A review of the week’s plant-based nutrition news 20th November 2022

This week I cover nutrition and cancer, non-alcoholic fatty liver disease, kidney failure and the impact of animal agriculture on infectious threats.

WHAT SHOULD I EAT? This is a very common question I get asked as a cancer doctor. The answer should be simple and straight forward but somehow patients and their physicians are exposed to varying degrees of nutrition misinformation resulting in confusion and inaction.

It’s great to see the integrative oncology community putting the record straight and endorsing the World Cancer Research Fund and American Cancer Society guidelines on a healthy diet for cancer prevention and for surviving well after a diagnosis of cancer. We should be supporting patients and the public to consume a diet rich in fruit, vegetables, whole grains, beans, nuts and seeds. These are the only foods that are known to promote good health and to be associated with reduction in cancer risk.

The review acknowledges the difficulties within the current UK healthcare system of accessing dietitians, who mainly support patients with undernutrition and prevention of weight loss rather than being available for general health promotion and preventative care. In the ideal world patients would have the option of one to one dietary counselling with a suitably qualified professional and group support to make sustainable behaviour changes. The role of the doctor in cancer care will never replace a qualified dietitian but we should be able to provide accurate information and resources to our patients.

The authors state that ‘Plant-based eating is the recommended healthy dietary pattern to follow. This diet emphasises the use of plant foods such as a variety of non-starchy vegetables, whole vegetables and fruits with variety of colours, whole grains, legumes, nuts, and seeds. Animal products, if included, are kept to a small proportion of the overall plate’. This type of diet is high in health promoting and cancer preventing nutrients, including fibre, polyphenols, vitamins, minerals and many other bioactive phytonutrients.

Relevant to the next article, and by the same author Dr Urvi Shah, when surveyed, patients with cancer (in this case plasma cell myeloma) are highly motivated to make healthy dietary changes but are often having to seek advice from non-medical sources. The research highlights the need for oncologists to be familiar with dietary guidelines for people living with cancer and have the confidence to impact this knowledge and signpost to useful resources.

PLANT-BASED DIET AND MYELOMA OUTCOMES: This is a pretty ground breaking 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.

PLANT-BASED DIET AND NON-ALCOHOLIC FATTY LIVER DISEASE (NAFLD): This condition is at epidemic proportions and is very much associated with a Western diet and lifestyle. Data from this year demonstrates that the worldwide prevalence of NAFLD is 32.4% and in people with overweight and obesity, the prevalence is around 70%. The key drivers of NAFLD are obesity, dyslipidaemia, insulin resistance and metabolic syndrome. The specific components of diet that are associated with an increased risk include, saturated fat, red and processed meat, refined carbohydrates and fructose (from sugar and high fructose corn syrup).

There is compelling evidence that a plant-based diet, be it Mediterranean, DASH, vegetarian or vegan, is associated with a lower risk of NAFLD. This study reports the association of diet with risk of NAFLD using the plant-based diet index (PBDI) in participants of the NHANES study from the US. 3900 participants (2028 women and 1872 men) with a mean age of 49.2 years were included in the analysis. During the follow-up, 1686 participants were diagnosed with NAFLD (a rather shockingly high number giving an age-standardised prevalence of 42.5%!).

The results showed that participants consuming a plant-based diet had a lower body mass index (BMI), but even after adjusting for BMI in the statistical model, a healthy plant-based diet was associated with a 46% reduction in risk of NAFLD. An unhealthy plant-based diet did not appear to be protective. The association with healthy plant-based diet seemed to be stronger in males and non-Hispanic white participants. The authors conclude ‘These results support the guidelines to increase healthy plant foods intake and reduce the intake of less healthy plant foods and certain animal foods in NAFLD prevention’.

These data strengthen already established guidelines for dietary interventions for prevention and management of NAFLD summarised below and taken from this excellent review paper.

1. Calorie restriction with a 500–1,000 kcal daily deficit is an extremely effective lifestyle intervention for both the prevention of NAFLD and histological improvement in patients with established disease. The goal of calorie reduction should be to achieve ≥10% overall body weight loss.
2. Reduce intake of red and processed meats
3. Reduce/eliminate refined carbohydrates and especially fructose
4. Increased fibre intake through the consumption of fruits, vegetables, whole grains and legumes
5. Replace dietary saturated fatty acids with mono-unsaturated and poly-unsaturated fatty acids
6. Coffee consumption is protective against the development of NAFLD and disease progression. Moderate to heavy alcohol consumption should be avoided in the presence of obesity, NAFLD, and other metabolic risk factors. Abstinence is advised for patients with advanced fibrosis.

DIETARY PHOSPHORUS IN ADULTS ON HAEMODIALYSIS: Many of the concerns around eating a plant-based diet for people with kidney failure have been shown in clinical trials to only be theoretical rather than a genuine clinical concern. In fact, plant-based diets are associated with a lower risk of kidney failure, slower rates of progression in those with established kidney failure and may even delay the need for dialysis. Once on dialysis, plant-based diets can support better health than a meat-based diet.

This paper demonstrates that concerns around dietary phosphate should not prevent people with kidney failure adopting a plant-based diet. Higher dietary and blood phosphate levels are associated with an increased risk of death in people with kidney failure. This study examined dietary intake of phosphate in 8110 adults on haemodialysis. During a median 3.8 years of follow-up, there were 2953 deaths, 1160 cardiovascular-related. Higher intake of total dietary phosphate was associated with an increased risk of all-cause and cardiovascular mortality. However, this was mainly related to phosphorus intake from processed foods. No association was found with animal foods. In contrast, phosphorus from plant foods was associated with a lower risk of death.

This study provides further evidence that although plant foods tend to be higher in phosphate, this is not a clinical concern. The phosphate in plant foods is less bioavailable as it is mostly in the form of phytate, which humans are unable to digest, thereby decreasing the bioavailability of phosphorus in these foods. Inorganic phosphorus, such as phosphates added to foods during processing, has an absorption rate of greater than 90%. Therefore, most of the phosphate consumed in a Western-style diet pattern is from dairy and animal protein and also from the preservatives used in processed and fast foods.

There is now growing support for plant-based diet for kidney health. It is great to see that the National Kidney Foundation in the United States is also supportive of plant-based diets providing some excellent patient information.

ANIMAL AGRICULTURE AND INFECTIOUS DISEASES: We have had a lot of coverage of the impact of animal agriculture on the climate and ecological crises, but it’s often overlooked that animal agriculture is a major driver of infectious disease risk. This is not only due to factory or industrial farming methods, but due to habitat destruction that occurs as land is cleared for grazing animals and growing crops to feed them. This puts human in contact with species that we would not normally interact with and which carry diseases that can harm. In addition, animal farming practices globally use 70% of all antibiotics sold, thus being a major driver of the health risks associated with antibiotic-resistant infections.

It is good to read this excellent review on the topic. It summarises how infectious diseases have risen four-fold over the last 4 decades, mostly due to zoonoses. 50% of zoonotic infections are associated with animal agriculture. The main driver at the core of these issues is the rising global demand for meat. Elimination of beef production and consumption would go a long way to reducing the climate impacts of our food system. However, moving to more chicken consumption, which seems to be the most common replacement, would lead to more industrialisation of farming, increased use of antibiotics and increased risk of zoonotic infections. The only viable solution is to move towards plant-rich diets, which not only have benefits for the environment but significantly reduce the risk of chronic conditions, whilst having the potential to free up 75% of farmland globally. The land released could instead be used for re-wilding and carbon capture.

We are currently in World Antimicrobial Awareness Week, which is a global campaign that is marked annually to improve awareness and understanding of antimicrobial resistance and encourage best practices among the public. The most recent analysis of the problem demonstrates that 1.3 million people died in 2019 from antibiotic-resistant infections, making this the 12th leading cause of death and killing more people than HIV infection and malaria combined. In the UK, the organisation The Alliance to Save Our Antibiotics is doing an excellent job at highlighting the use of antibiotics in animal farming and PBHP UK are proud to be alliance members.

It really is not difficult to transition to a plant-based diet and can be easily down on a small budget as highlighted in this week’s article from our team in the Independent. Check out our free Plant-Based Eatwell Guide.

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