Part III: Chronic disease

Chronic disease

Chronic diseases are conditions that span over one year, need medical attention and/or limit daily activities. As per the CDC, they are caused by a short list of risk behaviors, including poor nutrition. Several chronic conditions linked to diet warrant exploration as we consider adopting a more plant-forward way of eating to prevent disease.

Overweight and obesity

Many observational studies, including the Adventist Health Study (AHS), the European Prospective Investigation into Cancer and Nutrition study (EPIC-Oxford), the EPIC-PANACEA (an offshoot of EPIC-Oxford), and the Swedish Mammography Cohort, have looked at the influence of dietary patterns on body weight. The dietary patterns examined include a variety of vegetarian diets – vegan, lacto-ovo, ovo, pescetarian and flexitarian – as well as the omnivorous diet. The research shows that:

• increases in BMI are directly correlated to increase in animal foods in the diet
• vegans exhibit significantly less weight gain as they age, compared to omnivores
• a plant-based diet seems to protect against weight gain, as does a pescetarian diet for women
• as total meat consumption increases, so does weight gain, after adjusting for energy intake
• those following a dietary pattern that includes less meat have a lower prevalence of overweight and obesity, compared to omnivores.

In addition, a study of nearly 50,000 Taiwanese adults found that those following a vegetarian diet had a significantly lower BMI than those on a non-vegetarian diet. The findings also indicated that the risk for obesity decreased by 7 percent every year a vegan diet was followed. A recent journal article,  Systematic Review and Meta-Analysis of Changes in Body Weight in Clinical Trials of Vegetarian Diets, noted that vegetarian diets reduce mean body weight, which suggests the high value of dietary intervention for the prevention and management of overweight and obesity.

Although vegetarian diets appear to have remarkable benefits for weight reduction, more long-term trials are needed not only to better understand the effects of this way of eating on sustainable weight control but also to explore how the quality of these diets may impact BMI.

Heart disease and stroke

Risk factors for heart disease and stroke include overweight and abdominal obesity, high blood pressure, unhealthy blood cholesterol levels and elevated blood glucose. The Academy of Nutrition and Dietetics’s position is that vegetarian diets can reduce the risk of cardiovascular disease by improving several risk factors. 

This way of eating also decreases inflammatory markers like C-reactive protein, reduces oxidative stress and protects from atherosclerotic plaque formation. So those on a plant-based diet are less likely to develop and die from ischemic heart disease. In addition, data from the Women’s Health Initiative suggests that adherence to the so-called Dietary Portfolio, which combines established plant-based cholesterol-lowering foods with monounsaturated fat, was associated with fewer cardiovascular and coronary events, as well as heart failure.

In the Adventist Health Study-2, results show that protein from meat increases cardiovascular mortality risk, whereas protein from plants is protects the heart. The academy says the EPIC study suggests that those who follow a plant-based diet had 32 percent lower risk of being hospitalized or dying from heart disease. Data from the Atherosclerosis Risk in Communities research, a study spanning the years from 1987 to 2016, suggests that higher adherence to a plant-based diet was associated with a 19 percent lower risk of cardiovascular disease. So diets higher in plant foods and lower in animal foods are thought to lower the risk of cardiovascular death in a general population.

When looking at the risk factors for heart disease and stroke, a systematic review and meta-analysis suggests that those on a plant-based diet are significantly more likely to experience reductions in blood pressure compared to those on an omnivorous diet. In addition, a systematic review and meta-analysis from the Journal of the American Heart Association, “Provides evidence that vegetarian diets effectively lower blood concentrations of total cholesterol, low‐density lipoprotein cholesterol, high-density lipoprotein cholesterol, and non–high‐density lipoprotein cholesterol. Such diets could be a useful nonpharmaceutical means of managing dyslipidemia, especially hypercholesterolemia.”

That said, there are some concerns about the quality of a plant-based diet and heart-related events. With improvements in plant-based diet quality over a 12-year period, risk for heart-related mortality went down and consumption of an unhealthy plant-based diet – one high in ultra-processed foods – was associated with higher risk.

So though a whole foods plant-based diet is generally accepted as heart-protective, we must consider the quality of the diet to ensure its inherent benefits. Guidance and support from a qualified nutrition or medical professional or both to assist with planning and implementation could best support optimal health.

Type 2 diabetes

A varied vegetarian diet is associated with lower risk of Type 2 diabetes, according to the Academy of Nutrition and Dietetics. “The Adventist Health Study-2 reported that meat eaters had more than twice the prevalence of diabetes compared with lacto-ovo vegetarians and vegans, even after correcting for BMI.” A systematic review and meta-analysis of controlled trials looking into correlations between vegetarian diets and glycemic control concluded that vegetarian diets reduce long-term blood sugar levels, suggesting that a plant-based way of eating could be help prevent and manage of Type 2 diabetes. 

Several observational studies and randomized controlled trials suggest a whole foods plant-based diet brings positive health benefits for people with diabetes: “The consumption of whole grains, legumes, fruits, and vegetables in conjunction with the elimination of animal products reduces the risk of developing type 2 diabetes. In individuals with type 2 diabetes, a low-fat, plant-based diet improves body weight, glycemic control, plasma lipid concentrations, and blood pressure, while reducing the risk of CVD and microvascular complications.”

But the quality of a vegetarian diet must be considered for diabetes control. A vegetarian diet high in ultra-processed foods, refined grains, saturated fats and added sugars is positively associated with Type 2 diabetes, compared to a vegetarian diet rich in vegetables, fruits, whole grain, legume, nuts and seeds. More research is needed to understand how food quality of vegetarian diets affects the development of Type 2 diabetes. 

So effective prevention and management of Type 2 diabetes can be achieved with guidance and support from a qualified nutrition or medical professional or both who can assist with planning and implementation, including offering specific guidance on food choice.

Cancer

Of the many cancers, the effects of a plant-forward diet on breast, prostate, colorectal and gastrointestinal cancers have been studied and published on the most, and evidence points to the significant protective effect of a whole foods plant-forward diet. Data from a 2018 study shows that “Nutritional interventions in the prevention of various cancers offer a significant benefit to currently used medical  therapies, and should be employed more often as an adjunct to first-line medical therapy.” It is also noted that “With the unsustainable nature of current cancer treatment regimens, focus on prevention, especially through diet and lifestyle changes, presents an important paradigm shift with the potential to make a marked impact on the burden of disease.”

According to a systematic review with a meta-analysis of observational studies, a varied vegetarian diet can significantly reduce mortality from cancer. In addition, based on results from the Adventist Health Study-2, the Academy of Nutrition and Dietetics states that “Vegetarian diets are associated with a lower overall cancer risk, and especially a lower risk of gastrointestinal cancer.” And investigation into mortality and cancer in vegetarians revealed that vegetarians had an 18 percent lower incidence of cancer mortality than non-vegetarians. 

Although more research is urgently needed to assess the use of the whole foods plant-forward diet for the prevention of cancer mortality, the academy suggests that research has consistently highlighted that regular consumption of whole plant-based foods like fruit, vegetables, legumes, and whole grains is associated with a reduced risk of certain cancers. And the vast array of phytochemicals in these whole foods may be cancer-protective, since they are known to interfere with several cellular activities involved in the advancement of cancer.

There are many factors that contribute to a person’s risk for cancer, 30 percent of which is deemed as uncontrollable. But diet is one factor that can be controlled. With research pointing toward the cancer-protective effects of a whole foods plant-based diet, using dietary interventions could help mitigate risk and shift health outcomes for Americans.

Covid-19

Based on a review of risk factors for severe and critically ill Covid-19 patients, the link between diet-related disease and Covid-19 severity seems evident: 63.5 percent of Covid-19 hospitalizations through 2020 could be attributed to several diet-related diseases, including obesity, heart disease and diabetes. Emerging research suggests that a significant portion of Covid-19 hospitalizations in the U.S. are attributable to cardio-metabolic conditions.

Data on the effects of a whole foods plant-forward diet on Covid-19 severity is limited because to the novelty of the virus. But it seems that those following plant-based diets as well as a pescetarian diet had less risk of moderate to severe Covid-19. And a prospective cohort study revealed that “Poor metabolic health and unhealthy lifestyle behaviors have been associated with higher risk and severity of Covid-19.” Moreover, a whole foods plant-forward diet was associated with a lower risk and severity of Covid-19. 

Although more research is needed on diet and lifestyle choices and Covid-19 response and outcome, preliminary findings suggest that food and nutrition play a critical role in immune response, duration and outcome. It is believed that a healthy diet in addition to “supplementation with high-dose vitamin C, vitamin D, minerals, short-chain fatty acid and omega-3 fatty acid, adequate protein and carbohydrate content, Mediterranean diet, and high-fiber diet might be beneficial in mounting an adequate immune response to fight against SARS-CoV-2 infection and diminish the inflammation leading to a severe clinical course and poor outcomes.”