A review of the week’s plant-based nutrition news 31st October 2021
This week I cover a number of studies on diet and cancer survivorship, whether dairy is required for bone health and ahead of COP26, a reminder that switching to a plant-based diet is the single most impactful action you can take for planetary health.
NUT CONSUMPTION FOR BREAST CANCER SURVIVAL: Eating nuts is best established for improving cardiovascular biomarkers such as cholesterol and triglyceride levels and endothelial function and reducing the incidence and mortality of heart disease. There are mixed data to date on the role of nut consumption on cancer outcomes.
This study examined the role of nut consumption (both peanuts and tree nuts) after a diagnosis of breast cancer and whether it had an impact on remission and survival. The study included 3575 participants of the Shanghai Breast Cancer Survival Study (SBCSS) who survived over 5-years following a cancer diagnosis. They were enrolled 6.5 months after the diagnosis and a questionnaire was used to collect data on diet and lifestyle factors and comorbidities with follow-up surveys conducted at 18 months and 3, 5 and 10 years. At the 5-year post-diagnosis survey, a comprehensive dietary survey was conducted using a validated food frequency questionnaire.
Most of the participants in the study (3148) were nut consumers and they were more likely to have favourable diet and lifestyle habits and socioeconomic factors than those who did not consume nuts.
After a median of 8 years follow up, nut consumers had a significantly higher chance of being in remission and being alive. There was a dose response such that nut consumption greater > 17.3 g/week resulted in a 52% reduction in cancer recurrence, metastasis or breast cancer-specific death compared to those not consuming nuts. The benefit of nut consumption was shown to be independent of overall diet quality and greatest in those with stage 1 or 2 cancer compared to stage 3 or 4.
There are a number of reasons why nut consumption may be beneficial, including that they are are rich in beneficial nutrients such as unsaturated fatty acids, protein, fibre, vitamins, minerals and other bioactive constituents such as phytosterols and phenolic compounds. The beneficial dose of nuts in this study was tiny when you think that for cardiovascular disease prevention a dose of 30g on most days is recommended
Of course this type of observational study can’t prove cause and effect and there are several limitation discussed by the authors including the impact of residual confounding factors. However, we know from prior studies that swapping animal protein for plant sources of protein, including nuts, is beneficial for reducing the risk of cardiovascular disease and premature death. These benefits are hugely important for cancer survivors as they have an increased risk of other chronic conditions and of course getting a second cancer. You can read my previous article on breast cancer here.
DIETARY FAT; WHICH IS BEST?: The debate about the role of dietary fat and which is best continues. For me the science is clear. Replacing saturated fat (mainly from animal foods) for unsaturated plant sources of fat is consistently associated with significant health benefits. Whether you choose to eat a low fat or higher fat plant-based diet comes down to which health gains are most important to you. Fat quality is certainly more important than quantity.
New analysis from the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial from the USA, which included 101,832 participants and recorded 24,141 deaths over a median follow-up of 17 years. These deaths included 7,161 from cancer, 7,534 from cardiovascular disease (CVD), and 9,446 from all other causes combined. Intakes of saturated fatty acids (SFAs), trans-fatty acids (TFAs), monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) were assessed via food frequency questionnaires. Fat intake was correlated with total, CVD, and cancer mortality.
The results showed that a higher intake of saturated fat was associated with a 13% increase in all-cause mortality. Higher intake of PUFAs was associated with a 21% and 34% reduction in all-cause and CVD mortality, respectively. Higher intake of MUFAs was associated with a 9% and 15% reduction in all-cause and CVD mortality, respectively. The inverse association for monounsaturated fat was only observed for plant-derived and not animal-derived monounsaturated fat. No association was observed for trans fat. None of these dietary fats was associated with cancer mortality. The authors conclude ‘this study observed the detrimental effects of SFA intake on total mortality. A higher intake of PUFAs or MUFAs, especially Plant-MUFAs, was associated with lower risks of death from any cause or cardiovascular cause. Overall, these data support current dietary recommendations to replace SFAs with PUFAs and Plant-MUFAs for the prevention of chronic diseases and premature deaths’.
The body of evidence is now undeniable that the consumption of plant sources of fat, especially when replacing animal sources of fat, results in health benefits. This may be in part due to the more healthy packaging of plant foods, which includes fibre, numerous phytonutrients and are devoid of harmful substances found in animal foods, such as cholesterol, haem iron, nitrites/nitrates and production of less advanced glycation end products. Of course, saturated fat increases LDL-cholesterol levels in a linear fashion and LDL-cholesterol is a direct cause of atherosclerosis (fatty plaques in the arteries). Despite the lack of impact on cancer mortality in this study, people who have had cancer often have a shortened life expectancy and a higher risk of CVD, so these findings still remain very important.
BEST FOODS FOR COLORECTAL CANCER SURVIVORS: It is alarming for most to learn that more than 50% of cases of colorectal cancer could be prevented through the adoption of healthy lifestyle habits such as eating more dietary fibre, avoiding red and processed red meat and alcohol, maintaining a healthy weight and taking up regular physical activity. Despite this knowledge, the greatest rise in cases is occurring in people under the age of 50 years. The good news is that its never too late and people with a diagnosis of colorectal cancer can improve their chances of remission and survival by adopting healthy lifestyle habits. Most of the research has focused on the benefits of a healthy diet and regular physical activity.
The current study assessed the impact of dietary fibre, fruit and vegetable consumption on fatigue, chemotherapy-induced peripheral neuropathy (CIPN) and gastro-intestinal problems in 459 participants with stage I-III colorectal cancer who were followed prospectivtly from 6 weeks to 24 months post treatment. These participants were from the Energy for life after ColoRectal cancer (EnCoRe) study involving patients from 3 Dutch hospitals.
Higher intakes of fibre, fruits and vegetables were associated with better physical functioning and less fatigue. Just a 10g/day increase in fibre and a 100g/day increase in fruits and vegetable consumption was associated with benefits. No associations were found for CIPN and gastro-intestinal problems.
Its worth noting that the mean dietary fibre intake was 21g/day with only 7.8% of participants meeting the World Cancer Research Fund recommendations to consume >30g fibre per day. Mean vegetable and fruit consumption was 131g/day and 120g/day respectively and only 18.9% of participants managed the 5 recommended portions or 400g per day.
The authors propose that their finding may be due to the association between fibre consumption and lower levels of inflammation, with inflammation being associated with fatigue. The authors conclude, ‘Our results suggest that survivors who increase their dietary fibre intake after treatment report better functioning and less fatigue and that survivors who eat more fruit and vegetables report less fatigue in the first two years after the end of treatment’. I would be interested to see a study in which most people meet the cancer recommendations of consuming 30g/d of fibre and at least 5 portions of fruits and vegetables as there may be a dose effect that was not apparent in this study. Of cause eating this much fibre may be a challenge for people with a stoma after cancer surgery.
These results are concordant with other studies that have shown that a more plant-based diet with less animal foods results in a longer remission and better survival after a diagnosis of colorectal cancer. In addition, regular physical activity can reduce the risk of dying by around 30–40%. This is why we have teamed up with the Chartwell Cancer Trust to offer people with colorectal cancer support and guidance to adopt a healthy plant-based diet and other healthy lifestyle habits. You can find more information here. Please do share this with your loved ones.
THE IMPACT OF CALCIUM AND PROTEIN ON HIP FRACTURE AND FALLS: I don’t normally cover studies on dairy as to me they seem completely unnecessary. Dairy production is harming the planet, is wholly unethical for the animals involved and all the nutrients contained can be found in a healthier form in whole plant foods. However, this study has been published in an influential medical journal and hit the mainstream media too. I was pleased to have been given the opportunity to comment on the study by the Independent (although I was asked prior to the study being published!).
Overall this was not a bad study as such. 7195 care home residents who had a calcium intake of <600g and protein intake of <1g/kg, but who were not vitamin D deficient, were randomly assigned to continue their usual diet or have the addition of milk, yoghurt, and cheese that contained 562 mg/day calcium and 12 g/day protein achieving a total intake of 1142 mg calcium/day and 69g/day protein (1.1 g/kg body weight). Overall, the dairy food intake increased from 2.0 to 3.5 servings daily in the intervention group.
After 15–24 months the results showed a significant reduction in the risk of falls and fractures in the intervention group. There was a 33% reduction in risk of fractures of any type, a 46% reduction in risk of hip fractures, and an 11% reduction in risk of falls relative to controls. The numbers needing treatment to prevent any fracture, hip fracture, or a fall were 52, 82, and 17, respectively. The impact of fracture reduction was similar to that expected by medications used to treat osteoporsis. The authors hypothesise that based on their additional results, the reduction in falls and fractures may be due due to better muscle mass, slowing of bone loss and an increase in IGF-1 levels in the intervention group.
Things to note are that the median age of participants was 86 years. They had a median of 9–10 underlying medical conditions and were on a median of 11–12 medications. Over half had cognitive impairment. So not a healthy group of older adults. There were no details provided on the quality of diet being consumed or levels of physical activity, which would be presumed to be low given the co-morbidities of the participants.
The study was indeed funded by the dairy industry organisations, which should always make one question the results as industry funding is more likely to find in favour of the product being studied. Nonetheless, this was a valid study design and analysis. However, all we can conclude is that adequate protein and calcium intakes are important in older adults with additional medical conditions. To the credit of the authors, they don’t conclude dairy has any magic properties only that increasing dietary intake of protein and calcium in elders who are not consuming enough is of benefit. I can not disagree with this. We also have to acknowledge that dairy consumption is only relevant for Caucasian populations as non-Caucasians have a high incidence of lactose malabsorption (the natural state after weaning).
You won’t be surprised to learn that there are a number of studies now supporting the consumption of plant protein instead of animal protein for healthy ageing and there are many healthy plant sources of calcium to support the higher intakes. Regular physical activity and muscle strengthening activities are just as import as diet quality for healthy ageing and bone health. I was pleased to find these recommendations for protein intake from the PROMISS (PRevention Of Malnutrition In Senior Subjects), a European program aiming at preventing malnutrition among older people. We have an excellent factsheet on bone health and meeting calcium requirements.
SUSTAINABLE DIETS HAVE CO-BENEFITS FOR HEALTH AND CLIMATE: Ahead of COP26, this is study is hugely important. The data comes from the well known EPIC (European Prospective Investigation into Cancer and Nutrition) cohort study, including 443 991 participants (mostly female with an average age of 52 years at recruitment) from 10 European countries followed for a median of 14 years. It is the largest analysis to assess the co-benefits of a nutritionally adequate yet sustainable diet on human and planetary health. The Eat-Lancet planetary health diet was used as the example of an evidence-based healthy and sustainable diet pattern. Planetary impacts were assessed by considering diet-related greenhouse gas (GHG) emissions and land use.
The results are obvious and clear. Diets heavy in meat and dairy, and thus contributing more to GHG emissions and land use, were shown to be associated with an increased risk of all-cause, coronary heart disease, CVD and cancer death. Remarkably, diets that are worst for the planet also increased the risk of developing up to 14 of 20 specific cancers investigated.
Overall, by choosing a climate-friendly diet such as the Eat-Lancet planetary health diet, up to 19–63% of all deaths and up to 10–40% of cancer could be prevented whilst at the same time reducing GHG emissions up to 50% and land use up to 62%. Any small shift towards the Eat-Lancet recommendations yielded significant benefits for health and planet, hence the range in percent points given in the text.
The authors conclude ‘Our findings, suggest that co-benefits to human health and the environment could be achieved by adopting diets that consider both nutritional quality and planetary impact, such as the EAT–Lancet diet. Addressing dietary patterns that represent co-benefits could help in climate change mitigation, in addition to reducing other sources of greenhouse gas emissions, and might help reduce the incidence of diet-related mortality and cancers’. Of note, the Eat-Lancet planetary health diet allows for 13% of calories from animal-derived foods, amounting to around one portion of red meat, 2 portions of poultry and 3 eggs per week. The rest should come from a variety of fruits, vegetables, whole grains, beans, nuts and seeds.
Prior studies have shown that reductions of up to 10% in premature mortality could be achieved mostly through a reduction in red meat consumption, which would also reduce food-related GHG emission by around 50%. Of course a vegan diet is the best way to reduce food-related climate impacts as shown by this analysis of two large cohorts (Adventist Health Study-2 and EPIC-Oxford) of which a third of participants are vegetarian or vegan. Meat and dairy free diets could reduce food-related GHG emission by 60%. A vegan diet also has the benefits of releasing around 75% of land currently used for animal agriculture back to nature thus providing a significant ‘carbon opportunity’ whereby carbon can be removed from the atmosphere.
With this knowledge it is shocking to learn that beef will be served at COP26. I have no words to describe this contradiction and lack of understanding of the science.