Dec 11, 2022
The Top Science Papers of 2022 supporting plant-based nutrition
This past year the world has been in turmoil. This has affected food security globally. Diet quality has significantly deteriorated, yet the evidence supporting plant-based diets for cardiovascular disease, type 2 diabetes, cancer and obesity management has only strengthened. Here are my highlights.
NOT GOOD NEWS: Published on December 6th, this year’s report makes for a depressing read. In the 2021 report it was identified that 26% of all deaths globally and 31% of premature deaths in Europe and USA were attributable to dietary risk factors. The current report describes how all forms of malnutrition, that is hunger to obesity, have increased. Diets across the world are failing to meet the minimum standards for health and sustainability resulting in rising rates of obesity and diet-related non-communicable diseases. Around 40% of all adults and 20% of all children globally are now overweight or obese. When assessing dietary intakes of certain foods, red meat consumption globally is more than 200% higher than the recommended maximum intake, whilst consumption of healthy-promoting plant foods; fruit, vegetables, whole grains, legumes and nuts, are well below the recommended intakes. The reasons for these findings are complex and the solutions will require engagement from Governments, policy makers, the food industry, farmers, charities, NGOs, academics and civil society organisations.
THE STATE OF THE FOOD SYSTEM IN THE UK: This annual report from the Food Foundation describes the broken food system in the UK, which is failing to support the needs of the most vulnerable in our society. Healthy diets remain inaccessible and unaffordable to those that need them the most. The food system is not meeting our health or climate needs. Back in 2021, the National Food Strategy for England identified four key areas where dietary shifts were needed to ensure a healthy and sustainable future: increased consumption of fibre, and fruit and vegetables; and decreased consumption of meat, and high fat, salt and/or sugar (HFSS) foods. Yet more than a year later, the situation has only worsened. Here are the headline messages from this year’s report.
·The poorest fifth of UK households would need to spend 47% of their disposable income on food to meet the cost of the Government-recommended healthy diet. This compared to just 11% for the richest fifth.
· 22% of workers in the food system earn the National Minimum Wage or below, compared to 8% of workers across the whole UK economy.
· More healthy foods are nearly three times as expensive per calorie as less healthy foods.
· More sustainable alternative milks are approximately 60% more expensive than dairy milk.
· School food standards are not adequately monitored, and school children are experiencing food insecurity.
· More than 1 in 4 (26%) places to buy food are fast-food outlets.
· 71% of sandwiches available from high street retailers contain meat or fish, with no significant improvement in the last 3 years.
· Only 7% of breakfast cereals and 4% of yogurts marketed to children are low in sugar. Approximately a third (32%) of food and soft drink advertising spend goes towards less healthy foods, compared to just 1% for fruit and vegetables.
· The percentage of children with obesity in their first year of school has risen by 50% in one year, affecting twice as many children in the most deprived fifth compared to the least deprived fifth.
· Nearly 10,000 amputations are carried out for type 2 diabetes every year, an increase of 23% in 5 years.
· Healthy life expectancy in the most deprived tenth of the population is 20 years less for women and 18 years less for men than in the least deprived 10th.
· If current trends continue then, amongst children born this year, 1 in 4 will suffer overweight or obesity by the time they start school, rising to 3 in 4 by age 65.
· If things continue as they are, by 2050 emissions from the food system will be four times higher than the level that is needed if the UK is to meet its net zero target.
The recent UK Government food strategy published in June 2022 fails to address most of these issues, which makes me feel pretty hopeless. We need to do better for our health and the health of the planet.
MEDICAL PROFESSIONALS SUPPORT PLANT-BASED NUTRITION: This is a major turning point in the narrative for my profession. This editorial in a prestigious American medical journal is a call to action. It aligns with the ‘One Health’ approach to healthcare, the definition of which is ‘a collaborative, multisectoral, and transdisciplinary approach with the goal of achieving optimal health outcomes recognizing the interconnection between people, animals, plants, and their shared environment’.
The authors highlight the strong evidence supporting plant-based diets for individual and planetary health and for the animals with which we share this planet. They discuss the contribution of meat-heavy diets and industrial farming practices to pandemic risk, antibiotic resistance and the adverse impacts on both physical and mental health of people working in the meat industry. They dispel prevalent myths that meat consumption is ‘natural’ and ‘necessary’ while citing the enormous amount of evidence supporting meat-free diets for prevention and management of chronic conditions. They also suggest that nutrition equity is a moral imperative and that currently, in the USA, access to healthy food is unjustly distributed, thus contributing to health inequalities.
It is time the medical profession stepped up and took action, starting with ourselves. The authors conclude ‘The medical profession can help to move the needle by embracing radical change when possible — especially within our own ranks — and incremental change when necessary to promote harm reduction. We owe it to the profession, to our patients, and to the planet we share’.
NUTRIENT INTAKE IN MEAT VERSUS PLANT-BASED DIETS: This is a surprisingly useful paper given that it is written by two employees of the company Unilever. The aim of the study was to assess the nutritional adequacy of meat-based diets compared to plant-based diets (mainly vegetarian and vegan). This is a systematic review of observational and intervention studies published between 2000 and January 2020 and included a total of 141 (101 studies on meat eaters, 118 vegetarians, 63 vegans) mostly from Europe, South/East Asia, and North America.
There is a lot of detail in the text, which is well worth reading. Overall, all diet patterns were found to have nutritional inadequacies. Meat-eaters were at risk of inadequate intakes of fibre, polyunsaturated fatty acids (PUFA), alpha-linolenic acid (ALA), folate, vitamin D, E, calcium and magnesium. Vegetarian and vegans had lower intakes of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), vitamin B12, vitamin D, iron, zinc, iodine, calcium and lower levels of bone turnover markers than meat eaters. Vegans had the lowest vitamin B12, calcium and iodine intake, and also lower iodine status and lower bone mineral density. Fibre, PUFAs, folate, vitamin C, E and magnesium intakes were high in plant-based diets. Average fibre intake amongst vegans was 44g/d compared to 28g/d in vegetarians and 21g/d in meat eaters. All diet groups met protein and energy requirements. There was no mention of saturated fat intake which I assume was high in meat eaters.
The table below summarises the findings.
The authors’ conclusion is eminently sensible. ‘There were nutrient inadequacies across all dietary patterns, including vegan, vegetarian and meat-based diets. As plant-based diets are generally better for health and the environment, public health strategies should facilitate the transition to a balanced diet with more diverse nutrient-dense plant foods through consumer education, food fortification and possibly supplementation.’ Unilever have come out as surprising leaders in supporting a transition to a plant-based diet. Whatever their underlying motivation, they have made a valuable contribution to the literature on plant-based diets.
FOOD CHOICES AND LIFE EXPECTANCY: Good news! Our food choices really can add years to life. In this study, researchers used existing meta-analyses and data from the Global Burden of Diseases study to build a model that enables the instant estimation of the effect on life expectancy (LE) of a range of dietary changes. Based on prior data, an optimal diet was considered to be higher intakes of whole grains, legumes, fish, fruit, vegetables, and included a handful of nuts, while reducing red and processed meats, sugar-sweetened beverages, and refined grains.
The optimal diet was similar to the Eat-Lancet Planetary Health Plate and included the following quantities of various foods per day. Whole grains 225g (fresh weight) or 75g (dry weight), vegetables 400g, fruit 400g, nuts 25g, fish 200g, eggs 25g (half an egg), dairy 200g, refined grains 50g, red and processed meat 0g, white meat 50g, sugar sweetened beverages 0g, oils 25g.
The results showed that a sustained change from a typical Western diet to the optimal diet from age 20 years was estimated to increase life expectancy by 10.7 years in women and 13 years in men. The largest gains were shown to occur by eating more legumes (females: 2.2 years; males: 2.5 years), whole grains (females: 2.0; males: 2.3 years), and nuts (females: 1.7 years; males: 2.0 years) and less red meat (females: 1.6; males: 1.9 years) and processed meat (females: 1.6 years; males: 1.9 years). Changing from a typical diet to the optimal diet at age 60 years was estimated to increase LE by 8.0 years for women and 8.8 years for men, and 80-year-olds would gain 3.4 years. Even a halfway transition towards an optimal diet was predicted to increase LE by 6.2 years for 20-year-old women from the United States and 7.3 years for men. Results were presented based on US data, but similar trends were found when considering data from China and Europe.
The authors conclude ‘sustained change from a typical to an optimised diet from early age could translate into an increase in LE of more than 10 years’. Of note, a previous report from the Nurses’ Health Study and Health Professionals Follow-Up study has shown that the extra years derived from healthy diet and lifestyle habits are spent in good health rather than chronic ill health.
The model used in the study is also now available as a publicly available online tool called the Food4HealthyLife calculator (https://food4healthylife.org/).
WHAT IS ALREADY KNOWN ABOUT NUTRITION AND CANCER: This is a fantastic summary of the current knowledge on diet and cancer. The following key points are highlighted.
•Plant-based diets are associated with a lower risk of developing cancer.
•Plant-based diets reduce the risk of metabolic disorders such as obesity and type 2 diabetes that increase the risk of cancer.
•Plant-based diets reduce the risk of chronic conditions after a diagnosis of cancer.
•Plant-based diets may positively impact response to anti-cancer treatments, but more studies are needed.
•Mechanisms involved include reduced inflammation, insulin and insulin-like growth factor 1 levels and healthier gut microbiome.
•This is because plant-based diets are high in fibre, phytochemicals and support increased production of short chain fatty acids by gut microbes.
The article concludes: ‘The results of this review suggest that the collective evidence supports plant-enriched diets for the reduction of cancer risk and the improvement of metabolic disorders in survivors’.
Coincidentally, Dr Laura Freeman and I have published an opinion piece highlighting the importance of diet and lifestyle counselling as part of cancer care, providing both a doctor and patient perspective. We cover very similar information to the JAMA review. Find our full article here.
LOWER RISK OF CANCER IN THOSE AVOIDING MEAT CONSUMPTION: In case you needed any more reasons to eliminate meat from the diet, this study will help. It included 472,377 adult participants of the UK Biobank study with a mean age in the 50’s at recruitment and followed for 11.4 years. Participants were categorised into regular meat-eaters (n = 247,571), low meat-eaters (n = 205,385), fish-eaters (n = 10,696), and vegetarians (n = 8685).Regular meat eaters consumed meat more than 5 times per week. Low meat eaters, less than 5 times per week. The vegetarian group included 466 vegans. Participants also had blood measurements of insulin-like growth factor 1 (IGF-1), testosterone and sex hormone binding globulin. During the follow-up period 54,961 cancers were diagnosed.
The data analysis showed that vegetarians and fish-eaters had a lower body mass index, were younger, more likely to be never smokers, have a university/college degree, and report consuming less alcohol at recruitment compared to regular meat-eaters
The results showed a stepwise reduction in cancer incidence as meat and fish were reduced/eliminate from the diet. Compared with regular meat eaters, vegetarians had a 14% reduction in the risk of all cancers and fish-eaters had a 10% lower risk. Low meat-eaters had an 11% reduction in the risk of colorectal cancer. There was no significant difference in risk of colorectal cancer for fish-eaters and vegetarians, potentially due to lack of power (not enough participants) as the estimates suggested lower risks in both these non-meat-eating diet groups.
Post-menopausal women who were vegetarian had an 18% lower risk of breast cancer, but this was likely due to being a lower body mass index. In men, not eating meat was associated with a 20% reduction in the risk of prostate cancer and being vegetarian reduced the risk by 31%.
Regarding blood biomarkers, there did not seem to be a strong interaction between diet, IGF-1 levels and cancer risk in this cohort. Prior analysis of this cohort has shown IGF-1 levels to be slightly lower in vegetarians. In the current study, vegetarian women did have slightly lower circulating IGF-I concentrations, which may have benefited their risk of breast cancer. However, for prostate cancer the analysis did not suggest that IGF-1 levels were mediating the lower risk in vegetarians. Of note, prior studies have documented lower IGF-1 level in vegans but given the low number of vegans in this studies the difference between diet groups was not that significant.
There are so many plausible reasons for these results, including reduced exposure to carcinogens in meat and increased consumption of anti-cancer compounds in plant foods. These data are in line results from the EPIC-Oxford and Adventist Health Studies that show vegetarians and vegans have a lower risk of cancer, with a greater benefit in vegans. The current study did not have enough vegan participants to draw any conclusions but a meta-analysis from 2017 demonstrated a 15% reduction in the risk of cancer in vegans.
PLANT-BASED DIETS AND GASTROINTESTINAL CANCERS (GI): This huge study assessed the impact of a plant-based diet on the risk of GI cancers and has pretty robust findings that should form the basis of cancer prevention guidelines.
The report is a meta-analysis of 49 studies, both cohort (n=18) and case-control (n=31), with >3 million participants mainly from Europe, North America and Asia and assessed the impact of a plant-based diet on the risk of GI cancers. The term ‘plant-based’ included several dietary patterns that emphasise the consumption of healthy plant foods with the reduction or avoidance of animal-derived and processed foods. The study included participants on vegan, semi vegetarian (eat dairy, eggs and some red meat, poultry, and fish >= 1 time/month but <1 time/week), prudent (high intakes of vegetables, fruit, noodle, potatoes, soy products, mushroom, and seaweed), vegetarian, Mediterranean and pesco-lacto-ovo-vegetarian diets.
The results showed that a plant-based diet was protective against the development of GI cancers with a risk reduction in the order of 20–30% Plant-based diets reduced the risk of pancreatic cancer by 29%, colorectal by 24%, rectal by 16%, colon by 12%, gastric by 19%, liver by 39%. The risk reduction was similar in males and females and between geographical areas. The impact of a vegan diet was assessed separately and found to be similar to other plant-based dietary patterns.
PLANT-BASED DIET AND MYELOMA OUTCOMES: This is a pretty groundbreaking study as it is the first time that diet quality has been shown to impact outcomes in people living with myeloma.
Myeloma is a cancer of plasma cells that reside in the bone marrow. It is not conventionally thought of as a cancer that is influenced by diet and lifestyle factors, in part because extensive research into this area has not been conducted. However, it is one of the cancers that is associated with obesity, in part due to the inflammatory state associated with adiposity. In the EPIC-Oxford study, 65 of the 61, 647 participants developed multiple myeloma. Those following a vegetarian or vegan diet had a 77% reduction in the risk of developing myeloma. Diets associated with higher levels of inflammation may increase the risk of myeloma. An analysis from the Nurses’ Health Study and Health Professionals Follow-up Study that included 165,796 individuals with 423 multiple myeloma cases and 345 deaths, those with a healthier diet prior to diagnosis, based on the alternative healthy eating index 2010, had a longer survival than those with less healthy diets.
The top line summary of this new study is taken from the first authors’ social media (on IG urvishahMD, twitter UrviShahMD). The study hypothesis was that dietary factors impact the gut microbiome in people with myeloma and this may be associated with outcomes from treatment. The study analysed the impact of dietary factors, stool metabolites and the microbiome on sustained deep remission (MRD negative). It included 32 patients with sustained deep remission and 36 patients in which there remained evidence of residual disease. The results showed that higher stool butyrate (produced by healthy gut bacteria) and increased bacterial diversity were associated with a sustained deep remission. Healthier dietary protein (plant and seafood) correlated with butyrate levels and remission. Of note, seafood and plant proteins include seafood, nuts, seeds, soy products (excluding beverages), and legumes (beans and peas). Dietary flavonoids also correlated with butyrate levels. The authors conclude ‘this is the first study to show that dietary and microbiome factors may be associated with sustained MRD negativity in plasma cell disorders. Our study suggests that lifestyle modification in the form of dietary change may potentially contribute to multiple myeloma control’.
I look forward to the results of larger, longer interventional studies from Dr Shah.
DAIRY CONSUMPTION AND PROSTATE CANCER: We have known for a while that there may be is an association between dairy consumption and an increased risk of prostate cancer. This is acknowledged by the World Cancer Research Fund but the strength of evidence is considered weak or limited given that not all studies confirm this association and a dose response is not always apparent. In their summary they state that in general, studies show that 400g (386ml milk) of total dairy consumption per day increases the risk of prostate cancer by around 7%. It has been postulated that it may be the calcium in dairy that causes this increased risk given that there are also data suggesting higher consumption of calcium from all sources increases the risk of prostate cancer. The mechanism may be that higher intakes of calcium down regulates the formation of vitamin D3, which drives cell proliferation. The other proposed mechanism is that higher exposure to the growth factor IGF-1 through dairy consumption is increasing cancer risk.
It is good to have this analysis from the Adventist Health Study-2 cohort in which researchers have assessed the contribution of both dairy consumption and calcium separately, with the inclusion of participants who are vegan and thus do not consume dairy and obtain calcium from alternate sources. The study included 28,737 Seventh-day Adventist men in the United States and Canada, of whom 6389 were of black ethnicity. 11.7% (3370 participants) had very low (≤10 g/d) or no intake (2302 participants) of dairy. In total, 1254 (190 advanced) cases of prostate cancer were diagnosed during an average 7.8 years of follow-up. Participants were analysed in quintiles of dairy consumption with comparisons made between the midpoints of the upper and lower quintiles of dairy consumers (430 versus 20.2 g/d).
The results showed that men consuming 430g/d of dairy compared to those consuming 20.2g/d had a 27% increased risk of developing prostate cancer. The association was similar for advanced and non-advanced cases of cancer, in people of black ethnicity and after excluding vegans from the analysis. The major rise in risk of prostate cancer was seen to occur between the zero-intake category and second quintile of the dairy users, with the risk then remaining high but plateauing. Compared to participants consuming zero dairy, those consuming the most had a 60% increased risk. The increased risk was mainly seen with the consumption of milk with no association found for cheese and yogurt. In contrast, higher intakes of non-dairy and supplemental calcium did not increase the risk of prostate cancer.
The authors conclude ‘these data from a population with a wide range of dairy and calcium exposure do not clearly support a connection between calcium intake and prostate cancer. However, they do suggest that risk of prostate cancer is causally associated with higher intake of dairy products or some unknown causal factor that is strongly associated with dairy intake’. I think it’s time to seriously rethink our reliance on dairy for nutrients. We can definitely do better.
VEGETARIAN DIET AND DEMENTIA RISK: This is a timely and much needed study. There has always been a concern that diets that exclude fish may increase the risk of dementia given the lower blood levels of long-chain omega-3 fatty acids. The only study we had to date was a preliminary report from the Adventist Health Study suggesting that meat eaters had a significantly higher risk of developing dementia compared to vegetarians.
This paper analysed data from the prospective Tzu Chi Vegetarian Study. It included data from 5710 participants who were aged 50 years or older at the time of recruitment in 2005 and followed till 2014.The participants were all Buddhist volunteers, 3154 who were non-vegetarian and 1737 who were vegetarian. Vegetarians were classified based on not eating meat, fish, or poultry for at least a year prior to recruitment. The vegetarians were less like to consume alcohol and smoke tobacco and had significantly less diabetes, cerebrovascular disease, and substance use disorder compared to the non-vegetarians.
During the average follow up of 9.2 years follow up period there were 121 cases of dementia (37 vegetarians and 84 non-vegetarians) identified and vegetarians has a 33% reduction in the risk of dementia. Subgroup analysis found that vegetarians were specifically protected against dementia under the age of 75 years. However, these results were not statistically significant due to low case numbers, which in part is likely to be due to the fact that researchers only considering cases of dementia that required medical attention.
The reasons for this benefit of a vegetarian diet includes lower risk of co-morbidities and that plant-based diets address the key drivers of dementia; dyslipidaemia, glucose dysregulation, oxidative stress, inflammation and an abnormal gut microbiome.
There are several limitations with these data as discussed in the paper. In addition, the Taiwanese diet differs from the Western vegetarian diet being higher in soya foods, rice, wheat and salt and less consumption of dairy. Overall, these data provide some reassurance that excluding fish and meat from the diet does not negatively impact brain health and may even be of benefit.
In fact, there are accumulating data supporting the protective role of plant-based foods for maintaining brain health and preventing cognitive decline. This recent paper summarises current literature on plant-based nutrients and their impact on cognition and finds supportive evidence for a plant-based diet for optimising cognitive health and potentially helping to prevent dementia. You can read my recent review on the topic here.
ULTRA-PROCESSED FOOD (UPF) CONSUMPTION, MEAT AND MORTALITY: UPFs have become a centrepiece of Western diet patterns. In the UK and US more than 50% of foods consumed are classified as ultra-processed. The designation of UPF is based on the NOVA classification. UPF consumption is associated with increased calorie intake and a higher risk of various chronic conditions including cardiovascular disease, overweight/obesity, type 2 diabetes, autoimmune conditions and more.
This paper reports finding from the Adventist Health Study-2 and specifically examines the impact of both UPF and animal food consumption on the risk of mortality (death). The study included 77,437 participants who were followed for an average of 7.5 years. Around a third of participants in this cohort are vegetarian or vegan.
The median consumption of UPFs was 27.4% of energy. Comparing the 90th centile of UPF consumption ( 47.7% of dietary energy) to the 10th centile (12.1% of dietary energy) there was a 14% higher risk of total mortality. This association persisted after adjustment for a more animal-based diet suggesting that UPFs regardless of whether animal-derived or plant-based are detrimental to health. Interestingly, UPF consumption was not associated with cardiovascular disease or cancer mortality, but primarily with mortality from neurological (particularly Alzheimer disease and Parkinson disease) and respiratory causes. The association of UPF consumption with mortality appeared stronger among those with chronic diseases at baseline, suggesting the potential for greater impact among those with higher mortality risk.
There was no significant association between total animal food intake and mortality. But it should be noted that in this cohort consumption of animal foods was very low with a median of 9.8% of calories derived from animal foods. However, consuming just 6.2% of total calories from red meat compared to zero calories was associated with a 14% increase in risk of mortality.
The researchers also examined the impact of replacing UPFs with moderately processed or unprocessed foods and found that UPFs were associated with a higher risk than both moderately processed and unprocessed foods.
Overall, both higher UPF and red meat consumption adversely affected health and increased the risk of death in this population who are generally healthier than the average American.
PROTEIN INTAKE AND FRAILTY: I am very pleased to read the results of this paper as the erroneous and prevalent narrative continues to be that animal protein is superior to plant-based sources of protein for prevention of frailty in older people.
The analysis included 85,871 women aged 60 years and above from the Nurses’ Health Study. Participants were aged 30–55 years at the start of the study in the 1970’s and had been followed for 22 years. The study assessed the impact of protein intake on the risk of frailty. Frailty was defined as having at least three of the following five criteria from the Fatigue, Resistance, Ambulation, Illnesses and Loss of Weight (FRAIL) scale; fatigue, low strength, reduced aerobic capacity, 5 or more chronic conditions and loss of weight of ≥5%. The occurrence of frailty was assessed every 4 years from 1992 up to 2014 and dietary intake on at least 9 occasions. The main food sources of plant protein were bread, cereals, pasta, nuts, beans, and legumes; main food sources of animal protein included processed and unprocessed red meat, poultry, fish and seafood, eggs, and dairy products.
The results showed that comparing women consuming the most plant-based protein to the least (6.2g per day vs 3.8g per day), higher plant protein intake was associated with a 14% reduction in risk of frailty. In contrast, high animal protein intake was associated with a 7% increased risk of frailty. Replacing 5% of energy from animal protein with plant protein was associated with a 38% lower risk of frailty with a positive impact from replacing both dairy and non-dairy protein.
The authors conclude ‘among older adults, a higher intake of plant protein was associated with reduced risk of frailty. Moreover, these data suggest that replacing animal protein with plant protein might help to avoid the development of the frailty syndrome’.
Prior reports from the Nurses’ Health Study have reported that healthy dietary patterns characterised by a greater consumption of whole plant foods are associated with a lower risk of frailty, whilst red meat consumption increases the risk. So, all in all, a useful endorsement for emphasising plant sources of protein in the diet, even in older adults.
PLANT-BASED DIET FOR ELDERS: There is often concern raised when older adults are following a plant-based diet. Caloric needs generally decrease with age but the requirements for some nutrients increase. For example, protein is less well absorbed and used less efficiently with ageing, regardless of diet pattern, and therefore there may be a higher protein requirement (1.0–1.2g/kg after age of 65 years). Older people synthesise vitamin D less efficiently from the sun and may spend less time outdoors and therefore are more likely to require supplements. Care should be taken to maintain calcium requirements and therefore it may be useful to incorporate fortified foods, such as plant-based milks and calcium-set tofu. Atrophic gastritis is common among people over the age of 50 years and can result in decreased absorption of vitamin B12 regardless of diet pattern, therefore B12 supplements are required as per any plant-based diet and some advocate for a higher dose with age. The sublingual route may also be preferable in order to bypass the stomach. Iron requirements in general decrease in post-menopausal women. The conversion rate of short chain omega-3 fatty acids to long chain decreases with age and it may be prudent to recommend higher intakes of ALA (at least 2.2 grams for females and 3.2 grams for males per day) and a micro-algae supplement. Overall, it is important to ensure that the foods being eaten are nutrient-dense, with a focus on a variety of healthy plant-based foods. There is also a natural loss of muscle mass (sarcopenia) with ageing and older people can be at risk of malnutrition. Overweight is an increasing issue, and this can co-exist with low muscle mass. Despite all these concerns, an increasing body of evidence supports plant-based diets for healthy ageing.
This study uses the plant-based diet index (PDI) to assess the impact of a plant-based diet in community-dwelling older adults in Spain. Researchers analysed data from 1880 individuals with a median age of 68.7 years from the Spanish Seniors ENRICA-1 cohort. During the 3.3 years for follow-up, there were 136 cases of frailty. Those participants most adherent to a healthy plant-based diet had a 57% reduction in the risk of frailty compared to those who were least adherent. Participants consuming the most unhealthy plant foods as per the unhealthy PDI had a 289% increased risk of frailty.
Regarding individual foods, vegetables, vegetables oils and fish/seafood were associated with a lower risk of frailty. Of note however, data on how much of each food participants were consuming has not been provided, therefore it is not clear whether some foods, such as beans, were actually being consumed at high levels.
There are several reasons why a diet high in healthy plant-based foods would be associated with a lower risk of frailty. This type of diet pattern is rich in fibre, antioxidants and anti-inflammatory compounds. It supports better gut health and reduces the risk of other chronic condition. More data on 100% plant-based diets for elders would be beneficial.
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.
PLANT-BASED DIETS FOR SOUTH ASIANS: South Asians are more likely than other ethnic groups to consume a vegetarian diet, yet people from the South Asian subcontinent have a greatly increased risk of cardiometabolic conditions compared to Whites and on average develop conditions such as type 2 diabetes and cardiovascular disease 10 years earlier. Thus, understanding the impact of diet on the risk of chronic conditions is vitally important given that it is a significant modifiable risk factor.
This study analysed data from 891 participants of South Asian ancestry in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study. Overall, the results showed that adherence to a healthy plant-based diet, as defined by the hPDI, was associated with significantly better cardiometabolic health, including lower fasting glucose levels, improved insulin sensitivity, lower LDL-cholesterol levels, lower body weight, less visceral fat, lower levels of inflammation (high sensitivity CRP — although this lost significance after adjustment for BMI) and higher levels of adiponectin (a fat-derived hormone that protects against diabetes and atherosclerosis). Of note. For each 5-unit higher hPDI score, there was an 18% lower risk of type 2 diabetes. The opposite was true for an unhealthy plant-based diet, which in general was associated with worse cardiometabolic health.
This is an important dietary study for people of South Asian descent, as there are limited options available for prevention of cardiometabolic diseases that do not involve pharmaceuticals. The authors conclude ‘while consuming an overall plant-based diet was associated with lower cardiometabolic risks, the risks were much lower for those consuming a healthy plant–based diet. Future intervention and policy efforts to lower cardiometabolic risks in this high-risk population should focus on promoting a healthy plant–based diet, since it is associated with better health outcomes and is also environmentally sustainable’.
OPTIMAL NUTRITION FOR CARDIOVASCULAR HEALTH: Cardiovascular disease (CVD) is the general term given to a group of disorders that affect the heart and blood vessels. The INTERHEART and the INTERSTROKE studies demonstrated that modifiable lifestyle and psychosocial factors were responsible for 90% of the risk of developing a heart attack or stroke. Therefore, our approach to reducing the incidence and mortality from these conditions should focus on addressing these risk factors. This new practice statement from the American Society for Preventive Cardiology brings us up to date with the evidence on the optimal nutritional approach for prevention of atherosclerotic cardiovascular disease.
The evidence really hasn’t change for decades but has strengthened through the availability of additional studies. The recommendations are that health professionals should recommend a plant-predominant diet centred around foods that promote health and prevent atherosclerosis i.e. fruit, vegetables, whole grains, legumes, nuts, seeds and fatty fish. The recommendations can be met by following a Mediterranean, DASH (dietary approaches to stop hypertension), healthy vegetarian or exclusively plant-based diet. The main difference between these diet patterns is the amount of animal products included, with the Mediterranean and DASH diet patterns including fish, lean meats and low fat-dairy. They share in common the minimisation of processed meats, refined carbohydrates and sugar-sweetened beverages, limiting the amount of dietary cholesterol and sodium, replacing saturated fat with monounsaturated and polyunsaturated fats, and avoiding trans fats.
The guidelines do continue to recommend the consumption of fatty fish without addressing the environmental sustainability of this approach. The main benefits of consuming fish appear to be mainly a substitution effect (if you are eating fish you are generally eating less of other types of animal flesh) and the long-chain omega-3 content (DHA/EPA). Algae-derived omega-3, the primary source for fish, has a similar effect on blood omega-3 levels as the consumption of fish and plant-exclusive/healthy vegan diets have significant benefits for cardiovascular health. The additional benefit of fish is yet to be established.
The guidelines warn against an animal-based low-carbohydrate or ketogenic diet given the adverse impact on long term cardiovascular health. In theory, a low-carbohydrate plant-based approach may be beneficial but there are no long-term studies with hard clinical outcomes. In addition, there is no strong evidence that intermittent fasting has additional benefits to calorie restricted diets for weight loss or cardiometabolic health.
I am pleased to see paediatric nutrition included and the negative impact that socioeconomic disparities and racism can have on access to healthy nutrition and consequent health outcomes. The document is open access and well worth reading.
PLANT-BASED DIETS AND OBESITY: We have known for many years that people eating a meat-free diet tend to have a lower body weight, with vegans having the lowest BMI of all diet patterns. This is one of the major advantages of a plant-based diet as foods consumed tend to be low in calorie density yet nutrient-rich. You can read my article on plant-based diets and body weight here.
It is good to see this study, which brings together data from 9 prospective cohort studies that have used the PDI to assess the impact of plant-based diets on weight management. All studies were conducted in Western populations except for one study in South Korea
The results confirm that adherence to a plant-based diet is associated with lower body weight, with a greater impact when a healthy plant-based diet is followed. However, the uPDI showed that a diet composed of unhealthy plant foods had no advantage for body weight.
The authors conclude ‘A healthful plant-based diet provides a framework that can be used to create individualised diets that are socio-culturally appropriate, acceptable, and sustainable for lifelong health that reside within planetary health boundaries’.
It is great to see that this years weight management guidelines from New Zealand specifically mention the benefits of a whole food plant-based diet for long-term sustainable weight loss. In addition, the guideline acknowledges that ‘vegetarian diets, including vegan diets, are associated with improved cardiometabolic risk factors, and a reduced risk of type 2 diabetes and cardiovascular disease’.
DIETARY INTERVENTIONS FOR TYPE 2 DIABETES REMISSION: Remission should be the aim of diet and lifestyle interventions for people living with type 2 diabetes. There are several dietary approaches that can lead to remission, defined as HbA1c <6.5% for at least 3 months with no surgery, devices, or active pharmacologic therapy for the specific purpose of lowering blood glucose. This new expert consensus statement has reviewed all the evidence on dietary interventions and come up with a recommendation for the optimal dietary approach taking into account short and long-term impacts on health outcomes, plus adherence and sustainability. The authors concluded that, ‘Diet as a primary intervention was considered most effective when emphasising whole, plant-based foods including whole grains, vegetable, legumes, fruits, nuts and seeds, with minimal consumption of meat and other animal products’. It is well worth reading the full document, which is open access.
Read my updated summary on the role of plant-based diets in prevention and treatment of type 2 diabetes here.
LOW-CARB VEGAN DIET: Low-carbohydrate or low-carb diets have gained popularity for the treatment of type 2 diabetes. In the short term (<12 months) they show a benefit for weight loss, better glucose control and support people to reduce or eliminate their medications. However, there are concerns about the long term impacts of a low-carb animal-based diet with observational studies suggesting an increased risk of cardiovascular disease, cancer and premature death. In addition, recommending an increased consumption of animal foods when we are in a climate and ecological emergency should be considered irresponsible.
There may indeed be a benefit to lowering carbohydrate consumption in people living with type 2 diabetes. This can be achieved with a plant-based eating plan. This was first shown by Dr David Jenkins in 2009 and then in 2014with his Eco-Atkins diet. This is a healthy vegan/plant-based diet composed of 26% of energy from carbohydrates and the rest from plant sources of protein and fat. When compared to a high carbohydrate (58% of energy from carbs) lacto-ovo vegetarian diet, the low-carb vegan diet showed an improved ability to lower blood lipid levels.
This latest study from the same team of researchers is in people with type 2 diabetes. One hundred and sixty-four male and female participants with type 2 diabetes were randomly assigned to advice on either a low-carbohydrate vegan diet, high in canola oil and plant proteins, or a vegetarian therapeutic diet, for 3 months, with both diets recommended at 60% of calorie requirements. On the low-carbohydrate (32% of energy) vegan diet, participants were provided with a canola oil–enriched bread and high-protein simulated meat products (Loblaw Companies; Gardein Protein foods). The vegetarian diet emphasised fruit, vegetables, and low-fat dairy products, with avoidance of meat and snack foods and carbohydrates were 56% of energy.. Participants were also provided with wholewheat bread and with liquid egg whites to reduce dietary cholesterol intake (Blue Menu, Loblaw Companies). The vegetarian diet was similar to the DASH diet. Both diets were prescribed at 60% of energy requirement.
The results showed that both diets were similarly effective for weight loss, reduction in waist circumference, reduction in blood pressure and LDL-cholesterol, including small particle LDL-cholesterol, and improvements in diabetes control. Both diets demonstrated a reduction in absorption of cholesterol due to the increased consumption of plant sterols.
The major difference between the two dietary approaches was a significant reduction of more the 50% from baseline of greenhouse gas emissions with the vegan diet. This was a significantly greater reduction than the vegetarian diet, which did of course still resulted in a reduction in food-related greenhouse gas emissions. The authors conclude ‘our data indicate that diets higher in vegetable oils and plant proteins appear suitable as weight-reducing diets in type 2 diabetes. More plant-based diets can also have the advantage of being more environmentally sustainable while reducing risk factors for cardiovascular disease and diabetes complications’.
This study is a useful addition to the literature on plant-based diets. However, it would have been useful to have an animal-based, low-carb diet and a low-fat/higher carb vegan diet (like the dietary approach of Dr Neal Barnard and his research team) as comparator groups. It is also not possible to confirm whether the benefits are merely due to the reduction in calorie consumption or truly a reflection of the benefits of a plant-based diet.
For me, this study confirms that a low-carb vegan diet is feasible with benefits for cardiometabolic health, whilst being significantly more environmentally sustainable than a vegetarian diet or a meat-based low-carb diet.
NUT CONSUMPTION AND IMPACT ON HEALTH OUTCOMES: We have decades worth of data supporting the consumption of nuts as part of a healthy diet pattern. Yet globally we are just not consuming enough. According to the 2022 Global Nutrition Report, the recommended intake is 25g per day, but on average we consume around 8g per day. I have reviewed this topic very recently.
This study extracted evidence from 89 articles on the consumption of nuts and relevant health outcomes, including 23 articles with meta-analysis on disease and mortality, 66 articles on biomarkers for disease, and 9 articles on allergy/adverse outcomes. The results showed that nut consumption was associated with reduced risk of cardiovascular diseases and related risk factors. For example, an intake of 28 g/day compared with not eating nuts was associated with a 21% reduction in cardiovascular disease (including coronary heart disease incidence and mortality, atrial fibrillation, and stroke mortality), an 11% risk reduction of cancer deaths, and 22% reduction in all-cause mortality. Nut consumption was also inversely associated with mortality from respiratory diseases, infectious diseases, and diabetes; however, associations between nut consumption and diabetes incidence were mixed.
Dose–response analysis suggested optimal intake levels of 15–40 g/d with generally limited benefits in increasing intake beyond 28 g/day. Allergy and adverse reactions to nuts were observed in only 1–2% of adult populations. The authors conclude that ‘Overall, the current evidence supports dietary recommendations to consume a handful of nuts and seeds per day for people without allergies to these foods.
ENVIRONMENT IMPACT OF FOOD CHOICES: In case you needed more evidence that a plant-based diet is the best choice for planetary health, this paper could not make it clearer.
The aim of the study was to assess the environmental impact of a selection of meals from different cuisines (chilli, lasagne, curry and teriyaki meals) and their meat-based, vegetarian, vegan, and whole-food vegan recipe variations. The environmental impacts (global warming, freshwater eutrophication, terrestrial acidification and water depletion potential) of 13 meals, made with 33 different ingredients, were estimated from cradle to plate using Life Cycle Assessment (LCA). The unique aspect of this study is that it makes a clear distinction between different types of meat-free meals and analyses vegetarian, vegan and whole-food vegan meals separately, instead of together under the general term of ‘vegetarian’ as done in prior research. No studies to date have included whole-food vegan meals in their analysis.
The results showed that regardless of the type of cuisine, the plant-based version of meals (vegan and whole-food vegan) had substantially lower environmental impacts across all impact categories than their vegetarian and meat-based versions. On average, meat-based meals had 14 times higher environmental impact, while vegetarian meals had 3 times higher environmental impact than vegan meals
The conclusions are clear ‘Swapping animal-based meals for plant-based versions, and preferably transitioning to plant-based diets, present important opportunities for mitigating climate change and safeguarding environmental sustainability’. The study is hugely detailed and open access so well worth a reading and sharing.
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