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Opinion - The top science papers of 2021 supporting plant-based nutrition

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The Top Science Papers of 2021 supporting plant-based nutrition by Dr Shireen Kassam

The science in 2021 is overwhelmingly supportive of plant-based nutrition for promoting better health. Sadly, diet-related chronic illness continues to rise and the global community has failed to take sufficient action to repair our broken food system. It was a tough job, but here are my top evidence-based papers.

2021 Global Nutrition Report

This year’s report makes for very sad reading. It clearly describes that globally we are way off course in dealing with the issues of malnutrition, which include stunting, wasting and high BMI. Worldwide, 149.2 million children under five years of age are stunted, 45.4 million are wasted and 38.9 million are overweight. Over 40% of all men and women (2.2 billion people) are now overweight or obese. Diet-related disease and mortality continue to rise with poor diets resulting in one in four deaths globally (26%). The proportion of premature deaths attributed to dietary risks is highest in Northern America and Europe (31% each), and lowest but also at notable levels in Africa (17%).

Diets remain insufficient in healthy plant foods, whilst being too high in meat, salt and sugar. Fruit and vegetable intake remains 50% below the recommended level of five servings per day that is considered healthy, and legume (e.g. lentils, chickpeas and kidney beans) and nut intakes are each more than two thirds below the recommended two servings per day. In contrast, red and processed meat intake is on the rise and almost five times the maximum recommended level of one serving per week, while the consumption of sugary drinks - which are not recommended in any amount - is also going up.

The report finds that our food system continues to harm the planet creating more than a third (35%) of all greenhouse gas (GHG) emissions and using substantial and rising amounts of environmental resources, with animal-sourced foods responsible for the majority of GHG emissions and land use.

As a result, the cost to society of dealing with the consequences of our broken food system and unhealthy diets is astronomical and unsustainable. Therefore, we need urgent initiatives to transform food systems, increase the intake of health-promoting foods and reduce consumption of animal-based foods to ensure diets are healthy and sustainable for people and the planet. Of course, in high income countries, most of us don’t need to wait for these policy changes; we can immediately change our diets by focusing on plant-based foods.

Impact of Dietary Patterns on All-Cause Morality

Given that foods and nutrients are not consumed in isolation, it’s increasingly clear that it is more useful for clinical practice to investigate the impact of dietary patterns rather than individual components. This is because ”nutrient and food analyses cannot account for the interactions among or the degree of independent variation of coingested nutrients and food components”.

This study was performed by the Dietary Guidelines Advisory Committee, convened by the US Department of Agriculture and Department of Health and Human Services, and the researchers asked ”What is the association between dietary patterns consumed and all-cause mortality?”.

The systematic review included 153 articles (involving 6,550,664 individuals), of which one was from a randomised clinical trial and 152 were from observational studies. It is worth noting that the randomised study included in this review was the well-publicised PREDIMED study, which investigated the impact of a Mediterranean diet intervention for primary prevention of cardiovascular disease (CVD). The majority of the observational studies (72%) examined dietary pattern and quality using dietary indices or scores such as the Alternate Healthy Eating Index, Mediterranean diet index and the plant-based diet index. Different diet patterns were also examined including the Mediterranean, Dietary Approaches to Stop Hypertension (DASH), vegetarian and vegan, and country-specific diet patterns such as the Japanese diet.

The results showed that common features of the dietary patterns associated with improved all-cause mortality were relatively higher intake of vegetables (with or without potatoes); legumes; fruit; nuts; either whole grains specifically, cereals unspecified, or non-refined grains; fish and/or seafood; lean meat or poultry, when meat was included; and unsaturated fats in place of saturated fats; and relatively lower intake of red and processed meat and/or meat and meat products; high-fat dairy; refined grains; added sugars and/or sugar-sweetened beverages; solid fats, saturated fats, and/or trans fat; and excessive sodium. The results were similar regardless of the country or diet pattern being studied.

Many of the dietary indices considered alcohol consumption in low to moderate amounts or within a threshold (e.g. 10–25 g per day (/d); 0.5–1.5 drinks/d for women and 0.5–2.0 drinks/d for men) as a positive factor within a healthy diet pattern.

Interestingly, although not surprisingly, when adherence to dietary patterns was combined with other healthier lifestyle factors (e.g. not smoking and meeting recommended physical activity levels), stronger associations were observed with greater reductions in mortality.

Regarding plant-based diets, five of the included studies examined the impact of diet patterns that avoid animal foods. This included the results from the EPIC-Oxford and Adventist Health Study-2 cohorts. Only two of the included studies demonstrated a benefit in terms of mortality, the Adventist Health Study-2 and results from the Nurses’ Health Study and Health Professionals Follow-up Study. In addition, two studies showed that greater adherence to the healthy plant-based diet index was associated with lower all-cause mortality. the ARIC (Atherosclerosis Risk in Communities) study and the US National Health and Nutrition Examination Survey study cohort, which I reviewed on 22nd August 2021, was not included in the systematic review. This additional study reported further data from the US National Health and Nutrition Examination Survey with more than 40,000 participants and found a reduced risk of all-cause mortality in those most adherent to a healthy plant-based diet.

Overall, the data confirm that nutrient-dense diet patterns characterised by higher intake of:vegetables; legumes; fruits; nuts; either whole grains, cereals, or non-refined grains; fish; and unsaturated vegetable oils and by lower or no consumption of animal products (red and processed meat, meat and meat products, and high-fat dairy products), refined grains, and sweets (i.e. higher in added sugars) improve longevity and reduce the risk of death from all causes. On this basis, it can be assumed that a healthy plant-based diet that avoids all animal foods may also be associated with improved longevity but, at the moment, we don’t have as many studies on healthy 100% plant-based diets to be absolutely certain.

Plant-Based Diets and Mortality

This paper specifically assessed the impact of a plant-based diet on mortality. The term “plant-based diet” can at times be confusing as it does not have a precise definition. In the medical literature this includes vegan, vegetarian and sometimes even pesco-vegetarian diets. To more accurately define healthy versus unhealthy plant-based diets, a number of studies have used the plant-based diet index (PDI) to analyse data from food frequency questionnaires and assess the impact on health outcomes.

This study brings together data from a range of prospective cohort studies that use a broad definition of plant-based diet, including PDI, and vegetarian, vegan, semi-, lacto-, lacto-ovo-, and pesco-vegetarian diets and that reported all-cause, CVD, site-specific and total cancer mortalities as well as other causes of death in adult participants. The review includes 12 prospective cohort studies with 508,861 participants and 42,697 deaths, from publications dated between 1988 and 2020. Study durations ranged from 4.8 to 25 years. Only one study reported outcomes for participants on a vegan diet separately, while the others analysed outcomes for vegans together with vegetarian participants.

The results showed that a greater adherence to a plant-based diet was associated with a 10% reduction in risk of all-cause mortality. A vegetarian diet pattern was associated with an 8% reduction in CVD mortality and a 23% reduction in the risk of coronary heart disease mortality. There was no association with plant-based diets and cancer mortality or other causes of death. It was found that the association with all-cause mortality reduction was mainly from studies conducted in the US and of shorter duration but with larger numbers of participants. However, after controlling for body weight and alcohol consumption, these results became insignificant. In addition, controlling for energy intake also reduced the significance of the results.

Overall, the study has tried to answer the million dollar question as to whether a healthy plant-based diet can improve survival and reduce the risk of death from a number of chronic diseases. The results show the difficulty in analysing data from studies with heterogenous data sets, using different definitions of a plant-based diet and in which participants are adherent in varying degrees to a healthy plant-based diet as opposed to one that is high in processed foods and refined carbohydrates. Despite the inherent limitations of such a study, there is a definite signal of a reduction in mortality with a plant-based diet. With a larger number of studies, a vegetarian diet pattern does consistently show benefit for heart health. These findings are likely to be due to the reduction in various risk factors in people consuming a plant-based diet; for example, reduction in the risks of hypertension, high cholesterol, weight gain and type 2 diabetes plus the benefits of a healthier gut microbiome. The other aspect to note is that there is certainly no evidence of harm caused by the consumption of a healthy plant-based diet.

The impact on cancer is difficult to determine with certainty as cancer is not just one disease, with so many varying factors making up our personal cancer risk and there just have not been enough studies. One study not included in this review is from the NutriNet-Sante cohort in which those most adherent to a plant-based diet had a 15% reduction in the incidence of cancer over the five year follow-up period. In addition, the two largest studies on vegetarian and vegan health- the Adventist Health Study-2 and EPIC-Oxford studies - do demonstrate a significant reduction in cancer risk in vegetarians and vegans in the order of 10–20%.

The study adds to the growing amount of data supporting a healthy plant-based or vegan diet as an excellent choice in terms of human health. As always, more data and studies would be useful but I am not sure we will ever have the perfect study on vegan or 100% plant-based diets due to the inherent difficulties of conducting such a study.

It's Never too Late to Reduce your Risk of Type 2 Diabetes

Type 2 diabetes is at epidemic proportions, with 1 in 10 people over the age of 40 in the UK having the condition. Globally, more than 400 million people are living with type 2 diabetes with a greater rise in prevalence in low- and middle-income countries. We already know that a healthy plant-based diet is best for preventing type 2 diabetes. But what about changes to the diet over time? How does that impact risk?

This paper from the Nurses’ Health Study and Health Professionals Follow-up Study included over 200,000 participants followed for more than 30 years. The analysis examined the impact of adherence to a healthy plant-based diet every four years and how changes in adherence impacted subsequent risk of type 2 diabetes. The study used the plant-based diet index to analyse dietary data and the quality of the diet.

The results showed that changes in diet quality during follow-up had an impact on the future risk of diabetes. Those participants that had a higher adherence to a plant-based diet over a four year period had a significantly reduced risk of type 2 diabetes over the subsequent four years. For every 10% improvement in adherence there was a 7-9% subsequent reduction in risk. For those participants whose diet veered away from a healthy plant-based diet there was a 12-23% increased risk of type 2 diabetes in the subsequent four years. Participants with the greatest increase in animal food consumption over time had a 10% higher future risk of type 2 diabetes. Some of this increased risk was due to higher body weight.

The authors conclude ”shifting consumption of animal foods away towards more consumption of healthy plant foods over time is followed by a lower [type 2] diabetes risk”.

From previous studies, we also understand the mechanism by which plant-based foods protect against type 2 diabetes. Plant-based diets have anti-inflammatory and anti-oxidant properties, they are higher in fibre and polyphenols (which, amongst other things, benefit the gut microbiome), and are lower in both saturated fat and heme iron intake. Such diets also promote better weight management.

The data supporting plant-based diets for prevention and treatment of type 2 diabetes is so compelling that the American College of Lifestyle Medicine endorses a predominantly whole food plant-based diet as the number one diet intervention in this setting.

Plant-Based Diet and Cardiovascular Disease

The most well-established benefits of a plant-based diet are the impact on CVD, importantly given that CVD remains the top cause of mortality globally. We know that plant-based diets reduce the incidence of CVD risk factors including high blood pressure and cholesteroloverweight/obesity, type 2 diabetes and inflammation. It’s also useful to consider actual CVD outcomes such as incidence and mortality.

This paper brings together data from 13 cohort studies including 410,085 participants. These studies assessed the impact of a plant-based diet using the plant-based diet index and also included studies with vegetarian and vegan participants (78,672 in total).

The results showed that adherence to a healthy plant-based diet significantly reduced the risk of developing CVD (10.2% reduction) and dying from CVD (8.1%). In most studies, vegetarians and vegans tend to be analysed together and there was a definite consistent reduction in CVD incidence, particularly seen in vegetarians, but the impact on mortality is less obvious given the heterogeneity in diet quality. Unhealthy plant-based diets were shown to increase the risk of CVD.

The authors conclude that ”This study provides important evidence to suggest a possible protective role of plant-based dietary patterns against cardiovascular mortality and CVD among the general population”.

This sounds like a good reason to promote plant-based diets as the default!

Obesity and Cardiometabolic Health

This large systematic review includes 84 papers that investigate the efficacy of vegan, vegetarian and plant-based whole foods (PBWF meaning exclusively plant-based or minimal animal foods including eggs and dairy) diets in treating obesity, hyperlipidaemia, insulin resistance, glycaemic control, type 2 diabetes, CVD and hypertension.

The paper reviews the impact of each of the three diet patterns on the various health outcomes listed above. Overall, the findings confirm that all three types of diet reduce body weight to a greater extent than healthy omnivorous diets (including those recommended by the American Heart Association (AHA), American Diabetes Association and the National Cholesterol Education programme) and, in some studies, performed better than the comparison calorie-restricted diet. Studies have also shown greater loss of subcutaneous, visceral and intramuscular fat with a plant-based diet.

All three diets improved glucose control and insulin sensitivity, and resulted in reductions in HbA1c in people with type 2 diabetes, with the ability to reverse the condition in some. This has also been shown in the community setting amongst free-living people (The BROAD Study).

Plant-based diets were found to be very effective at lowering total and LDL-cholesterol but less effective for reducing triglyceride (TG) levels and may unfortunately result in lower HDL-cholesterol levels. A Mediterranean diet was better at lowering TG levels compared to vegetarian or vegan diets. Plant-based diets were also effective at lowering blood pressure but this may not be superior to other therapeutic healthy diet patterns, such as the DASH diet. A vegan diet has been shown to be more effective at lowering high sensitivity CRP (a marker of inflammation) compared to the AHA recommended diet in people with coronary artery disease. Studies by Dean Ornish have confirmed that a low-fat vegetarian diet has the potential to ‘reverse’ coronary artery disease.

Overall, the differences between the three categories of plant-based diets were less important than the differences between them and the conventional comparator diet. Based on the results the authors conclude that recommendations in clinical practice should include a plant-based diet comprised mainly of whole plant foods.

Accepting that there is a need for more high quality, randomised studies, the authors conclude that ”All motivated patients with type 2 diabetes and cardiovascular disease should be informed of the potential reversibility or at least halting of progression of these illnesses with comprehensive lifestyle modification that includes plant-predominant eating patterns”.

Health of Modern Day Vegan Children

This year has seen more scaremongering in the media around vegan diets for children, despite the fact that The Vegan Society works with the British Dietetic Association to show those who choose a vegan diet that well-planned vegan diets can support healthy living in people of all ages. We don’t have a great deal of contemporary data on the health of vegetarian and vegan children but the cross-sectional VeChi diet study from Germany has provided us with valuable and reassuring information. The previous report from this study cohort assessed the energy and macronutrient intake and growth of 430 children aged one to three years following either an omnivorous, vegetarian or vegan diet. There were no significant differences in calorie intake, height or weight between the different diet groups. Protein requirements were easily met. Fat and added sugar intakes were higher in children following an omnivorous diet and fibre intake higher in children following a vegan diet. Omnivores were also more likely to be overweight. The authors concluded ”Our results indicate that a vegan and vegetarian diet in early childhood provides comparable amounts of energy and a macronutrient pattern in accordance with recommendations and can ensure normal growth”.

This 2021 paper reported the anthropometric measurements, dietary intakes and nutritional status in a cohort of 149 vegetarian, 115 vegan and 137 omnivore children and adolescents between the ages of 6–18 years. The results showed that dietary supplement use was most common in vegan children with most taking vitamin B12 and D3 supplements. Iron supplementation was more common in the vegetarian group. Calorie intake did not differ between diet groups. Protein intake exceeded the recommended 0.9g/kg in all diet groups with carbohydrate intake higher in the vegan and vegetarian groups. Vegans had a lower intake of free sugar and saturated fat, but a higher intake of fibre and polyunsaturated fatty acids.

Micronutrient intakes differed between diet groups with vegans having the highest intakes of vitamin E, vitamin B1, folate, vitamin C, magnesium, iron and zinc. Intakes of calcium were lowest in vegans at 305g per 1000kcal, but calcium intake was below the reference range in all diet groups. Vitamin B2 (riboflavin) intake was also lower in vegans. It is worth noting that vegetarians had a lower than recommended vitamin B12 intake suggesting vegetarians, in addition to vegans, should be encouraged to take vitamin B12 supplements.

Looking at blood parameters, vegans had higher folate levels and lower total cholesterol, LDL-cholesterol and ferritin concentrations. Vitamin D3 and B2 were low in a notable proportion of participants regardless of diet groups. This is the first study to assess vitamin B2 levels in children and the clinical relevance of lower than recommended levels in not clear, but intakes can be optimised through the consumption of mushrooms, legumes, textured vegetable protein (TVP) or fortified plant-based dairy alternatives.

The paper highlights that the main nutrient that should be optimised in a vegan diet is calcium, especially given recent reports of increased risk of fractures in vegans. Nonetheless, the study concludes once again, ”The results of the VeChi Youth Study confirm the position of several national nutrition or paediatric societies that a vegetarian, including a vegan, diet can meet the recommended nutrient requirements in childhood and adolescence”.

On 12th December, I covered an additional paper from the same study cohort on micronutrient and fatty acid intakes in vegan children aged 1–3 years. The results confirmed that a well-planned vegan diet with appropriate supplementation can easily provide the necessary micronutrients with a more favourable profile of fatty acid consumption (more polyunsaturated fats rather in saturated fats). Special attention needs to be paid to calcium, iron and vitamins D, B12 and B2.

All in all, this is a very reassuring study supporting a healthy vegan diet as a healthy option for children.

More on Vegan Diets in Children

This is an extremely useful review of the data summarising both the benefits and cautions relating to raising vegan children. The take-home message is that, from the available data, it is likely that a vegan diet can provide all the necessary nutrients for normal growth and development of children with some clear advantages for cardiometabolic health.

The review included 437 publications and the authors assessed the adequacy of vegans’ diets to provide certain nutrients and to support growth and development. Starting with energy and protein intake, it’s clear that a vegan diet can provide sufficient calories and more than enough protein, often exceeding recommended intakes. Iron intake is often higher than recommended in vegan children, but because of the lower bioavailability this often translates into lower ferritin levels (stored iron) and is not necessarily a negative finding. Differences in haemoglobin levels and presence of iron deficiency anaemia are less obvious when comparing vegans to omnivores but iron status does seem to vary significantly between different studies. In general, calcium intakes in vegan children are lower than recommended as is vitamin D, although the latter remains an issue for all diet patterns. Vitamin B12 is not an issue when children are appropriately supplemented. Folate deficiency is a concern amongst omnivorous children and adults but, as would be expected, this is less of a concern in vegan children consuming a healthy diet.

Most studies confirmed that vegan children have growth rates well within the normal range. Some but not all studies have shown a slightly reduced height in younger vegan children, around 1–3 cm, compared to omnivores – it should be noted that our current normal ranges relate only to omnivorous diets and the impact of these small differences is unlikely to be clinically relevant or impact health outcomes. As expected, vegan children display a healthier body mass index than omnivorous children.

In the discussion, the authors go on to detail the numerous potential advantages of a vegan diet in children. These include the lower intake of saturated fat, the increased consumption of fibre and phytonutrients, and lower body weight and body fat. The authors conclude that there is still limited data on vegan diets in children and, as always, more studies are desirable. The authors state that with appropriate supplementation and attention to key nutrients, a vegan diet can support normal growth and development with some health advantages.

The Mediterranean Vs Vegan Diet

For the last four years the Mediterranean diet has been voted by top nutrition experts as the best diet for health in the US News and World Report survey. The vegan or plant-based diet loses marks for being restrictive and difficult to follow (I know that most vegans would disagree with this statement!). However, the Ornish diet (low-fat vegan) has been voted the top diet for heart health 10 years in a row. I am looking forward to the 2022 rankings!

Until this year we did not have a direct comparison between the Mediterranean diet and a low-fat whole food plant-based). Thankfully, the Physicians Committee for Responsible Medicine stepped in to conduct this unique study. 62 overweight adults were randomised to either a Mediterranean diet or vegan diet for 16 weeks. After a four week washout period in which participants returned to their baseline diet, they then crossed over to the alternate diet for a further 16 weeks. Both groups could eat as much as they wanted without calorie restrictions. The Mediterranean diet was executed as per the well-known PREDIMED study and included 50g of olive oil daily. The vegan diet was intended to be approximately 75% carbs, 15% protein and 10% fat from whole plant sources and a B12 supplement. Body weight, blood pressure (BP), body composition, insulin resistance and glucose tolerance were measured before and after each phase.

What were the results? The actual fat intake was 43% of calories in the Mediterranean group and 17% in the vegan group. Although participants could eat as much as they wanted, the vegan group consumed around 500 fewer calories per day. The vegan group also had a higher intake of fibre and lower intakes of saturated fat and cholesterol. The vegan group lost an average of 6kg but the Mediterranean group lost no weight. The vegan group also had significant reductions in body fat and visceral fat. The vegan group improved blood total and low-density lipoprotein (LDL)-cholesterol levels and insulin sensitivity with no change in the Mediterranean group. Both groups had reductions in BP but a greater effect was seen in the Mediterranean group. The Mediterranean group also had a greater reduction in triglyceride levels whereas the vegan group did not, although this did not reach statistical significance.

Overall, the vegan diet held its own against the Mediterranean diet with certainly more going in its favour in this comparison and definitely better for weight loss. The authors hypothesise that the greater reduction in BP in the Mediterranean group may have been due to more consumption of vitamin E in olive oil and its anti-oxidant function. Dairy, which is included in the Mediterranean diet, may have a BP lowering effect. It may have also been related to the nut consumption in the Med group. I wonder how the vegan diet would have fared with a daily tablespoon of flaxseed added.

This study is the only one of its kind so far as previous comparisons of a vegetarian/vegan diet with the Mediterranean diet have not been whole food or low fat. The Mediterranean diet has been compared with a vegetarian diet in a randomised study - the CARDIVEG study randomised 118 overweight participants with high blood lipids or glucose, but who were not on any medication, to either one of the two diet patterns. It was a three month intervention with both diet groups having the same but reduced calorie intake. Both diets were effective in reducing body weight, body mass index and fat mass, with no significant differences between them. There was no significant change between the groups in glucose and insulin levels and measures of insulin resistance. However, the vegetarian diet was more effective in reducing LDL-cholesterol levels, whereas the Mediterranean diet led to a greater reduction in triglyceride levels.

In a very small study comparing the vegan diet to the Mediterranean diet for cardiovascular health in young, healthy volunteers, the Mediterranean diet led to improvements in microvascular function and the vegan diet led to a greater reduction in total cholesterol and weight loss. It is worth noting that the vegan diet in this study was not a low-fat intervention, with participants consuming 35% of calories from fat. This level is similar to healthy eating guidelines, it’s important for everyone to include fat sources in their meals for the absorption of carotenoids and vitamins D, E and K. 

This paper contains a lot of detail, thus it is worth reading in full. All in all, this is a pretty reassuring study supporting a low-fat vegan dietary approach albeit in the short term. I would like to see a follow-up study of a healthy vegan diet including extra virgin olive oil, flaxseeds or nuts - or all three!

 More evidence for switching to plant-derived protein sources: This paper reported findings from the UK Biobank study and included almost 500,000 men and women, mostly white, who were followed for a median of eight years. Diet data was collected at recruitment and for 69,000 participants the diet data was collected at least a further three times.

The results suggested that consumption of red and processed meat at a level of 70g/day was linked to significantly increased 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/day was linked to increased 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 associations with 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 was linked with increased the risk of a number of these chronic diseases.

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

In my opinion,  there are multiple benefits of choosing plant sources of protein instead of meat, including the fact that animal products do not provide fibre. There are many plausible mechanisms that might explain an 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 iron and, of course, the lack of anti-oxidant and anti-inflammatory compounds in meat. If you are eating more meat, you are likely to be eating much less of the healthy plant foods that are associated with better health outcomes.

While there may be a higher risk of iron deficiency in this study in those consuming the least red meat, with some knowledge and skill it is perfectly possible to obtain enough iron from a plant-based diet. For example, eating plenty of lentils, beans, tofu, green leafy vegetables, cashews and dates are great ways of consuming non-heme iron. In fact, heme iron from animal foods is one of the reasons meat may increase the risk of heart disease and type 2 diabetes. Here is some excellent information on iron consumption from  The 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.

Which is the Best Source of Protein?

This is a much-needed study as it asks an important question by performing substitution analysis. In nutrition science, it’s not enough to ask what impact foods might have on health, we have to ask ‘compared to what?’.

The study included data from 29,682 participants from six US cohort studies followed for a median of 19 years and maximum of 31 years. Researchers determined the impact of protein source on CVD and all-cause mortality. They examined the impact of replacing eggs, processed meat, red meat, poultry and fish with nuts, legumes and whole grains.

The results showed that fish, nuts, legumes and whole grains, when used as substitutes for eggs, processed meat, red meat and poultry, significantly reduced the risk of CVD and all-cause mortality. Even swapping out one portion per week resulted in a benefit, with a greater benefit for daily replacement of these foods. There was a greater impact for those consuming the most animal foods. Overall, there was up to a 14% absolute reduction in CVD and premature death.

This is the first study to provide substitution analysis for all major sources of non-dairy protein and its association with CVD and premature death. 31% of participants were non-Caucasian, predominantly black and Hispanic. It is worth noting that consumption of legumes had a smaller than expected impact on outcomes, mainly because legume consumption was overall so low in these cohorts — a median of just 0.4 servings per week per 1000kcal. The authors summarise their data by stating ”Based on this study, nuts and whole grains appeared to be the healthiest, and eggs and processed meat the unhealthiest, sources of protein. Fish was found to be the single not unhealthy source of animal protein. Substituting two or more protein foods for other protein foods, even for a small amount such as one serving per week, was associated with appreciably lower risks of CVD and premature death”.

So, once again, plant sources of protein for the win. It would have been good to see a similar analysis for dairy protein consumption. In addition, although fish was not shown to be unhealthy in this analysis, there was no evidence to suggest fish consumption was necessary or contributing to good health, rather that it is just better than eating red and processed meat — no surprises here.

The Health Benefits of the Mighty Mushroom

Mushrooms are my top pick of health promoting foods of 2022 We already know mushrooms are a very healthy food. They are low in calories yet packed with nutrients, including phytochemicals (alkaloids, phenolic acids, flavonoids and carotenoids), fibre, selenium, vitamins (e.g. niacin, thiamin, riboflavin, ascorbic acid, and vitamins B and D) and important antioxidants ergothioneine and glutathione (thought to play a significant role in the prevention of cancer).

This year we have seen pretty convincing evidence of the true power of consuming mushrooms on a regular basis. This study brought together data from 17 observational studies, including 19,732 cases of cancer. Most of the studies were from Asian countries. The results showed that compared to those eating the least (less than once a week), those eating the most mushrooms (more than five times a week) had a 44% reduced risk of cancer, with benefits for breast cancer being most apparent.

In addition, a paper from the US reported a benefit of mushroom consumption on reducing the risk of death. The study included 15,546 participants followed for up to 20 years and found that people consuming mushrooms compared to those that did not had a 16% reduction in risk of death. This benefit was observed with as little as 10g of mushrooms per day with a dose-response observed (the more consumed, the greater the benefit) suggesting the association is indeed real. Consuming one serving of mushrooms per day instead of one serving of processed or red meats was associated with a 35% lower risk of death,a pretty remarkable finding!

So, mushrooms are a great addition to any diet pattern. I personally don’t worry about the individual foods I am eating but concentrate on eating a variety throughout the week but mushrooms are a must on the shopping list.

Animal Vs Plant Protein for Athletes

There is no doubt that athletes can thrive on a plant-based diet and animal foods are not necessary for optimal performance. It’s great to see this backed up by more and more scientific papers. This small but well conducted study investigated the impact of protein source on muscle mass and strength. 19 vegan and 19 omnivorous men undertook 12 weeks of supervised resistance training. Their protein intake was adjusted to obtain 1.6g/kg/day, including from protein supplements, either soya or whey. Various measures of muscle mass and strength, including muscle biopsies, were performed at the beginning and end of the study. The results showed that both groups had equal gains in muscle mass and strength, demonstrating that plant protein is not inferior to animal sources of protein.

The results of this study are in-keeping with a previous meta-analysis that demonstrated that soya protein was as effective as various sources of animal protein for building muscle mass and strength, but of course without increasing the risk of heart disease and cancer! Small studies have been conducted, including one that directly examined the heart function by echocardiography and maximum oxygen consumption of vegan and omnivore amateur runners. Each group had 22 participants and the results suggested better heart function and cardiorespiratory fitness and endurance for those on a vegan diet. Another study in young, physically active women tested endurance and muscle strength in 28 vegans and 28 omnivores and reported better exercise performance in the vegan group with no disadvantage for muscle strength.

So, in addition to numerous benefits for overall health, athletes who adopt a well-planned plant-based diet can expect to have no negative impact on athletic performance - with a chance that their performance will improve even further.

Plant-Based Diets and Risk and Severity of Covid-19

I have been keenly following the results of studies investigating the association between diet and COVID-19 outcomes. The findings are summarised with updates on the Plant-based health professionals UK COVID-19 webpage.

The paper highlighted reports results from the now famous Zoe COVID symptom study. The study 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, including its anti-inflammatory and anti-oxidant properties, the ability to maintain a healthy gut microbiome (and hence healthy immune system) and the reduction in underlying health 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 behaviours, social determinants of health, and virus transmission measures”.

It is worth reminding ourselves of this insightful editorial from 2020, rightly stating that nutrition is key to global pandemic resilience. I hope the international community starts to pay attention and act on these key findings.

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 the 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 migrant or refugee communities.

This paper examines county-level rates of COVID-19 in the US and whether the presence of large meatpacking 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 meatpacking 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 meatpacking 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 meatpacking 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”.

The harm caused to meatpacking workers and their families is tragic 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 if we are able to replace meat.

Sustainable Diets have Co-Benefits for Health and Climate

We were all hopeful that the COP26 conference would address the impact of animal agriculture on climate health given the overwhelming evidence demonstrating the harmful impact of the industry. Sadly, we were all disappointed. The evidence that a plant-based food system is one of the major solutions to the climate and ecological crises continues to grow.

This study analysed data 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 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 63% of all deaths and up to 40% of cancer could be prevented whilst at the same time reducing GHG emissions by up to 50% and land use by up to 62%. Any small shift towards the EAT-Lancet recommendations yielded significant benefits for health and planet.

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”. Note that the EAT-Lancet planetary health diet allows 13% of calories from animal-derived foods, amounting to around one portion of red meat, two portions of poultry and three 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 emissions by around 50%. Of course,   vegan diets are 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 were vegetarian or vegan. Meat and dairy-free diets could reduce food-related GHG emissions by up to 60%. The adoption of vegan diets globally has the potential to release 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.

Is a Plant-Based Diet More Expensive?

One of the barriers often cited to adopting a plant-based diet is the cost. To dispel this myth, certainly in high income countries, we now have this excellent study from Marco Springmann and the Oxford Martin Programme on the Future of Food. The researchers aimed to estimate the costs of healthy and sustainable diets around the world. The analysis included food costs from 150 countries and assessed the affordability of healthy and sustainable diet patterns, including flexitarian, pescatarian, vegetarian and vegan. In addition, the cost of diet-related illness and diet-related impacts on climate change were factored in, a novel aspect of this study. The costing also took into account regional preferences for certain foods.

The results showed that the average cost of diets in 2017, including food waste by households, was $5.7 per person per day (range $2.2–9.7). In low-income and lower-middle-income countries, staple crops accounted for the greatest proportion of costs (33–35%), followed by legumes and nuts (11–27%), meat (11%), vegetables (9–14%) and fruits (9–12%). In comparison, in high-income and upper-middle-income countries, meat accounted for the greatest proportion of costs (32–34%), followed by staples (18%), vegetables (11–24%) and fruits (8–9%). Food waste accounted for around 30% of costs.

In high income and upper-middle income countries, all dietary patterns - except for the pescatarian diets - were less expensive than current diets with the greatest reduction in cost for vegetarian and vegan diets (22–34% reduction in cost). In lower-middle-income and low-income countries, all dietary patterns analysed were more expensive (18–45%). The diet-related costs of climate change and healthcare increased the average cost of current diets by 16%, but taking into account the projected cost of food and changes to diet by 2050, the climate and health impacts of diet were projected to increase the cost of diets by up to 50%. The projected rise in cost was much lower with vegetarian and vegan diets.

Overall, vegetarian and vegan diets focusing on whole grains and legumes were the most affordable, whereas pescatarian diets focused on fish, fruits and vegetables were the least affordable. Fish as a food group had one of the highest prices per calorie.

Overall, the findings confirm that, in high and upper-middle income countries, adopting vegetarian or vegan diets would not only be healthier and better for the planet, but would be less expensive for households. Thus, government policy needs to incentivise these choices. In lower-income countries, development policies need to support the transition to a healthier, more diverse plant-based diet and counter the current trends of shifting to a Western diet pattern that is harming both personal and planetary health.

Plant-Based Diets are Becoming Mainstream

It’s wonderful to read that more and more people are now at least considering switching to a plant-based diet for personal and planetary health – and, of course, for the animals.

If you would like to learn more about nutrition, please visit the nutrition and health page of The Vegan Society website for regularly updated information and resources produced by our dietician team.


This article has been reproduced from the original source with permission. 

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