A review of the week’s plant-based nutrition news 22nd August 2021

This week I cover the risk of cardiovascular disease in South Asians, how lignans reduce the risk of heart disease, the impact of healthy habits on the risk of lupus, plant-based diets and risk of death and the impact of diet on COVID-19.

ATHEROSCLEROTIC CARDIOVASCULAR DISEASE (CVD) IN SOUTH ASIANS: We have known for several decades that people of South Asian ancestry are at higher risk of various chronic diseases, including heart disease and type 2 diabetes. Not only that, these diseases occur around 10 years earlier than in Caucasians.

The current study included participants from the UK biobank prospective cohort and included 8124 middle-aged participants of South Asian ancestry and 449 349 participants of European ancestry with a median age of 57 years at enrolment. Over the 11 years of follow-up, South Asians had a greater than two-fold increased risk of developing atherosclerotic CVD compared to European participants. However, the study showed that the clinical tools used to predict the risk of CVD were not sufficient to identify this significantly increased risk amongst South Asians. This may be in part due to the fact that these scores were developed without sufficient representation from South Asian participants. Hypertension, diabetes, and central adiposity contributed significantly to the higher risk of CVD. Shockingly, in this cohort, 41.8% of South Asians had hypertension and 19.5% had type 2 diabetes. Diabetes in South Asians occurs at a lower body weight when compared with Caucasians and the current study highlighted this same finding. However, even after accounting for a range of conventional lifestyle and socioeconomic CVD risk factors, there remained a residual increased risk that was seemingly accounted for. The authors suggested this residual higher risk may be due to delayed diagnosis or under-treatment of comorbidities, genetic variation, or as yet unidentified or unmeasured factors.

All in all, these data confirm once again the substantially higher risk of atherosclerotic CVD in South Asians. Although more research is needed to understand the exact cause, we need better public health focus on supporting South Asians to meticulously prevent and control the known risk factors using a dietary and lifestyle approach. The MASALA study in the US is trying to identify what factors lead to heart disease in South Asians. One of their findings is that healthy plant-based diet can reduce cardiometabolic risk factors in South Asian participants.

At Plant-Based Health Professionals UK we are passionate about promoting culturally appropriate, healthy plant-based diets for all communities. Read this article on why we believe healthy diets are so important for the South Asian community.

LIGNANS AND HEART DISEASE: Lignans are a range of polyphenolic compounds found in a range of plant foods including seeds, whole grains, fruits, vegetables, wine, tea, and coffee. In plants, these compounds have functions including antifungal and antiseptic activity. In humans, these plant lignans are processed by the gut bacteria to produce enterolignans, which are then absorbed into the body. These enterolignans are a type of phytooestrogen, have anti-inflammatory and anti-oxidant effects and may have a role in preventing atherosclerosis. However, to date, the impact of lignan consumption on clinical outcomes has been less well established.

This large study reports data from the Nurses’ Health Study and Health Professionals Follow-up study, including more than 200,000 participants, and assessed the impact of the major food sources of 4 lignans on coronary heart disease (CHD). The results showed that total lignan intake reduced the risk of CHD by 15%. In addition, the individual 4 lignans (matairesinol, secoisolariciresinol, pinoresinol, lariciresinol) also significantly reduced the risk of CHD. For total lignan intake, a plateau in benefit occurred once 300mcg/day was reached. The effect seen was independent of other established risk factors for CHD. Interestingly, there was a stronger inverse association between lignan consumption and CHD in those participants with higher levels of physical activity and a synergistic impact with fibre consumption.

These data are inline with other studies that demonstrate the benefits of foods rich in polyphenols. For example, a meta-analysis examining the impact of flavonoids on the risk of CHD reported a 15% reduction in risk in those consuming the most versus the least with a dose-response effect. A meta-analysis examining the impact of flavonoid consumption on the risk of stroke reported an 11% reduction in risk in those consuming the most with and a dose effect. A prior report from the Nurses’ Health Study and Health Professionals Follow-up study reported the impact of isoflavone consumption on CHD. The study found that the consumption of one of more serving of tofu a week compared to less than one serving per month reduced the risk of CHD by 18%.

Overall, we have plenty of data supporting the benefits of consuming polyphenols, which are found in a variety of plant foods. Lignans are found in flaxseeds, whole grains, and various fruits and vegetables. This paper provides information on the concentration found in various foods. For example, 10 grapes have around 62mcg, 1 kiwi 112mcg and an orange 160mcg. All of us on a plant-based diet know that flaxseeds and sesame seeds are a powerhouse of lignans. For example, a tablespoon of flaxseeds has 34505mcg!

HEALTHY LIFESTYLE HABITS AND RISK OF SYSTEMIC LUPUS ERYTHEMATOSUS (SLE). Although we know that healthy lifestyle habits reduce the risk of our commonest chronic diseases, the impact on the risk of various autoimmune diseases is less frequently reported, in part due to the lower prevalence of this diseases. However, the incidence of various autoimmune conditions is increasing and therefore understanding the contribution of lifestyle habits is important in reducing individual and population risk.

This study reports finding from the two Nurses’ Health Study cohorts, which included 185,962 women with 203 cases of SLE diagnosed during the follow-up. It is the first study to report the impact of a combination of healthy lifestyle factors on the incidence of SLE. The researchers used the same definition of health lifestyle as prior studies — the healthy lifestyle index score (HLIS). This includes never smoking, BMI in normal range, moderate alcohol consumption (5g/day or higher), regular physical activity, equivalent to 30 minutes of brisk walking per day, and a healthy diet (highest 40th percentile of the Alternative Healthy Eating Index — AHEI). Of note the AHEI gives positive marks to the consumption of whole plant foods and food rich in omega-3 fatty acids and negative marks for the consumption of red and processed red meat and processed foods.

At a median follow-up of 10.8 years, the results showed that the greater the adherence to a healthy lifestyle, and hence a higher HLIS, was associated with an incremental reduction in the risk of developing SLE. Those adherent to all five healthy lifestyle factors had a 58% reduction in the risk of SLE. Overall, the data suggested that if the population was adherent to at least 4 healthy lifestyle behaviours, the risk of SLE could be reduced by more than 50%. The authors conclude ‘Our findings have implications for SLE prevention and the promotion of multiple lifestyle behaviors to derive the greatest benefit. We also provided further insight into the pathogenesis of SLE as a greater than expected proportion of SLE risk may be attributable to modifiable lifestyle factors.’

The authors hypothesise that healthy lifestyle factors may be preventing SLE by reducing inflammation, oxidative stress, preventing DNA damage, helping to support the immune system and positively impacting gene expression.

I am a bit weary of suggesting that alcohol consumption at ‘moderate’ levels should be part of a healthy lifestyle for preventing autoimmune conditions. There is a narrow therapeutic window for alcohol and when it comes to cancer prevention there is no safe limit. Due to it’s addictive properties, it is easy to over-consume and this quickly leads to more harm than benefit and at high doses can worsen autoimmune conditions. Alcohol-related chronic conditions are on the rise. This article nicely summarises our current knowledge of alcohol consumption and autoimmune conditions.

The findings of the current study are pretty remarkable, as we often tell patients that autoimmune diseases have very little to do with lifestyle factors and are mainly due to genetics, unknown environmental factors and bad luck. This study gives us hope that we can not only prevent autoimmune conditions but that may be lifestyle interventions could help prevent progression and be a part of the treatment.

HEALTHY AND UNHEALTHY PLANT-BASED DIET AND IMPACT ON MORTALITY: I have now reported a number of studies that have used the plant-based diet index (PBDI) to analyse diet data and study the impact of both a healthy and unhealthy plant-based diet on disease outcomes. The PBDI is a way of analysing dietary information and gives positive points to healthy whole plant foods and negative points to all animal foods and unhealthy plant foods, included processed foods and sugar-sweetened beverages.

The current prospective cohort study examined the impact of a plant-based diet on overall and cause-specific mortality using data from the US National Health and Nutrition Examination Survey and included 40,074 participants with a mean age of 47.3 years. During the 7.8 years follow-up, 4904 deaths were documented including 1029 CVD-specific deaths and 1068 cancer-specific deaths.

The results showed that a greater adherence to an overall plant-based diet (regardless of whether it was healthy or unhealthy) was associated with a 20% reduced risk of dying from any cause and a 32% reduced risk of dying from cancer, but there was no association with CVD-related mortality. A healthy plant-based diet was associated with a 14% lower risk of death but there was no association with CVD or cancer-related mortality. An unhealthy plant-based diet was associated with a 33% increased risk of death from all causes and 42% increased risk of death from CVD. The impact of individual foods on mortality was assessed and only a weak positive association was found for consumption of vegetables and nuts. These results further highlight the importance of overall diet quality rather than a focus on individual foods.

The surprising finding was the lack of impact of a plant-based diet on CVD mortality given prior data that supports a fibre-rich diet low in animal foods for CVD prevention. The authors hypothesis that this may be due to inaccuracies in recording of cause of death or that participants who were diagnosed with CVDs may change their dietary habits due to their health conditions. Overall, the authors conclude ‘Guidelines and interventions highlighting the importance of increasing intake of plant foods, while decreasing intake of less healthy plant foods and certain animal foods may therefore promote health and longevity’.

Once again this study provides us with evidence that any incremental increase in the consumption whole plant foods is beneficial for health but warns us that processed foods, even if they are plant-based, negatively impact health outcomes. It is also the first study using the PBDI to show a huge impact on reducing the risk of cancer-related mortality.

DIET AND COVID-19: I have been doing some research for my talk at Global Vegfest, an online event from Vegfest UK taking place on Sept 18th/19th. I’ll be talking on diet and COVID, a topic I have been following and writing about since the start of the pandemic.

Many researchers and scientists suggested early on in the pandemic that a healthy diet may reduce the risk of severe infection from SARS-CoV-2 by supporting the immune system. As time has gone by, we have had studies that have shown that the health of the gut microbiome, mainly determined by dietary factors, is important in predicting disease severity and that consumption of fermented vegetables may be helpful (likely by promoting gut health). In addition we now have two studies demonstrating an association between a plant-based diet and reduced COVID-19 severity. The first to be published was a study of nearly 3000 healthcare workers showing that those consuming the most plant foods had a reduction in the risk of severe infection, whereas the opposite was true for participants reporting consumption of more low-carb, high fat foods. The second study, available in pre-print, is from the Zoe COVID study and includes more than 500,000 participants from the US and UK. The results showed that a healthy plant-based diet reduced the risk of catching COVID-19 by 10% and the risk of developing a severe infection by 40%.

The study highlighted is from the UK biobank and included 37,988 participants for whom there was dietary data and information on COVID-19 test results. The significant findings were that consumption of coffee, vegetables and being breastfed were associated with a lower risk of infection and processed red meat a higher risk. These foods all have bioactive compounds that support a healthy immune system.

Of course these results are merely hypothesis generating but when you start putting all the data since the start of the pandemic together, we begin to get stronger evidence supporting a healthy plant-based diet for reducing the risk associated with this pandemic virus. What’s to lose? The only side effects are a lower risk of weight gain (another problem during lockdowns), heart disease and type 2 diabetes, all factors increasing the risk of a worse outcome from COVID-19.

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