A review of the week’s plant-based nutrition news 6th March 2022

This week I cover studies on ultra-processed food consumption and mortality risk, fibre and dementia risk, low-carb diets for weight loss, the clinical use of plant-based diets and a dire warning from the latest IPCC report on climate change.

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ULTRA-PROCESSED FOOD (UPF) CONSUMPTION AND MORTALITY: UPFs have become a centre-piece 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.

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FIBRE INTAKE AND DEMENTIA RISK: I have summarised a few useful papers on diet, lifestyle and dementia risk in the last few weeks. Despite the rising burden of dementia globally, we know that at least 40% of cases could be prevented or delayed by addressing both lifestyle and socioeconomic risk factors. Prevention of chronic conditions is key, as underlying illnesses such as hypertension, high cholesterol, type 2 diabetes, heart disease and stroke significantly increase the future risk of dementia by up to 2.5 fold. Dietary risk factors are important too, with diets high in meat and saturated fat increasing the risk of dementia whilst the consumption of healthy plant foods reducing the risk. In particular, leafy greens and berries are protective as are foods rich in flavonoids and carotenoids. Adequate intakes of vitamin E, vitamin B12, folate and omega-3 fatty acids are also important. Recent data suggests meat free diets may provide an extra advantage for the prevention of dementia.

The current study examines the impact of fibre consumption on the risk of dementia that required care under national insurance in Japan. It reports results from the Circulatory Risk in Communities Study, involving 3739 Japanese individuals aged 40–64 years at the time of the dietary surveys. After almost 20 years of follow-up, a dose dependent/linear inverse relationship between fibre consumption and dementia risk was identified. Compared to those consuming the least fibre, 8.9g/day, those consuming the most, 21.4g/d, had a 26% reduction in risk. The association was strongest for the consumption of soluble fibre and potatoes but not other fruit and vegetables. It is likely that the relationship between fibre and dementia risk is due to the fact that fibre-rich diets are associated with a lower risk of hypertension, high cholesterol type 2 diabetes and overweight/obesity. The other proposed mechanism is through the beneficial action of fibre on the gut microbiome thus reducing inflammation, including neuroinflammation. A previous study has suggested that metabolites generated by gut bacteria from the consumption of polyphenol-rich foods are also protective against cognitive decline.

Overall, a plant-based diet meets all the criteria for a brain healthy diet. You can read more about fibre and the benefits to health here.

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LOW-CARBOHYDRATE DIETS FOR WEIGHT MANAGEMENT: The debate on whether low-carb diets are better than other weight loss diets and for managing cardiovascular risk factors continues. The literature is muddied by the fat that the definition of low-carb varies between studies. For this review, a low-carb diet was one where <45% of energy was obtained from carbohydrates and the results were compared to ‘balanced’-carbohydrate weight-reducing diets with 45–65% of energy from carbohydrates. Low-carbohydrate diets are implemented in different ways, but they generally restrict grains, cereals and legumes, and other carbohydrate-containing foods; such as dairy, most fruit and certain vegetables. These foods are then typically replaced with foods higher in fat and protein; such as meats, eggs, cheese, butter, cream, oils.

The review included data from 61 studies with 6925 participants randomised to either low-carbohydrate or balanced-carbohydrate weight-reducing diets. All trials were conducted in high-income countries except for one in China. The analysis was divided into studies in people with and without type 2 diabetes. Overall, the results showed that there was little to no difference in weight reduction and changes in cardiovascular risk factors (blood pressure, cholesterol, HbA1C) up to two years’ follow-up, when overweight and obese participants without and with type 2 diabetes were randomised to either low-carbohydrate or balanced-carbohydrate weight-reducing diets. A similar degree of weight loss and improvement in cardiovascular risk factors was achieved regardless of carbohydrate intake.

One study of note included in the review is the DIETFITS study that was a well-designed and conducted study comparing a high quality low-carb versus low-fat diet, and also investigated whether there were any genetic predictors of efficacy of one diet over the other. Again there was no difference in the weight loss achieved between groups and predicted genetic traits did not associate with outcome.

When it comes to healthy sustainable weight loss, its difficult to beat a healthy plant-based diet centred around fruit, vegetables, whole grains and beans. This type of diet pattern is naturally low in calorie density whilst being fibre and nutrient-dense. A recent systematic review of the effects of plant-based diets on weight status included 22 publications from 19 studies. Most of the studies include were randomised controlled trials comparing a low-fat vegan diet to an omnivorous diet in participants with overweight, type 2 diabetes and/ or cardiovascular disease. All studies reported weight reductions. The authors concluded ‘this review suggest that a transition from an omnivore diet to a plant-based diet is associated with weight reduction in a majority of subjects, when applied in intervention studies’.

Compared to an animal-based low-carb diet that restrictions whole grains and beans, a plant-based diet has a number of advantages for long-term health. A metabolic ward study of a animal-based keto diet versus a low-fat plant-based diet showed a spontaneous reduction in calorie intake in the plant-based group with greater loss of fat mass and lowering of cholesterol levels. In contrast, the low-carb group lost muscle mass and had a reduction in insulin sensitivity/impairment of glucose tolerance. Observational studies have also demonstrated that a low-carb diet reliant on animal fat and protein increases the risk of cardiovascular disease, cancer and death.

Overall, the best diet for maintaining a healthy weight is the one that you can stick to. Check out our factsheet on healthy weight management on a plant-based diet.

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A REVIEW OF PLANT-BASED DIETS: A useful and up to date review on plant-based diets (vegetarian and vegan) and their beneficial role in clinical practice. The review summarises the data supporting plant-based diets for maintaining a healthy body weight, addressing cardiovascular risk factors (hypertension and high cholesterol), preventing diabetes and reducing the risk of certain cancers. Fibre-rich plant-based diets are also beneficial for the health of our gut microbiome. In addition, plant-based diets have been shown to be effective treatment options (alongside ‘conventional’ treatments) for established coronary heart disease, type 2 diabetes, overweight/obesity and early stages of prostate cancer.

The review reminds us that well planned, plant-based diets are appropriate for all life stages and able to support optimal health in various settings, including maximising athletic potential. The review discusses various nutrients that need more attention with a plant-based diet including calcium, zinc, iron, omega-3 fatty acids, iodine, vitamin D and B12. The review also provides a reminder that bone health requires attention on a plant-based diet given recent data on increased risk of fractures in those following a vegan diet. This risk may be mitigated by ensuring a vegan diet is adequate in calcium, protein, vitamin D and that body mass index is not too low. However, more research is required on optimising bone health and it should not be forgotten that weight bearing and resistance exercise is key to maintaining bone health with ageing.

It’s worth noting that a recent systematic review of plant-based and meat-based diets highlighted the fact that all diet patterns require appropriate planning and have different nutrients that require extra attention and focus. However, the health and environmental benefits of a plant-based diet outweigh any potential risks and thus our focus should be to provide appropriate education and changes to the food environment to support people to make more healthy plant-based choices.

The authors of this current review conclude ‘Significant health benefits are associated with vegetarian, including vegan, diets. Plant-based diets, even if not completely vegetarian, also offer significant health benefits. Health professionals should discuss the benefits of vegetarian and near-vegetarian diets with their clients and provide supportive, reliable, evidence-based information and resources. If the practitioner is unfamiliar with vegetarian nutrition, clients should be referred to other health professionals with expertise in this area, such as registered dietitians.’

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DIRE WARNING FROM THE LATEST IPCC REPORT: The latest report from the United Nations Intergovernmental Panel on Climate Change (IPCC), which was published earlier this week said the threat that climate change poses to human wellbeing and the health of the plant is “unequivocal”. The report warns of a brief and rapidly closing window of opportunity for action to slow climate change and secure a liveable and sustainable future. Human-induced climate change is causing dangerous and widespread disruption in nature and affecting the lives of billions of people around the world, despite efforts to reduce the risks. People and ecosystems least able to cope are being hardest hit,

Carbon Brief have produced an in depth Q&A which provides a very helpful summary of some key facts and conclusions, which can be accessed here. Below are the main summary points.

  • Climate change has already caused “substantial damages and increasingly irreversible losses, in terrestrial, freshwater and coastal and open ocean marine ecosystems”.
  • It is likely that the proportion of all terrestrial and freshwater species “at very high risk of extinction will reach 9% (maximum 14%) at 1.5°C”. This rises to 10% (18%) at 2°C and 12% (29%) at 3°C.
  • Approximately 3.3 to 3.6 billion people “live in contexts that are highly vulnerable to climate change”.
  • Where climate change impacts intersect with areas of high vulnerability, it is “contributing to humanitarian crises” and “increasingly driving displacement in all regions, with small island states disproportionately affected”.
  • Increasing weather and climate extreme events “have exposed millions of people to acute food insecurity and reduced water security”, with the most significant impacts seen in parts of Africa, Asia, Central and South America, small islands and the Arctic.
  • Approximately 50–75% of the global population could be exposed to periods of “life-threatening climatic conditions” due to extreme heat and humidity by 2100.
  • Climate change “will increasingly put pressure on food production and access, especially in vulnerable regions, undermining food security and nutrition”.
  • Climate change and extreme weather events “will significantly increase ill health and premature deaths from the near- to long-term”.

The report provides a clear and stark warning about the consequences of inaction. Global warming of more than 1.5°C will have dire effects globally. We are already experiencing heatwaves, droughts and floods, which have led to food and water insecurity.

The reason why I keep highlighting the impact of climate change is because our food system is central to many of our global crises, including health, climate and biodiversity. Not only are unhealthy diets the cause of one in 4 deaths globally and a third of premature deaths in Europe and the US, food production is a key driver of climate change and biodiversity loss. At least a third of all greenhouse gas emissions are generated by our food system, of which 60% is from the production of food from animals. A shift to a plant-based diet is a key part of the solution. It would release 75% of farmland that could then be used for nature-based solutions for storing carbon and restoring biodiversity.

Of course, dietary change is only one part of the solution but without addressing the food system we will not be able to limit global warming. Why not make the change to a plant-based diet today. You can sign up for our FREE 21-day plant-based health challenge which comes with live support from our nutritionist Leila Dehghan.

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