Review of the plant-based nutrition and lifestyle medicine news August 2024
This month I cover studies on some of our commonest causes of ill health, including cardiovascular disease, type 2 diabetes and dementia.
There are a number of risk factors that increase the risk of developing chronic conditions and ultimately contribute to the reasons we die. The Global Burden of Disease has provided an updated analysis of risk factors across 204 countries that are determining health outcomes globally. The risk factors were categorised into behavioural, metabolic and environmental/occupational.
The data show that particulate matter air pollution was the top contributor to the global disease burden, accounting for 8.0% of total disability associated life years (DALYs: years lived in ill health), followed by high systolic blood pressure (7.8%), smoking (5.7%), low birthweight and short gestation (5.6%), and high fasting plasma glucose (5.4%). There was a notable decline in DALYs attributable to behavioural risks (-20.7%) and environmental/occupational risks (-22.0%), contrasted by a significant increase in DALYs due to metabolic risks (+49.4%). These metabolic risk factors are high blood pressure, high blood glucose, high blood cholesterol, high body mass index and kidney dysfunction. When considering behavioural risk factors, the top contributors to ill health include smoking, alcohol, diets low in fruit, vegetables, whole grains and omega-6 fatty acids and high in sodium.
The analysis underscores the need for sustained efforts to minimise risk factors, particularly in low Socio-Demographic Index regions. The study advocates for advancing policies that address leading risk factors such as air pollution and high blood pressure, with a focus on emerging risks associated with obesity and metabolic syndrome. Lifestyle medicine approaches address most of these risk factors and must be a key component of all healthcare interventions.
Lancet commission on Dementia. 2024 update.
Alzheimer’s disease and other dementias are now the leading cause of death in the UK. Currently more than 55 million people are living with dementia worldwide, and there are nearly 10 million new cases diagnosed every year. In 2019, the estimated total global societal cost of dementia was US$ 1.3 trillion, and these costs are expected to surpass US$ 2.8 trillion by 2030 as both the number of people living with dementia and care costs increase. Nearly 85% of costs are related to family and social rather than medical care. In the UK, Alzheimer’s disease and other dementias are now the leading cause of death.
Since 2017 the Lancet Commission on Dementia has been highlighting the potential for prevention. The original report suggested that 35% of cases could be prevented through modifiable lifestyle risk factors. These risk factors include tobacco smoking, physical inactivity, depression, hypertension, obesity, diabetes, hearing loss and social isolation. The second report from 2020 added three additional risk factors; excessive alcohol consumption, air pollution and traumatic brain injury. The updated report from 2024 adds two further risk factors; visual loss and high LDL-cholesterol. With these 14 risk factors, it is now predicted that up to 45% of cases of dementia could be prevented or delayed. The 2024 report specifically recognises the importance of healthy diets with a focus on the Mediterranean and MIND (Mediterranean-DASH Diet Intervention for Neurodegenerative Delay) diet. It should be noted that the studies informing these recommendations are mostly performed in high income countries, whereas the burden of dementia is greater in low- and middle-income countries and therefore the potential for prevention may be even greater.
The underlying pathogenic mechanisms in dementia include inflammation, oxidative damage, vascular endothelial damage, dyslipidaemia, glucose dysregulation and insulin resistance. The neuropathology of the disease includes the accumulation of amyloid beta plaques, neurofibrillary tangles, neurone and synapse loss. The onset of AD is preceded by a long preclinical phase, as long as 15 to 20 years, which includes changes in biomarkers and metabolic and behavioural parameters. This long pathological process offers opportunities for prevention. Another interesting observation made in the Lancet Commission report is that cognitive reserve i.e. preservation of cognition or everyday functioning, can be increased or maintained despite the presence of brain pathology and neuropathological changes associated with dementia. Early-life factors, such as less education, affect the resulting cognitive reserve. Midlife and old-age risk factors influence age-related cognitive decline and triggering of neuropathological developments.
It is clear that lifestyle approaches throughout the life course have a key role in supporting brain health and preventing dementia. Recent studies show that the beneficial impact of healthy habits are independently associated with a lower risk of cognitive impairment and dementia, regardless of genetic risk or the presence of brain pathology determined at autopsy.
Read my updated article on diet and lifestyle for brain health.
Traditional rural dietary pattern and all-cause mortality in a prospective cohort study of elderly Costa Ricans: the Costa Rican Longevity and Healthy Aging Study (CRELES)
Many traditional diet patterns are associated with better health than the typical Western or modern diet pattern. This is typified by the Blue Zones, regions around the world where people live longer, healthier lives than the rest of the world. They share in common 9 lifestyle habits but when it comes to diet, they all consume a plant-predominant diet and beans play are key role in the health-promoting effects of these diets.
This new study assessed the diet of 2827 elderly Costa Ricans (60 years at baseline) recruited to the prospective Costa Rican Longevity and Healthy Aging Study (CRELES,), which started in 2004. Dietary intake was assessed using a food frequency questionnaire (FFQ), and principal component analysis was employed to identify dietary patterns and the association with all-cause mortality.
The analysis defined four common dietary patterns. The traditional rural diet pattern was the only one to be associated with a lower risk of all-cause mortality during the 15 year follow up. Those most adherent to the traditional diet pattern had an 18% lower risk of death. The benefit was most obvious in men. When it came to the impact of individual foods, higher consumption of beans was associated with a 21% lower risk of death and a higher consumption of rice had a 25% lower risk of death but only in men.
The beneficial impact of the traditional diet pattern is thought to be due to the high fibre intake and the lower consumption of saturated fat. Plus, beans contain a number of phytonutrients which are beneficial to health, leading to lower levels of inflammation and improved health of the gut microbiome.
Association between total, animal, and plant protein intake and type 2 diabetes risk in adults: A systematic review and dose-response meta-analysis of prospective cohort studies
There is a continued obsession with protein consumption, despite the fact that all diet patterns, even those that are meat-free can easily meet protein requirements at all ages and stages of life. What matters most is the source of protein, with numerous studies demonstrating that plant sources of protein have a superior impact on health, being association with lower risks of cardiovascular diseases, type 2 diabetes, cancer and all-cause mortality. Any shift towards consuming more plant sources of protein, including beans, soya and nuts, in place of meat, dairy and eggs, is beneficial.
The current systematic review and meta-analysis specifically assesses the impact of protein source on the risk of type 2 diabetes. The analysis included 16 prospective cohort studies, involving 615,125 participants and 52,342 cases of type 2 diabetes. The results showed that protein intake from animal sources increased the risk of type 2 diabetes with a dose dependent effect. Participants with the highest intake of animal protein had a 18% increased risk of type 2 diabetes, with every 20g increase associated with a 7% increase in risk. Consumption of plant sources of protein did not show this same effect. Instead, substitution analysis showed that replacing animal with plant protein intake (per each 20g) was associated with a 20% reduction in the risk of type 2 diabetes.
There are numerous potential reasons for these findings. Animal protein has higher levels of branch chain amino acids – leucine, isoleucine and valine – which are associated with insulin resistance and an increased risk of type 2 diabetes. Animal protein comes packages with saturated fat, haem iron, nitrates and nitrites (processed meat) and create higher levels of advanced glycation end products. All of these compounds are associated with higher levels of inflammation and cellular stress and implicated in the development of type 2 diabetes. In contrast, plant proteins are packaged with fibre, numerous phytonutrients and are low in saturated fat. These properties are associated with a healthier gut microbiome, which is very important for glucose regulation, and lower levels of inflammation and cellular stress.
The authors conclude ‘These findings indicate that future dietary guidelines should consider the origin of dietary protein in their recommendations for T2D prevention and advise a reduction in consumption of animal protein and an increased intake of plant-based protein sources’.
Interestingly, a new observational study that analysed plasma metabolic biomarkers and metabolomic profiles found that increased intake of haem iron is associated with an increased risk of developing type 2 diabetes and is correlated with unfavourable plasma profiles such as insulinaemia, abnormal blood lipids and inflammation.
Another huge analysis of a number of cohorts from around the world has confirmed the association between meat consumption and an increased risk of type 2 diabetes with a dose-related response. Poultry, unprocessed red meat and processed meat consumption all increased the risk (8-15% increased risk) over a 10-year period, with the greatest risk associated with processed meat consumption. Some but not all of this increase in risk was due to the association between meat consumption and higher body mass index. Replacing processed meat with unprocessed red meat or poultry was found to reduce the risk of type 2 diabetes. But replacing unprocessed red meat with poultry did not impact the risk. The authors conclude ‘This study is, to our knowledge, the most comprehensive evidence base to date on the consumption of different types of meat and the risk of developing type 2 diabetes and, together with previous evidence, provides support for public health initiatives to reduce the consumption of meat to improve human health and planetary sustainability.’
Plant and Animal Fat Intake and Overall and Cardiovascular Disease Mortality
Similar to protein, we know that plant sources of fat are healthier than fats from animal sourced foods. This is because saturated fat, predominantly found in animal source foods, has a direct effect of blood cholesterol level by down-regulating LDL-receptors in the liver. The more saturated fat consumed the higher the LDL-cholesterol level, the key cause of atherosclerosis. In addition, saturated fat is associated with higher rates of type 2 diabetes, dementia and adversely impacts the health of the gut microbiome.
This is just one of many studies that demonstrate the health benefits of consuming fats from plant sources. The paper analyses data from the National Institutes of Health–AARP Diet and Health Study, which included 407 531 men and women with a mean age of 61.4 years. Median daily dietary fat intake from plant and animal sources was 24.7 g and 29.3 g, respectively. After 24 years of follow, the results showed that participants consuming higher amounts of plant sources of fat had significantly lower rates of cardiovascular and all-cause mortality. Fats from grains and vegetables oils were found to be particularly beneficial. In contrast, greater intake of fat from total animal fat, dairy, and egg sources was associated with increased risks of overall mortality and CVD mortality. These associations remained significant even after adjusting for other known risk factors for mortality. Replacing 5% energy from total animal fat, red meat fat, dairy fat, or egg fat with an equivalent amount of total plant fat, fat from grains, or vegetable oils was associated with a 4% to 24% lower risk for overall mortality and a 5% to 30% lower risk for CVD mortality. Of note, fish fat was not associated with adverse health outcomes and replacing fish with plant sources of fat did not affect outcomes. Similarly, replacing white meat with plant sources of fat did not alter health outcomes.
Of course, this type of study cannot prove causality as it is observational. In addition, dietary data was collected only at baseline. However, there are plenty of other prior studies that have shown similar findings and all dietary guidelines recommend minimising saturated fat consumption from animal sources foods.
The low-carbohydrate diet remains popular amongst many healthcare professionals, especially for management of type 2 diabetes. The trouble is that this often prioritises animal sources of protein and fat. Recent studies demonstrate concerns around restricting carbohydrates, which appears to reduce glucose tolerance, lead to elevated LDL-cholesterol and apolipoprotein B levels and negatively impact the gut microbiome. In contrast, in a short-term randomised study that replaced saturated fat with unsaturated fats from plant sources resulted in a significant lowering of LDL-cholesterol in just 4 weeks, although there was some variation in response to the intervention.
Effects of genetic risk on incident type 2 diabetes and glycemia: the T2D-GENE lifestyle intervention trial
Lifestyle medicine interventions are hugely important in preventing and managing type 2 diabetes. This study specifically investigated the impact of a lifestyle intervention on the development of type 2 diabetes in people with different genetic risk for the condition. It included 973 men from the Metabolic Syndrome in Men (METSIM) cohort, aged 50-75 years, body mass index ≥25 kg/m2, fasting plasma glucose 5.6-6.9 mmol/L, haemoglobin A1c < 48 mmol/mol. They were divided into low and high genetic risk groups based on a genetic risk score calculated from the analysis of 76 known genetic variants related to diabetes. Population controls (n = 589) were selected from the METSIM cohort and had similar inclusion criteria as the participants in the intervention group, but they were invited only for 3-year measurements.
The 3-year intervention included group sessions on the importance of a healthy diet and physical activity. Dietary guidance followed Nordic and Finnish nutrition recommendations, emphasising appropriate energy intake; meal frequency; consumption of fruits, vegetables, and berries; and quality of dietary fat and carbohydrates, including fibre and sugar intake. Regarding weight management, the minimum goal for the participants was weight maintenance. The goal for physical activity was brisk walking or other types of physical activity ≥30 minutes/day at least 5 times a week.
After 3 years, in the intervention arm, the conversion to diabetes was 7.7% in the low and 7.9% in high genetic risk groups. In the population control arm, 8.2% of the participants in the low genetic risk group and 14.1% of the participants in the high genetic risk group developed type 2 diabetes. Overall, the intervention lowered the risk of type 2 diabetes by 52%. Among the participants with a high genetic risk for type 2 diabetes, the intervention lowered the risk of type 2 diabetes by 70% whereas among the participants with a low genetic risk for type 2 diabetes, there was no significant difference in incident type 2 diabetes between the intervention and control arms. However, the intervention effect was not significantly different between the high and low genetic risk groups, suggesting that the participants having a low genetic risk for type 2 diabetes also benefitted from lifestyle intervention. The participants in the intervention arm lost more weight and had a larger decrease in BMI compared with the population controls, irrespective of genetic risk. Dietary intake of saturated fatty acids decreased and intakes of monounsaturated fatty acids, polyunsaturated fatty acids, fibre, and fruits, vegetables, and berries increased significantly in the intervention arm and similarly in both genetic groups.
Overall, this study confirms that low-cost lifestyle interventions are effective at preventing the development of type 2 diabetes. The novel aspect was that the intervention was also effective in people at high genetic risk. The authors conclude ‘Our results suggest that all individuals at risk of type 2 diabetes should be encouraged to make lifestyle changes regardless of genetic risk.’
Maintaining a healthy weight is key for preventing type 2 diabetes. Once a diagnosis of pre-diabetes or diabetes is made, weight loss is the main goal. The UK has pioneered low calorie diets using meal replacement shakes and soups for inducing diabetes remission. Prof Roy Taylor and colleagues ran the seminal study called the DIRECT trial, which showed that their total diet replacement formula resulted in significant weight loss and could achieve diabetes remission. The 5 year follow up of this study has recently been published. This approach has been adopted within the NHS and real-world data has just been published using three months of total diet replacement and 12 months of behavioural intervention to support weight loss. The programme resulted in a 27% remission rate.
Once again we have a study demonstrating that not only are healthy habits effective at prevention chronic conditions and extending healthy life expectancy, but also results in lower healthcare cost. In this Taiwanese cohort, using data from the National Health Interview Survey cohort, 5 healthy lifestyle behaviours were defined and analysed: not smoking, avoiding excessive alcohol consumption, engaging in sufficient physical activity, ensuring sufficient fruit and vegetable intake, and maintaining a normal weight. A total of 19,893 participants with a mean age of 48.8 years were included and followed for a median of 15.6 years. As expected, people adhering the most to these 5 healthy habits had a longer life expectancy of up to 7 years. In addition, individuals adopting all 5 healthy lifestyle factors experienced an average annual health care expenditure reduction of 28% compared to those who adhered to one or none.
Unveiling the epigenetic impact of vegan vs. omnivorous diets on aging: insights from the Twins Nutrition Study (TwiNS)
This is the second publication from the Twins Nutrition Study. The first was published in November 2023 and covered in my end of year review, It investigated the cardiometabolic impact of a healthy omnivorous versus healthy vegan diet in 21 pairs of identical twins. The study has also been the subject of the Netflix Documentary ‘You Are What You Eat’.
This second publication provides analysis of various markers of biological age and ageing using quite complex scientific methods. Researchers assessed patterns of DNA methylation – that is, epigenetic changes affecting gene expression – before and after the 8-week dietary intervention. Distinct changes were seen in both groups, but the vegan diet resulted in epigenetic changes suggestive of slowing of biological ageing. In addition, the vegan diet results in lengthening of the telomeres, the caps at the end of our chromosomes. The researchers also examined epigenetic signatures related to specific body organs and biological functions. The vegan group showed beneficial changes related to inflammation, heart functions, hormones, liver and metabolic health. Epigenetic changes related to diabetes risk showed mixed results
Of course, this is only a short-term study and tells us little about the longer-term impact of a healthy vegan diet. It is also not clear if the beneficial changes were purely due to the vegan diet or due to some other confounding factor. This could be because the vegan group consumed around 200 fewer calories per day than the omnivore group and therefore lost more weight, which could have impacted the results. Much of the media coverage raised concerns about the risk of nutrient deficiencies on a long-term vegan diet. However, most people on a vegan diet are well aware of the need to supplement vitamin B12. Beyond that, a vegan diet is no different to other diet patterns, which all require an element of planning to meet nutrient requirement. The nutrients of focus may differ, but all diets require attention. This is also not the first study that has shown a positive impact on biological ageing from eating more plants. Given the benefits a 100% plant-based diet for reducing the risks of cardiovascular diseases, type 2 diabetes and certain cancers, it makes sense that there would be a beneficial effect on ageing. I look forward to further publications from the same study.
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