Chapter 31
Eat to Your Heart’s Content — Part 2
The Mediterranean diet is based on traditional foods that people – who were noted to be exceptionally healthy and longer living compared to Americans – consumed up until 30 years ago in countries like Italy, Greece and Spain. A recent review paper summarised information on the diet taken from a series of studies encompassing a total of 13 million participants and it was good news all the way for the Mediterranean diet. The review confirmed a robust link between the diet and reduced risk of death, cardiovascular diseases including heart attacks, some cancers, diabetes and brain diseases such as dementia. The foodstuffs included in the diet from the original studies have been expanded and the diet now broadly refers to foods detailed below with avoidance of sugars, starches and processed or refined foods. THE MEDITERRANEAN DIET Vegetables: Tomatoes, broccoli, kale, spinach, onions, cauliflower, carrots, brussels sprouts, cucumbers Fruits: Apples, bananas, oranges, pears, strawberries, grapes, dates, figs, melons, peaches Nuts and seeds: Almonds, walnuts, macadamia nuts, hazelnuts, cashews, sunflower seeds, pumpkin seeds Legumes: Beans, peas, lentils, pulses, peanuts, chickpeas Tubers: Potatoes, sweet potatoes, turnips, yams Whole Grains: Whole oats, brown rice, rye, barley, corn, buckwheat, whole wheat, wholegrain bread and pasta Fish and Seafood: Salmon, sardines, trout, tuna, mackerel, shrimp, oysters, clams, crab, mussels Poultry: Chicken, duck, turkey Eggs: Chicken, quail and duck eggs Dairy: Cheese, yogurt, Greek yogurt Herbs and spices: Garlic, basil, mint, rosemary, sage, nutmeg, cinnamon, pepper Healthy fats: Extra virgin olive oil, olives, avocados and avocado oil
Chapter 9: Eat to Your Heart’s Content
The basics of the diet are similar to Blue Zone diets. The Mediterranean lifestyle also involves sharing meals with other people and intergenerational social engagement – grandkids, parents, grandparents regularly eating together. Because the contribution of social engagement and pleasure is difficult to unravel from dietary constituents, all are recommended. Caloric restriction holds huge promise for deceleration of ageing and assisting with age-related changes in the basal metabolic rate. We have known for some time that calorie restriction prolongs lifespan. This is so for a number of species – for example, mice, worms, fish and monkeys. In rhesus monkeys, after 20 years of reduced calorie intake, eating less than half of the monkeys’ normal intake, the fasting monkeys are much younger looking, with more hair, no sunken eyes, fuller cheeks, more youthful posture and more energy than monkeys of the same chronological age who have eaten a normal diet for 20 years. Remarkably, the fasting monkeys also live 30 per cent longer. Photos A and B show a 20-year-old Rhesus monkey with normal lifelong dietary intake. Photos C and D show a monkey of the same age with 20 years of reduced calorie intake.
Chapter 9: Eat to Your Heart’s Content
Ketones are chemicals that break down fat. The body uses them for energy during times of fasting and exercise. The benefits of calorie restriction and fasting is all about ketone generation.
The above graph is an example of the typical eating pattern in most industrialised countries. Every day, the person eats breakfast, lunch, dinner and a late evening snack. With each meal, blood sugar levels rise and then return towards baseline over a period of several hours. Sugar is stored as glycogen in the liver. We use glycogen and therefore sugar as our main energy source when we have plenty of both. But elevated sugar levels are not good for us. Ketones are only formed when we fast and levels remain low when liver glycogen stores are plentiful. When liver glycogen levels drop, we are programmed to switch to a different means of energy production, using fatty acids to produce ketones and energy instead of glycogen. These ketones and their associated metabolic pathways are good for cells and overall health.
The above graph is an example of fasting for one day, followed by a three-meal feeding day (intermittent fasting). During the fasting day, glucose levels remain in the low normal range and ketone levels rise progressively, then fall when the first meal is consumed on the second day.
Chapter 9: Eat to Your Heart’s Content
The graph above is an example of an eating pattern in which all food is consumed within a six-hour time window each day. Glucose levels are elevated during and for several hours after the six-hour period of food consumption and then remain low for the subsequent 18 hours, until food is consumed the next day. Ketones are elevated during the last six to eight hours of the fasting period.
I delivered a lecture on this topic to an audience of medical doctors and one retired professor of ‘Obs and Gobs’ (Obstetrics and Gynaecology) was very agitated about the concept of fasting. He challenged the data, arguing that it couldn’t possibly be good to have ketones. He cautioned that this was something he always tried to avoid in his patients, particularly sick diabetic patients. Of course, he was partially correct. Ketones produced because of illness are an indication of how ill someone is and are different to the ketones we strive to produce with wilful fasting. I’m glad to say that I since heard that the same Obs and Gobs professor is now an ardent disciple of caloric restriction and thriving in his mid-eighties.
Chapter 9: Eat to Your Heart’s Content
There are a number of fasting programmes. For example, a 16–48-hour fast with little or no food intake and intervening periods of normal food intake, on a recurring basis. Or intermittent fasting, such as 60 per cent restriction on two days per week or every other day. Or periodic fasting, for example, a 5-day diet providing 750–1,100 kcal per day. A popular restrictive diet and my preferred choice, which many find easy to comply with, is the 18-hour fast. This is the time-restricted diet illustrated above, with food intake confined to the remaining six-hour window. So I will skip breakfast, eat two meals between midday and the evening (within six hours) and fast overnight and next morning (making up 18 hours). I find this to be the easier restriction regime to adhere to. To our knowledge, no regime is superior in respect of biological ageing, so you should choose whichever you find easiest to comply with. But whatever you choose, it will trigger a metabolic switch from glucose-based to ketone-based energy production. This in turn triggers a cascade of beneficial chemical reactions for cell preservation. All of these diets work because intermittent ketone-based energy slows cell ageing through beneficial chemical reactions.
Chapter 9: Eat to Your Heart’s Content
Fasting is not for everyone, for example people with diabetes or who have a tendency to faint or feel weak, have eating disorders or are pregnant or breast feeding. If you find fasting difficult, try to curtail eating to within an 8–10-hour window and, if possible, avoid snacking. If you need a snack, eat a piece of fruit or some nuts. I found I acclimatised to fasting – even though I do a busy clinic on a number of mornings, but it did take time to get used to it. Water should be taken throughout the day – it is really important not to become dehydrated. Calorie restriction by 30-40 percent on a daily basis is also a good approach. An interesting study in obese humans with early (pre) diabetes showed that eating between 7am and 3pm and fasting for the latter part of the day and through the night significantly lowered insulin (which is a good thing for reducing fats in cells). Personally, I found this fasting regime more difficult than morning fasting – so try out a few intermittent fasting regimens until you get the one that suits you best.
Chapter 9: Eat to Your Heart’s Content
You may well ask why we have evolved such that fasting confers benefits, and how it slows down ageing and diseases at a cell level. The survival and reproductive success of all organisms depends upon their ability to obtain food. We are what we eat. Accordingly, we have evolved behavioural and physiological adaptations to survive periods of food scarcity or absence. Some organisms become dormant during periods of food scarcity; for example, yeast enter a stationary phase and ground squirrels and bears hibernate. Mammals have organs such as the liver and fat tissue in which to store energy; this enables us to fast or starve for long periods of time, depending upon the species.
In mammals, many of the health benefits of intermittent fasting are not simply the result of reduced free radical production or weight loss. Intermittent fasting also triggers responses that suppress inflammation. During fasting, cells activate pathways that enhance defences against inflammation and stress and remove or repair damaged molecules, all linked with cell ageing. Caloric restriction triggers release from fat cells of the protein adiponectin which helps to guard against heart disease and high blood pressure because of its anti-atherogenic and anti-inflammatory effects. In animals, caloric restriction reduces the chances of getting cancer and it is very likely that this is the case for humans.