Six Applications of Plant Based Diets for Health Promotion

Abstract

The field of medicine, despite its prominent influence in society, has invested little to promote healthy lifestyle choices. The consequence of this is reflected in our ever-rising chronic disease statistics, most notably obesity and diabetes rates. This is especially regrettable considering overwhelming evidence confirms most non-communicable disease is preventable by modifying our diets. In light of this critical knowledge that optimizing our nutrition could save innumerable lives, one would naturally assume physicians would be readily practicing its promotion with their patients. Yet, that is far from true. By no fault of their own. Medical schools, entrusted with the responsibility of educating our future healthcare leaders, have managed to largely bypass the topic of nutrition, arguably the most powerful healthcare intervention known to mankind. In fact, on average, medical schools offer an anemic number of hours of nutrition education over 4 years. ¹ What little is offered is focused on biochemistry and nutrient deficiencies, none of which prepares a physician in training for meaningful application in clinical care. This lapse in nutrition education continues throughout post-graduate training; in a recent survey of more than 600 cardiologists, 90% reported they had not received needed nutrition education during training. ² Although we agree that not all physicians must be experts in nutrition, in the very least all should have knowledge of rudimentary and essential facts. We offer this commentary on six vital clinical topics, to increase awareness amongst physicians as to the importance of diet and its role in human health.

“…It is time for all physicians across the globe to speak to the importance of diet and lifestyle in health.…”

1. Weight loss/maintenance. How do we best advise patients when asked, what diet is best for weight loss? Diet fads and quick fix schemes may offer transient success but rarely are sustainable. We have witnessed this most recently with the rise in popularity of ketogenic diets and fasting protocols. But what dietary pattern has been shown to be associated with maintenance of ideal body weight and reduced risk of death? In a prospective cohort study, which included more than 70 thousand participants, those who consumed a vegan diet could expect to weigh 4.2 kg less than their omnivore counterparts. This very same study went on to conclude that vegetarian diets were not solely of benefit to the scale but were also associated with lower all-cause mortality. ³ Plant-based diets, enriched in fruits, vegetables, whole grains, legumes, nuts, and seeds, offer abundant sources of both soluble and insoluble fiber. This indigestible carbohydrate offers myriad benefits including lowering cholesterol, enriching microbiome diversity, and, importantly for weight loss, confers satiety. Calorically speaking, plant powered diets are naturally low in fat and rich in carbohydrates, which is a relevant fact to convey to patients seeking weight loss, as 1 gram of fat confers 9 calories as compared to carbohydrates which offer less than half of that, at 4 calories per gram.

2. Cardiovascular disease. Heart disease remains the leading cause of death in the United States. More than 650 thousand Americans succumb to this leading killer largely fueled by poor dietary choices. The standard American diet composed primarily of animal derived foods rich in saturated fat and cholesterol are key drivers to cardiovascular risk. This adverse dietary pattern is also comprised of highly refined processed foods further contributing to weight gain, hypertension, and insulin resistance, all of which heighten cardiovascular risk. Conversely, the opposite effects are seen with plant-based dietary approaches. A pooled analysis of five cohorts found a 24% lower rate of coronary heart disease deaths among vegetarians when compared to omnivores. ⁴ In a recent metanalysis, LDL cholesterol, long recognized as a marker for cardiovascular risk was shown to be decreased by 13 mg/dl (.34 mmol/L) in those consuming a vegetarian vs an omnivore diet. This translates into an approximate 10% decrease in risk of cardiovascular disease. ⁵ Meaningful connections between the makeup of the gut microbiome and heart health have recently surfaced in recognition of the role trimethylamine N-oxide (TMAO) is playing in heart disease. Studies have shown consuming choline and L-carnitine, both found largely in animal sources, leads to gut microorganisms metabolizing these compounds to trimethylamine with subsequent conversion to TMAO at the liver. Trimethylamine N-oxide has been associated with increased cardiovascular risk. ⁶ This is yet another mechanism by which dietary choice is contributing to heart disease.

3. Cancer. Despite historic efforts to end cancer, most notably President Nixon’s declaration to launch a war on cancer with the signing of the National Cancer Act in 1971, little progress has been made in the past 50 years later. Cancer remains the second leading cause of death. In a recent British publication, authors reported for those born after 1960, 50% percent could expect to receive a cancer diagnosis during their lifetime. ⁷ Breast, prostate, and colon are among the most common cancers, all of which have been shown to have strong links to diet. Breast cancer is the most common cancer diagnosed in women, except for skin cancer. Breast malignancies are also amongst the leading causes of cancer deaths in women. Well-described gene mutations which include BRACA1 and BRACA2 have been linked to breast cancer, but these account for only about 5–10% of breast cancers. Yet, risk reducing behavior modifications which include maintaining an ideal body weight, minimizing alcohol intake, remaining physically active and consuming diets rich in vegetables, fruits, and whole grains, have the potential to reduce risk by as much as 50–70%. ⁸ Willett et al assessed the role fiber intake played during early adolescence in the Nurses’ Health Study II, concluding a lower risk of breast cancer was assigned to those with the highest intake of fiber. ⁹ Soy has been questioned as to its potential role in breast cancer risk. A large prospective study assessing soy consumption which included more than 300 000 Chinese women over a 10 year follow up, found no association between soy intake and breast cancer risk. The study’s investigators went on to complete a meta-analysis integrating their study’s findings along with other prospective studies from around the world, ultimately concluding that each 10 mg/day of soy isoflavone intake was associated with a 3% reduced breast cancer risk. ¹⁰ Apart from skin cancer, prostate cancer is the most common cancer diagnosed in American men. Dairy product consumption has been previously shown to be a risk factor for prostate cancer. Most recently, the Japan Collaborative Cohort study assessed dairy intake amongst a large population of men concluding highest intake of dairy, most notably milk, did indeed increase the risk of prostate cancer. ¹¹ Colon cancer is the third leading cause of cancer related deaths in the United States. The World Health Organization has reported colon cancer risk increases significantly with daily consumption of red and processed meats. Recognition of these facts resulted in the International Agency for Research on Cancer issuing a press release in October of 2015 designating red and processed meats as carcinogens. ¹² In sharp contrast, studies assessing the role of high fiber diets, which includes legumes, vegetables, fruit, and whole grains have shown a significant reduction in colorectal cancers.^13-15 A plant-based diet has the potential to finally do what Nixon’s National Cancer Act could not: take a meaningful bite out of cancer and save lives.

4. Diabetes. Diabetes is a leading cause of mortality globally. It is also responsible for significant morbidity, as the number one cause of renal failure, lower-limb amputations, and adult blindness. Currently, an approximate 34 million Americans are living with diabetes, and the CDC ominously predicts a tripling by 2050, when we can expect 1 in 3 will be living with diabetes. These forecasts are economically unsustainable, not to mention the immense burden of human pain and suffering. Solutions beyond developing new targets for drug development must be employed if we are to prevent doomsday scenarios for our already overtaxed healthcare systems. The necessary remedy is preventing type 2 diabetes and better managing it to reduce complications. Tonstad et al ¹⁶ assessed the role different dietary patterns might play in the prevalence of type 2 diabetes, finding vegan and lacto-ovo vegetarian diets were associated with an approximate 50% reduction in risk of type 2 diabetes when compared to non-vegetarian diets. A Harvard study which included participants from three large established cohorts, (the Health Professionals Follow-Up Study, Nurses’ Health Study, and the Nurses’ Health Study II) concluded those subjects who consumed a healthy plant-based diet rich in fruits, vegetables, and whole grains, could expect a 34% reduction in type 2 diabetes risk. ¹⁷ Plant-based diets are not only effective in preventing type 2 diabetes, but also act as a powerful treatment. A randomized clinical trial comparing a low-fat vegan diet to a portion-controlled diet, consistent with the American Diabetes Association (ADA) guidelines, resulted in significant improvement in HbA1c for the vegan cohort when compared to the ADA diet (1.23% vs .38% in those who made no change in medications). ¹⁸ A meta-analysis that included 6 studies in type 2 diabetics reported a plant-based diet offered an average decrease of .4 points in HbA1c when compared to conventional diets. ¹⁹ Undoubtedly, a significant contributor to improved glycemic control is the already established benefit of weight loss with vegan diets. Decreased fat deposition in liver and muscle cells results in increased insulin sensitivity and thus improved glycemic control. Plant-based diets should be recommended for the prevention and management of type 2 diabetes and are consistent with most recent practice guidelines (2020) by the American Association of Clinical Endocrinology. ²⁰ .

5. Alzheimer’s disease. The World Health Organization currently reports there are now more than 55 million people living with dementia globally. Dementia is a syndrome characterized by loss of cognitive function, and primarily affects the elderly. Alzheimer’s disease is the most common form of dementia and accounts for about 70% of cases. Alzheimer’s is a progressive and disabling neurodegenerative disease. Despite much investment in drug development for the treatment of Alzheimer’s over several decades only a handful of candidates have met regulatory approval, all of which have been ineffective in slowing progression. ²¹ The public health implications of this disease are daunting; as our population ages, we can expect a tripling of rates over the next three decades. It is now more important than ever before to identify viable pathways to prevention. In a recent publication of two prospective longitudinal studies with nearly 3000 participants, investigators assessed Alzheimer’s risk according to a composite score of healthy lifestyle behaviors including diet, physical activity, not smoking, minimal alcohol, and keeping engaged in cognitive activities. The Mediterranean-DASH Diet Intervention for Neurodegenerative Delay (MIND) diet score was calculated to assess diet quality. The MIND diet is focused on brain healthy food groups which include green leafy vegetables, other vegetables, beans, berries, nuts, and whole grains. Although it is not a strictly vegan diet, it is primarily plant-based. After a median follow up of nearly 6 years, investigators concluded that in those who adhered to all or most of the healthy behaviors there was a 60% lower risk of Alzheimer’s disease. ²² Although many questions remain unanswered regarding Alzheimer’s, there is substantive evidence that a plant enriched diet combined with other healthy behaviors can offer significant risk reduction for this menacing disease of which we have no cure or effective management. The additional benefit of adopting these optimal lifestyle choices is that they too serve to reduce risk of other leading causes of morbidity and mortality, including our number one killer, heart disease. What is good for our heart is indeed also good for our brains.

6. Covid-19. On March 11, 2020 the World Health Organization declared COVID-19 a global pandemic. The novel coronavirus, SARS-CoV-2, has since caused havoc leading to a historic number of hospitalizations and deaths on a worldwide scale. Early in its course, a clear signal surfaced regarding the role the chronic disease epidemic would be playing as it intersected with this acute infectious disease. In the CDC’s June 2020 Morbidity and Mortality Report, we learned that for those living with an underlying condition, hospitalization was six times more likely and deaths twelve times more likely than in those with no underlying conditions. ²³ This early recognition would be further substantiated six months later in a publication summarizing more than 900,000 COVID-19 hospitalizations in the United States, concluding 60% were attributable to obesity, hypertension, diabetes, or heart failure. ²⁴ We have learned much about the threatening role underlying health conditions is playing in COVID-19 outcomes. But are there additional measures that can influence both infection and course? In Harvard’s smartphone based COVID-19 Study, in which close to 600,000 subjects were enrolled and of which approximately 31,000 developed COVID-19, found that in those who consumed a primarily plant-based diet there was a 41% reduction in risk of severe COVID-19 as well as a 9% reduction in infection of any severity. ²⁵ Public health messaging to combat the virus has included effective infection control measures like hand washing, masking and social distancing combined with vaccination and development of therapeutics. But the one area that has been missed altogether is educating the public on the role underlying conditions are playing in the disease course. A meaningful addition to an effective strategy to battle this virus is dispensing advice on a healthful diet for starters. Taking meaningful steps toward addressing underlying cardiometabolic conditions, most of which are a consequence of poor diet and lifestyle, could serve to lessen morbidity and mortality significantly across the globe.

An overwhelming body of evidence convincingly indicates that by addressing the important role of diet, we can do more to improve the lives of patients affected by these and other chronic conditions. It is time for all physicians across the globe to speak to the importance of diet and lifestyle in health. We must move beyond an era that so heavily condemned our genes as the sole predictor of health outcomes to a new era of self-empowerment and awareness. These actions will catalyze a movement ushering in a shift in paradigm, a period where Prevention is finally heightened and primary in healthcare.

We can manifest this era by each doing our part, counseling patients in our exam rooms, assuring our hospitals provide healthy menus to our inpatients, volunteering to present a lecture in our local libraries, churches or schools, write articles, utilize social media venues to disseminate messaging, provide expert commentary for local, state, and national media. The possibility is there to manifest change in a meaningful fashion. Are we up to the task? We have a moral and ethical responsibility to do so. It is time to act on the solemn words of our Hippocratic oath, “I will prevent disease whenever I can, for prevention is preferable to cure.”