Review of the week’s plant-based nutrition news 7th March 2021

This week I cover more evidence supporting the benefits of consuming fruits and vegetables and the harms associated with meat consumption. I also cover the impact of underlying health conditions and more wondrous benefits of flaxseeds.

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MORE EVIDENCE THAT MEAT CONSUMPTION IS CAUSING MORE HARM THAN GOOD: This paper reports findings from the UK Biobank study and includes almost 500,000 men and women, mostly white, who were followed for a median of 8 years. Diet data was collected at recruitment and for 69,000 participants the diet data was collected at least a further 3 times.

The results showed that consumption of red and processed meat at a level of 70g/day significantly increased the risk of ischaemic heart disease, pneumonia, colonic polyps, diverticular disease and type 2 diabetes, in the order of a 10–30% increased risk. Higher poultry intake at levels of 30g/d increased the risk of gastro-oesophageal reflux, gastritis, duodenitis, diverticular disease, gallbladder disease and type 2 diabetes in the order of a 10–17% increased risk. Some, but not all, of the negative effects of meat consumption could be explained by the fact that those eating the most had a higher body mass index (BMI). Consumption of as little as 50g of unprocessed red meat and 20g of processed red meat per day increased the risk of a number of these chronic diseases.

The results also showed that those consuming unprocessed red meat and poultry had a lower risk of iron deficiency anaemia.

For me the weight of evidence in the paper points towards harm rather than benefit for meat consumption. These data are consistent with so many other studies showing the harms of consuming animal-derived foods and the benefits of choosing plant sources of protein instead. There are many plausible mechanisms that explain the adverse impact of meat consumption, including the saturated fat content, generation of advanced glycation end-products, nitrates and nitrites in processed meat, TMAO generation by the action of gut bacteria, the higher levels of branched chain amino acids and sulphur-containing amino acids in animal protein, the presence of haem iron and of course the lack of anti-oxidant and anti-inflammatory compounds in meat. If you are eating more meat you are eating much less of the healthy plant foods that are associated with better health outcomes.

Yes there is be a higher risk of iron deficiency in this study in those consuming the least red meat, but with some knowledge and skill it is perfectly possible to get enough iron from a plant based diet. Eating plenty of lentils, beans, tofu, green leafy vegetables, cashews and dates for example are great ways of consuming non-haem iron. I was embarrassed to be learning for the first time at this weeks Vegmed conference that lentils contain ferritin that can be directly absorbed by the gut and can contribute to providing significant amounts of iron on a plant-based diet. In fact haem iron from animal foods is one of the reasons meat may increase the risk of diseases such as heart disease and type 2 diabetes. Here is some excellent information on iron consumption from the UK Vegan Society.

So once again, it’s best to limit or avoid meat consumption and optimise plant sources of macro and micronutrients. I don’t think we need more studies to convince us.

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THE HEALTH BENEFITS OF EATING FRUITS AND VEGETABLES: This study includes a massive amount of data and once again demonstrates the benefits of eating fruits and vegetables. However, the results differ slightly from the previous meta-analysis in which there was a dose response with the more consumed the better.

This study included data from the Nurses’ Health Study and the Health Professionals Follow-up study in the US in which more than 100,000 men and women were followed for 30 years. The consumption of fruits and vegetables was correlated with risk of death from a number of different causes. The lowest quintile of consumption was 2 portions a day versus around 7.5 protions a day in the highest quintile. The results showed that the consumption of 5 portions of fruits and vegetables (2 fruits and 3 vegetables) per day was associated with a significant reduction in all-cause (23% reduction), CVD (22%), cancer (10%) and respiratory mortality (35%). A meta-analysis was also performing, which included data from 26 cohort studies and almost 1.9 million participants. The findings were very similar. Most fruits and vegetables were associated with a benefit except starchy vegetables, potatoes and fruits juice which did not impact mortality.

The authors comment that the previous meta-analysis by Aune et al published in 2017 did show a non-linear additional benefit of consuming up to 10 portions per day, but the current study is larger and therefore of greater statistical power. Nonetheless, consuming more fruits and vegetables means eating less of foods such as meat, dairy and eggs and processed foods in general, and so for me, there is no need to limit the consumption to only 5 a day.

There are so many reasons why fruits and vegetable consumption could reduce risk of death. They are high in potassium, magnesium, polyphenols and fibre. These nutrients reduce BP, cholesterol and oestrogren levels and have anti-oxidant and anti-inflammatory properties. The fibre content is associated with a number of benefits including improved weight, lower BP and better bowel health. The lack of impact of starchy vegetables on health outcomes may be due to their higher glycaemic load.

Of course, this type of observational data can not prove cause and effect and there are a number of limitations discussed by the authors. Nonetheless, the weight of evidence supports the daily consumption of fruits and vegetables and aiming for 5 portions a day seems a sensible approach given that only 28% of adults and 18% of children in the UK actually achieve this level of consumption.

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UNDERLYING HEALTH CONDITIONS AND IMPACT ON COVID-19: Since the start of the COVID-19 pandemic we have recognised that common underlying health conditions were leading to an increased risk of adverse outcomes from infection with SARS-CoV-2. This new paper from the US highlights the extend of this association.

The study examined over 900,000 hospitalizations in the US for COVID-19. It investigated the contribution of underlying health conditions to these admissions. The results demonstrated that more than 60% of hospital admissions were attributable to four cardiometabolic conditions: hypertension, type 2 diabetes, heart failure and obesity. These risks were higher in people of Black and South Asian origin

The authors conclusion states; ‘Clinicians should educate their patients who may be at risk and consider promoting preventive lifestyle measures, such as improved dietary quality and physical activity, to improve overall cardiometabolic health and potentially minimize the risk for coronavirus disease 2019 severity’.

This study is also a reminder that the current pandemic has brought to our attention the hidden pandemic of chronic illness which has made our society more vulnerable to the effects of the pandemic virus and directly impacts quality and quantity of life. The causes are complex and include socio-economic factors too. Policy makers can can no longer ignore this double pandemic and need to support clinicians to promote a healthy plant-based diet and lifestyle to improve health outcomes. The UK have a very similar burden of chronic disease to the US. We also need these healthy habits to be accessible to all. In the UK, the pandemic has increased food insecurity and widened health inequalities. The authors of a paper highlighting this issue state; ‘it is the government’s responsibility to protect population health, to guarantee household incomes, and to safeguard the economy. Millions of households were in poverty before the pandemic, and millions more will be so unless the government continues to protect household incomes through policy change’. Healthy food needs to be considered a human right and we should hold our Government to account on this issue. Even key workers such as Nurses have been driven to use food banks in this pandemic, which is shocking.

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MATERNAL HEALTH IS IMPORTANT FOR CHILD’S HEALTH: We already know that health-related habits of parents can impact the future health of their children. This is mainly through the resulting epigenetic changes that can be passed on to off-spring and of course shared lifestyle behaviours. In fact, epigenetic changes in grandparents as a result of lifestyle factors have also been shown to impact health outcomes in their grandchildren.

This paper highlights the importance of optimising cardiovascular health in pregnancy. The study examines the impact of cardiovascular health in 2302 women at 28 weeks gestation on their child at age 10–14 years. Participants were recruited from 6 different countries including US, Canada, UK, Thailand, Barbados and China. Maternal cardiovascular health was based on 5 risk factors; body mass index, blood pressure, total cholesterol, glucose level and smoking. Cardiovascular health in offspring was assessed using the same risk factors, except smoking.

The results showed that mothers who had the the most risk factors versus those who had the least had a 7.8 times greater risk of having a child with adverse cardiovascular risk factors by the time they reached early adolescence. Thus optimising health during pregnancy is an opportunity to improve the health of future generations.

The study did not include data on diet and physical activity of the mothers or the lifestyle habits of the children. These are all relevant factors to understanding how these risk factors can be modified. Nonetheless, we know that we need to foster healthy diet and lifestyle habits early in life and this study highlights how individual health can be impacted as far back as pre-conception and pregnancy.

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FLAXSEED CONSUMPTION AND ULCERATIVE COLITIS (UC): Those on a plant-based diet are familiar with the amazing properties of flaxseeds. They are a great source of essential omega-3 fatty acids, fibre and lignans, which are a type of phyto-oestrogen. Randomised studies have shown the ability of flaxseeds to lower blood pressure and even slow the growth of cancer cells.

This small randomised study from Iran examines the impact of flaxseed on clinical biomarkers, quality of life and disease activity in patients with UC. Of the 90 patients recruited, 75 (43 men and 32 women) completed the 12 week study. Data were available from 25 participants in 3 groups; a control group, 30g of grounded flaxseed per day or 10g of flaxseed oil per day.

After 12 weeks, both flaxseed intervention groups had a significant reduction in high-sensitivity CRP, a marker of inflammation, and significant improvements in disease activity and quality of life as determined by the Mayo score and IBDQ-9 questionnaire respectively. There was also a significant increase in IL-10 levels, an anti-inflammatory cytokine.

This study is small and of short duration and the changes documented are small, albeit, significant. The most interesting finding seems to be the ability to improve clinical measures of disease in such a short time and the study raises the question as to whether incorporation of flaxseeds in diet in the longer term should be part of the treatment approach in inflammatory bowel disease. A previous report from the same study showed that participants also benefited from significant reductions in waist circumference and blood pressure. Here is a great review on the health benefits of flaxseed consumption.

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