A review of the week’s plant-based nutrition news 25th July 2021
This week I cover the impact of diet quality on COVID-19 outcomes, review some highlights from the PCRM International conference on Nutrition in Medicine and a stark warning that human activity in the Amazon is leading to catastrophic effects.
PLANT-BASED DIETS AND RISK AND SEVERITY OF COVID-19: This paper is in a pre-print version only, which means it has not been peer reviewed. However, given the authorship I have no doubt that the results are sound and will be fully published soon. Since the start of the COVID-19 pandemic it has been clear that those with underlying chronic health conditions have suffered the most. Given that unhealthy diets are now the leading cause of chronic ill health, many have rightly concluded that one way of surviving this and future pandemics is to support citizens to adopt a healthy diet, one that is predominantly composed of fibre-rich plant foods. Several lines of inquiry have supported this theory, including the fact that those with a healthier gut microbiome have a less severe disease course.
This paper reports results from the now famous Zoe COVID symptom study. The paper analysed diet quality in more than half a million participants from the US and UK. During the follow-up period, 31,815 COVID-19 cases were documented. Adherence to a healthy plant-based diet was calculated using the healthy plant-based diet index which gives positive marks to healthy plant foods and negative marks to unhealthy plant foods and all animal foods. Those eating a healthy plant-based diet as defined by the healthy plant-based diet index had a 10% reduction in risk of getting COVID-19 and a 40% reduction in getting severe disease. The impact of a healthy diet was greatest in those from lower socioeconomic groups and independent of underlying chronic health conditions, body mass index, smoking and physical activity.
Based on these results, it was calculated that nearly a quarter of COVID-19 cases could have been prevented if these differences in diet quality and wealth had not existed.
Of course, this is not a perfect study. It is observational with self-selected participants, self-reported dietary information and for the primary outcome of COVID-19 infection, a validated symptom-based algorithm was used rather than PCR test results. However, this is likely to be the best evidence we can expect to have outside of a randomised study.
There are a number of reasons why a plant-based diet may have shown these advantages. It’s anti-inflammatory and anti-oxidant properties, the ability to maintain a healthy gut microbiome and hence healthy immune system and the reduction in underlying healthy conditions (although the results were adjusted for this). Even though the theory is obvious, it is great to see real life applicability in the setting of an infectious threat
The authors conclude ‘Our data provide evidence that a healthy diet was associated with lower risk of COVID-19 and severe COVID-19 even after accounting for other healthy behaviors, social determinants of health, and virus transmission measures’
Back in March 2020 I wrote an article on foods that can support your immune system and no surprise it’s all the colourful plant foods, herbs and spices. If you want to start your transition to a healthy plant-based diet then join our 21-day plant-based health challenge and download our free Plant-Based Eatwell Guide.
PLANT-BASED DIET FOR MENOPAUSAL SYMPTOMS: Peri and post-menopausal symptoms can be a real challenge for women, adversely affecting quality of life later in life. Hot flashes are a particular problem. Many studies have suggested that diet and lifestyle habits are important in managing symptoms during this phase of life, with the potential to reduce or eliminate symptoms all together. This study put to the test for the first time the impact of a low-fat, healthy vegan diet with the addition of one portion (86g) of cooked whole soyabeans per day.
Thirty-eight participants were randomly assigned to either the vegan diet group or to continue their usual diet. The impact of the diet intervention on hot flashes was assessed after 12 weeks. There was a significant impact of the vegan diet in improving the frequency and severity of hot flashes. Total hot flashes decreased by 79% in the intervention group and 49% in the control group. Moderate-to-severe hot flashes decreased 84% in the intervention group and 42% in the control group. 59% of the vegan diet participants reported becoming free of moderate and severe hot flashes. There was no change in this variable in the control group. Measures of quality of life showed an improvement in psychosocial, physical, and sexual parameters. There was also a small amount of weight loss in the vegan diet group. Overall, the authors conclude ‘The frequency of hot flashes, particularly moderate-tosevere hot flashes, decreased to a significantly greater degree in the intervention group, compared with the control group. At 12 weeks, the majority of intervention-group participants reported no moderate-to-severe hot flashes at all’.
There are some good reasons for these findings. Soya beans contain isoflavones, a phytooestrogen, which have previously been shown to reduce the incidence of hot flashes. Isoflavones are converted to equol by gut bacteria and higher production of equol, associated with a better diet quality, has been associated with a lower frequency of hot flashes. Previous studies have shown that vegetarians and vegans are better at producing equol than meat eaters. There are some finding that can not be fully explained, including why the control group also reported improvements in their symptoms. Did they also make diet changes when they were not supposed to? I am not convinced that healthy plant sources of fat such as nuts and avocado need to be avoided in a vegan diet as stipulated in the trial protocol.
The critics will be quick to point out the small number of participants and the short duration of the study, but for me, there is nothing to lose by trying this approach for menopausal symptoms. After all, there will only be positive sides effects of such an approach including a significant reduction in coronary heart disease and cancer risk. The true burden of cardiovascular disease in women has recently been highlighted by a series of excellent articles in the Lancet and discussed here in an editorial piece in Nature.
DIET AND ACID LOAD: Although our body pH is tightly controlled and can not be fundamentally changed by diet, some foods are more alkaline and others more acid producing. In general, animal foods, higher in sulphur-containing amino acids such as methionine and cysteine, are acid forming and these changes need to be buffered by foods such as fruits and vegetables that are more alkaline. The dietary acid load can be calculated by two methods. Potential Renal Acid Load (PRAL) is an estimation of the effect of foods on acidity or alkalinity of the body, based on five nutrient values; protein, phosphorus, potassium, magnesium, and calcium. The Net Endogenous Acid Production (NEAP) assesses the ratio of dietary protein, the major source of nonvolatile acid, to dietary potassium, which is naturally bound to alkali precursors. A plant-based diet has a low acid potential and results in a higher urine pH compared to animal-based diets.
This study explored the impact of dietary acid load on various metabolic health outcomes in a 16-week randomised study of 144 participants. The intervention group followed a low-fat vegan diet (~75% of energy from carbohydrates,15% protein, and 10% fat) consisting of fruits, vegetables, grains, and legumes (beans, peas, and lentils) and were compared to the control group who did not make any diet changes. Compared to the start of the study, the two measures of dietary acid load fell significantly in the vegan group, with no change in the control group. This fall in dietary acid low was positively correlated with beneficial changes in body weight, fat mass, visceral fat and insulin resistance. The mean weight loss in the vegan group was 6.4kg, largely due to loss of fat, and the benefits of lowering dietary acid load remained significant even after adjusting for energy intake.
Overall, it can be concluded that dietary acid load impacts metabolic outcomes related to diet and that a low-fat vegan diet has a significant advantage over a meat-based diet. These results provide yet another mechanism by which a plant-based diet can benefit health outcomes.
CULTURALLY APPROPRIATE DIETS: This year’s PCRM conference did a fantastic job at highlighting traditional and cultural diet patterns. It will come as no surprise that traditional Indian, African and South American diets for example are predominantly plant-based and the shift to more Westernised meat-based and processed food diets is a consequence of recent colonial influences and industrialisation of our food system such that farmers have been pushed off their land to urban areas where the cheapest food is often the least healthy. Unfortunately, this has led to a significant deterioration in health outcomes, only compounded by negative socioeconomic factors faced by communities of colour.
People of Black and Asian dissent appear to have an increased incidence of chronic disease for a number of reasons. For Asians there is a particular predisposition for laying down viseral fat such that for any given body mass index level they are at greater risk of cardiovascular disease and type 2 diabetes compared to their white counterparts. This makes the adoption of a culturally appropriate plant-based diet even important for these communities.
Researchers at PCRM analysed the impact on a low-fat vegan diet in their randomised 16-week study in 244 participants. In the vegan group, 60 participants were black and 57 white. The results showed that both black and white participants had equally favourable responses to this diet with significantly reductions in body weight, body mass index, insulin resistance, fat mass, visceral fat, total and LDL-cholesterol and fasting plasma glucose. These results confirm the applicability of a low-fat plant-based diets for both white and black communities.
It seems that Black communities are ahead of the game as highlighted in this article in the Guardian newspaper. ‘In 2016, 8% of Black American’s indentified as vegan compared with 3% in the general population’. Of course, not all vegan diets are created equal and amongst South Asians who have traditionally consumed a predominantly plant-based diet, the quality of this diet has deteriorated making India the diabetes capital of the world. There has been an increased consumption of refined grains, sugar and dairy with less variety and insufficient consumption of fruits, vegetables, legumes and whole grains. In the UK, South Asians have a higher incidence of cardiovascular disease and type 2 diabetes. Rohini Bajekal and I were pleased to be able to highlight the importance of a healthy plant-based diet to combat these chronic diseases in the European Heart Journal.
AMAZON RAINFOREST NOW EMITTING CARBON: This is actually a terrifying paper. The Amazon forest is known as the lungs of the earth. It is the largest carbon sink on the planet and we have been encroaching into the land space over the last several decades. The main driver for clearing the Amazon forest is for grazing cows and growing soya for animal feed. As a consequence, this study finds that the Amazon rainforest is now emitting more carbon than it is able to absorb. The main source of carbon dioxide emissions are fires deliberately started to clear land. If this does not make us sit up and change our behaviour then I don’t know what will.
The global food system has to change. The increasing demand for meat and dairy is literally killing the planet and its inhabitants. The consequences are real and happening right now, with recent examples being the flooding in Europe and the heat waves occuring all over the globe. Of course its not only our food system that is contributing to the climate and ecological crises but shifting to a plant-based diet is one actionable change a large proportion of us in high income countries can make immediately without the need for legislation or policy change. As long as we demand the right to eat meat and dairy we will continue to destroy this planet. Yet another report this week from the Health and Climate Network called ‘Diet and Food Systems for Health, Climate and Planet’, calls for a global a transition to a healthy sustainable diet that should be accessible and affordable for all. This means a massive shift away from animal agriculture to sustainable plant-based agricultural practices.