Review of the week’s plant-based nutrition news 21st March 2021
This week’s studies show cholesterol levels DO matter but a low-carb diet is deterimental to blood lipids; healthy plant-based diets can reduce risk of stroke; mushrooms are good for cancer prevention and red meat and eggs are best left off the plate.
LDL-CHOLESTEROL LEVELS DO MATTER: We have known for a long while that lowering LDL-cholesterol levels in those at risk of or who already have cardiovascular disease is beneficial. Yet what is is less clear is whether everyone, regardless of their individual risk, would benefit from low LDL-cholesterol levels.
This study used a type of design called mendelian randomisation where genetic variants of know function are used to investigate the impact of a particular exposures (genetically determined obesity or alcohol excess) on health outcomes in an observational study. This type of study design reduces the risk of bias and can control better for reverse causation and other confounding variables.
In the current study genetic variants that determine LDL-cholesterol level were analysed in over 1 million participants. The results showed that a higher genetically determined level of LDL-cholesterol is associated with a shorter lifespan. A 1 standard deviation increase in LDL-cholesterol level reduced lifespan by 1.2 years. Around 40% of this reduction is due to increased risk of ischaemic heart disease and stroke.
Although the authors do mention the impact of healthy diet, they go on to suggest that cholesterol lowering medication may be useful for the general population.
We have to be clear. Our genes are not our destiny. Diet and lifestyle habits have a much greater impact on blood cholesterol levels in the general population. We know that any stepwise elimination of animal products from the diet will reduce cholesterol levels without the need for medication. Vegans have the lowest cholesterol levels of any diet groups. The therapeutic Portfolio diet, created by Dr David Jenkins and colleagues, is a plant-based diet pattern proven to lower blood cholesterol. It includes foods known to lower cholesterol; soya protein, nuts, viscous fibre and plant sterols. For more information check out our cholesterol factsheet.
A LOW-CARB KETO DIET IN NOT GOOD FOR LDL-CHOLESTEROL LEVELS: A low carbohydrate diet remains popular for weight loss and blood sugar control. There are indeed some short-term benefits but long-term observational data show an increased risk of cardiovascular disease, cancer and early death. Sadly, their continue to be vocal proponents of this type of diet that in essence limits the consumption of some of the healthiest foods on the planet; fruits, beans and whole grains, whilst replacing these foods with meat and eggs. The only good aspect is the removal of refined carbohydrates and sugar and processed foods in general.
One concern is that this type of meat-heavy diet, high is saturated fat, increases blood cholesterol levels and thus longer term risk of cardiovascular disease. This small study in 24 healthy women of normal body weight were assigned to a 4 week ketogenic high fat low-carb diet (4% carbohydrates; 77% fat; 19% protein) followed by a 4 week National Food Agency recommended control diet (44% carbohydrates; 33% fat; 19% protein). They then crossover to the opposite diet. The low-carb diet consisted of meat, fish and seafood, eggs, high-fat dairy, coconut fat, olive oil, raspberries, avocado, nuts, and above ground vegetables such as broccoli and aubergine.
17 women completed the diet. Interestingly 5 people withdrew during the first week eating the low-carb diet with side effects such as headache, fatigue and nausea (n = 4), and feeling depressed (n = 1). One additional person dropped out after 15 days of the low-carb diet due to persistent feelings of fatigue, nausea, and abdominal pain.
The results showed that during the low-carb diet phase low in fibre and high in animal foods, there was a significant elevation in LDL-cholesterol level in every single woman, including the small dense particles which are considered to be more harmful and an increase in ApoB indicating an increase in the total number of atherogenic lipoproteins in the circulation.
The authors conclude ‘The elevated LDL cholesterol should be a cause for concern in young, healthy, normal-weight women following this kind of low-carb high fat diet’. You can read more about the low-carb diet in my article here.
PLANT-BASED DIETS AND STROKE: We have been worried about risk of stroke on a vegan or plant-based diet since the publication of the report from the EPIC-Oxford study in 2019. It showed that vegetarians and vegans had an increased risk of haemorrhagic stroke. This had not been shown before and other studies have not shown similar results. In fact, in the Tzu Chi Taiwanese cohort, veggie diets reduced the risk of stroke.
This new study reports data from the Nurses’ Health Study and Health Professionals Follow-up Study. More than 200,000 men and women followed for over 30 years. Diet data were analysed using the plant-based diet index, which gives positive marks to healthy whole plant foods and negative marks to unhealthy plant foods and all animal foods.
The results showed that participants consuming the best healthy plant-based diet had a 10% REDUCED risk of stroke (ischaemic and haemorrhagic combined). There was no signal that plant-based diets increased risk of haemorrhagic stroke.
The advantage of this study over those conducted in vegans is that the quality of the diet is assessed. We know from a number of sources that eating fruits, vegetables and whole grains reduces the risk of stroke. In contrast processed plant-based foods can increase the risk of chronic diseases.
This study should allay fears around the the risk of stroke and once again emphasises that the quality of a plant-based diet is key to reducing disease risk. Check out my article on stroke.
MUSHROOMS AND CANCER: We already know mushrooms are a very healthy food. They are low in calories yet packed with nutrients, including phytochemicals (alkaloids, phenolic acids, flavonoids, carotenoids), fibre, selenium, vitamins (e.g., niacin, thiamin, riboflavin, ascorbic acid, and vitamins B and D) and important antioxidants ergothioneine and glutathione that are thought to play a significant role in the prevention of cancer.
So how good are mushroom for cancer prevention? 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 5 times a week) had a 44% reduced risk of cancer, with benefits for breast cancer being most apparent.
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.
FOOD ALLERGY IN THE UK: In the UK there are 14 allergens that need to displayed on food labels as they are common causes of allergy, intolerance or anaphylaxis. The 14 allergens are: celery, cereals containing gluten (such as barley and oats), crustaceans (such as prawns, crabs and lobsters), eggs, fish, lupin, milk, molluscs (such as mussels and oysters), mustard, peanuts, sesame, soybeans, sulphur dioxide and sulphites (if they are at a concentration of more than ten parts per million) and tree nuts (such as almonds, hazelnuts, walnuts, brazil nuts, cashews, pecans, pistachios and macadamia nuts).
This large study analyses hospital admissions over a 20 year period in the UK for anaphylaxis. 101,891 people were admitted during this time period. Numbers of admissions increased over the time period with the largest increase in children less than 15 years. 152 deaths were probably caused by food induced anaphylaxis. 86 of 187 (46%) of deaths were triggered by peanut or tree nut. Cow’s milk was responsible for 17 of 66 (26%) deaths in school aged children.
Conclusion: ‘In school aged children, cow’s milk is now the most common single cause of fatal anaphylaxis’
It’s interesting that schools and parents go to great lengths to avoid exposing children to nuts yet cow’s milk continues to be considered essential and actively promoted. Why is this ? A rhetorical question of course.
Cow’s dairy is not essential in the diet for children or adults. Let’s get away from dairy for our health and that of the planet. Great to see that Scotland is now offering plant-based mylk options in schools too.
CARDIOVASCULAR HARM FROM EGGS AND MEAT: This much needed review cuts through the noise and explains the ongoing confusion about red meat and eggs in the diet. The review explains that the reason some studies show no harm of meat and egg consumption is ‘wholly or in part by the low risk and young age of the participants; confounders such as smoking, socioeconomic status, and reverse causality; and unmeasured confounders.’ The review explains the impact of industry influence on study results too.
There are many ways red meat and eggs (mainly the yolk) can cause harm. There is a clear relationship with elevated cholesterol levels and also the generation of toxic metabolites from gut bacteria through metabolism of carnitine and choline. These foods most certainly increase the risk of cardiovascular disease, type 2 diabetes and renal failure. White meat is not given a green light here but has 4 x less carnitine than red meat and hence less generation of toxic metabolites in the gut.
The review summarises the benefits of a plant-based diet and confirms the harms of a low-carb diet approach when it emphasises animal foods. The authors conclude ‘Egg yolk and red meat should be avoided, and meat intake limited, to prevent cardiovascular disease and stroke. Adopting a more plant-based diet would also improve the sustainability of food sources and reduce harm to the environment from a meat-based diet’ Please do read this open access article.
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