Review of the week’s plant-based nutrition news 30th October 2022
This week I provide an update on studies that have investigated health outcomes in vegans. This includes cardiovascular health and the health status of vegan children and athletes.
A healthy vegan or 100% plant-based diet is suitable for all stages and ages of life, from cradle to grave, and can be associated with excellent health outcomes. However, we don’t have as much science-based information on the health of long-term vegans as we would like. From the available evidence, a vegan diet is associated with significant reductions in cardiovascular risk factors, including overweight/obesity, high blood pressure and high cholesterol. This is predicted to result in a lower risk of ischaemic heart disease. Vegans have around a 15% reduction in cancer risk and a 50% reduction in the risk of type 2 diabetes. It is also clear that bone health requires special attention. You can read my article on the topic here.
In this article I summarised some of the latest studies on the health of vegans.
OBESITY AND CARDIOMETABOLIC HEALTH: This large systematic review includes 84 papers that investigate the efficacy of vegan, vegetarian and plant-based whole foods (PBWF — exclusively plant-based or minimal animal foods including eggs and dairy) diets in treating obesity, hyperlipidaemia, insulin resistance, glycaemic control, type 2 diabetes, CVD and hypertension.
The paper reviews the impact of each of the three diet patterns on the various health outcomes listed above. Overall the findings confirm that all three types of diet reduce body weight to a greater extent than healthy omnivorous diets, including those recommended by the American Heart Association (AHA), American Diabetes Association and the National Cholesterol Education programme and in some studies performed better than the comparison calorie-restricted diet. Studies have also shown greater loss of subcutaneous, visceral and intramuscular fat with a plant-based diet.
All three diets improve glucose control, insulin sensitivity and resulted in reductions in HbA1c in people with type 2 diabetes, with the ability to reverse the condition in some. This has also been shown in the community setting amongst free-living people (The BROAD Study).
Plant-based diets were found to be very effective at lowering total and LDL-cholesterol but less effective for reducing triglyceride (TG) levels and may result in lower HDL-cholesterol levels. A Mediterranean diet was better at lowering TG levels compared to vegetarian or vegan diets. Plant-based diets were also effective at lowering blood pressure but this may not be superior to other therapeutic healthy diet patterns, such as the DASH diet. A vegan diet has been shown to be more effective at lowering high sensitivity CRP (a marker of inflammation) compared to the AHA recommended diet in people with coronary artery disease. Studies by Dean Ornish have confirmed that a low-fat vegetarian diet has the potential to ‘reverse’ coronary artery disease.
Overall, the differences between the three categories of plant-based diets were less important than the differences between the conventional comparator diet. Based on the results the authors conclude that recommendations in clinical practice should include a plant-based diet comprised mainly of whole plant foods. If animal foods are chosen to be included then this should be limited to fish and low-fat dairy. White flour products, sugar-sweetened beverages and ‘poor-quality’ animal foods (factory farmed beef and chicken and processed meat) should be limited/avoided.
Accepting that there is a need for more high quality, randomised studies, the authors conclude that ‘All motivated patients with type 2 diabetes and cardiovascular disease should be informed of the potential reversibility or at least halting of progression of these illnesses with comprehensive lifestyle modification that includes plant-predominant eating patterns’.
VEGETARIAN, VEGAN DIET AND CARDIOVASCULAR DISEASE (CVD). This latest meta-analysis on the topic of veggie and vegan diets and cardiovascular health includes 13 cohort studies with a total of 844,175 participants. During the follow up there were 115,392 cases of CVD, 30,377 cases of ischaemic heart disease and 14,419 cases of stroke. The results show that vegetarians have a 15% lower risk of CVD, 21% lower risk of ischaemic heart disease, and a non-significant 10% reduction in stroke risk when compared to omnivores. Results for vegans showed an 18% reduction in ischemic heart disease, which was of borderline significance, but less clear associations for CVD overall and stroke. However, the analysis of vegan diets was based on only 3 publications, which will have limited the statistical power to find a difference. Therefore more studies are needed to confirm these findings. Using World Cancer Research Fund criteria to assess the strength of evidence, the associations between vegetarian diets and CVD and IHD are considered probably causal.
Of note, the authors comment that none of the studies included effectively analysed the impact of quality of veggie/vegan diet on health outcomes and this may have played a role in the degree of risk reduction reported. We know that not all plant-based diets are created equal, and an unhealthy plant-based diet can be equally detrimental to CVD health as an omnivorous diet.
HEART FUNCTION AND PLANT-BASED DIETS: This is a novel cross-sectional study which examined the impact of dietary pattern on heart function as determined by echocardiography (ECHO). 133 participants over the age of 60 years were included from the Adventist Health Study-2. The mean age was 72.7, 48.1% were female, 33% were African American, and 71% were vegetarian (32 vegans and 31 lacto-ovo vegetarian).
As expected, vegetarians had a lower body weight and a lower prevalence of hypertension. In terms of heart function, there were significant differences between vegetarians and non-vegetarians. Vegetarians showed better left ventricular relaxation. Vegans showed even better heart function, which also included improved diastolic function (when the heart relaxes after contracting). The authors suggest this positive findings may partially be explained by the lower prevalence of obesity and hypertension. The authors conclude ‘This provides new evidence about a potential cardiac structural mechanism whereby diet may change risk’. Long-term impact of these finding on health outcomes need to be determined.
Interestingly, a study examining the heart function using echocardiography of vegan amateur runners compared to omnivores, found that vegans had favourable indicators of heart function including lower left ventricular wall thickness and better left ventricular systolic and diastolic function.
AGEs AND HEALTH OUTCOMES: Advanced glycation end products (AGEs) are a group of compounds that induce oxidative stress. They are formed by a spontaneous chemical reaction between an amino acid (protein) and a monosaccharide (glucose). Some AGEs are produced in the body every day. However, diet is the biggest contributor to AGE formation (along with tobacco products). AGEs from food are generated more readily from protein-rich foods, when cooking at high temperatures, for longer and with dry heat cooking (lower AGE formation when there is water/moisture present). Foods that generate the most AGEs are fried and processed foods and also animal-derived foods — meat, dairy, fried eggs. Plant foods such as fruits, vegetables, whole grains and legumes, generate the least amount of AGEs. AGE formation is also increased by altered glucose metabolism — i.e. when there is high blood sugars, insulin resistance and in the presence of diabetes. AGEs accumulate over time and the process for detoxification by the body is slow. AGEs have been shown to result in inflammation, oxidative stress, cellular damage and insulin resistance. AGEs have been implicated in the pathogenesis of a number of chronic diseases, including type 2 diabetes, kidney failure, dementia, cancer and atherosclerosis
The aim of this study was to assess the effects of a low‐fat plant‐based diet on dietary AGEs and test the association with body weight, body composition, and insulin sensitivity. 224 participants who were overweight were randomly assigned to a low‐fat vegan diet (n = 122) or a control group (n = 122) for 16 weeks. The low‐fat vegan diet was composed of ~75% of energy from carbohydrates, 15% protein, and 10% fat and consisted of fruits, vegetables, grains, and legumes (beans, peas, and lentils), while the control group was requested to make no dietary changes. Before and after the intervention both body composition and insulin sensitivity were measured and correlated with an estimate of dietary AGE consumption.
The results showed that a vegan diet was associated with a significant reduction in AGE consumption, by 79%. About 55% of the reduction of the dietary AGEs in the intervention group was due to the reduction of meat intake, 26% due to decreased dairy intake, and 15% was attributable to the decreased use of added fats. This reduction in AGE consumption was correlated with the observed weight loss, reductions in fat mass and improvements in insulin sensitivity. In the vegan group participants lost a mean of 6.4kg (7% body weight) compared to a non-significant reduction of 0.5 kg in the control group. This weight reduction was mostly due to the loss of body fat and visceral fat. Insulin sensitivity significantly increased in the vegan group.
It is proposed that a reduction in dietary AGEs favourable alters satiety hormones and reduces inflammation, both contributing to weight loss. This provides yet another mechanism by which healthy vegan diets can support a healthier body weight and reduce the risk of type 2 diabetes and metabolic syndrome.
VEGAN DIETS IN CHILDREN: This is an extremely useful review of the data summarising both the benefits and cautions relating to raising vegan children. The take home message is, that from the available data it is likely that a vegan diet can provide all the necessary nutrients for normal growth and development of children with some clear advantages for cardiometabolic health.
The review included 437 publications and the authors assessed the adequacy of vegans diets to provide certain nutrients and to support growth and development. Starting with energy and protein intake, it’s clear that a vegan diet can provide sufficient calories and more than enough protein, often exceeding recommended intakes. Iron intake is often higher than recommended in vegan children, but because of the lower bioavailability this often translates into lower ferritin levels (stored iron), which is not necessary a negative finding. Differences in haemoglobin levels and presence of iron deficiency anaemia are less obvious when comparing vegans to omnivores but iron status does seem to vary quite a bit between difference studies. In general, calcium intakes in vegan children are lower than recommended as is vitamin D, although the latter remains an issue for all diet patterns. Vitamin B12 is not an issue when children are appropriately supplemented. Folate deficiency is a concern amongst omnivorous children and adults but as would be expected this is less of a concern in vegan children consuming a healthy diet.
Most studies confirmed that vegan children have normal growth rates, well within the normal range. Some but not all studies have shown a slightly reduced height in younger vegan children, around 1–3 cm, compared to omnivores but it should be noted that our normal ranges relate only to omnivorous diets and the impact of these small differences are unlikely to be clinically relevant or impact health outcomes. As expected, vegan children display a healthier body mass index than omnivorous children.
In the discussion the authors go on to discuss the numerous potential advantages of a vegan diet in children. These include the lower intake of saturated fat, the increased consumption of fibre and phytonutrients and lower body weight and body fat. The authors conclude that there is still limited data on vegan diet in children and as always more studies are desirable but state that with appropriate supplementation and attention to key nutrients, a vegan diet can support normal growth and development with some health advantages.
HEALTH OF MODERN DAY VEGAN CHILDREN: We don’t have a great deal of contemporary data on the health of vegetarian and vegan children but the cross-sectional VeChi diet study from Germany has provided us with valuable and reassuring information. The previous report from this study cohort assessed the energy and macronutrient intake and growth of 430 children aged 1–3 years following either an omnivorous, vegetarian or vegan diet. There were no significant differences in calorie intake, height or weight between the different diet groups. Protein requirements were easily met. Fat and added sugar intakes were higher in children following an omnivorous diet and fibre intake higher in children following a vegan diet. Omnivores were also more likely to be overweight. The authors concluded ‘Our results indicate that a vegan and vegetarian diet in early childhood provides comparable amounts of energy and a macronutrient pattern in accordance with recommendations and can ensure normal growth’.
This 2021 paper reported the anthropometric measurements, dietary intakes and nutritional status in a cohort of 149 vegetarian, 115 vegan and 137 omnivore children and adolescents between the ages of 6–18 years. The results showed that dietary supplement use was most common in vegan children with most taking vitamin B12 and D3 supplements. Iron supplementation was more common in the vegetarian group. Calorie intake did not differ between diet groups. Protein intake exceeded the recommended 0.9g/kg in all diet groups with carbohydrate intake higher in the vegan and vegetarian groups. Vegans had a lower intake of free sugar and saturated fat, whilst a higher intake of fibre and polyunsaturated fatty acids.
Micronutrient intakes differed between diet groups with vegans having the highest intakes of vitamin E, vitamin B1, folate, vitamin C, magnesium, iron and zinc. Intakes of calcium were lowest in vegans at 305g per 1000kcal but was below the reference range in all diet groups. Vitamin B2 (riboflavin) intake was also lower in vegans. Of note, vegetarians had a lower than recommended vitamin B12 intake suggesting vegetarians, in addition to vegans, should be encouraged to take vitamin B12 supplements
Regarding blood parameters, vegans had higher folate levels and lower total cholesterol, LDL-cholesterol and ferritin concentrations. Vitamin D3 and B2 were low in a notable proportion of participants regardless of diet groups. This is the first study to assess vitamin B2 levels in children and the clinical relevance of lower than recommended levels in not clear, intakes can be optimised through the consumption of mushrooms, legumes, textured vegetable protein (TVP) or fortified plant-based dairy alternatives.
The main nutrient highlighted that should be optimised in a vegan diet is calcium, especially given recent reports of increased risk of fractures in vegans. Nonetheless, the study concludes once again, ‘The results of the VeChi Youth Study confirms the position of several national nutrition or paediatric societies that a vegetarian, including a vegan, diet can meet the recommended nutrient requirements in childhood and adolescence’.
I have previously covered an additional paper from the same study cohort on micronutrient and fatty acid intakes in vegan children aged 1–3 years old. The results confirmed that a well-planned vegan diet with appropriate supplementation can easily provide the necessary micronutrients with a more favourable profile of fatty acid consumption (more polyunsaturated fats rather in saturated fats). Special attention needs to be paid to calcium, iron, vitamins D, B12 and B2.
All in all a very reassuring study supporting a healthy vegan diet as a healthy option for children.
SKELETAL MUSCLE, VASCULAR FUNCTION AND VEGAN DIETS: More and more data suggest that you can achieve optimal physical and athletic performance whilst following a healthy vegan diet. There may even be some advantages, especially with the lower risk of cardiovascular disease and the anti-inflammatory effects. Yet there are prevailing myths that animal protein is required to build muscle strength and function. This is despite a number of studies showing equivalence to plant protein.
This study is not large but still useful in that it performs detailed investigations into muscle structure and function and vascular function in 16 omnivore and 9 vegan men (vegan for at least 6 months). The 25 participants were young (early 20's), healthy men with no history of resistance or endurance exercise training in the preceding six months. Dietary assessments were conducted and a variety of tests performed.
The results showed that despite significant differences in nutrient intake between the two groups, vegan and omnivorous men did not differ with regard to vascular and skeletal muscle structure and function, or cardiovascular fitness.
As mentioned, we have a number of studies confirming at the very least that vegan diets are equivalent when it comes to sports performance. For example, a short study comparing whey protein supplements with a novel, proprietary plant protein supplement composed of pea and yeast protein had similar impacts on body composition, strength, power, and endurance performance over 8 weeks when tested in semi-professional Futsal players. The authors concluded ‘these results suggest that whey protein does not possess any unique anabolic properties over and above those of plant-based proteins when equated to an essential amino acid profile’.
A well designed and conducted study investigated the effects of soya protein supplementation in a vegan group compared to whey protein supplementation in an omnivorous group on changes in muscle mass and strength in healthy young men undertaking resistance training. After 12 weeks of supervised resistance training and an equivalent protein intake of 1.6g/kg/day, no differences were found in muscle strength and mass accrual. The authors concluded ‘protein source does not affect resistance training-induced adaptations in untrained young men consuming adequate amounts of protein’. A prior meta-analysis found no difference between supplementing with soya protein versus animal protein in muscle mass and strength in response to resistance exercise
A GUIDE FOR HEALTH PROFESSIONALS: Despite the fact that vegan diets are considered to be suitable for all stage of life and have significant benefits for planetary health, many health professionals do not feel suitably trained to support their vegan patients or clients. In fact, a recent survey of General Practitioners and Paediatricians in France suggested that half of physicians would try and persuade their patients from switching to a vegan diet with their main concerns around protein and iron deficiency.
This up-to-date guide covers all the basics of meeting protein and micronutrient requirements on a vegan diet and provides an excellent resource for all health professionals and anyone who wants to optimise their vegan diet. If you cannot access the current article, then this equally excellent, prior article is open access and covers similar information, whilst this article summarises knowledge on the impact of plant-based diets on individual and planetary health.
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