully combined diet- and exercise-based interventions to reduce the incidence of diabetes by 58%.23–25
More recently, the large Look AHEAD (Action for Health in Diabetes) trial found that an intensive lifestyle intervention significantly improved major cardiovascular risk factors compared with standard diabetes support and education.26
These risk factors included weight, cardiovascular fitness, glycated hemoglobin, systolic and diastolic blood pressure, HDL and triglycerides. The positive changes seen were sustained for 4 years. It is difficult to fully compare the Look AHEAD study with ours, however, because they did not consider compound measures of risk (i.e., Framingham 10-year risk or metabolic syndrome).
Strengths and limitations
The pragmatic design of our trial, in which both the intervention and control interventions were similar to care in the community, increases its generalizability and applicability to real-world settings.
We did not observe a sufficient number of cardiovascular events to compare the incidence between groups. Although we used validated estimates of composite risk of cardiovascular disease, we do not know whether our estimates are over- or under-estimates of the true differences in absolute risk of events between groups. We lost an appreciable number of patients to follow-up, and we did not model the possible impact of loss to follow-up on the results.
The incidence of metabolic syndrome at baseline was nonsignificantly higher in the intervention group than in the control group. Although we adjusted for baseline values in our analysis, we cannot rule out the possibility of regression to the mean as a source of bias in our results.
We asked whether naturopathic care, in addition to usual primary care, reduces the cardiovascular risk of postal workers. Some may perceive this as an unfair comparison and would prefer that we had asked whether the addition of, for example, 7 sessions of naturopathic care to usual care reduced cardiovascular risk compared to the addition of 7 sessions with a family physician. The design of such a trial would have endeavoured to ensure a similar number of exposures to health care providers in both groups. Those who would prefer us to have asked the latter question might reasonably suggest that our design was unfair and was geared toward showing a benefit in the intervention group.
Our intervention differed from routine clinical practice in both study groups. In the enhanced usual care group, naturopathic doctors measured risk factors 3 times during the course of the study, and participants were encouraged to report the results to their family physicians. Presumably, this additional measurement and communication to physicians within the control group would have enhanced standard care and decreased any differences between the intervention and control groups.
We did not assess for possible contamination between groups and, as such, this could have biased the results. However, this bias, if present, would have diluted the comparative beneficial results seen in the naturopathic group. Based on the pragmatic study design and the large number of therapies suggested, the contribution of conventional lifestyle modification compared with the use of natural products to reduce risk in the naturopathic group is unclear.
Also because of the pragmatic design, this trial did not, nor could not effectively, blind trial participants or clinicians to allocation. As a result, the results are susceptible to expectation bias and potentially to measurement bias
According to the American Heart Association, the “prime emphasis in management of the metabolic syndrome per se is to mitigate the modifiable, underlying risk factors (obesity, physical inactivity, and atherogenic diet) through lifestyle changes. … Then, if absolute risk is high enough, consideration can be given to incorporating drug therapy to the regimen.”5
Primary health care that provides in-depth counselling around diet and lifestyle is uniquely poised to help comanage metabolic risk factors. We have shown that naturopathic care is a feasible and potentially effective adjunct to usual medical care in reducing the incidence of metabolic syndrome and cardiovascular risk.
Further investigation of the potential for complementary naturopathic care to support general practice in preventing chronic diseases, including cardiovascular disease, is warranted. Future trials should include larger sample sizes and robust measures to ensure participant adherence to individual elements of treatment, potentially improving attribution of the results to individual therapies.