A review of the week’s plant-based nutrition news 11th April 2021

This week I cover plant-based diets for kidney disease, how nitrate-rich vegetables support muscle strength and function, the role of fruits and vegetables in preventing depression and how the corporate food system is fuelling deforestation.

PLANT-BASED DIETS AND KIDNEY DISEASE: We have come along way in a short period of time. Plant-based diets are more readily accepted as a way of preventing and slowing the progression of renal failure. A whole issue from the Journal of Renal Nutrition has a strong plant-based theme. A pioneer and advocate in the field Dr Shivam Joshi provides a comprehensive summary of the main themes and findings in this excellent editorial that accompanies the articles.

It is now accepted that a plant-based or plant-predominant diet where at least 50% of protein is derived from plant-based sources have the ability to ameliorate metabolic acidosis, delay the progression of chronic kidney disease, prevent hyperphosphatemia, reduce medication use, reduce the incidence of renal stones, reduce overall mortality and improve the health of the microbiome. Plant-based diets have the added benefit of preventing and reversing the two major causes of renal failure; type 2 diabetes and essential hypertension.

The concerns around high potassium and phosphate intake with a plant-based diet have been overstated. Dr Joshi explains that plant sources of phosphate are less bioavailable due to the present of phytates and actually the dietary phosphate most likely to contribute to blood phosphate levels comes from animal foods such as poultry, milk, beef and cheese, and phosphate additives in processed foods and fizzy drinks. Regarding potassium, there is little evidence that a healthy plant-based diet adversely impacts blood potassium levels.

As with all diseases, the health of the gut microbiome is also important for patients with renal failure. A small pilot study in this journal issue reported that a healthy plant-based diet has the potential to reduce the generation of uraemic toxins in patients with renal failure but an unhealthy plant-based diet may increase the level of these toxins. Rising TMAO levels in patients with renal failure, associated with an unhealthy gut microbiome, are associated with disease progression and an increased risk of cardiovascular disease and mortality. There is not yet much in the way of interventional studies addressing this issue but the evidence to date suggests that a plant-based diet may have the potential to reduce the risk of cardiovascular disease, mortality, and even progression of renal failure through a reduction in TMAO levels.

Overall, this Journal issue is well worth reading and provides new strategies for helping patients prevent and slow the progression of renal failure, in the words of Dr Joshi, ‘one meal at a time’.

WHOLE FOOD PLANT-BASED DIETS FOR CHRONIC KIDNEY DISEASE: This is an excellent resource for patients and healthcare professionals alike. Many patients are choosing to use plant-based diets to improve health and in the setting of renal failure this often needs support from a specialist dietitian. Once again the information on the benefits of a whole food plant-based diet for kidney failure are summarised. They include, lower protein content and hence less strain on the kidneys, the abundant antioxidants and anti-inflammatory compounds that help prevent progression of kidney failure, the lower absorption of phosphate that is beneficial, the alkaline nature of the diet compared to the more acid forming properties of animal foods and of course the lower risk of several common chronic diseases associated with kidney damage. There is also a patient information sheet to use in your clinical practice.

BENEFITS OF DIETARY NITRATES: We have all heard about the benefits of nitrate rich vegetables (mainly leafy greens and beetroot) for cardiovascular health. These dietary nitrates are converted to nitric oxide, which is essential for the health of endothelial cells that line blood vessels and help keep blood vessels dilated. Randomised studies have shown that regular consumption of beetroot juice is as effective as medication in reducing blood pressure in people with hypertension. Dr Esselsytn insists his patients eat (chewing well) nitrate rich vegetables, with vinegar to increase the activity of nitric oxide synthase, 6 times a day.

This study examined whether habitual nitrate intake affected muscle strength and function. The study included 3759 men and women from the Australian Diabetes, Obesity, and Lifestyle Study. Dietary intake was examined at least twice over a 12 year period from 2000–2012. In 2011/2012, muscle function was quantified by knee extension strength (KES) and the 8-ft-timed-up-and-go (8ft-TUG) test. Physical activity was also assessed by questionnaire.

The median intake of nitrates was 65 (52–83) mg/d, with 81% derived from vegetables. Participants in the highest tertile of nitrate intake (median intake: 91 mg/d) had 2.6 kg stronger KES (11%) and 0.24 second faster 8ft-TUG (4%) compared with individuals in the lowest tertile of nitrate intake (median intake: 47 mg/d). These results were statistically significant (P < 0.05). Physical activity level did not impact this association. The impact of nitrates reached a plateau at 90mg/d

These data help us understand the role of nitrates in the diet. Most prior studies have examined short term intake, but this study assessed longer term intakes. This same study group has previously shown that older women with higher nitrate intake have stronger hand-grip strength and faster TUG. Intakes of 90mg is easily obtainable with 1 cup of nitrate-rich green-leafy vegetables daily (e.g., raw spinach, ∼81 mg; rocket, ∼196 mg; or lettuce, ∼85 mg). This paper provides a database of nitrate content in vegetables.

The study concludes ‘Considering that poor muscle function is linked to numerous adverse clinical outcomes, including mortality and injurious falls, a diet with an abundance of nitrate-rich vegetables could be a novel strategy to promote muscle function. If supported by causal evidence, public health messages should continue to encourage higher vegetable intake, while highlighting the importance of nitrate-rich vegetables, such as green-leafy vegetables and beetroot, for musculoskeletal health to facilitate healthy aging’.

People often ask why the nitrates in vegetables don’t get converted to toxic N-nitroso compounds in the gut like the nitrates in processed meat. The low protein content of vegetables and the presence of anti-oxidant vitamins prevents this from happening.

FRUITS AND VEGETABLES CONSUMPTION FOR DEPRESSION: There is often scaremongering in the media about diets that avoid animal foods increasing the risk of mental health disorders. This could not be further from the truth. In fact, the same mechanisms that are at play that give rise to physical health problems contribute to mental health problems, namely inflammation. Therefore, plant-predominant diets are essential for mental health and well-being.

This study is again from the Australian Diabetes, Obesity, and Lifestyle Study with 4105 men and women followed for 12 years. Depressive symptoms were assessed using the validated 10-item Centre for Epidemiology Studies Short Depression Scale at 12 years follow-up. The results showed that 425 (10.4%) participants had some depressive symptoms. However, habitual fruits and vegetables consumption was inversely associated with depressive symptoms. Participants consuming a median of 317 g/day has a 20% lower odds of having any depressive symptoms in comparison to those in the lowest quartile of fruits and vegetable intake (median 223 g/day). Consuming more than around 250-300g per day did not provide further benefit. Yellow/orange/red and leafy green vegetables were the key vegetable types driving this association. Higher vegetable diversity (4–6 different vegetables/day) was associated with a 24–42% lower odds of having depressive symptoms when compared to < 3 different vegetables/day.

So once again, more fruits and vegetables with a diverse intake is best for mental well-being. Of course this shows association and not causation, however, this is a low cost, low risk intervention and 300g is no more than 4 portions a day. There are plausible mechanism since plant-rich diets are associated with a healthier gut microbiome, which is involved in regulating inflammation, immune responses and making brain active hormones such as serotonin. In addition, we know that people with depression tend to have lower levels of certain nutrients found in fruits and vegetables such as beta carotene, vitamin C, fibre, and folate, higher oxidative stress and anti-oxidant capacity. These results are also in keeping with the most recent meta-analysis of observational studies which shows a clear association with fruit and vegetable consumption and reduced risk of depression.

The authors conclude ‘These results suggest that a healthy diet rich in fruits and vegetables, with an emphasis on yellow/orange/red and leafy green vegetables, may benefit mental health’.

DEFORESTATION FOOTPRINT OF INDIVIDUAL NATIONS: Deforestation is a major contributor to the climate and ecological crises. It is mainly driven by the agricultural industry with forests cleared for cattle grazing and growing soya for animal feed but also by our demand for palm oil, coffee, chocolate and timber. As usual, richer nations are contributing the most to this problem which is occurring predominantly in poorer nations. For example, more than 90% of the deforestation footprint in UK, Germany, France, Italy and Japan is occurring abroad with around half from tropical forests. Even though some countries like China and India have curbed deforestation at home, they are outsourcing this deforestation to other countries by importing goods. In 2015, residents in the G7 countries each contributed to the loss of 3.9 trees.

Forests cover around a third of global land and are essential for sequesting carbon and protecting biodiversity. Deforestation is now the largest source of greenhouse gas emissions and the UN’s Food Agricultural Organisation estimates that only half the world’s forests are in tact. Most of this deforestation is occurring as a response to the global demand for meat, timber, and products that use palm oil.

As always, we can make an individual choice to change our purchasing habits and thus reduce the demand for deforestation. Eliminating meat from the diet and foods and products containing palm oil would be a great start. A nice summary of this study can be found here.

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