Take It To Heart: Low Fat Versus Plant Based Diet

By Dr. Sean M Wells, DPT, PT, OCS, ATC, CSCS, CNPT, NSCA-CPT, Cert-DN

Since the 1980s many dietary guidelines promoted the notion of a low-fat diet in order to reduce cardiovascular disease (CVD) risk. Over the next 30 to 40 years healthcare providers and nutrition researchers found that simply lowering dietary fat alone is not the only answer to reducing heart disease. This is likely because those consuming a low-fat diet may still include junk foods, meat, and smoking -- which have all be directly correlated with higher risk of heart disease, comorbidities, and mortality. Data show that most plant-based oils and fats from sources like nuts, seeds, and some oils can actually be beneficial in lowering heart disease risk. Could a plant-based diet, which includes fats from plant-sources, be better than a low-fat diet? A recent publication provides physical therapists and other providers just the answer.

The new research, coined Coronary Artery Risk Development in Young Adults study (CARDIA), enrolled 5115 Black and white men and women in 1985-1986. During more than 30 years of follow up, there were 280 cases of cardiovascular disease, 135 cases of coronary heart disease, and 92 cases of stroke among the study participants.

To assess dietary patterns the researchers conducted three detailed diet history interviews over the follow-up period. These diet history questionnaires determined what participants ate. For example, participants who reported eating meat in the past 30 days would be asked what meat items and how much they consumed. This process was done for ~100 areas of the diet. Based on this information, the researchers calculated scores for all participants based on both the Keys Score of the A Priori Diet Quality Score (APDQS).

The researchers, after factoring for various factors including socioeconomic status, educational level, energy intake, history of cardiovascular disease, smoking and body mass index, found that having a more plant-based diet (higher APDQS Scores) and consuming less saturated fat (lower Keys Scores) were both associated with lower LDL levels. However, lower LDL levels did not necessarily correlate with lower future risk of stroke, but we know that lower LDL levels can correlate to lower heart disease risk. Higher APDQS scores, but not lower Keys Scores, were strongly associated with a lower risk for CVD, possibly due to the lower LDL.

Obviously more research is needed and some limitations exist for this current study. First, it was a questionnaire-based study which can often be riddled with errors. Subjects can forget what they've eaten, exaggerate or under-report certain dietary patterns, or simply fabricate data. Second, the lower LDL levels didn't actually translate into lower stroke prevalence within the group; such a finding seems dubious but may suggest that other factors such as exercise, stress management, or smoking, which were controlled for, may be stronger predictors of stroke than what was measured.

While the study has some limitations the findings are important as it shows that there may be other factors contributing to heart disease than simply fat. Saturated fat does increase LDL and promotes CVD. As such, guidelines were onced focused on simply reducing fat consumption as big priority, without much concern on the source of the fat. As this data show, plant-sources of fat (e.g. from nuts, seeds, and some fish) may be beneficial -- but also the removal of animal products seems to strengthen the CVD risk reduction. Data show that meat contains heme iron, TMAO, and may negatively impact the gut microbiome. Dairy is chock full of naturally occurring bovine hormones and growth factors. Could these factors be the other driving forces for CVD risk? Possibly, but more studies are needed to clearly extract factors for their risk modification.

The study's findings are relevant to doctors of physical therapy (DPTs) and physical therapy practice in several ways. PTs working in cardiac rehabilitation often engage their clients several times per week in order to improve their endurance, strength, and recover from cardiac interventions (like bypass). During such sessions an emphasis on dietary and lifestyle changes is critical, as many who have heart disease will often have a recurrence of that disease again later. For physios working in the general population, prevention ought to be a major aspect of care as it relates to reduce the burden of disease and other conditions. In other words, if you can improve a person's general health and lifestyle you likely will see improvements across many realms and systems (e.g. better health = less pain and better movement). Cardiovascular disease is not just about the heart: it can affect tissue healing peripherally, cognition, sexual function, and muscle performance. Moreover, most of cardiac disease starts in childhood with fatty streaks and foams cells found in teenagers' coronary arteries! Much of this early disease prevalence can be related to poor dietary patterns at school and home. As such, pediatric PTs need to be armed with good nutritional knowledge on how diet can prevent future heart disease for our citizens. In the end, PTs need to work with dieticians, physicians, and nurses to optimize our patients' health through diet, and it seems that choosing a predominantly plant-based diet may just be that mechanism.

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