Review of the plant-based nutrition news May 2023
A busy month with a large number of studies. I cover healthy diet patterns for cardiovascular health and type 2 diabetes, the impact of plant-based meat alternatives and fruit and veg on cardiometabolic risk factors, plant-based diets for athletes and the role of diet transition for planetary health.
It’s official, food really is medicine, as stated in the world’s most impactful medical journal Nature. This editorial clearly outlines how dietary interventions are a powerful tool for prevention and treatment of chronic conditions. We have known this for decades, but implementing effective strategies to improve diet quality at a population level remains elusive. Many strategies haven been trialled, including medical tailored meals with dietitians or nutritionists designing meals that are then delivered to the patient; counselling to support people to understand how to shop for food or prescribing healthy foods such as fruit and vegetables to those who do not usually have access. Where I disagree with the some of the narrative is around the need to personalise dietary advice based on certain characteristics of the individual patient, such as their genetics or microbiome composition. Of course, some level of personalisation is required based on taste and preferences and in dealing with certain conditions, such as heart failure and chronic kidney disease. Yet for most people, a focus on consuming a healthy plant-based diet would be a huge improvement on their current diet pattern and greater resource should be made available to make healthy foods accessible and affordable for all.
The Food Foundation in the UK has produced a series of policy briefings exploring the potential health, environmental, resilience and biodiversity impacts of increasing fruit and vegetable production and consumption in the UK. Their assessment makes it clear that there are benefits for both population and planetary health by increasing the consumption of particularly vegetables, but also fruit in place of sugary snacks and meat (see new meta-analysis on fruit and vegetable below). This will require Government and policy support to encourage increased consumption, ensure access to fruit and vegetables regardless of income, support for farmers to increase production and significant changes to the wider food environment, including restaurants and public sector catering to increase meals with fruit and vegetables.
I could not agree more with the concluding statement of editorial in Nature; ‘It is indisputable that food has a huge impact on mental and physical health. With the convergence of public and private initiatives promoting the centrality of food and diet for improving health, the time is ripe for clinical testing of specific approaches for the prevention or treatment of disease using food as medicine. Prescription pharmaceuticals are commonplace and widely accepted by patients, physicians and insurers. A dietary prescription should also be on the table’.
DIET AND TYPE 2 DIABETES: Despite understanding a huge amount about the causes of type 2 diabetes, the incidence globally continues to rise, with the COVID-19 pandemic worsening this trajectory. Diet is a huge contributor to this risk and with this regard diet quality globally has continued to deteriorate, with no country meeting healthy eating guidelines.
This huge study provides us with a figure for the contribution of dietary factors to the risk of type 2 diabetes. Suboptimal diets were found to be implicated in 14 million or 70% of new cases of type 2 diabetes, with a range of 52–86% depending on geographical region and affecting men more than women. Excess intake of harmful dietary factors was shown to be a greater contribution to this risk than insufficient intake of protective factors. Overall, the specific dietary factors can be summarised by the fact that diets are currently too high in red and processed red meat, sugar sweetened beverages and insufficient in whole plant foods as seen in this figure. Of note, yogurt is considered protective as controlled studies have shown a positive impact on glucose regulation, likely due to the probiotic effect and impact on the microbiome. Potatoes were assumed to have a negative impact on diabetes risk due to prior studies showing an association with overweight and obesity and type 2 diabetes. Of note, the results suggest a direct effect of these dietary factors that were not merely due to their impact on body mass index.
These results are truly depressing and confirm that in most cases, type 2 diabetes is entirely preventable. The accompanying editorial makes the following statements:
- A sustainable food environment that ensures the availability of health-promoting foods, while limiting foods clearly shown to promote ill health, requires large-scale government action.
- There must be less reliance on refined grains and red meats, with increased production of environmentally sustainable whole grains, vegetables, fruit and legumes, an important source of plant-based protein.
- Population health and environmental sustainability require much stronger action — advice that governments ignore at their peril.
NEW DIETARY GUIDELINES FOR DIABETES: This is a very useful and timely guideline given the discourse amongst health professionals around ‘the best’ dietary approach for prevention and treatment of type 2 diabetes.
For prevention of diabetes, the recommendations align with general healthy eating guidelines that all include an emphasis on whole plant foods e.g. Mediterranean, Nordic and vegetarian diets. The key is to avoid overweight and obesity, which is much easier when following a dietary pattern that is plant rich.
For diabetes management and remission, there is acknowledgment that a number of dietary approaches that support weight loss can be effective. However, there is a strong emphasis on consuming a fibre-rich diet through the consumption of whole grains, vegetables, legumes, seeds, nuts and whole fruits in order to meet fibre recommendations of 35g/day Very low carbohydrate intakes, such as with ketogenic diets, are not recommended although it is acknowledged that carbohydrate counting may be a useful approach to determine mealtime insulin dose. The guideline also notes that low-carbohydrate plant-based diets may be useful.
There are clear recommendations that dietary fats should come from plant-based foods and that saturated fat intake, mainly from animal-sourced foods, should be minimised. Regarding protein intake, it is stated that ‘Insufficient evidence exists from clinical trials in people with type 2 diabetes to indicate preferential intake of either animal or plant protein. However, high animal protein diets may exceed recommendations for saturated fat intakes (<10% total energy), with serum cholesterol concentrations and markers of blood glucose control generally lower for diets higher in protein from plants.’
I am pleased that environmental sustainability is addressed in the guideline with a clear statement that a diet centred around healthy plant-based foods can promote health and have a lower environmental impact.
The overarching theme of the guideline endorses a diet centred around whole grains, legumes, fruits, vegetables and nuts.
WHICH POPULAR DIETS ARE HEART HEALTHY: Dietary guidelines for promotion of cardiovascular health recommend the consumption of fruit, vegetables, whole grains, legumes, nuts and seeds, whilst limiting or avoiding red and processed meat, sugar sweetened beverages and ultraprocessed foods. Plant sources of protein and fat should be prioritised. In most guidelines, fish consumption continues to be promoted. The 2021 American Heart Association guidelines to not consider meat essential, but write ‘if meat or poultry is desired, choose lean cuts and unprocessed forms.’
This new statement from the American Heart Association examines 10 popular dietary patterns in the US and considers how well they align with their 2021 guidance on heart healthy diets. The diets considered are DASH (Dietary Approaches to Stop Hypertension-style), Mediterranean-style, pescetarian, ovo/lacto-vegetarian, vegan, low fat, very low-fat, ow-carbohydrate, Paleolithic (Paleo), and very low-carbohydrate/ketogenic patterns. They are ranked Tier 1–4 based on how well they meet heart healthy dietary guidelines.
The analysis shows that Tier 1 and 2 dietary patterns are all plant predominant. Tier 1 includes Mediterranean, vegetarian and pescatarian. Tier 2 vegan and low-fat diets. Vegan diets rank lower than vegetarian because the authors consider it restrictive and difficult to sustain over the longer-term. In addition, concerns are raised around protein and vitamin B12 sufficiency.
All the low-carb, meat heavy diets are ranged in Tier 3 and 4 showing lower alignment with optimal nutrient intakes.
I find this statement a positive endorsement of meat-free diets. The avoidance of fish does not seem to present the authors with any specific concerns but instead they state; ‘The budgetary savings and environmental benefits of ovo/lacto-vegetarian diets relative to animal flesh–containing diets may be a desirable feature for some patients.’ There is also emphasis on respecting cultural practices and food preferences. For those of us that have followed a vegan diet for several years can reassure others that it is neither restrictive nor unsustainable but joyful and delicious. With a small amount of knowledge and skills, any concerns about nutrient deficiencies are easily be overcome.
This is a thumbs up for veggie and vegan diet for cardiovascular health.
PLANT-BASED DIETS AND BONE HEALTH: There has been concern raised around the impact of meat-free and vegan diets on bone health with three prior studies showing an increased risk of fracture in vegetarians and vegans. The data are of course nuanced and I have previous summarised my thoughts on the topic in this article. None the less, vegans and those following a 100% plant-based diet should pay attention to bone health, which involves more than just diet and should incorporate all pillars of lifestyle medicine.
It is nonetheless reassuring to see two publications using the plant-based diet index (PDI), which provides a way of assessing the impact of a plant-based diet on health outcomes, whilst addressing the issue of diet quality.
The first study is a cross-sectional study from China and included 9613 community-dwelling adults over the age of 60 years. 62.8% of participants were female and 19.2% (1848) had a diagnosis of osteoporosis. A healthy plant-based diet was found to reduce the risk of osteoporosis by 36%, even after adjustment for other lifestyle-related factors. In contrast, an unhealthy plant-based diet increased the risk by 41%. The association of the healthy PDI with the risk of osteoporosis was found to be more pronounced in people over 80 years of age and in female participants. In terms of single foods, whole grains, fresh fruits, fresh vegetables, nuts, legumes, and tea were found to be major contributors to the benefit seen for osteoporosis. In contrast, among unhealthy plant foods, higher intakes of refined grains, sugary drinks and desserts were associated with a higher risk of osteoporosis. Of note, seaweed, egg and fish consumption was also found to be associated with better bone health, whereas meat was found to be harmful. Dairy consumption was overall neutral.
The second study is a case-control study of post-menopausal women with osteoporosis, including 131 cases and 131 controls. The association between the plant-based diet index and bone mineral density in the femoral neck and lumbar vertebrae was assessed. A healthy plant-based diet was shown to be associated with better bone mineral density, whereas the reverse was true for an unhealthy plant-based diet. The authors conclude; ‘Overall, the findings indicated that in postmenopausal women with osteoporosis, a healthy plant-based diet could prevent bone loss, and an unhealthy plant-based diet might have detrimental effects’.
I accept that the two studies are not of the highest quality, but they do provide some reassurance and guidance on how to optimise a plant-based diet. As always, quality of the diet is key.
IMPACT OF PLANT-BASED MEAT ALTERNATIVES (PBMAs): Even though PBMAs are not required in the diet, they provide an additional option for people transitioning away from consuming meat. It’s therefore good to see more studies addressing their health impacts when compared to meat consumption.
The aim of this meta-analysis was to assess the short-term effects of meat substitutes on important cardiometabolic biomarkers (total cholesterol, TC; LDL-cholesterol, LDL-C; HDL-cholesterol, HDL-C; triglycerides, TG; systolic blood pressure, SBP; diastolic blood pressure, DBP; fasting blood glucose, FBG and weight) in controlled clinical trials. The analysis included 12 studies and separated plant-based meat alternatives from mycoprotein products. The results showed that the consumption of meat substitutes is associated with significant reductions in TC, LDL-C, and TG when compared with the consumption of omnivorous diets. In addition, PBMAs did not have an impact on HDL-C, in contrast to some studies on plant-based diets which show a reduction. PBMAs did not appear to impact the other markers of cardiometabolic health that were assessed — SBP, DBP, FBG and weight — but the level of certainly of these results was low.
There are many reasons why PBMAs, including mycoprotein, may have a benefits on cardiometabolic health when compared to meat. In contrast to meat, PBMAs have fibre, are absent in cholesterol, may have lower levels of saturated fat and may have a positive benefit on gut health with greater formation of short chain fatty acids by gut bacteria. However, a major disadvantage currently is the high salt content, and some products are contain coconut oil and hence are high in saturated fat.
These results are reassuring given the need to move away from meat consumption for environmental concerns. Demonstrating that PBMAs can be healthier than meat should hopefully support their inclusion within public health guidelines.
FRUIT AND VEGETABLE CONSUMPTION AND HYPERTENSION: This is a timely publication for the UK, as it coincides with a report from the Office of National Statistics showing that 32% of adults living in private households in England had high blood pressure (hypertension) and 3 in 10 of those (29%) were undiagnosed; this equates to approximately 4.2 million adults with undiagnosed hypertension.
This new systematic review and meta-analysis of 18 cohort studies, including 451, 291 participants and 145, 492 of hypertension and assessed the impact of fruit and vegetable consumption on the risk of hypertension. The results show that for every 200g/d of fruit and vegetables combined and total fruit consumed, there was a 3% and 7% reduction in risk, respectively. There was no association observed for intake of total vegetables. There was a linear reduction in risk across the range of intakes with an 11% reduction in risk with consumption of 800g/d versus 40g/day for fruit and vegetables combined and a 19% reduction in risk with consumption of 550g/day versus 8 g/day of total fruit. The authors used the World Cancer Research Fund criteria to assess the strength of evidence and found that the associations for fruit and vegetables combined and total fruit are probably causal.
When considering individual foods, apples or pears, blueberries, raisins or grapes, avocado, broccoli, carrots and lettuce were found to be associated with a lower risk of hypertension. Intake of potatoes overall, and in particular fried potatoes, was associated with a significant increase in risk of hypertension, while the association for non-fried potatoes was less clear. Surprisingly, cantaloupe, Brussels sprouts, cruciferous vegetables, were associated with a high risk of hypertension, but given the small numbers of studies involved (n=3) and lack of plausible biological mechanism, the results cannot be considered certain.
There are many potential reasons for these findings. Fruit and vegetables contain nutrients such as fibre, potassium and magnesium that are associated with lower blood pressure. In addition, those eating higher quantities of fruit and vegetables will be consuming less of the foods that are harmful to vascular health, such as meat and ultra-processed foods. There will also be benefits to the gut microbiome, which results in lower inflammation and oxidative stress.
The authors conclude ‘Clinicians can recommend an increased fruit and vegetable intake for patients with or at risk of hypertension (e.g., persons with overweight or obesity, or with type 2 diabetes) and the findings support recommendations to increase fruit and vegetable intake in the general population as well’. The impact of individual foods could benefit from further investigation. Increasing intake to 800g/day (10 portions) may be challenge given only 28% of UK adults consume 5 portions a day and the UK does not even produce enough fruit and vegetables to meet healthy eating recommendations as outlined in these excellent policy briefs from the Food Foundation. Plant-based diets, both vegetarian and vegan, have been associated with additional benefits for lowering blood pressure when compared to omnivorous diets. The consumption of beans, whole grains and nuts are all beneficial for prevention of hypertension.
It seems that swapping meat for PBMAs and adding more fruit and vegetables to the diet would be a good way to reduce the risk of cardiometabolic diseases.
VEGAN DIETS CAN SUPPORT ATHLETES: This might sound like an obvious statement to make given the growing number of elite athletes who thrive and excel on a plant-based diet. Nonetheless, there remains scepticism amongst those following an omnivorous diet about whether a plant-based or vegan diet can support equivalent muscle growth.
This small but useful study from the UK asked the question as to whether a vegan diet can support resistance training-induced skeletal muscle remodelling to the same extent as animal-derived protein sources. In phase 1 of the study, 16 young adults with a median age of 23 years were assigned to a 3-day high-protein (1.8g/kg) dietary intervention of protein either derived from animals or plants. At the same time they performed daily unilateral leg resistance exercise. Phase 2 involved 22 young adults completed a 10 week, high-volume (5 d/week), progressive resistance 11 exercise programme whilst consuming either an animal-based or plant-based diet. Mycoprotein products were used as substitutes for animal protein sources. Various measures of muscle protein synthesis were untaken before, during and after the intervention. Overall, the results showed equivalent results in both groups with all participants managing to increase lean muscle mass. The authors conclude ‘a carefully designed vegan diet is capable of supporting optimal skeletal muscle adaptive responses to resistance training.’
Another recent study called the SWAP-MEAT Athlete study enrolled 12 recreational runners and 12 resistance trainers who were assigned to three diets — WFPB (whole food plant-based), PBMA (plant-based meat alternative), and Animal — for 4 weeks each, in random order. During the WFPB phase participants consumed at least two meals consisting of vegetables, legumes, fruits, nuts and seeds, and whole grains each day. Common meals consisted of protein sources including quinoa, beans, and tofu. During PBMA, participants consumed at least two servings of plant-based meat alternative protein sources per day. Common protein sources included Beyond Burger, Impossible Burger, and Gardein. No consumption of animal meat was allowed. Fish consumption was allowed once per week, which seems a shame and unnecessary. The Animal group had to eat 2 meals with red meat or poultry per day, keeping fish consumption to once per week.
The aim of the study was to assess the impact of 2 different predominantly plant-based diets on endurance and muscular strength. The results showed no significant difference in any of the measures of performance assessed between the diet groups. Amazingly the authors state, ‘Our study is one of the first to investigate plant-based meat alternatives and athletic performance, and to our knowledge, this is one of the largest randomized crossover trials (n = 22) conducted on plant-based diets and athletic performance.’ So another green light for athletes to consume a plant-based diets, especially when there will be expected benefits for cardiometabolic health.
If you want some more in depth detail on how to adopt a healthy plant-based diet to support athletic training, why not download this fantastic resource called the Plant-Based Playbook from Switch4Good. If you are new to sports or just keen to get involved with a fantastic new campaign, join me and many others in signing up for Running on Plants.
THE CLIMATE AND ECOLOGICAL CRISIS: Health professionals in the UK came together in April for Extinction Rebellion’s event ‘The Big One’. It was wonderful to see thousands of health professionals coming together with a shared passion and mission to effect change. For me, it was uplifting to finally see health professionals align over food system change and demand that the Government follow the science and support food system transition to one which is plant-based. At the same time we need healthcare organisations to promote plant-based meals and provide education to patients and staff around adopting a health plant-based diet.
This timely review in The Lancet Planetary Health puts health professionals front and centre of the fight against climate catastrophe and again acknowledges the crucial role of a global plant-based dietary transition, with hospitals and healthcare organisations leading by example. Several hospitals have now paved the way for a more widespread adoption of plant-based menus. New York City hospitals have adopted plant-based meals as the default. University of Florida hospital offers a fully plant-based menu, the Tzu Chi hospital in Taiwan serves only vegetarian food and the Hayek Hospital in Lebanon is the World’s only fully vegan/plant-based hospital.