Chapter 30
Eat to Your Heart’s Content — Part 1
It is imperative that animals (including us) keep a constant core body temperature for organs to function and survive. To keep a constant body temperature, a small animal must oxidise food and produce energy at a high rate to maintain body temperature. One of the smallest mammals is a shrew, a distant relative of the elephant. They weigh only about four grams. These animals have a metabolic rate that is too high to allow them to live much more than 12 months. To maintain this metabolic rate, they have a very fast heart rate of 600 beats per minute (compared with humans, at 60–80 beats per minute) and they eat nearly their own weight in (mostly) insects every 15 minutes to sustain themselves. They will starve to death in just a few hours if deprived of food and rarely stop to sleep. Because of the constant need for food, the shrew possesses a venom that paralyses its prey, keeping it alive for up to 15 days. The shrew then moves it to a cache. How shrewd, you might say. There are exceptions to the rule that couple body size, basal metabolic rate, heart rate and life expectancy – these make for a tantalising area of ageing science. For example, rats and pigeons are pretty much the same size and have the same basal metabolic rate but pigeons live seven times longer than rats. The reason for this difference is that leakage of toxins and waste products during the creation of energy by the mitochondria is much less in pigeons, despite having the same metabolic rate as rats. As you can imagine, if researchers could understand why pigeon mitochondria are more leak-proof, then we might be able to use the information to modify human cell leakage and waste accumulation, which is key to ageing. If we crack this, could we apply the knowledge to human cell ageing and thus live seven times longer? That’s a possibility that would shake our world big time. Obesity is closely related to mitochondrial function. The obesity epidemic is accelerating and is now global; in fact, obesity is rising faster in middle-income countries than the West. In our study, we found that 70 per cent of people over 50 in Ireland are overweight or obese. This is similar to data from other European countries, although Ireland and the UK are top of the obesity league compared with other European jurisdictions. Look around you – how many of your friends are at their appropriate body weight? The big issue with this is that with obesity comes accelerated ageing and early presentation of diseases – sometimes by as much as 20 years early – such as heart disease, high blood pressure, arthritis, liver diseases and skin problems. The basal metabolic rate of overweight and obese people is higher than people of normal weight although the BMR per kg of body weight is lower.
Chapter 9: Eat to Your Heart’s Content
As with animals, heart rate is also higher to keep up with metabolic rate. This is one of the factors contributing to poor health outcomes from obesity. Obesity, a disease of excessive fat deposition, is essentially a consequence of chronic energy imbalance, with energy intake consistently exceeding expenditure. In other words, we eat more than we burn. This leads to the storage of surplus energy in white fat. We need to be much better educated about what fat is and how the body controls it if we are to get on top of the obesity epidemic, particularly as we age and body fat increases. It’s easy to lump ‘fat’ into a single category: the stuff beneath the skin that makes our stomach wobble and can raise the risk of diabetes and heart disease. But not all fat is created equal. For years, scientists have known that fat tissue comes in at least two different shades. White fat, which most of us are familiar with, stores energy in big oily droplets throughout the body and, in large quantities, causes obesity. Brown fat contains both smaller droplets and high amounts of iron-rich mitochondria that lend the tissue its chestnut colour. Green tea, cabbage, berries, spinach, hot peppers and coffee are examples of foods that increase brown fat production. Mitochondria, the cell’s power plants where energy is produced, use these fatty droplets to generate heat. Brown fat is turned on when we get cold and is of interest because it can regulate conversion of fat into fuel or energy. Exercise can also stimulate hormones, such as irisin, which activate brown fat and thereby trigger energy release. So, to all intents and purposes, brown fat is good fat. Scientists are exploring new ways to harness this tawny tissue and irisin for therapeutic purposes to use in weight reduction because of the potential to turn fat into energy. White fat can turn into brown fat by exposure to lower temperatures of 19 degrees or less for a couple of hours a day. This may also be a further reason why cold water exposure, including cold showers, is beneficial. While the solution to obesity is ostensibly as simple as reducing calorie intake (e.g., avoid energy-dense food) and increasing energy expenditure (increase physical activity), the failure of decades of public health initiatives to remove the ‘obesogenic’ environmental factors clearly indicates that obesity is a problem far more complex than the prevailing wisdom of ‘low willpower’. Indeed, we are yet to fully understand the sophisticated interactions between genetics, physiology and cognitive behaviour that regulate energy and body weight.
Chapter 9: Eat to Your Heart’s Content
Several lines of evidence suggest that our bodies have ‘switches’ that influence how quickly we age. These switches are not set in stone; they are adjustable and provide the potential to extend our years of youthful vigour and simultaneously postpone the troublesome conditions expressed at later ages. Diet and body weight hold the key to many of the switches and are a major factor in turning on or off components of cell ageing. ‘Let food be thy medicine and medicine be thy food.’ This oft-quoted adage from Hippocrates from over 2,000 years ago remains relevant today as there is a growing renaissance in our appreciation of the importance of diet in maintaining health of body and brain.
The respective diets in the Blue Zones are a good starting point for examining foods that enhance ageing. Centenarians in the Blue Zones have well-described dietary patterns that contribute to longevity and compressed ill health in later years. Exploring these diets shines a light on potential ‘good foods’. Indeed, the centenarians’ diet shares many features with the well-known Mediterranean diet. In brief, they are 95 per cent plants, high in fish, very low in red meat, moderately low in dairy and eggs, very low in sugars and devoid of processed foods. The Okinawa diet includes a lot of turmeric and ginger. Blue Zone residents eat a wide variety of vegetables in addition to pulses such as beans, lentils, peas and chickpeas. The diets are high in varied fruits, whole grains, nuts and seeds. At least half a cup of cooked beans and two ounces of nuts are consumed daily.
Chapter 9: Eat to Your Heart’s Content
In most of the Blue Zones, cow’s milk products are not included in significant amounts. People in Ikaria and Sardinia consume goat’s and sheep’s milk products. Eggs are consumed two to four times per week, usually one at a time and incorporated into a dish, rather than as a main protein source. In most Blue Zones, people eat up to three servings of fish each week. These are typically middle-of-the-food-chain species, like sardines, anchovies and cod, that are not exposed to high levels of mercury or other harmful chemicals. Meat is consumed sparingly. It is eaten on average five times per month, in portions that are about 60 grams or less. Rather than occupying the centre of the plate, meat is a small side; it’s thought of as a celebratory food or a way to flavour primarily plant-based dishes. People in Blue Zones consume a fifth of the added sugar intake per day of North Americans. Sugar is enjoyed intentionally as a treat and not hidden in processed foods or consumed out of habit. Meals are primarily home-cooked, with breakfast as the largest and dinner the smallest. With very few exceptions, there are just four beverages: water, coffee, tea and wine. In all Blue Zones, tea is sipped daily.
In Okinawa, green tea not only provides essential antioxidants but also a healthy catalyst for socialising with family and friends. Green tea is incorporated into a meal or into a ritual for receiving visitors. It has been shown to contain catechin, which, in mice, slows down brain ageing and increases nerve circuits and the adaptability of brain nerve cells by manipulating genes which have these functions. In most of the Blue Zones, one to three small glasses of red wine are consumed per day. In Sardinia, wine consumption is part of a daily ‘happy hour’ ritual combining social engagement, chit chat and a couple of glasses of wine.