Review of the plant-based lifestyle medicine news February 2024
There was too much choice this month. I cover brain health, prostate cancer, fatty liver, plant-based pregnancies, healthy ageing and more.
HEALTHY LIFESTYLE AND BRAIN HEALTH: Deteriorating brain health is a concern for all of us as we age. We know from prior research that up to 40% of cases of dementia could be prevented or significantly delayed if we paid attention to 12 risk factors: low education, hypertension, hearing impairment, smoking, obesity, depression, physical inactivity, diabetes, low social contact, excessive alcohol consumption, traumatic brain injury, and air pollution.
This new paper reminds us of the importance of a healthy lifestyle habits for preserving brain health. This cohort study used data from the Rush Memory and Aging Project, a longitudinal clinical-pathologic study with autopsy data from 1997 to 2022 and up to 24 years of follow-up. Participants included 754 deceased individuals with data on lifestyle factors, cognitive testing close to the time of death and post-mortem examination of the brain. Of note, mean age of death was 91 years. Researchers collected information on lifestyle and demographic factors at regular intervals and participants received annual cognitive (brain function) tests. Participants were categorised as living a healthy lifestyle if they scored well in five categories: Moderate or vigorous physical activity for 150 minutes per week, non-smoker, limited alcohol consumption (one to two drinks per week), regularly cognitive/brain activity such as played card games or did puzzles, and followed the Mediterranean-DASH Diet Intervention for Neurodegenerative Delay diet (MIND diet).
The results showed that for every one-point increase in the healthy lifestyle score, there were significantly fewer units of beta-amyloid load (pathology associated with Alzheimer disease) in the brain and higher scores in cognitive performance. The benefits of a healthier lifestyle for better brain health were apparent even if there was evidence of brain pathology on post-mortem. Overall, the results showed that more than 88% of a person’s cognitive/brain functioning was directly associated with lifestyle factors, leaving less than 12% related to the presence of dementia-related brain pathology such as beta-amyloid plaques.
The authors propose that the mechanistic link between lifestyle factors and brain health is in part attributable to the antioxidant and anti-inflammatory capacities of each lifestyle factor (e.g., nutrition and physical activity) and cognitive reserve (e.g., cognitive activities). In addition, healthy lifestyle habits reduce the risk of hyperlipidaemia, high blood pressure and type 2 diabetes, all of which contribute to an increased risk of dementia.
The main take home message ‘A healthy lifestyle may provide a cognitive reserve to maintain cognitive abilities independently of common neuropathologies of dementia’.
These results are pretty remarkable when you put them into the context of the global burden of Alzheimer disease and related dementias. These conditions now affect over 55 million people worldwide with an estimated economic burden of over $800 billion annually. This figure is projected to increase with the prevalence of dementia expected to triple over the next 30 years. To date, there is no cure to stop or reverse disease progression, underscoring the critical need for the development of primary or secondary prevention strategies that target modifiable risk factors to delay or prevent the onset of clinical symptoms.
PLANT-BASED DIETS AND PREGNANCY OUTCOMES: This study may be a cause for concern for some, especially since media outlets such as the Daily Mail published sensationalised headlines. As always, it's good to put the results into context and take away relevant learning.
The study from Denmark included 66,738 women who had pregnancies between 1996–2002 and in whom dietary information was available. 65, 872 women identified themselves as omnivores, 666 as fish/poultry vegetarians, 183 as lacto/ovo vegetarians, and 18 as vegans. Based on a questionnaire completed mid-pregnancy, investigators found that protein intake was lower among lacto/ovo vegetarians (13.3% of energy), and vegans (10.4%) compared with omnivorous participants (15.4%). Micronutrient intake was also much lower among vegans, but when dietary supplements were considered, no major differences were observed. In terms of pregnancy outcomes, vegan mothers had a higher prevalence of preeclampsia, and their babies weighed an average of 240 g less.
The important points to note are that there were only 2 of 18 vegan pregnancies affected by pre-eclampsia. With such small numbers it is impossible to postulate why this may have occurred or if in fact this was merely a chance finding. The vegan mothers, as expected, had a lower BMI than omnivores, which may have in part explained the lower birth weight. Prior studies have also shown lower birth weights in babies born to vegan mothers, but there is no reason to believe based on the available evidence that this leads to future health harms. In fact omnivores with a higher BMI have more issues relating to abnormally high birth weight and larger babies, which can lead to complications at the time of delivery. In addition, the babies in this cohort were born more than 20 years ago when information about and support for healthy vegan pregnancies was less readily available.
There is no doubt that when planning a vegan pregnancy one needs to mindful of obtaining sufficient calories, protein and micronutrients. However, this is the case for all pregnancies. A 2019 review supports this by concluding, “Vegetarians and vegans are at risk of nutritional deficiencies, but if the adequate intake of nutrients is upheld, pregnancy outcomes are similar to those reported in the omnivorous population. So updated evidence highlights that well-balanced vegetarian and vegan diets should be considered safe for the mother’s health and for offspring during pregnancy and lactation.”
LIVING WELL AFTER A DIAGNOSIS OF PROSTATE CANCER: There is growing evidence to support the role of plant-based diets for preventing prostate cancer and surviving well after diagnosis and treatment. In fact all six pillars of lifestyle medicine are important for prostate health. I have previously summarised the data in this article. I mention this current study at the end, which has now been published in full.
The study included 3505 men from the Health Professionals Follow-up Study with a diagnosis of non-metastatic prostate cancer. Dietary data were used to calculate the overall and healthy plant-based diet indices. This was correlated with indicators of quality of life measured at a mean time of 7 years post treatment for cancer. The quality of life domains included were sexual function, urinary irritation/obstruction, urinary incontinence, bowel, and hormonal health.
The results showed that adherence to an overall and healthy plant-based diet was associated with better sexual function/erectile function, less urinary irritation/obstruction and urinary incontinence, better bowel function and higher scores in the hormonal health domain.
The authors discuss how their results are in keeping with the results of prior studies. The positive effects of a plant-based diets are likely due to the higher fibre intake and the impact of numerous anti-inflammatory and antioxidant compounds in plants, along with the absence of harmful nutrients found in animal-sourced food. The authors mention that none of the participants were following a full plant-based or vegan diet and therefore there could be additional benefit for those consuming a whole food plant-based diet. Unusually, the authors dedicate a whole paragraph to reminding us of the benefits of eating a plant-based diet for planetary health and implying that since there are no downsides to this way of eating, this should be the default eating pattern.
The authors conclude ‘individuals with prostate cancer should be advised that incorporating a greater amount of plant-based foods into their diet could not only reduce the risk of comorbid conditions but also contribute to improved functional outcomes.’
PROTEIN INTAKE AND MALNUTRITION: Another paper that will provide reassurance that plant sources of protein are adequate and in fact may be superior to animal protein for preventing malnutrition in older adults. The study combined data from two Spanish cohorts: the Seniors-ENRICA 1 and Seniors-ENRICA 2 and included 2,965 community-dwelling adults aged 62–92 years. The aim of the study was to assess the impact of protein intake on nutritional status. Malnutrition was assessed according to the Global Leadership Initiative on Malnutrition (GLIM) consensus on diagnostic criteria for malnutrition in adults, and includes significant weight loss, low BMI, low grip strength and low muscle mass.
The results showed that animal protein intake comprised 65.7% of total protein. The main animal protein sources were, from largest to smallest, meat, dairy, fish, and eggs. The main vegetable protein sources were cereals, legumes, and nuts. Higher intakes of protein were associated with improved nutritional status. When source of protein was considered, plant protein consumption had a greater protective effect on nutritional status than animal sources with most of the benefit coming from the consumption of cereal protein. It’s worth noting that consumption of other sources of plant protein such as legumes and nuts was very low in this cohort. Each 0.25g/kg intake of animal protein was associated with a 15% greater odds of improved nutritional status. However, each 0.25g/kg intake of plant protein improved the odds by 77%. Replacing 0.25 g/kg/day of total animal protein, meat, or fish protein, but not dairy or egg protein, with vegetable protein was associated with improvements in nutritional status.
The potential reasons for a greater benefit from plant protein include lower levels of inflammation (as shown in the supplemental analysis), improved gut microbial health and the association with lower rates of chronic conditions. Overall, more evidence to support plant protein sources as being adequate for older adults.
PLANT-BASED DIETS AND FATTY LIVER: I missed this paper last year, which is a useful addition to the literature on fatty liver disease, now called metabolic dysfunction-associated steatotic liver disease (MASLD). The primary driver of this condition is diet and lifestyle although genetic variants can also increase the risk. The underlying disease mechanisms are associated with obesity and include insulin resistance, inflammation and high blood lipids.
This study used data from the UK biobank and included 159,222 participants (58.0 ± 8.0 years old, 55.7% female) free of fatty liver disease at recruitment. Dietary data were categorised using the plant-based dietary index into the overall plant-based diet index (PDI), the healthful plant-based diet index (hPDI), and the unhealthful plant-based diet index (uPDI). A polygenic risk score was also calculated. New onset of fatty liver was the primary outcome and a subset of participants also had MRI scan performed to assess liver fat content.
At a median of 9.4 years follow up there were 1541 new cases of fatty liver. The results showed that adherence to an overall and healthy plant-based diet reduced the risk of fatty liver disease by around 25%. However, an unhealthy plant-based diet increased the risk by 24%. Liver fat content assessed by MRI was lower in people following a more plant-based diet, with an unhealthy plant-based diet leading to increased levels of liver fat. When considering genetic risk, a plant-based diet was beneficial for all levels of risk although the combination of low genetic risk and a healthy plant-based diet was the most protective.
Once again, healthy plant foods are shown to reduce the risk of fatty liver disease and the study confirms benefits regardless of underlying genetic risk.
MYCOPROTEIN FOOD PRODUCTS: Although plant-based meat alternatives (PBMAs) are not required in the diet, they can be a convenient addition to a plant-based diet and in some instances a healthy source of protein. It’s good to see more clinical studies that assess health outcomes, or at least biomarkers of health outcomes.
This study included 72 participants who were overweight with high cholesterol levels and were randomised into 2 groups for a 4-week intervention trial. One group was supplied with home deliveries of meat and fish and the other group mycoprotein PBMAs from the company Quorn.
The results showed that both groups had a similar calorie, carbohydrate and fat intake. Fibre intake was higher in the mycoprotein group, since the product does contain fibre (36g/d versus 20g/d). Fat intake was fairly similar between groups, including saturated, polyunsaturated and monounsaturated fats intakes. Dietary cholesterol consumption was lower in the mycoprotein group.
After four weeks, total, LDL-cholesterol, and non-HDL cholesterol levels fell in the mycoprotein group by 6%, 10%, and 6% respectively, whereas there was no change in the meat/fish group. There were no differences in HDL-cholesterol or triglyceride levels between the groups. Blood glucose and C-peptide levels (and indicator of insulin secretion) both fell more in the mycoprotein group.
The researchers suggest that the improvements in cardiometabolic biomarkers may be due to the higher fibre intake and the beta-glucans present in the mycoprotein product. This may lead to beneficial changes in the gut microbiome. Overall, the study provides further data to support a role of PBMAs in the diet especially if replacing meat.
ENVIRONMENTAL BENEFITS OF A PLANT-BASED DIET: Although we don’t need more persuasion on the benefits of moving away from animal foods to a plant-based diet for planetary health, this new paper from Sweden is a useful addition. It models the environmental, nutritional and economic benefits of replacing animal foods with plant-based alternatives (PBAs; meat, dairy and seafood) or whole plant foods and compares this to the typical Swedish diet. The researchers modelled six dietary scenarios; vegan, vegetarian and flexitarian for both PBAs and whole foods.
All six dietary scenarios led to improved nutritional profile compared to the current Swedish diet, with improvements in fibre intake, iron, folate, unsaturated fats, magnesium and lowering of saturated fat intakes. The short fall nutrients were vitamin D and B12 and selenium (a concern for all diet scenarios including the current Swedish diet). Salt intake increased in the PBA scenario but decreased in the whole food scenario. The PBA and whole food vegan scenarios had the greatest benefit for environmental health, including 52–56% reduction in greenhouse gas emissions and 32–44% reduction in land use. There were smaller benefits for reducing water use although a whole food vegan diet was estimated to use similar amounts of water to the current Swedish diet due to increased consumption of fruit and vegetables. The PBA scenarios increased food costs by a small amount (3–5%), whereas a whole food approach had the greatest potential to reduce food costs, with the whole food vegetarian scenario reducing costs the most, by 17%.
Overall, the researchers conclude that there are significant environmental benefits from replacing animal foods in the diet with plant-based foods without compromising nutritional quality. ‘Our findings highlight that minimising animal-sourced food consumption has a larger influence on reducing the environmental impact than choosing between PBAs or whole foods as replacements. This suggests that the different, more plant-based dietary scenarios that we assessed should be viewed as complementary, targeting different groups that strive to reduce the intake of animal foods. Including PBAs in dietary guidelines, as already prevalent in some countries, can promote the uptake of more sustainable diets based on consumer preferences by presenting a wider choice of plant-based products to select from’.
The prevailing narrative around regenerative farming continues to suggest that grazing animals are necessary and support increased carbon sequestration in pasture lands. However, there are now clear data to the contrary. A new study published in Nature Communications concludes that it is not feasible for the global livestock industry to sequester enough carbon to cancel out its planet-warming emissions. The study finding are summarised in this excellent article.
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