> [!summary] Progressive Summary # Structured Notes ## Definitions ## Chapter Summaries ### Chapter 2 - Why do we love food? Our nose contains 400 smell receptors. They capture thousands of natural chemicals and can distinguish a trillion combinations of odours. The role of our mouth is to quickly decide whether to spit or swallow food. It is a sophisticated defense against poisons. Our tongue is highly sensitive to textures and tastes. Saliva contains mucus, salt, enzymes and water which help to release aromas. Chewing exposes more surface area and increases the taste of food. Soft rounded foods taste sweet than sharp angular ones. Apples cut in a smooth semi-circular shape will taste sweeter than ones cut with sharp corners. Astringency is a drying sensation in the mouth. It is caused by tannins that make the proteins in our salive stick together. Milk in black tea helps to block the astringent effects of the tea. There are taste receptors in other parts of the body, including men's testicles. Smell is the only sense that has a direct link to the brain. > A 2014 study looked at 3,000 Americans aged fifty-seven to eighty-five and tested them with five classic smells – rose, leather, fish, orange and peppermint – and followed them for five years. Those with problems smelling had a fourfold risk of death. > Temperature also changes taste. If food is eaten straight from the refrigerator, the sweetness is masked, whereas a warm fizzy drink tastes much sweeter. On a plane journey, food also tastes less sweet because of the decreased pressure reducing the spread of the volatile flavour molecules and the reduced ability of your smell receptors. Airlines select sweeter fruit varieties and saltier dishes to compensate for this – and with all the extra intestinal gases and smelly socks surrounding you on long flights this loss of smell can be a bonus. ### Chapter 3 - What foods are really healthy? **Top five tips for healthy eating:** 1. Foods that are good for your health are also good for your gut microbes. 2. Eat plenty of plants and a variety of them. I recommend aiming for thirty different plants per week. 3. Select plant foods high in the defence chemicals called polyphenols, and fibre. 4. Eat fermented foods regularly. 5. Eat foods in their whole, natural form to maintain the optimal matrix, and avoid UPFs. --- Plants inherited the ability to turn sunlight into energy from algae, who in turn inherited it from bacteria. Plants have thousands of enzymes which turn them into chemical factories. Polyphenols are protective chemicals that act as sunscreen or toxins. Examples are alkaloids like nicotine and caffeine. Fast growing leaves or the tips of young sprouts are richest in polyphenols, because they need protection the most. They also have the most flavour compounds. Colours are a clue to what polyphenols are present. By eating fruits and vegetables with different colours, we can ensure that we get a variety of polyphenols that are important for our health. The blood orange is rich in a polyphenol called anthocyanin, which protects it from the temperature extremes of Sicily. In 1749, James Lind, a British naval doctor, performed an experiment with 12 scurvy-inflicted sailors. He divided them into 6 treatment groups, giving them: 1) 6 spoons of vinegar; 2) a quart of cider; 3) half a pint of seawater; 4) spicy barley water; 5) dilute sulphuric acid; or 6) oranges and lemons. Only the ones who ate citrus got better. He wrote up his findings in 1753. It was only in 1795 that his cure was officially approved, and Britain began dominating citrus-growing trade routes. From then on, British sailors were given rations of limes (hence they were called limeys). Britain dominated the oceans for the next hundred years. Vitamin C (ascorbic acid) was discovered in 1927, and was touted as a miracle cure. The pancreas is an organ next to the liver which releases enzymes that break down carbohydrates and complex sugars into simpler glucose and fructose molecules that can be absorbed into the bloodstream. It also supplies the hormone insulin that regulares how quickly glucose and protein gets absorbed into the bloodstream and organs. Cholesterol is the main way in which fat gets absorbed, stored and re-used. The gut microbiome plays an important role in breaking down fats. They help breakdown liquid produced by the liver into bile salts, which then process fat. --- **Food matrix** - composition and complexity of food - what form we consume our foods makes a difference, eg whether a fruit is eaten whole, or as a smoothie > Chewing is an important way of giving your body more time to react to food arriving. For example, an average apple produces a three times lower blood sugar peak compared to the equivalent unsweetened apple juice. If you ate your apple as mashed-up baby food or as a smoothie, its sugars would be more rapidly accessible because the cell walls containing the starch would be already broken down. This means it would produce a higher glucose peak in the blood, and less would reach the colon. > This matrix effect is also seen with fat levels in nuts which are less accessible when eaten whole than when crushed into a nut powder in processed foods. Changing the matrix of the nuts, from whole almonds to powdered almonds, for example, by crushing and destroying their structure, changes both the blood lipid levels (fat) and energy levels (calories) from the same amount of whole almonds. Like sugar peaks, having high levels of circulating blood fat six hours after a meal is bad for your metabolism and triggers low levels of inflammation as described earlier. Over time this accumulated stress causes permanent changes such as heart disease, type 2 diabetes and weight gain. --- **Gut microbiome** > We don’t understand many of the mechanisms yet, but what is certain is that by interacting with and fermenting our food, microbes can control the rate at which both fat and sugar are absorbed into the body as seen by the spikes in our blood and the way they affect our metabolism. Whatever your starting point, having a diverse range of microbes and a good ratio of good to bad bugs means you can eat the same amount of carbs or fats but have less harmful effects. Keeping the microbes well fed means they produce many chemical metabolites such as butyrate and other short chain fatty acids, key vitamins like vitamin K, biotin, folate B6 (important in pregnancy) and small amounts of B12, as well as having a major role in supporting our immune system. > After five years collecting over 11,000 samples from citizen scientists around the world, the American/British Gut Project team produced its first findings. What turned out to be more important for gut health than whether you were a paleo follower, a fruitarian, a vegetarian or even a vegan, was the number of different plant species you ate each week. **Thirty different plants per week appeared to be optimal**. We adjusted for all kinds of possible biases, such as education level, age, social status, smoking, alcohol, constipation, number of children, pets, body weight, diseases, medications, but all the data pointed to the same powerful effect – the diversity of plants you regularly eat. --- **Small and large intestine** The small intestine absorbs most of the nutrients in our food - sugars, fats and proteins. > The rate at which this happens and subsequent changes in the blood which occur are crucial to our health and vary in all of us. Most highly processed and refined food doesn't get past the small intestine. Only food which has structure and fibre reaches the large intestine (which is only 1-2 metres long), where polyphenols are released by microbes to be used directly or made into more complex polyphenols. **Polyphenols** > Some polyphenol chemicals are used by microbes directly as energy like rocket fuel, enabling them to replicate and also create a waste by-product that might actually be an invaluable chemical component for us: short chain fatty acids (SCFAs). These tiny molecules have many functions. When SCFAs reach the human cells lining our gut they supply them with energy, literally keeping them alive and letting them replicate. They are key for sending signals to our immune cells, keeping down inflammation and suppressing allergies. They also act on our brain and gut hormones, suppressing appetite. An example of one such SCFA is butyrate which helps our gut barrier, that separates the contents of our gut from our blood supply, to remain intact and prevent what is known as ‘leaky gut’. The thin single-cell gut barrier is delicate and recurring infections, poor diet and high stress can result in it breaking and causing unhelpful gut contents to ‘leak’ into our circulatory system, causing more inflammation and damage. This is a real issue if you are ill with inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis, or severe malnutrition, but it has been exaggerated as a major cause of problems in healthy people. While gut hyperpermeability is a possible factor in poor health associated with eating unhealthy foods and chronic stress, it is massively over diagnosed and linked with false ‘miracle cures’ for leaky gut. > There is a growing interest in eating older heritage varieties of plants, like purple carrots or potatoes, which are naturally higher in polyphenols, and we are hopefully dumping some blander varieties, where the polyphenols have been lost in intensive breeding. Our tongue and mouth also give us clues to the polyphenol content. Polyphenols are defensive chemicals for a plant, and they are generally bitter and astringent on your tongue, such as strong red wine, good-quality black tea or olives. Through trial and error our ancestors knew that these plants, if they didn’t kill you, were probably good for you. We need to regain that skill. **Appetite** > Having a diverse and balanced community of gut microbes is crucial for our health and evidence is accumulating that microbes are also in part responsible for regulating our appetite. When a particular microbe species runs out of its food supply, it will send out signals to the brain asking for more. When a particular species or group is sated and its population has doubled, they fill the available space in the gut community and send a signal to the brain, saying ‘No more apples please.’ This takes about twenty to thirty minutes – the same time it takes for us to get sensations of fullness after eating. **Fermented foods** > While many foods are made with a fermenting process – sourdough bread, pickles, chocolate, coffee, wine and beer, etc. – only a few actually contain live microbes in the end product. As well as well-known foods like cheese, yogurt and fermented tofu, kefir, kombucha, kraut and kimchi (see page 154) – the K-rations as I call them – are becoming more popular as natural probiotics you can create at home. As they contain live microbes they contribute to your gut microbiome diversity. ### Chapter 4 - What foods are unhealthy? **Top five unhealthy foods** 1. Ultra-processed foods (UPFs) – with extra fat, sugar and salt as well as other preservatives and additives. 2. Artificial sweeteners in foods or drinks. 3. Highly refined carbs – these are usually UPFs and low in fibre. 4. Foods that produce high blood sugar and blood fat peaks after meals with a lack of natural matrix or fibre. 5. Snacks containing a lot of sugar or low-quality fats – even if they have ‘healthy’ labels saying they contain protein or ‘natural’ sugars. --- > As a general rule, foods made in a factory that are completely lacking in a variety of plant fibre, plant polyphenols or probiotic microbe species will not be good for us if we choose to eat them regularly or in excess. Good examples might be doughnuts, rice cakes, or most protein bars. Another general rule is that foods that get absorbed fast in the upper part of the gut (the small intestine) and rapidly enter the bloodstream as fats and sugars, leaving nothing for the colon (or large intestine), are usually unhealthy. These foods produce sugar peaks and dips and increases in blood fats that the body finds hard to deal with on a regular basis and this, as we have seen, causes overeating and inflammation. Although this is true of some natural foods, such as honey or sweet fruits like dates or figs, most of the foods in this category are ‘ultra-processed foods’ or UPFs. > The concept of UPFs was introduced in 2018 by the Brazilian scientist Carlos Monteiro who noticed that although the amount of sugar and salt purchased by consumers was decreasing, the amount of sugar and salt consumed was increasing, which was due to the increased consumption of industrialised foods. > The simplest way of classifying UPFs is that they are made up of complex mixtures of chemicals and food extracts which don’t resemble the original parts of whole foods – such as potato starch extract used instead of potatoes. > A practical way to identify an ultra-processed product is to check its list of ingredients for food substances never or rarely used in kitchens (high-fructose corn syrup, hydrogenated or ‘unesterified’ oils, and hydrolysed proteins), or classes of additives designed to make the final product palatable or more appealing. There are over 2,000 approved food additives, and even more enzymes, including flavour enhancers, colours, emulsifiers, emulsifying salts, sweeteners, thickeners, and anti-foaming, bulking, carbonating, foaming, gelling and glazing agents. UPF labels usually list over ten such ingredients. ### Chapter 5 - Can foods boost your immune system? **Top five tips to support your immune system** 1. Eat fermented foods, which contain helpful probiotics. 2. Eat foods rich in a variety of prebiotic fibres, such as leeks, onions, artichokes, cabbages. 3. Eat foods rich in polyphenols, such as colourful blueberries, beetroot, blood oranges, and nuts and seeds. 4. Eat foods that dampen any inflammation after meals such as green leafy vegetables. 5. Reduce consumption of meat and non-fermented dairy to occasional meals. ### Chapter 6 - Can we choose better foods? **Five key factors to consider in making better food choices** 1. Labels and certificates can be misleading. 2. None of us is good at estimating risks of food choices. 3. Companies can easily produce data and papers to falsely claim their product is ‘healthy’ and back it up through marketing. 4. Food fraud is rife and increasing: much of our food is not what it seems. 5. Knowledge of seasonality can help us bypass the labels and enjoy a varied and nutritious diet. ### Chapter 7 - How does storing, processing and cooking alter food? ### Chapter 19 - Fungi and mushrooms ### Chapter 33 - Final word **Twenty tips to keep you and your microbes healthy** 1. Sleep well and exercise regularly. 2. Avoid snacking and allow occasional long fasting intervals. 3. Try to eat up to thirty plant varieties a week, including nuts, seeds and spices. 4. Drink only moderate amounts of ideally high-polyphenol alcohol. 5. Eat fruit and vegetables high in polyphenols and fibre. 6. Eat less but higher-quality meat and fish. 7. Ignore calorie counts and seek out the higher nutritional quality of foods with the same calorific value. 8. Think about origins and ingredients – and how they affect your microbes. 9. Support small food producers and local shops instead of supermarkets. 10. Think about the environmental impact of your food choices. 11. Eat fungi regularly. 12. Don’t use supplements unless you are ill or pregnant. 13. Always opt for real food when you have a choice. 14. If eating convenience foods, choose the least processed ones, with the fewest ingredients. 15. Don’t follow blindly what someone else says is good for them – no one is average. 16. Understand that food is medicine and the right diet can be as effective as many drugs. 17. Eat something fermented every day and become an expert in fermenting. 18. Cook for yourself whenever you can. 19. Try to look at all food through a different lens. 20. Experiment on yourself and try something new. # Quotes # References