10 Important Plant Diet (Vegan) Research Studies of 2018
Gauged by the “noise” on social media and trends like the ketogenic and carnivore diets, some might wonder if the science backing predominantly or completely plant diets has faltered. In reality, 2018 saw some important advances in understanding the impact of “beans not beef” and 10 of those studies are highlighted here.
1) Environment https://www.ncbi.nlm.nih.gov/pubmed/30318102
Lancet Planet Health. 2018 Oct;2(10):e451-e461. doi: 10.1016/S2542–5196(18)30206–7.
Health and nutritional aspects of sustainable diet strategies and their association with environmental impacts: a global modelling analysis with country-level detail.
Sustainable diets are intended to address the increasing health and environmental concerns related to food production and consumption. Although many candidates for sustainable diets have emerged, a consistent and joint environmental and health analysis of these diets has not been done at a regional level. Using an integrated health and environmental modelling framework for more than 150 countries, we examined three different approaches to sustainable diets motivated by environmental, food security, and public health objectives.
In this global modelling analysis, we combined analyses of nutrient levels, diet-related and weight-related chronic disease mortality, and environmental impacts for more than 150 countries in three sets of diet scenarios. The first set, based on environmental objectives, replaced 25–100% of animal-source foods with plant-based foods. The second set, based on food security objectives, reduced levels of underweight, overweight, and obesity by 25–100%. The third set, based on public health objectives, consisted of four energy-balanced dietary patterns: flexitarian, pescatarian, vegetarian, and vegan. In the nutrient analysis, we calculated nutrient intake and changes in adequacy based on international recommendations and a global dataset of nutrient content and supply. In the health analysis, we estimated changes in mortality using a comparative risk assessment with nine diet and weight-related risk factors. In the environmental analysis, we combined country-specific and food group-specific footprints for greenhouse gas emissions, cropland use, freshwater use, nitrogen application, and phosphorus application to analyse the relationship between the health and environmental impacts of dietary change.
Following environmental objectives by replacing animal-source foods with plant-based ones was particularly effective in high-income countries for improving nutrient levels, lowering premature mortality (reduction of up to 12% [95% CI 10–13] with complete replacement), and reducing some environmental impacts, in particular greenhouse gas emissions (reductions of up to 84%). However, it also increased freshwater use (increases of up to 16%) and had little effectiveness in countries with low or moderate consumption of animal-source foods. Following food-security objectives by reducing underweight and overweight led to similar reductions in premature mortality (reduction of up to 10% [95% CI 9–11]), and moderately improved nutrient levels. However, it led to only small reductions in environmental impacts at the global level (all impacts changed by <15%), with reduced impacts in high-income and middle-income countries, and increased resource use in low-income countries. Following public health objectives by adopting energy-balanced, low-meat dietary patterns that are in line with available evidence on healthy eating led to an adequate nutrient supply for most nutrients, and large reductions in premature mortality (reduction of 19% [95% CI 18–20] for the flexitarian diet to 22% [18–24] for the vegan diet). It also markedly reduced environmental impacts globally (reducing greenhouse gas emissions by 54–87%, nitrogen application by 23–25%, phosphorus application by 18–21%, cropland use by 8–11%, and freshwater use by 2–11%) and in most regions, except for some environmental domains (cropland use, freshwater use, and phosphorus application) in low-income countries.
Approaches for sustainable diets are context specific and can result in concurrent reductions in environmental and health impacts globally and in most regions, particularly in high-income and middle-income countries, but they can also increase resource use in low-income countries when diets diversify. A public health strategy focused on improving energy balance and dietary changes towards predominantly plant-based diets that are in line with evidence on healthy eating is a suitable approach for sustainable diets. Updating national dietary guidelines to reflect the latest evidence on healthy eating can by itself be important for improving health and reducing environmental impacts and can complement broader and more explicit criteria of sustainability.
2) Nutrition for Children and Mothers https://www.ncbi.nlm.nih.gov/pubmed/30577451
Nutrients. 2018 Dec 20;11(1). pii: E5. doi: 10.3390/nu11010005.
Vegan Nutrition for Mothers and Children: Practical Tools for Healthcare Providers.
As the number of subjects choosing vegan diets increases, healthcare providers must be prepared to give the best advice to vegan patients during all stages of life. A completely plant-based diet is suitable during pregnancy, lactation, infancy, and childhood, provided that it is well-planned. Balanced vegan diets meet energy requirements on a wide variety of plant foods and pay attention to some nutrients that may be critical, such as protein, fiber, omega-3 fatty acids, iron, zinc, iodine, calcium, vitamin D, and vitamin B12. This paper contains recommendations made by a panel of experts from the Scientific Society for Vegetarian Nutrition (SSNV) after examining the available literature concerning vegan diets during pregnancy, breastfeeding, infancy, and childhood. All healthcare professionals should follow an approach based on the available evidence in regard to the issue of vegan diets, as failing to do so may compromise the nutritional status of vegan patients in these delicate periods of life.
3) Cardiometabolic Health https://www.ncbi.nlm.nih.gov/pubmed/30571724
PLoS One. 2018 Dec 20;13(12):e0209086. doi: 10.1371/journal.pone.0209086. eCollection 2018.
Cardiometabolic risk factors in vegans; A meta-analysis of observational studies. Benatar JR1, Stewart RAH1.
There is increasing evidence that plant based diets are associated with lower cardiovascular risk.
To evaluate effects of a vegan compared to an omnivorous diet on cardio-metabolic risk factors.
Meta-analysis of observational studies published between 1960 and June 2018 that reported one or more cardio-metabolic risk factors in vegans and controls eating an omnivorous diet were undertaken. Macro-nutrient intake and cardio-metabolic risk factors were compared by dietary pattern. The Newcastle Ottawa Scale (NOS) was used to assess the quality of each study. The inverse-variance method was used to pool mean differences. Statistical analyses were performed using RevMan software version 5•2 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen.
40 studies with 12 619 vegans and 179 630 omnivores were included. From food frequency questionnaires in 28 studies, vegans compared to omnivores consumed less energy (-11%, 95% confidence interval -14 to -8) and less saturated fat (- 51%, CI -57 to -45). Compared to controls vegans had a lower body mass index (-1.72 kg/m2, CI -2.30 to -1.16), waist circumference (-2.35 cm, CI -3.93 to -0.76), low density lipoprotein cholesterol (-0.49 mmol/L CI -0.62 to -0.36), triglycerides (-0.14 mmol/L, CI -0.24 to -0.05), fasting blood glucose (-0.23 mmol/, CI -0.35 to -0.10), and systolic (-2.56 mmHg, CI -4.66 to -0.45) and diastolic blood pressure (-1.33 mmHg, CI -2.67 to -0.02), p<0.0001 for all. Results were consistent for studies with < and ≥ 50 vegans, and published before and after 2010. However in several large studies from Taiwan a vegan diet was not associated with favourable cardio-metabolic risk factors compared to the control diets.
In most countries a vegan diet is associated with a more favourable cardio- metabolic profile compared to an omnivorous diet.
4) Anti-inflammatory Heart Diet: A Prospective Study https://www.ncbi.nlm.nih.gov/pubmed/30571591
J Am Heart Assoc. 2018 Dec 4;7(23):e011367. doi: 10.1161/JAHA.118.011367.
Anti-Inflammatory Effects of a Vegan Diet Versus the American Heart Association-Recommended Diet in Coronary Artery Disease Trial.
Background Dietary interventions may play a role in secondary cardiovascular prevention. hsCRP (High-sensitivity C-reactive protein) is a marker of risk for major adverse cardiovascular outcomes in coronary artery disease. Methods and Results The open-label, blinded end-point, EVADE CAD (Effects of a Vegan Versus the American Heart Association-R
ecommended Diet in Coronary Artery Disease) trial randomized participants (n=100) with coronary artery disease to 8 weeks of a vegan or American Heart Association-recommended diet with provision of groceries, tools to measure dietary intake, and dietary counseling. The primary end point was high-sensitivity C-reactive protein. A linear regression model compared end points after 8 weeks of a vegan versus American Heart Association diet and adjusted for baseline concentration of the end point. Significance levels for the primary and secondary end points were set at 0.05 and 0.0015, respectively. A vegan diet resulted in a significant 32% lower high-sensitivity C-reactive protein (β, 0.68, 95% confidence interval [0.49–0.94]; P=0.02) when compared with the American Heart Association diet. Results were consistent after adjustment for age, race, baseline waist circumference, diabetes mellitus, and prior myocardial infarction (adjusted β, 0.67 [0.47–0.94], P=0.02). The degree of reduction in body mass index and waist circumference did not significantly differ between the 2 diet groups (adjusted β, 0.99 [0.97–1.00], P=0.10; and adjusted β, 1.00 [0.98–1.01], P=0.66, respectively). There were also no significant differences in markers of glycemic control between the 2 dietgroups. There was a nonsignificant 13% reduction in low-density lipoprotein cholesterol with the vegan diet when compared with the American Heart Association diet (adjusted β, 0.87 [0.78–0.97], P=0.01). There were no significant differences in other lipid parameters. Conclusions In patients with coronary artery disease on guideline-directed medical therapy, a vegan diet may be considered to lower high-sensitivity C-reactive protein as a risk marker of adverse outcomes.
5) TMAO Production from Red Meat vs Plant Foods https://www.ncbi.nlm.nih.gov/pubmed/30535398
Eur Heart J. 2018 Dec 10. doi: 10.1093/eurheartj/ehy799. [Epub ahead of print]
Impact of chronic dietary red meat, white meat, or non-meat protein on trimethylamine N-oxide metabolism and renal excretion in healthy men and women.
Carnitine and choline are major nutrient precursors for gut microbiota-dependent generation of the atherogenic metabolite, trimethylamine N-oxide (TMAO). We performed randomized-controlled dietary intervention studies to explore the impact of chronic dietary patterns on TMAO levels, metabolism and renal excretion.
METHODS AND RESULTS:
Volunteers (N = 113) were enrolled in a randomized 2-arm (high- or low-saturated fat) crossover design study. Within each arm, three 4-week isocaloric diets (with washout period between each) were evaluated (all meals prepared in metabolic kitchen with 25% calories from protein) to examine the effects of red meat, white meat, or non-meat protein on TMAO metabolism. Trimethylamine N-oxide and other trimethylamine (TMA) related metabolites were quantified at the end of each diet period. A random subset (N = 13) of subjects also participated in heavy isotope tracer studies. Chronic red meat, but not white meat or non-meat ingestion, increased plasma and urine TMAO (each >two-fold; P < 0.0001). Red meat ingestion also significantly reduced fractional renal excretion of TMAO (P < 0.05), but conversely, increased fractional renal excretion of carnitine, and two alternative gut microbiota-generated metabolites of carnitine, γ-butyrobetaine, and crotonobetaine (P < 0.05). Oral isotope challenge revealed red meat or white meat (vs. non-meat) increased TMA and TMAO production from carnitine (P < 0.05 each) but not choline. Dietary-saturated fat failed to impact TMAO or its metabolites.
Chronic dietary red meat increases systemic TMAO levels through: (i) enhanced dietary precursors; (ii) increased microbial TMA/TMAO production from carnitine, but not choline; and (iii) reduced renal TMAO excretion. Discontinuation of dietary red meat reduces plasma TMAO within 4 weeks.
6) Plant Diets and Insulin Sensitivity
Eur J Epidemiol.2018 Sep;33(9):883–893. doi: 10.1007/s10654–018–0414–8. Epub 2018 Jun 8.
Plant versus animal based diets and insulin resistance, prediabetes and type 2 diabetes: the Rotterdam Study.
Vegan or vegetarian diets have been suggested to reduce type 2 diabetes (T2D) risk. However, not much is known on whether variation in the degree of having a plant-based versus animal-based diet may be beneficial for prevention of T2D. We aimed to investigate whether level of adherence to a diet high in plant-based foods and low in animal-based foods is associated with insulin resistance, prediabetes, and T2D. Our analysis included 6798 participants (62.7 ± 7.8 years) from the Rotterdam Study (RS), a prospective population-based cohort in the Netherlands. Dietary intake data were collected with food-frequency questionnaires at baseline of three sub-cohorts of RS (RS-I-1: 1989–1993, RS-II-1: 2000–2001, RS-III-1: 2006–2008). We constructed a continuous plant-based dietary index (range 0–92) assessing adherence to a plant-based versus animal-based diet. Insulin resistance at baseline and follow-up was assessed using homeostasis model assessment of insulin resistance (HOMA-IR). Prediabetes and T2D were collected from general practitioners’ records, pharmacies’ databases, and follow-up examinations in our research center until 2012. We used multivariable linear mixed models to examine association of the index with longitudinal HOMA-IR, and multivariable Cox proportional-hazards regression models to examine associations of the index with risk of prediabetes and T2D. During median 5.7, and 7.3 years of follow-up, we documented 928 prediabetes cases and 642 T2D cases. After adjusting for sociodemographic and lifestyle factors, a higher score on the plant-based dietary index was associated with lower insulin resistance (per 10 units higher score: β = -0.09; 95% CI: — 0.10; — 0.08), lower prediabetes risk (HR = 0.89; 95% CI: 0.81; 0.98), and lower T2D risk [HR = 0.82 (0.73; 0.92)]. After additional adjustment for BMI, associations attenuated and remained statistically significant for longitudinal insulin resistance [β = -0.05 (- 0.06; — 0.04)] and T2D risk [HR = 0.87 (0.79; 0.99)], but no longer for prediabetes risk [HR = 0.93 (0.85; 1.03)]. In conclusion, a more plant-based and less animal-based diet may lower risk of insulin resistance, prediabetes and T2D. These findings strengthen recent dietary recommendations to adopt a more plant-based diet
7) Hypertension Therapy https://www.ncbi.nlm.nih.gov/pubmed/30069127
Ci Ji Yi Xue Za Zhi. 2018 Jul-Sep;30(3):176–180. doi: 10.4103/tcmj.tcmj_91_17.
Vegetarian diet and blood pressure in a hospital-base study.
Previous studies have reported that a vegetarian diet may lower blood pressure (BP), but the effect of diet on BP in asymptomatic participants with proteinuria is unknown. We examined the association of diet and BP in individuals with or without proteinuria.
MATERIALS AND METHODS:
This cross-sectional study analyzed data from participants who were more than 40 years old and received physical checkups at Taipei Tzu Chi Hospital from September 5, 2005, to December 31, 2016. Diets were assessed at baseline by a self-reported questionnaire and categorized as vegan, lacto-ovo vegetarian, or omnivore. There were 2818 (7.7%) vegans, 5616 (15.3%) lacto-ovo vegetarians, and 28,183 (77.0%) omnivores. The effect of different parameters on BP was determined using a multivariate multiple linear regression model with no intercept, with control for important characteristics and lifestyle confounders.
The vegan group had a lower mean systolic BP (-3.87 mmHg, P < 0.001) and diastolic BP (-2.48 mmHg, P < 0.001) than the omnivore group. Participants with proteinuria had a higher systolic BP (4.26 mmHg, P < 0.001) and diastolic BP (2.15 mmHg, P < 0.001) than those without proteinuria. Interaction analysis indicated that vegan participants with proteinuria had a lower systolic BP (-2.73 mmHg, P = 0.046) and diastolic BP (-2.54 mmHg, P = 0.013) than other participants with proteinuria. However, individuals in the lacto-ovo group with proteinuria had a BP similar to other participants with proteinuria.
A vegan diet was associated with lower BP in asymptomatic participants with proteinuria. This diet could be a nonpharmacologic method to reduce BP.
8) Rheumatoid Arthrits and Vegan Diets. Increasing Data https://www.ncbi.nlm.nih.gov/pubmed/29515679
Open Rheumatol J. 2018 Feb 8;12:19–28. doi: 10.2174/1874312901812010019. eCollection 2018.
Role of Diet in Influencing Rheumatoid Arthritis Disease Activity.
Patients with Rheumatoid Arthritis (RA) frequently ask their doctors about which diets to follow, and even in the absence of advice from their physicians, many patients are undertaking various dietary interventions.
However, the role of dietary modifications in RA is not well understood. Several studies have tried to address these gaps in our understanding. Intestinal microbial modifications are being studied for the prevention and management of RA. Some benefits of vegan diet may be explained by antioxidant constituents, lactobacilli and fibre, and by potential changes in intestinal flora. Similarly, Mediterranean diet shows anti-inflammatory effects due to protective properties of omega-3 polyunsaturated fatty acids and vitamins, but also by influencing the gut microbiome. Gluten-free and elemental diets have been associated with some benefits in RA though the existing evidence is limited. Long-term intake of fish and other sources of long-chain polyunsaturated fatty acids are protective for development of RA. The benefits of fasting, anti-oxidant supplementation, flavanoids, and probiotics in RA are not clear. Vitamin D has been shown to influence autoimmunity and specifically decrease RA disease activity. The role of supplements such as fish oils and vitamin D should be explored in future trials to gain new insights in disease pathogenesis and develop RA-specific dietary recommendations.
Specifically more research is needed to explore the association of diet and the gut microbiome and how this can influence RA disease activity.
9) Insulin Resistance: A Prospective Study https://www.ncbi.nlm.nih.gov/pubmed/29425120
Nutrients. 2018 Feb 9;10(2). pii: E189. doi: 10.3390/nu10020189.
A Plant-Based Dietary Intervention Improves Beta-Cell Function and Insulin Resistance in Overweight Adults: A 16-Week Randomized Clinical Trial.
The aim of this study was to test the effect of a plant-based dietary intervention on beta-cell function in overweight adults with no history of diabetes. Participants (n = 75) were randomized to follow a low-fat plant-based diet (n = 38) or to make no diet changes (n = 37) for 16 weeks. At baseline and 16 weeks, beta-cell function was quantified with a mathematical model. Using a standard meal test, insulin secretory rate was calculated by C-peptide deconvolution. The Homeostasis Model Assessment (HOMA-IR) index was used to assess insulin resistance while fasting. A marked increase in meal-stimulated insulin secretion was observed in the intervention group compared with controls (interaction between group and time, Gxt, p < 0.001). HOMA-IR index fell significantly (p < 0.001) in the intervention group (treatment effect -1.0 (95% CI, -1.2 to -0.8); Gxt, p = 0.004). Changes in HOMA-IR correlated positively with changes in body mass index (BMI) and visceral fat volume (r = 0.34; p = 0.009 and r = 0.42; p = 0.001, respectively). The latter remained significant after adjustment for changes in BMI (r = 0.41; p = 0.002). Changes in glucose-induced insulin secretion correlated negatively with BMI changes (r = -0.25; p = 0.04), but not with changes in visceral fat. Beta-cell function and insulin sensitivity were significantly improved through a low-fat plant-based diet in overweight adults.
10) Healthy Plant Diets and All-Cause Mortality https://www.ncbi.nlm.nih.gov/pubmed/29659968
J Nutr. 2018 Apr 1;148(4):624–631. doi: 10.1093/jn/nxy019.
Healthy Plant-Based Diets Are Associated with Lower Risk of All-Cause Mortality in US Adults.
Plant-based diets, often referred to as vegetarian diets, are associated with health benefits. However, the association with mortality is less clear.
We investigated associations between plant-based diet indexes and all-cause and cardiovascular disease mortality in a nationally representative sample of US adults.
Analyses were based on 11,879 participants (20–80 y of age) from NHANES III (1988–1994) linked to data on all-cause and cardiovascular disease mortality through 2011. We constructed an overall plant-based diet index (PDI), which assigns positive scores for plant foods and negative scores for animal foods, on the basis of a food-frequency questionnaire administered at baseline. We also constructed a healthful PDI (hPDI), in which only healthy plant foods received positive scores, and a less-healthful (unhealthy) PDI (uPDI), in which only less-healthful plant foods received positive scores. Cox proportional hazards models were used to estimate the association between plant-based diet consumption in 1988–1994 and subsequent mortality. We tested for effect modification by sex.
In the overall sample, PDI and uPDI were not associated with all-cause or cardiovascular disease mortality after controlling for demographic characteristics, socioeconomic factors, and health behaviors. However, among those with an hPDI score above the median, a 10-unit increase in hPDI was associated with a 5% lower risk in all-cause mortality in the overall study population (HR: 0.95; 95% CI: 0.91, 0.98) and among women (HR: 0.94; 95% CI: 0.88, 0.99), but not among men (HR: 0.95; 95% CI: 0.90, 1.01). There was no effect modification by sex (P-interaction > 0.10).
A nonlinear association between hPDI and all-cause mortality was observed. Healthy plant-based diet scores above the median were associated with a lower risk of all-cause mortality in US adults. Future research exploring the impact of quality of plant-based diets on long-term health outcomes is necessary.
Overall, 2018 provided important new data from prospective studies, epidemiologic studies, biochemical studies and environmental studies to indicate that the single diet for the health of the human body and the health of the planet is a plate with fruits, vegetables, legumes, whole grains and soy prepared as close to nature as possible.