A review of the week’s plant-based nutrition news 15th August 2021
This week I cover important studies on diet and cardiovascular disease, a review of ketogenic diets, B12 supplementation in vegans and the latest IPCC report on climate change.
PLANT-BASED DIETARY PORTFOLIO AND CARDIOVASCULAR DISEASE (CVD): We have known for many years that diets which emphasise whole plant foods (fruits, vegetables, whole grains, beans, nuts and seeds), whilst limiting or avoiding animal and processed foods, significantly reduces the risk of CVD, particularly ischaemic heart disease. This is one of the major advantages of a vegetarian and vegan diet. The greater the elimination of animal foods, the greater the reductions in blood pressure and cholesterol, major risk factors for CVD. In addition, this type of diet reduces the risk of type 2 diabetes, another major cause of CVD, by up to 50%.
We now have two more studies highlighting the importance of plant foods for prevention of CVD. The first study highlighted is from the well known Women’s Health Initiative cohort conducted in post-menopausal women in the US. The current analysis included 123,330 women followed for a median of 15 years and evaluated whether or not diets that included a dietary portfolio of plant-based foods with U.S. Food and Drug Administration-approved health claims for lowering cholesterol levels (known as the “Portfolio Diet”) were associated with fewer CVD events.
The Dietary Portfolio, or Portfolio Diet, is a plant‐based dietary pattern that was developed in the early 2000s by Dr David Jenkins and his research team to lower low‐density lipoprotein cholesterol (LDL‐C). The basis of the diet is that it is low in saturated fat and cholesterol with the addition of a “portfolio” of four cholesterol‐lowering foods and nutrients: nuts, plant protein (soya and pulses), viscous fibre (oats, barley, psyllium, eggplant, okra, apples, oranges, and berries), and phytosterols (originally provided as enriched margarine). A modification of the diet includes adding monounsaturated fats (such as sunflower/olive/canola oil or avocado). Results from a controlled randomised controlled trial showed that the Portfolio diet lowered LDL‐C to a similar degree to the control diet taken with 20mg lovastatin (−28.6% versus −30.9%). A systematic review and meta‐analysis of controlled trials showed that the Portfolio Diet significantly lowered LDL‐C by 17% and other CVD risk factors, including non‐high‐density lipoprotein cholesterol by 14%, apolipoprotein B by 15%, and C‐reactive protein by 32%. Up and till now, it was not known whether these reported benefits translated into a lower risk of CVD events, such as heart attacks, strokes and heart failure.
The results of the current study showed that women most adherent to the Portfolio Diet had an 11% reduced risk of developing any type of CVD, 14% reduced risk of coronary heart disease and 17% reduced risk of developing heart failure. There was a dose-response effect, such that the greater the adherence to the dietary portfolio the greater the reduction in risk of CVD. There was no association between following the Portfolio Diet and the occurrence of stroke or atrial fibrillation.
This is the first time a study has evaluated the impact of the Portfolio diet on prevention of CVD. The authors highlight that this diet pattern also benefits from having a small ecological footprint, emphasising plant‐based components with low environmental impact (eg, legumes, oats, barley, temperate fruit, etc). They conclude ‘Given the increased interest in plant‐based foods and diets around the world, and growing concerns related to ethical and environmental implications of diet, the Portfolio Diet warrants attention from healthcare professionals as another therapeutic dietary approach for cardiovascular disease risk reduction’.
PLANT-BASED DIETS AND CVD IN YOUNGER ADULTS: This study examined whether long-term consumption of a plant-centred diet and a shift towards such a diet starting in young adulthood is associated with a lower risk of CVD in midlife. The study included 4,946 adults enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study, aged 18- to 30-years, free of CVD at the time of enrolment (1985–1986), and followed for a median of 32 years. This study included similar numbers of white and black men and women. The quality of the participants diets was scored based on the A Priori Diet Quality Score (APDQS) composed of 46 food groups and calculated at years 0, 7 and 20 of the study. The food groups were classified into beneficial foods (fruit, avocado, beans/legumes, green vegetables, yellow vegetables, tomatoes, other vegetables, nuts and seeds, soya products, whole grains, vegetable oil, fatty fish, lean fish, poultry, alcohol (beer, wine, and liquor), coffee, tea, and low-fat milk/cheese/yogurt); adverse foods (fried potatoes, grain dessert, salty snacks, pastries, sweets, high-fat red meats, processed meats, organ meats, fried fish/poultry, sauces, soft drink, whole-fat milk/cheese/yogurt, and butter); and neutral foods (potatoes, refined grains, margarine, chocolate, meal replacements, pickled foods, sugar substitutes, lean meats, shellfish, eggs, soups, diet drinks, and fruit juices) based on their known association with CVD. The difference between this diet quality score and the plant-based dietary index is the latter gives negative marks to all animal-derived foods, whereas the APDQS makes allowances for small amounts of animal foods such as fish and poultry and also alcohol.
The results showed that those with higher APDQS scores and thus a higher consumption of the foods in the healthy category had a 52% reduction in the risk of developing CVD, after adjusting for potential confounding factors. In addition, between year 7 and 20 of the study when participants ages ranged from 25 to 50, those who improved their diet quality the most (eating more beneficial plant foods and fewer adversely rated animal products) were 61% less likely to develop subsequent CVD, in comparison to the participants whose diet quality declined the most during that time.
The authors conclude ‘Our findings are consistent with assertions that a nutritionally rich plant-centred diet help prevent the development of cardiovascular disease. However, it appears that the complete exclusion of animal foods from diet is not necessary’. I do agree with these conclusions but the authors fail to acknowledge that animal foods are not essential in the diet and that it is perfectly possible to optimise cardiovascular health on a 100% plant-based diet. I acknowledge that this viewpoint plays into my own bias and that more people will align with the moderate recommendations of the study, more plants and less animal foods.
RISKS AND BENEFITS OF THE KETOGENIC DIET: This is an excellent and comprehensive review of ketogeneic diets, a type or low-carb diet that minimises carbohydrate intake to 10–25% of energy, replacing it predominantly with fat and in some protocols higher amounts of protein. The data supporting a keto diet are strongest for the treatment of drug-resistant epilepsy but more recently has been used as a treatment for weight loss and type 2 diabetes. In the short term there is no doubt that this type of diet pattern can have some benefits. The problems arise with the potential side effects, the difficulty of sustaining such a diet and longer-term adverse health outcomes when carbohydrates are replaced with animal sources of fat and protein.
The premise of such a diet is to alter the primary source of fuel of the body from glucose, derived from carbohydrates, to ketones, derived from fat metabolism. In the short-term there is also loss of water (which is stored with glycogen and lost as glycogen stores are used up) and loss of lean muscle mass, as protein is utilised to make glucose. This contributes to the initial weight loss but losing muscle mass is clearly not desirable. With an extreme keto diet there is undoubtably a deterioration in diet quality as healthy carbohydrate-rich foods such as starchy vegetables, beans and whole grains are eliminated from the diet with consumption of many fruits limited too. This can lead to micronutrient deficiencies and the need for supplements. The resulting low fibre diet adversely affects the health of the gut microbiome.
Low-carb and keto diets can be effective at supporting weight loss, in part due to appetite suppression and also due to the initial water and muscle loss. The most recent meta-analysis comparing the short-term impact of a low-fat to a low-carb diet (6–12 months duration) found in favour of the low-carb diet but with a mean weight difference of only 1.3kg and with the detrimental effect of raising LDL-cholesterol levels. For type 2 diabetes, the Scientific Advisory Committee on Nutrition in the UK have thoroughly reviewed the literature on lower carbohydrate diets and concluded that there may be benefit in the short-term (less the 6 months duration) for blood sugar control but reported that their are no longer term data to support this diet pattern which can be difficult to sustain and adversely impacts the overall quality of the diet. It also recommends that those eating a low-carb diet should still aim to consume 30g or fibre a day and emphasise the consumption of fruits, vegetables and whole grains (a bit of a contradiction).
The data suggests that the potential longer term harms from a low-carb or keto diet make such a diet difficult to recommend. Evidence shows that a diet high in animal fat and protein puts extra strain on the kidney and increases the risk of renal failure with plant-based diets reducing the risk. There is also an increased risk of cardiovascular disease, in part due to the elevation in LDL-cholesterol, increased risk of cancer and premature death. In pregnancy, the review describes the increased risk of neural tube defects. These side effects are in part because the diet drastically reduces, if not eliminates, some of our healthiest foods, fruits, vegetables, whole grains and beans, which we know help prevent these chronic diseases.
Some key studies that helps us understand the differences between a plant-based diet and an animal-based keto diet comes from Dr Kevin Hall’s team at the National Institute of Health. He conducted a study in 17 participants who were admitted to a metabolic ward where all the food was provided, and detailed metabolic tests were performed. The study found that a ketogenic diet was associated with an increase in markers of inflammation and in LDL-cholesterol and did not improve insulin sensitivity or glucose regulation. A subsequent metabolic ward study from the same research team tested a plant-based diet head-to-head with a low-carb animal-based diet. For this particular study, participants could eat as much as they wanted. On the plant-based diet, participants naturally consumed significantly less calories. Both diets led to improvements in fasting glucose and insulin levels, but the plant-based diet resulted in greater weight and body fat loss and improvements in cholesterol levels. The low-carb group lost mainly water weight and muscle mass, developed a degree of insulin resistance and a rise in LDL-cholesterol levels. The low-carb diet did improve triglyceride levels, which worsened on the plant-based diet.
An animal-based keto diet is unsustainable for the planet, which is now at crisis point. Therefore, it’s recommendation in my view is wholly unethical. In the words of Dr David Katz ‘without a healthy planet their are no healthy people’. If you do want to try a lower carb diet it may be better to do so in the context of a plant-based diet, increasing plant-derived fats and protein. Dr David Jenkins has pioneered the Eco-Atkins diet, a plant-based low-carb diet, which may indeed have some benefits over a higher carb plant-based diet. However, we still need longer term studies to truly understand the impact on health outcomes.
VITAMIN B12 SUPPLEMENTATION IN VEGANS: Vegans and those on a 100% plant-based diet require a regular and reliable source of vitamin B12. The easiest way to obtain vitamin B12 is by taking a supplement. There are different formulations and dosing schedules that can be used. The most common forms are cyancobalamin (cyanCbl) and methylcobalamin (methylCbl). MethylCbl is the active form of the vitamin but it is still disassembled by the body after consumption and then reassembled prior to use. CyanCbl is a synthetic compound that is more shelf stable but requires conversion to the active form prior to use in the body. There may be some very rare reasons why a cyanide containing form of B12 is not desirable, for example in severe renal failure. Overall, there does not seem to be superiority of one form over the other in terms of how the body utilises it. Vitamin B12 binds to transcobalamin (holoTC) and is thereby available for use by cells. HoloTC is a much better predictor of B12 status than total B12 and becomes reduced prior to any clinical consequences of B12 deficiency. Vitamin B12 absorption is an extremely complex process and it is known that the intake of supplements is optimal either in lower and more frequent doses (when absorption is mainly achieved with the help of intrinsic factor), or in high doses, 1‑2 times a week (when absorption with intrinsic factor is saturated and absorption relies on passive diffusion).
This study included 42 vegans, 25 men and 17 women, with an average age of 34 years and investigated the effectiveness of two forms of vitamin B12 in maintaining holoTC within the normal range. The participants fell into 3 groups based on the type of vitamin B12 supplementation. Vegans who supplemented with cyanCbl (group 1, n=21), vegans who supplemented with methylCbl (group 2, n=14) and vegans who supplemented with products identified as ‘natural’ and about which they read/think are rich in B12 (algae, kombucha, borscht, yeast) (group 3, n=7). The impact of frequency of supplementation was also investigated.
The results showed that holoTC values were significantly higher in the group that supplemented using cyanCbl. Frequency of consumption was also a factor in predicting holoTC levels, with those supplementing daily having a higher level compared to those supplementing 1–2 times per week. HoloTC levels were much lower in group 3 (natural forms).
On the basis of these results, it appear that cyanoCbl taken daily is the best way to obtain vitamin B12 on a vegan diet. The usual recommended dose is 25–250mcg per day as an oral tablet with older adults requiring higher doses. Sublingual formulations and forms that dissolve in the mouth (chewable) are available but it is not clear from the available data whether these are superior to tablet formulations.
OUR HOUSE IS ON FIRE: The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the UN, consisting of leading climate scientists from around the globe, formed in 1988, to provide objective, science based information on the climate, the role of humans in climate change, its impacts and response options. Its first report in 1990 warned of the consequences of rising greenhouse gas emissions, and led to the UN Framework Convention on Climate Change, the parent treaty to the 2015 Paris Agreement. The 3949 page, first part of their 6th report has just been released. Part 2 on the impacts of the climate crisis and part 3 on ways of reducing those impacts will be released next year.
To say the news is not good would be an understatement. António Guterres, the UN secretary general, calls this ‘a code red for humanity’.
It is ‘unequivocal’ that human activity has warmed the atmosphere, the ocean and the land on a scale that is ‘unprecedented’ over thousands of years. Already human-induced climate change is affecting many weather and climate extremes in every region across the globe. Many changes due to past and future greenhouse gas emissions are ALREADY IRREVERSIBLE for centuries to millennia, especially changes in the ocean, ice sheets and global sea level. The biggest contributors to the ongoing rising greenhouse gas concentrations are fossil fuel use, land use change and agriculture.
We know that animal agriculture, in addition to its contribution to greenhouse gas emissions, is the biggest driver of wildlife and biodiversity loss, species extinction, land use change and land degradation, deforestation, freshwater use, water pollution and ocean destruction. The terrible impact of climate change and ecosystem destruction on our planetary life support systems has led to an unprecedented threat to the survival of the human species.
The goal to limit warming to 1.5 degrees C over pre-industrial levels is still possible, but only with rapid and drastic reductions in greenhouse gases in this decade. One of the solutions has to be a global shift to a plant-based food system.
Thank you to Plant Based Canada for providing this summary
Read more from Seed The Commons on how the global community can change the course of this impeding disaster and find a way back to restoring health. ‘To avert climate disaster, significant investment must be made to support small veganic farmers and in promoting and rapidly transitioning farmers to sustainable agricultural models, with proportional divestment of subsidies and other public funds from animal agriculture’.