Review of the week’s plant-based nutrition news 2nd May 2021

Happy No Meat May! This week I cover the impact of meat packing facilities on rates of COVID-19, omega-3 fatty acids and mortality, risk of cancer in people with diabetes, impact of obesity on second cancers and cutting meat consumption to combat climate change.


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UNINTENDED CONSEQUENCES OF COVID-19: Once again we are reminded that the meat industry not only harms non-human animals but also humans that work within it. Early in the pandemic we learnt that slaughterhouse and meat workers were at high risk of contracting SARS-CoV-2 infection due to the nature of their working conditions. In the US, these approximately half a million workers were classed as essential and had little choice but to continue working, often being from migrants or refugee communities.

This paper examines county-level rates of COVID-19 in the US and whether the presence of large meat-packing plants have an impact on the rates of infection. The study finds that within 60 days after the emergence of COVID-19 in a given county, the presence of a meat packing facility increased per capita infection rates by 110–160% compared to counties without packing plants. This translated into 334, 000 COVID-19 cases being attributable to large meatpacking operations. This estimate includes both direct infections to meatpacking workers as well as community spread outside the operations but attributable to those facilities.

The study finds that previous reports have underestimated the impact of meat packing plants on COVID-19 case rates and also believes their estimates are likely to have missed cases too. For example, if the worker contracted COVID-19 at work but lived outside the county and transmitted it to his/her community, these cases would not have been attributed to the meat packing plant.

The authors conclude ‘that the COVID-19 mortality and morbidity associated with large packing plants has generated more than $11.6 billion in economic costs to the rural economy with beef and pork facilities’.

Given that meat consumption is not essential, the harm caused to meat packing workers and their families is unforgivable and violates human rights. If we ourselves could not work in such a facility then we should not expect our fellow kin to do so on our behalf.

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BLOOD OMEGA-3 FATTY ACID LEVELS AND IMPACT ON MORTALITY: The impact of omega-3 polyunsaturated fatty acids on health outcomes have been extensively studied but with inconsistent results. Here we are talking about the 18-carbon, plant-derived alpha-linolenic acid (ALA,) as well as the 20–22-carbon, long-chain eicosapentaenoic (EPA), docosapentaenoic (DPA), and docosahexaenoic (DHA) acids. In general, there appears to be health benefits from consuming fish, especially when this is instead of other animal-derived foods such as red and processed red meat. It is thought that these benefits are predominantly due to DHA/EPA in fish, yet randomised studies of DHA/EPA supplements have not conclusively demonstrated a benefit. Measuring blood levels of omega-3 fatty acids is a more reliable method of documenting intake.

This study analysed data on omega-3 fatty acid blood levels (both plant- and seafood-derived) from 17 prospective cohort studies, including 42,466 participants, and assessed the impact on all-cause mortality and mortality from cardiovascular disease (CVD), cancer, and all other causes. The average age of participants at baseline was 65 years (range 51–81 years) with a median follow up of 16 years (range 5–32 years).

The results showed that higher blood levels of long-chain (LC) omega-3 fatty acids (DHA/EPA) were associated with significantly reduced all cause mortality (15–18% reduction) but ALA levels were not. LC omega-3 fatty acids levels were associated with lower risk of death from CVD, cancer and all other causes combined (10–15% risk reduction). Again ALA levels were not.

Proposed mechanisms reported in the literature by which LC omega-3 fatty acids impacts health includes, lowering triglycerides, reducing blood pressure, anti-platelet effects, improved endothelial function, anti-inflammatory effects and slower rates of telemore shortening.

Most dietary LC omega-3 fatty acid is obtained from eating fish. For those of us that don’t consume fish, the jury is still out as to whether DHA/EPA supplements are required for all adults. Vegan and vegetarian diets certainly reduce the risk of ischaemic heart disease and cancer but don’t consistently improve mortality. Whether adding DHA/EPA supplements to an already healthy plant-based diet will improve health outcomes further is unknown. An algae-derived DHA/EPA supplement may be a good option for vegans, especially for older adults.

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TYPE 2 DIABETES AND RISK OF CANCER: Many chronic diseases share underlying pathogenic mechanisms driven by the same risk factors. Most chronic diseases arise from a combination of inflammation, insulin resistance, dyslipidaemia and dysbiosis (abnormal gut microbiome). This is why diseases cluster in the same individuals. Cancer is also driven by these same mechanims and underlying chronic illness increases the risk of cancer.

This paper examines the association between type 2 diabetes and risk of cancer in the Nurses’ Health Study and the Health Professionals Follow-up Study, a cohort of almost 200,000 participants from the US followed for over 30 years. The results showed that participants with a new diagnosis of type 2 diabetes during the follow-up period had a significantly increased risk of developing cancer, particularly, colorectal, lung, pancreas, oesophageal, liver, thyroid, breast, and endometrial cancers. This risk was increased in the first 8 years following diagnosis of type 2 diabetes but not after this. Overall, there was a 21% increased risk of total cancer, 28% increased risk of obesity-related cancer, and 25% increased risk of diabetes-related cancer comparing participants with and without diabetes.

Some participants had data available on C-peptide and HBA1c levels. C-peptide levels are a marker of endogenous insulin levels, which was evelvated in the first 8 years following diagnosis of type 2 diabetes and then tended to fall (as the pancreas became unable to produce insulin). HBA1c levels remained stable over a 15 year period. These data suggest that higher insulin levels may be driving the increased risk of cancer rather than higher glucose levels per se. These results are in line with those that show patients with type 1 diabetes are not at increased risk of cancer as their insulin levels are low/absent. In addition, other studies have shown higher circulating insulin levels are associated with an increased risk of cancer.

The best way to prevent type 2 diabetes and thus lower the risk of cancer is by adopting healthy diet and lifestyle habits. A plant-based diet significantly reduces the risk of type 2 diabetes and cancer and helps maintain a healthy weight.

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BODY MASS INDEX AND RISK OF SECOND CANCER IN WOMEN WITH BREAST CANCER: Those who have had a first cancer are at increased risk of a second cancer, in part because the same risk factors persist in these individuals. Women who have had breast cancer are at increased risk of developing a second cancer. This study examined the association between body mass index (BMI) at initial breast cancer diagnosis and the incidence of second primary cancers among a large cohort of women diagnosed with invasive breast cancer within two Kaiser Permanente (KP) health plans in the US.

The retrospective review included 6,481 women aged 20–84 years at diagnosis of their first cancer between the years 2000–2014. During the 88 months of follow-up, 822 (12.7%) women developed a second cancer of which 508 (61.8%) were obesity-related and 333 (40.5%) were breast cancer. For every 5kg/m2 increase in BMI there was a 7% increase in risk of second cancer.

There are plausible mechanisms for this finding given that obesity increases the level of circulating oestrogen, oetradiol increases the production of insulin-like growth factor 1, implicated in driving cancer growth, and obesity increases inflammation and insulin resistance, also associated with cancer cell growth. Overweight and obesity is the second commonest cause of cancer after tobacco smoking and known to increase the risk of 13 different cancers. Addressing risk factors before and after a diagnosis of cancer is crucial. We have evidence from the Women’s Health Initiative study that a healthy diet can improve remission rates and survival after a diagnosis of breast cancer.

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NO MEAT MAY: This weekend sees the start of the international campaign No Meat May. I am delighted that my workplace, King’s College Hospital, London, is supporting this campaign by asking it’s more than 10,000 staff members to adopt a plant-based diet for May and beyond. At least 60 of the executive staff, including the CFO, have pledged their support. This is being driven by the NHS’s sustainability agenda as the NHS have pledged to become carbon neutral by 2040. It is clear that addressing the food environment is a major part of this endeavour. This week, Dr Laura Freeman and I presented the case for family doctors to encourage their patients to reduce and eliminate red meat from the diet at the Plantetary Health Alliance annual conference.

We can no longer deny the impact of eating meat, fish and dairy on the health of the planet. The issue of meat consumption has been further highlighted in mainstream media in recent days. Animal agriculture is a major cause of greenhouse gas emissions, land use change, deforestation, land and water pollution, biodiversity loss and species extinction.

Healthcare services need to do their part in the fight against climate change. Healthcare without harm has produced this new report and road map for health care decarbonisation. One of the 7 recommendations is a ‘plant-forward, sustainable diet’. Healthy diets are also a solution to reducing the burden of chronic illness and use of healthcare systems and medications.

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