Eating throughout the day can trigger insulin release, promoting cell growth and potentially cancer. As soon as food enters the bloodstream as glucose, the body releases the hormone insulin, which activates a cellular switch driving growth and proliferation. While this mechanism is essential for survival, too much cell proliferation increases the likelihood of random DNA mutations and, over time, a greater risk of cancer. It also fuels the growth of visceral fat, a damaging form of internal fat linked to metabolic disease. Eric Verdin, president and chief executive of the Buck Institute for Research on Aging in California, says the body needs time away from eating to focus on repair. “There is a lot of evidence for this – 12 hours fasting and repairing, and 12 hours eating and building is more conducive to healthy ageing,” he notes.
The hidden toll of constant grazing
Modern food availability means many people spend most of their waking hours eating, whether full meals, snacks or desserts. Scientists have found it is not uncommon to graze at some point during all 16 or so waking hours. Each feeding episode prompts an insulin response, and a constant stream of meals and snacks leaves little opportunity for the body to switch into repair mode. Over time, this continuous cycle of insulin signalling promotes excessive cell division, more DNA replication errors and an accumulation of visceral fat, all of which accelerate biological ageing and disease risk.
AGEs: the toxins that age you from the inside out
Advanced glycation end products, or AGEs, are toxins implicated in virtually every familiar aspect of ageing: wrinkles, stiffness, cataracts, loss of heart elasticity and even Alzheimer’s disease. They form through a chemical process called glycation, in which sugars in the body react with proteins or fats. The most visible consequence is the damage done to collagen, the protein that gives skin its youthful elasticity, turning it into a drier, stiffer form. Jaime Uribarri, a kidney doctor at the Icahn School of Medicine at Mount Sinai in New York and a leading expert on AGEs, explains that “AGEs change protein structure and, at the same time, cause a large amount of inflammation.”
Glycation accelerates when the bloodstream contains excess sugar, which occurs after eating sweets containing fructose – a rapidly absorbed simple sugar – or easily digestible refined carbohydrates such as white rice, white pasta and pizza dough. But AGEs can also be created within food itself, particularly in protein- and fat-rich items such as meat, cheese and fish, when they are grilled, barbecued or fried at high temperatures. Uribarri’s research found that just three slices of bacon fried for five minutes contain 91,577 AGEs, compared with 23 in a tomato. To limit AGE accumulation, experts recommend eating more whole grains such as brown rice and choosing slow-cooking or stewing over high-heat methods.
Saturated fat, fibre and the ageing immune system
Saturated fat – found mostly in animal products such as red meat, cheese and ice-cream – is broken down in the body into ceramides. These molecules can reprogram immune cells in the gut into a more inflammatory state, leading to a leaky or permeable gut wall that allows microbes and toxic metabolites to leak into the bloodstream. Over time, this accelerates immune system ageing. Niharika Duggal, assistant professor in the University of Birmingham’s department of inflammation and ageing, says: “We’ve found that two of the biggest dietary features associated with immune ageing are higher consumption of saturated fat and lower consumption of fibre.” However, the gut can handle a certain amount of saturated fat if sufficient fibre and omega-3s are consumed. Oily fish, for instance, actively helps resolve gut inflammation. Scientists recommend consuming the equivalent of 1g of omega-3s per day – achievable by eating one mackerel fillet or two to three salmon fillets once a week – and at least 40g of fibre daily from whole grains and legumes.
B vitamins: turning genes on and off
B vitamins are critical for healthy ageing. The body uses them to make chemicals called methyl donors, which enable it to switch certain genes on or off at the right times – for example, keeping tumour suppressor genes active to defend against cancer. Without sufficient methyl donors, this control becomes less precise with age. One key B vitamin is vitamin B3, found in turkey, tuna and anchovies, which the body uses to produce NAD+, a molecule that plays a critical role in cellular energy management. Another is vitamin B12, found in salmon, tuna, beef, eggs and dairy products. Deficiency in B12 can increase the risk of a leaky gut and precipitate memory loss and slower brain processing speeds. For people over 50 experiencing signs of cognitive decline, ensuring adequate B12 levels is particularly important. Research from the UK indicates that an estimated 9 to 12 per cent of older adults suffer from folate deficiency, mainly due to low dietary intake, and a systematic review found a high prevalence of low intakes of folate, vitamin B6 and riboflavin among older adults in Western countries. Optimising B-vitamin status may help promote cognitive health by modulating gut microbiota and immune function.
The acid test: balancing protein and potassium
Protein is essential, but balance matters. Epidemiologists are increasingly concerned that many people consume a high dietary acid load from their food. This arises because typical diets contain large amounts of protein, added salt and phosphoric acid – a common preservative and flavour enhancer in ultra-processed foods – which the body metabolises into acidic substances. Meanwhile, intake of dietary potassium from fruits, vegetables and dried herbs is often insufficient to counterbalance these acids. The kidneys are the body’s main acidity regulators, and over many years the stress of a high acid load has been linked to chronic health conditions. Lynda Frassetto, a kidney specialist and professor at the University of California, San Francisco, explains: “As your kidneys fail, your ability to get rid of these acids goes down, so the problem gets progressively worse.” Ageing researchers advise eating twice as much fruit and vegetables as protein with each meal.
Phytochemicals: boosting the brain’s own clean-up crew
Brightly coloured fruits and vegetables contain phytochemicals, compounds that Alzheimer’s Research UK has highlighted as being linked to a lower risk of cognitive decline. At a conference two years ago, Norwegian ageing scientists presented data suggesting that regularly consuming passion fruit may protect against brain ageing. Similar findings have been made for pomegranates, strawberries, grapefruit, tomatoes and various teas. Ageing experts believe that when the body metabolises these fruits, it may rev up the brain’s immune cells, prompting them to work more efficiently to clear toxins and promote repair. Phytochemicals are often anti-inflammatory or antioxidant agents, and certain compounds, such as curcumin, have shown potential in modulating Alzheimer’s disease pathology.
The importance of when you eat
Timing matters as much as content. Most people eat their largest meal in the evening, but this may be counterproductive. Big meals at night disrupt sleep – a vital period for bodily repair – and deliver a large number of calories when metabolism is at its most sluggish. “Our insulin sensitivity is much better in the first half of the day,” says Satchin Panda, a professor at the Salk Institute in San Diego, California. “This allows us to manage [the blood sugar rise after eating a meal] much better.” Research on time-restricted eating, which involves confining food intake to a specific daily window, has shown it can prevent and even reverse chronic diseases, improve metabolic health and increase healthy lifespan. A UK community science study found that eating within a 10-hour window was associated with higher energy, improved mood and lower hunger levels. Panda’s work indicates that when we eat may be as important as what we eat: “Our results open the door for looking more closely at how this nutritional intervention activates genes involved in specific diseases, such as cancer.”
One example of a longevity-focused eating pattern that incorporates these principles is a low-calorie, nutrient-dense menu that concentrates protein-heavy meals in the first half of the day when metabolism is most efficient. It includes an egg, spinach and mushroom muffin for breakfast; a smoked mackerel salad for lunch; a chickpea, spinach and coconut curry with brown rice and cauliflower for dinner; and a snack of one medium pear with three tablespoons of walnut halves, accompanied by two cups of green tea. This menu provides two portions of leafy greens to minimise dietary acid load, a heavy dose of omega-3s from the mackerel, and 40–50g of fibre to support gut and immune health.
