Three recent studies link plant-based diets to reduced health risks 09/23/2019
Folks who read our newsletter regularly might react to our headline with the “wait, what?”.
That’s because, in a recent article — Plant-Heavy Diets May Harm Brain Health — we conveyed a British nutritionist’s concerns about a lack of key brain nutrients in plant-based diets that include very few or no animal foods.
While meats and fish generally have much more choline than plant foods — with a few exceptions, like soybeans — there isn’t any evidence of significant choline deficiencies amongst people following such diets.
Choline deficiencies may be rare among vegans and vegetarians, but a recent European study linked higher intakes of choline — from diets featuring animal foods — to better brain performance and reduced dementia risk: see The “Secret” Brain-Saver in Meat and Seafood.
On the other hand, the results of three recent studies suggest that plant-based diets featuring the most nutritious plant foods reduce the risk for heart-related deaths, diabetes, and chronic kidney disease.
By “plant-based” diets, researchers mean eating patterns like the Mediterranean diet, which is dominated by fruits, vegetables, nuts, seeds, extra-virgin olive oil, whole grains, legumes, and beans.
The Mediterranean and other plant-based diets typically feature fish, poultry, eggs, cheese, and/or yogurt most days of the week, includes meat (e.g., lamb, beef, pork, goat) once a week or less, and has very few starches (i.e., white flour products or pastries) and sugary drinks or sweets.
While vegan diets exclude all animal foods, vegetarian diets often include some eggs, dairy foods, and fish; vegetarian diets that include fish are also called pescatarian diets.
Let’s look at each of three recent studies whose results suggest that plant-based diets can significantly boost heart, metabolic, and kidney health.
Harvard study links plant-based diets to reduced diabetes risk
Earlier studies had suggested that plant-based diets might help reduce the risk for type 2 diabetes.
But researchers at the Harvard School of Public Health believe that the medical literature lacked a review of the evidence from good-quality epidemiological studies — which compare the lifestyles and health outcomes of groups of people over time.
According to the study’s lead author, Frank Qian, “Plant-based dietary patterns are gaining popularity in recent years, so we thought it was crucial to quantify their overall association with diabetes risk, particularly since these diets can vary substantially in terms of their food composition.”
The Harvard team selected the best-quality studies among those that would allow them to compare health outcomes among two groups:
- People who followed a plant-based diet the most closely and consistently.
- People who followed a plant-based diet the least closely and consistently.
Those criteria led them to select nine epidemiological (population) studies published through February of 2019 — involving a total of 307,099 participants — that had collected data from diet surveys and medical records.
Their analysis compared health outcomes between people who fell into two categories of plant-based diets, all of who reported eating some animal foods:
- People whose diets emphasized healthful plant-based foods.
- People who consumed significant amounts of less-healthy plant foods, such as skinless potatoes, white flour, and sugar.
And the Harvard team’s analysis led them to two conclusions:
- People who followed plant-based diets — whether highly or less healthful — the most closely and consistently were 23% less likely to develop type 2 diabetes, compared to those who followed a plant-based diet less closely and consistently.
- The reduction in diabetes risk was greatest — 30% — for people who ate the most-healthful plant-based diets, compared to those who followed a plant-based diet less closely and consistently.
These findings weren't very surprising, since healthful whole plant foods — such as fruits, vegetables, beans, and nuts — tend to reduce diabetes risk factors such as insulin resistance, high blood pressure, weight gain, and systemic inflammation.
As the study’s senior author, Qi Sun, said, “Overall, these data highlighted the importance of adhering to plant-based diets to achieve or maintain good health, and people should choose fresh fruits and vegetables, whole grains, tofu, and other healthy plant foods as the cornerstone of such diets.”
Plant-based diets linked to better heart health
A new analysis of data from a prior study is one of the first studies to compare the health effects of plant-based versus animal-based diets in the general population.
And the authors’ analysis — published in the Journal of the American Heart Association — appears to confirm that plant-based diets protect heart health and reduce the risk of dying from a heart attack, stroke, or other heart-related cause (Kim H et al. J Nutr 2019).
Prior studies found heart-health benefits from plant-based diets but were conducted among people — such as avowed vegetarians or Seventh Day Adventists — who ate a mostly vegan diet, rather than plant-based diets with substantial proportions of animal foods.
The researchers — from Johns Hopkins University and the University of Minnesota — reviewed food intake information from the previously published ARIC (Atherosclerosis Risk in Communities) study.
The new analysis of data from the ARIC study covered 12,168 people aged 45-64 years (56% women). None of the participants had cardiovascular disease at the outset, and the ARIC researchers followed them for almost 30 years, from 1987 through 2016.
The team behind the new analysis of ARIC study data categorized the participants’ eating patterns according to the proportion of plant foods they ate versus animal foods.
People who ate the most plant-based foods enjoyed these risk reductions, compared with those who ate the least amount of plant-based foods:
- 16% lower risk for heart attacks, stroke, or heart failure.
- 32% lower risk of dying from a cardiovascular-related cause.
- 25% lower risk of dying from any cause.
The results prompted these comments from Casey M. Rebholz, Ph.D., of the Johns Hopkins Bloomberg School of Public Health: “… to reduce cardiovascular disease risk people should eat more vegetables, nuts, whole grains, fruits, legumes and fewer animal-based foods. These findings are pretty consistent with previous findings about other dietary patterns, including the Dietary Approaches to Stop Hypertension, or DASH diet, which emphasize the same food items.”
Most-healthful plant-based diets may lower kidney disease risk
A new, unprecedented study detected links between healthful plant-based diets and better kidney health.
The team behind this study was the same as the one behind the heart-health study described above. And, like the heart-health study, this kidney-health study analyzed diet-health data from the ARIC study (Kim H et al. CAJSN 2019).
Of course, the nutritional and health quality of plant-based foods varies widely. Whole, unprocessed fruits, vegetables, beans, nuts, seeds, and grains have more micronutrients in antioxidants than processed versions, with fruit juices and refined grains (e.g., white rice and bread) being least nutritious and healthful.
Encouragingly, the results of the team’s analysis indicate that — compared with less healthful plant-based diets — diets featuring nutrient-rich plant foods may help protect against chronic kidney disease (CKD).
The authors of the new study analyzed data collected during the previously published Atherosclerosis Risk in Communities study, which involved 14,686 middle-aged adults who’d participated in the ARIC study and were followed for an average of 24 years.
They compared the risk of developing chronic kidney disease or CKD among people whose answers to diet surveys indicated that their plant-based diet was least or most healthful:
- Least-healthful plant-based diet = 11% higher risk for CKD
- Most-healthful plant-based diet = 14% reduction in CKD risk
In addition, closer adherence to any plant-based diet or to a healthy plant-based diet was linked to a slower age-related decline in kidney function.
The statistical link between plant-based diets and CKD risk was more pronounced among the participants who were of normal, healthy weight at the start of the study.
As lead author Casey M. Rebholz, Ph.D., said, “For kidney disease risk, it appears to be important to choose healthy options for plant sources of food, including fruits, vegetables, whole grains, nuts, and legumes. Also, our finding … suggests that following a healthy eating pattern may be particularly beneficial before becoming overweight or obese.”
- Hu EA, Steffen LM, Coresh J, Appel LJ, Rebholz CM. Adherence to the Healthy Eating Index-2015 and Other Dietary Patterns May Reduce Risk of Cardiovascular Disease, Cardiovascular Mortality, and All-Cause Mortality. J Nutr. 2019 Sep 16. pii: nxz218. doi: 10.1093/jn/nxz218. [Epub ahead of print]
- Kim H, Caulfield LE, Garcia-Larsen V, Steffen LM, Coresh J, Rebholz CM. Plant-Based Diets Are Associated With a Lower Risk of Incident Cardiovascular Disease, Cardiovascular Disease Mortality, and All-Cause Mortality in a General Population of Middle-Aged Adults. J Am Heart Assoc (JAHA). 2019 Aug 20;8(16):e012865. doi: 10.1161/JAHA.119.012865. Epub 2019 Aug 7.
- Kim H, Caulfield LE, Garcia-Larsen V, Steffen LM, Grams ME, Coresh J, Rebholz CM. Plant-Based Diets and Incident CKD and Kidney Function. Clin J Am Soc Nephrol (CJASN). 2019 May 7;14(5):682-691. doi: 10.2215/CJN.12391018. Epub 2019 Apr 25.
- Qian F, Liu G, Hu FB, Bhupathiraju SN, Sun Q. Association Between Plant-Based Dietary Patterns and Risk of Type 2 Diabetes: A Systematic Review and Meta-analysis. JAMA Intern Med. 2019 Jul 22. doi: 10.1001/jamainternmed.2019.2195. [Epub ahead of print]