A review of the weeks plant-based nutrition news 6th October 2019
New ‘guidelines’ suggest that there is no need to reduce consumption of red and processed meat? WHAT! Five new systematic reviews and meat-analyses were published in Annals of Internal Medicine and based on the results dietary recommendations have been made. Here are some of the salient points and hopefully you can see that the correct conclusion still remains that processed and red meat consumption should be minimised or eliminated completely.
a. This guideline is NOT based on a new study or data but reanalysis of existing data. There are 5 systematic reviews and meta-analyses and 3 of them continue to show negative health effects of consuming processed and red meat, with statistically significant association of lower consumption of red meat and processed meats and lower total, cardiovascular disease (CVD), and cancer mortality and incidence of type 2 diabetes. However, the authors conclude that the quality of the data is low and the effect size is small.
b. The method used to judge the quality of evidence — GRADE — was not designed for judging nutritional science but for randomised studies involving pharmaceutical drugs, so the methodology is hugely flawed. If the same methodology was used to examine the effects of smoking and lung cancer, sugar and heart disease, fruit and veg consumption and health etc then we would still be denying that smoking and sugar consumption are bad for health and fruit and veg consumption good for health.
c. An analysis of the health benefits of reducing red and processed meat consumption by 3 portions/week concluded that this small reduction only led to small benefits. Nonetheless, their analysis still showed that this small reduction in processed and red meat consumption would lower total mortality by 13% , CVD mortality by 14%, cancer mortality by 11% and type 2 diabetes risk by 24%. At a population level this is a hugely significant effect. Also, the effect size would be greater if the consumption of red and processed meat was limited to 1 or less servings a week. Of course small changes result in smaller benefits. It’s like saying if you cut the number of cigarettes smoked from 20 per day to 15 per day you will only derive a small benefit therefore just keep smoking!
d. One of the papers examined whether people enjoyed eating meat and their preferences for continuing to eat red and processed meat. The report states that based on their analysis people do not want to stop eating meat and therefore it may not be acceptable for the medical profession to advise limiting consumption of red and processed meat. WHAT!! We shouldn’t tell people the truth because they don’t want to hear it !!
e. One systematic review examined the effects of long-term red meat reduction trials on health outcomes. However, no such trial has ever been conducted. Two randomized studies that examined long-term health outcomes were identified, but neither were relevant because they were not actually meat reduction trials. The reviews do not included any of the data on plant-based diets or studies including vegetarian and vegans who don’t eat red and processed meat at all.
f. This advice goes against every national and international recommendation on the consumption of red and processed meat without there being any new data to support this new guideline. The WHO classifies processed meat as a group 1 carcinogen (it causes cancer) and red meat a group 2A carcinogen (probably causes cancer). The American Heart Association, the World Cancer Research Fund, the WHO and Public Health England have all concluded that the less red and processed meat eaten the better for human health.
g. The guidelines accept that they have not taken into account the ethical or environmental consequences of their recommendations to continue eating red and processed meat. Given that we have reached a point of climate catastrophe and that animal agriculture is one of the leading causes of green house gas emissions, deforestation, loss of biodiversity, ocean dead zones….. this is wholly irresponsible.
h. One of the lead authors failed to declare previous funding from the food industry and thus potential bias. In addition, not all of the authors even agreed with the conclusions of the review.
All in all, recommendations have not changed. Limiting red and processed meat consumption is most certainly beneficial for health. Many reputable institutions and nutrition scientists have written to the Annals of Internal Medicine to withdraw these papers. Here are links to some of these articles and you can also support calls for withdrawal of these guidelines by signing the petitions. Harvard School of Public Health, Sign the petition from the World Cancer Research Fund, PCRM have filed a federal petition, Dr Steven Lome Cardiologist.
LOW CARB DIET. WHAT DOES THE SCIENCE TELL US? The National Lipid Association has reviewed the evidence for low-carbohydrate and very low-carbodydrate diets (including ketogenic diets) for weight loss and cardiometabolic risk factors and written a statement based on their findings. These are the take home messages from their press release;
- Low- and very-low-carbohydrate diets, including ketogenic diets, are not superior to other weight loss diets and may severely restrict nutrient-dense foods that offer cardiovascular benefits.
- While they may have advantages on appetite and reducing triglyceride levels and diabetes medication use, current evidence showed mixed effects on low-density lipoprotein cholesterol levels.
- There is no clear evidence for advantages related to other cardiometabolic risk markers.
- While some patients prefer a low-carbohydrate eating pattern, which may be reasonable for short periods of time (<6 months), long-term compliance is challenging, and long-term benefits and risks are not fully understood.
- Regardless of the weight loss strategy chosen, a patient-clinician discussion about the risks and benefits and patient preference is of vital importance, since many patients follow the diets without medical supervision, which can increase the risk of adverse effects.
Some further points of clarification include;
🌱there may be some short term advantages in preventing weight gain but the initial weight loss is due to water loss and there is a greater loss of lean muscle mass. There is no advantage over other diet patterns in the short or long term.
🌱Effects on blood cholesterol and LDL is variable with some having a rise in LDL due to high intakes of saturated fat. Triglycerides levels do fall and HDL levels rise, although the latter is not maintained in the longer term.
🌱No advantage for type 2 diabetes when compared to low fat diets but there is a short term advantage in helping people get off diabetes medication. Short term gains do not translate to a greater benefit at 1 year.
🌱Effects on BP are inconsistent and most studies do not show an advantage for those with hypertension.
🌱No advantage for lowering CRP, a marker of inflammation, and negative changes in the gut microbiome, including greater generation of TMAO, which is implicated in the pathogenesis of CVD, type 2 diabetes and renal failure.
🌱low carb diet associated with INCREASED risk of DEATH, adverse side effects and people find it difficult to adhere to in the longer term.
AUTHORS CONCLUSIONS: patients should be encouraged to eat a diet composed of fruits, vegetables, whole grains, legumes, nuts and seeds due to consistent long term benefits for health. This diet pattern can also be lower carb if desired with the help of a dietitian.
MY CONCLUSIONS: don’t risk long term health for inconsistent short term gains because it feels like the easier choice. It is not worth the gamble.
NUT CONSUMPTION AND LONG TERM WEIGHT CHANGE; Published in BMJ nutrition, this study analysed data from three prospective, longitudinal cohorts among health professionals in the US. It included 27 521 men (Health Professionals Follow-up Study, 1986 to 2010), 61 680 women (Nurses’ Health Study, 1986 to 2010), and 55 684 younger women (Nurses’ Health Study II, 1991 to 2011). The study examined the association between changes in nut consumption over 4-year intervals and concurrent weight change over 20–24 years of follow-up. The average weight gain across the three cohorts was 0.32 kg each year. Increases in nut consumption, per 0.5 servings/day (14 g), was significantly associated with less weight gain per 4-year interval −0.19 kg for total consumption of nuts, -0.37 kg for walnuts, -0.36 kg for other tree nuts, and -0.15 kg for peanuts. Increasing intakes of nuts, walnuts, and other tree nuts by 0.5 servings/day was associated with a lower risk of obesity. In substitution analyses, substituting 0.5 servings/day of nuts for red meat, processed meat, French fries, desserts, or potato, chips (crisps) was associated with less weight gain (p<0.05 for all). The study concludes; ‘Our results indicate that increased consumption of total nuts or any types of nut (including peanuts) is associated with less long-term weight gain, despite being calorically dense. Incorporating nuts as part of a healthy dietary pattern by replacing less healthful foods may help mitigate the gradual weight gain common during adulthood, and beneficially contribute to the prevention of obesity. Our findings support food-based dietary recommendations and support the incorporation of nuts as an effective strategy for making attainable dietary modifications for the primary prevention of obesity’.
What are the potential mechanisms for these findings? Nuts require considerable chewing and this process may help reduced consumption of food in general. The high fibre content of nuts can delay gastric emptying, increase satiety, suppress hunger and the desire to eat, and promote fullness. The fibre in nuts can bind fatty acids in the gut, leading to greater faecal excretion and hence calorie absorption. A number of studies have examined the efficiency of energy absorption from nuts and have shown that consumption of varying types of nuts resulted in substantive increases in faecal energy loss ranging from 5% to >20%. There is evidence that the high unsaturated fat composition of nuts elevates fatty acid oxidation and increases thermogenesis and resting energy expenditure, which may also contribute to the mitigation of weight gain.
So all in all, unless you have a nut allergy, a portion of nuts a day (30g serving) forms a healthy and nutritious part of a whole food plant-based diet.
MATERNAL NUTRITION DURING PREGNANCY; There is plenty of evidence that maternal nutrition before and during pregnancy and paternal nutrition pre pregnancy has an impact on the health outcomes of the child. This study examined the effect fruit and vegetable consumption during pregnancy and the effect of childhood behavioural problems. It included 1199 Japanese mothers and babies. Intake of total vegetables, green yellow vegetables and other vegetables were associated with 40–45% lower risk of low prosocial behaviour (behaviours that benefits others and society such as helping, donating, sharing), while other vegetables were also associated with 45% lower risk of hyperactivity problems. Total fruit, apples and citrus fruits were associated with lower risk of hyperactivity problems (34–45%), while citrus fruits were also associated with lower risk of emotional problems (39%) and conduct problems (57%). Higher maternal vitamin C intake during pregnancy was independently inversely associated with the risk for conduct and hyperactivity problems and low prosocial behavior in the children.
The study concludes;
Maternal intake of citrus fruit during pregnancy may be preventive against emotional problems.
Maternal intake of citrus fruit and vitamin C during pregnancy may be protective against conduct problems.
Maternal intake of other vegetables, total fruit, apples, citrus fruit, and vitamin C during pregnancy may be preventive against hyperactivity problems.
Maternal intake of total vegetables, green and yellow vegetables, other vegetables, and vitamin C during pregnancy may be protective against low prosocial behavior in children at the age of 5 y.
What are the potential mechanisms? Fruits and vegetables contain thousands of anti-oxidant compounds, including vitamin C. The ability of these anti-oxidants to scavenge reactive oxygen species in the developing brain may be beneficial. Vitamin C is required for normal development of the brain and plays a role in many signalling pathways in the brain.
DRINKING SUGARY BEVERAGES INCREASE THE RISK OF TYPE 2 DIABETES; This study followed up 76,531 women in the Nurses’ Health Study (1986–2012), 81,597 women in the Nurses’ Health Study II (1991–2013), and 34,224 men in the Health Professionals’ Follow-up Study (1986–2012). Changes in beverage consumption (in 8-ounce serving/day) were calculated from food frequency questionnaires administered every 4 years. During 2,783,210 person-years of follow-up, 11,906 cases of type 2 diabetes were documents. After adjustment for BMI and initial and changes in diet and lifestyle covariates, increasing total sugary beverage intake (including both sugar-sweetened beverages and 100% fruit juices) by >0.50 serving/day over a 4-year period was associated with a 16% higher diabetes risk in the subsequent 4 years. Increasing artificially sweetened beverage (ASB) consumption by >0.50 serving/day was associated with 18% higher diabetes risk. Replacing one daily serving of sugary beverage with water, coffee or tea, but not ASB, was associated with a 2–10% lower diabetes risk. Thus, increasing consumption of sugary beverages or ASBs was associated with a higher risk of type 2 diabetes. Of course this does not prove cause and effect and certainly for consumption of ASB the possibility of reverse causation (individuals already at high risk for diabetes may switch from sugary beverages to diet drinks) can not be excluded.
These findings were independent of weight and therefore other mechanisms may be at play. We know that consumption of free sugar can adversely affect the blood lipid profile and this can increase the risk of insulin resistance. Artifically sweeteners adversely affect the gut microbiome and result in glucose and hormone dyregulation that again can increase the risk of insulin resistance. Of course, the consumption of sugar sweetened beverages often goes hand in hand with other potentially unhealthy food habits, such as the consumption of unrefined grains and foods high in saturated fat.
The common sense advice remains, drink mainly water for thirst and include tea and coffee if you enjoy these drinks. If you are going to drink fruit juice, make it occasional and limit to 150mls per day.
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