Review of the week’s plant-based nutrition news 1st November 2020
This week I cover studies on sugar- and artificially-sweetened beverages, benefits of flavanols, cancer prevention and the impact of animal agriculture on nitrous oxide emissions.
SUGAR-SWEETENED BEVERAGES (SSB)DURING BREASTFEEDING: This study investigated the association between SSB consumption during breastfeeding and neurodevelopment in infants at 24 months. 88 mother and baby pairs were recruited and dietary data collected at 1 and 6 months postpartum along with rates of breastfeeding. Fructose consumption was specifically analysed. Mothers who reported greater consumption of SSBs and juices had children with worse cognitive development scores. The researchers speculate that added sugar/fructose from the mothers diet was passed to their infant through breast milk, and this exposure could potentially interfere with brain development.
The introduction of SSBs into the diet has really been a disaster for human health and this study highlights the extent of this harm. SSBs are any drink that is sweetened using a form of added sugar, including brown sugar, corn sweetener, corn syrup, dextrose, fructose, glucose, high-fructose corn syrup, honey, lactose, malt syrup, maltose, molasses, raw sugar, and sucrose. SSBs make up a significant proprotion of free sugar consumption in many countries. Although in general consumption of free sugar, including SSBs, has fallen in the UK amongst both adults and children, it remains higher than the recommended <5% of total energy/calories. Both children and adults are consuming more than 10% of calories from free sugar and around a third and a fifth of this sugar in adults and children, respectively, comes from SSBs (including fruit juices). Regular consumption of SSBs is associated with increased risk of overweight/obesity, type 2 diabetes, heart disease, kidney disease, non-alcoholic liver disease, tooth decay and cavities, and gout.
The harm from free sugar consumption seems to come predominantly from fructose. Here we are talking about free fructose and not fructose found in whole fruits and vegetables. The main sources of fructose in the diet that are contributing to harm are from table sugar (or sucrose, which is 50% glucose and 50% fructose) and high fructose corn syrup (sweetener made from corn starch and ubiquitous in processed foods and soft drinks). This free fructose can for the most part only be metabolised in the liver. Some is converted to glucose and also stored as glycogen but in excess it is also converted to triglycerides and uric acid. The conversion to triglycerides increases blood triglyceride levels and is stored in the liver, contributing to fatty liver and insulin resistance. The insulin resistance is associated with resistance to the hunger hormone leptin, decreasing satiety and increasing the feeling of hunger. The uric acid produced from fructose can contribute to the risk of developing kidney stones and gout and also inhibits nitric oxide production in blood vessels thus promoting endothelial dysfunction and increasing blood pressure. Unfortunately, fruit juice when consumed in excess can also cause these negative effects and thus most healthy eating guidelines suggest limiting fruits juice consumption to 150mls per day. However, fructose when consumed in whole fruits and vegetables is accompanied by fibre and a large array of vitamins, minerals and antioxidants and is not associated with these adverse effects.
Governments and policy makers have started to address the negative impact of SSB consumption through legislation. Many countries have introduced sugar taxes in different ways. In 2018, the UK introduced the Soft Drinks Industry Levy (SDIL), the tax puts a charge of 24p on drinks containing 8g of sugar per 100ml and 18p a litre on those with 5–8g of sugar per 100ml, directly payable by manufacturers to HM Revenue and Customs (HMRC). This does appear to have incentivised manufacturers to reduce sugar in their products, which has translated into a reduction in sugar sales. The impact on health outcomes is yet to be seen. Hungary was one of the first countries to introduce taxation on several unhealthy foods back in 2011. Four years after the introduction, more than 50% of citizens had reduced consumption of the targeted products, replacing them with healthier options. The money generated was used to raise wages of health workers and on healthy eating campaigns.
BEWARE OF ARTIFICIALLY-SWEETENED DRINKS (ASD): Zero calorie ASDs have been sold to us as a better choice than sugar-sweetened beverages but there is not much evidence to support this. This paper analysed data from the French NutriNet-Santé cohort to investigate the relationship between the risk of cardiovascular disease and consuming sugary drinks and artificially sweetened drinks.104,760 participants were included and they were asked to fill out three validated web-based 24-hour dietary records every six months. ASDs were defined as those containing non-nutritive sweeteners. Sugary drinks were those containing 5% or more sugar (soft drinks, syrups, 100% juice, fruit drinks). For each drink category, participants were divided into non-consumers, low consumers (approx 40mls/day) and high consumers (approx 180mls/day). During the follow up period between 2009 and 2019, compared to non-consumers, higher consumers of sugary drinks had a 20% increased risk of cardiovascular disease and consumers of artificially sweetened beverages a 32% increased risk of cardiovascular disease, even after accounting for a number of confounding factors. Clearly this does not prove causation, only association, but nonetheless, should give us cause for concern.
Artificial sweeteners (AS)are not as harmless as the Industry may suggest. Even though they don’t have calories, they are intensely sweet (hundreds of time more so than sugar) and therefore promote the desire to consume sweet foods. AS’s can also cause a rise in insulin thus contributing to weight gain and metabolic syndrome. In addition, AS’s have a negative impact on the gut bacteria (microbiome) and hence contribute to insulin resistance. Studies have linked the consumption of AS’s with weight gain, type 2 diabetes and cardiovascular diseases, including stroke. So, don’t fall for the industry marketing and stick with water, tea and coffee as your main drinks.
FLAVANOLS AND BLOOD PRESSURE: Flavan-3-ol or flavanols are phytochemicals within the larger group of polyphenol compounds found in food. The main food source of flavanols are apples, tea, grapes, berries and cacoa. Studies suggest that flavanols can benefit vascular health. However, determining the intake of flavanols from population studies using food frequency questionaires can be challenging as it is estimated from the typical food composition values which can only provide data on average food content and not the composition of the foods actually consumed. Measuring nutritional biomarkers, such as the compound itself or its metabolite, in blood samples is a better reflection of the food consumed. The authors of this study have developed biomarkers of flavanol conumption and the current cross-sectional study investigated associations between biomarker-estimated flavanols intake and blood pressure in more than 25,000 participants of the Norfolk cohort of the European Prospective Investigation into Cancer Study (EPIC-Norfolk). The secondary objectives of the study were to investigate associations with other cardiovascular disease risk factors and prospective associations with cardiovascular disease risk.
The results showed that higher intake of flavanols was associated with significantly lower systolic and diastolic blood pressure. For systolic BP, higher flavanol consumption was associated with 2mmHg lowering and for diastolic BP a 1mmHg lowering. Although this seems a some change in BP, these findings were similar to that of the BP lowering effect of the Mediterranean diet in the PREDIMED study and moderate salt reduction with the DASH-sodium trial. There were small reductions in cholesterol and LDL cholesterol with higher flavanol consumption but not triglycerides or CRP and no impact on incidence of or mortality from cardiovascular disease.
For me this confirms what we already know, that bioactive compounds in plant-derived foods and drinks have a positive impact on cardiovascular health. Incorporating flavanol-rich foods, including tea, is beneficial. Having said this, the key is to centre the diet around a variety of whole plant foods to benefit from all the amazing phytonutrients they contain. At the end of the day, we know that those consuming the healthiest plant-based diets have the lowest risk of cardiovascular disease, type 2 diabetes and certain cancer. Plant-based diets, including vegetarian and vegan diets, are an effective dietary approach to maintaining a healthy blood pressure.
PREVENTION OF COLORECTAL CANCER: Colorectal cancer (CRC) is the third most common cancer globally with around 1.4 million cases per year, representing 10% of all new cancer cases. In the UK, 42,000 people are diagnosed with CRC per year. Alarmingly it seems that the incidence is rising in those less than 50 years. Cancer Research UK suggest that 54% of CRC care preventable. This systematic review brings together the latest data on CRC prevention and includes 80 relevant studies. For all the findings the degree of certainty of the evidence is low or very low. With regards to dietary components, the following were associated with a reduced risk of CRC with the range of effect in brackets; Magnesium from dietary sources or supplements at a dose of at least 225mg per day (11–22% reduction); folic acid, dietary or supplement (12–15% reduction); dairy products showing a dose effect for every 400g/day (13–19% reduction); Fibre (22–43% reduction); Fruits and vegetables with benefit for every 100g/day increase (8–52% reduction), Soya (5–15% reduction). No effect on CRC prevention was found for vitamin E, vitamin C, selenium, tea, garlic, vitamin D/calcium. There is uncertainty as to the contribution from coffee and fish consumption, calcium supplements, vitamin A/B and statins. There is an increased risk of CRC with meat (both total and red meat) consumption for every addition 100g/d consumed (12–21% increase) and alcohol (12–20% increase) consumption with even the lowest consumption of 1–2 drinks per day increasing the risk.
Dairy consumption has been associated with a reduced risk of CRC and the data are summarised in the WCRF report (Page 42 onwards). The proposed mechanisms include the high calcium content which acts to counter the negative effect of secondary bile acids in the bowel. Lactic acid-producing bacteria may also protect against colorectal cancer and the casein and lactose in milk may increase calcium bioavailability. Other nutrients or bioactive constituents in dairy products, such as lactoferrin, vitamin D (from fortified dairy products) or the short-chain fatty acid butyrate may also provide some protection against colorectal cancer.
The issue with promoting dairy consumption for CRC prevention is that dairy consumption is strongly associated with an increased risk of prostate cancer in men. For every 400g/d of dairy consumed there is a 7% increased risk. This is in part due to the high calcium content with 400mg/d of calcium increasing the risk by 5%. The high calcium intake is thought to down regulate the formation of vitamin D3 in the prostate and this promotes cell proliferation. Dairy intake may also be implicated in increasing the risk of endometrial cancer in women. So, for me, promoting dairy for CRC prevention is counterintuitive since the promotion of whole plant foods nad fibre would be a better strategy with no associated harms. In addition, there are better choices to make. For example, choosing soya milk rather than dairy milk can significantly reduce the risk of breast and prostate cancer and fortified plant milks can provide the same amount of calcium as dairy milk.
LIFESTYLE FACTORS CAN OVERCOME GENETICS IN GASTRIC CANCER: The incidence of gastric cancer is highest in Southeast Asian due to a combination of genetic and lifestyle factors. This study investigated the contribution of genetic and lifestyle in a meta-analysis and prospective cohort study in participants from China. The meta-analysis investigating genetic factors included 6 studies with 21,168 Han Chinese individuals, of whom 10,254 had gastric cancer and 10, 914 geographically matched controls did not. From this, a genetic score was derived and applied to a nationwide cohort of 100, 220 individuals from the China Kadoorie Biobank, with more than 10 years of follow-up. The genetic risk score was correlated with the following lifestyle factors; not smoking, never consuming alcohol, the low consumption of preserved foods, and the frequent intake of fresh fruits and vegetables.
The results showed that compared with individuals who had a low genetic risk, those with an intermediate genetic risk and a high genetic risk had a 1.5x and 2x greater risk of gastric cancer respectively. A similar increase in the risk of gastric cancer was observed across the lifestyle categories with a 2x higher risk of gastric cancer in those with an unfavourable lifestyle than those with a favourable lifestyle. However, participants with a high genetic risk and a favourable lifestyle had a 47% lower risk of gastric cancer than those with a high genetic risk and an unfavourable lifestyle. This was an absolute risk reduction of 12%. Thus, individuals with a high genetic risk score can significantly reduce the risk of gastric cancer by adopting healthy lifestyle behaviours.
NITROUS OXIDE EMISSIONS FROM FARMNG: We hear a lot about the detrimental effects of carbon emissions on climate change. However, two other gases emitted from farming, methane, and nitrous oxide, are equally problematic. This paper assesses the impact of nitrous oxide emission, a gas that is produced from the use of artificial fertilisers and by organic sources such as animal manure. Its heating effect is 300 times more than that of carbon dioxide. The livestock sector accounts for about a third of all nitrogen emissions and meat and dairy production alone breaches the lower limit of what is considered to be the the safe global level beyond which future existance on this planet is endangered. This issue is in addition to the carbon dioxide and methane being emitted from the food system. The overwhelming bulk of these emissions from animal farming, 68%, comes from artificial fertilisers applied to crops grown to feed animals, followed by nitrogen released by the build-up and management of manure. Nitrous oxide emissions are increasing at a rate of 1.4% a year and if this is not addressed we will be on track to exceed the 2 degree C warming limit set under the Paris agreement. The main driver of the increasing emissions is the growing demand for animal foods and hence animal feed. Nitrogen is required for soil health and the gas is released when microbes in the soil break down the excess fertiliser. Brazil, China and India have the highest growth in nitrous oxide emissions, due to the rapid increase in intensive animal farming and grain feed production. Global nitrous oxide emissions have increased by 30% over the past four decades. The other issues arising include water pollution, from nitrogen run-off into rivers and lakes, and air pollution from ammonia generation. There are many potential strategies to address this important issue based around agricultural practices and reducing the use of synthetic fertilisers. By far the quickest solution would be to greatly reduced or eliminate the consumption of meat. We currently produce enough food to feed at least 10 billion people yet nearly a billion people globally remain food insecure and hungry. Feeding grain to animals that are then consumed by humans is a hugely inefficient way of producing food. Just 55% of the world’s crop calories are actually eaten directly by people. 36% is used for animal feed but this then only supplies 12% of feed calories for human consumption in the form of meat and animal produces. For example, it takes 100 calories of grain to produce just 12 calories of chicken or 3 calories worth of beef. We could use vastly less land and fertiliser if farmland was dedicated to growing crops directly for human consumption. The land then no longer needed for farming could be rewilded.
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