Chapter 35
Eat to Your Heart’s Content to Sex and Intimacy
So diet is a key contributor in shaping the composition of the gut microbiota, exemplified in the contrast between the Western and the Mediterranean diet. Both diets exert distinct effects upon the composition of gut microbiota. The Western diet – rich in fats, salt and sugar – changes gut bacteria to typify the gut microbiota of obese people. In contrast, the Mediterranean diet affects gut microbiome by causing microbiome changes which we know are linked to better mental function, memory, immunity and bone strength. One hobby horse of mine is the ubiquitous ‘emulsifier’. Emulsifiers are found in all Western processed foods, such as burgers, ketchup and mayonnaise. Emulsifiers are purported to be ‘safe’ but they do increase the levels of microbes that produce chemicals associated with obesity and diabetes. Likewise, artificial sweeteners, although ‘safe’, also produce toxic chemicals via microbes. However, the doses used in laboratory experiments for both are often higher than in foodstuffs and further research on this topic is ongoing. Nonetheless, none of the diets that prolong healthy life – Mediterranean, Japanese or Blue Zone – contain refined or processed food emulsifiers. The Mediterranean diet is full of polyphenols and dietary fibres. It is not entirely clear whether its beneficial consequences on health are due to microbiome change or to other factors associated with the diet, or a combination of these factors, but the more we stick to a Mediterranean diet, the higher the levels of good bacteria in the gut that we know are linked to successful ageing will be. Many researchers now claim that the microbiome is the missing link in understanding the relationship between the gut and food. Whatever the association, it is never too late to start a healthy diet. Changes in the microbiome occur very rapidly – even within 72 hours – and this is so for all ages. The circumstantial evidence for benefits from changing our microbiome is very strong and we have lots of choice in the foods that do this. So there’s no excuse! To keep our microbiome in good shape, two options are currently recommended in addition to dietary change: prebiotics and probiotics. Prebiotics are substances such as inulin, a water soluble fibre sourced from chicory root, on which microbes thrive. Probiotics are microbes themselves, such as the lactobacillus and bifidobacterium species. While both prebiotics and probiotics can be taken as supplements, whether you should shell out for them is another matter: there is little evidence for which prebiotics or probiotics people should consume and when it comes to probiotics, it isn’t certain that the microbes will colonise your gut when they get there or if they will offer benefits to people who already have a healthy microbiome. As we get older, we get more infections – particularly of the chest and kidney – and use more antibiotics. These reduce bacteria and microbiome in the gut. If you are taking antibiotics or have irritable bowel syndrome, there is evidence that probiotics help. Ideally, we should try to combine a prebiotic and a probiotic. Sauerkraut (finely cut and fermented raw cabbage) or kimchi (spicy fermented cabbage) are examples of foods which combine pre and probiotic properties. There is a lot of active research in this area and no doubt in the near future it will be possible to have our individual gut microbiome analysed with tailored recommendations for dietary changes based on individual patterns.
Chapter 9: Eat to Your Heart’s Content
I want to share a short aside which is of interest. Remember the faecal transplant with a turkey baster in Tanzania? Well, believe it or not, this is not so out of the ordinary. Faecal transplant is a well-recognised treatment that works by giving new bacteria and microbiome to a diseased gut. This treatment is widely used in medical practice and, although the method is a bit more refined than the turkey baster, the principles are the same. Faeces from a healthy person are given via an enema to treat serious types of diarrhoea called membranous colitis, which can occur when older patients receive antibiotics.
When I was a junior doctor this was a common and dreaded complication of antibiotic use. The gut became sterile from antibiotics and devoid of microbiota, and consequently was colonised instead by a very toxic bacterium – Clostridium difficile – which took over the gut, covering the gut wall with a membrane that prevented absorption and caused severe diarrhoea – and often death. Clostridium difficile was referred to as the ‘superbug’. Then along came faecal transplants with dramatic curative results. In 1958, Ben Eiseman, a surgeon from Colorado, published a paper with his team describing the successful treatment by rectal faecal transplant of four critically ill people. It took another 30 years before faecal transplants were widely applied to patients with severe antibiotic-induced diarrhoea and even longer before we recognised the gut microbiome and its curative role in faecal transplants. Remarkably, 95 per cent of patients infected with the so called ‘superbug’ are now cured because the transplanted faeces contain new viable and diverse microbiota that fight off the toxin. Today, worldwide, faeces from healthy people are collected, prepared, frozen and stored for use as treatment enemas.
Chapter 10: Sex and Intimacy
I LOVE THIS TOPIC IN THE CONTEXT OF AGEING BECAUSE IT IS so positive and
when a physician takes the time to understand its import for a given patient, it is a rewarding experience. As medical students, we were taught to take detailed histories of all aspects of patients’ lives. Taking a good history from a patient thereafter became the cornerstone of my medical practice. I teach my students that medicine is 90 per cent history and 10 per cent examination and technology. Taking a good history includes asking questions about sexuality and sexual problems. However, in reality, physicians rarely include these details in the routine evaluation. As a medical student, I took my instructions seriously and diligently interrogated patients about sex. I recall how older patients visibly changed, from being meek and passive to engaged and animated, when speaking about their sexuality.
Similar observations inspired Stacy Lindau, a gynaecologist in the University of Chicago who specialises in age-related sexual problems. In her landmark paper on a large series of older US adults, published in 2007, she reported that the majority of adults regard sexual activity as an important part of life. Most are engaged in spousal or other intimate relationships and, a substantial number of men and women partake in vaginal intercourse, oral sex and masturbation even into the eighth and ninth decades of life. But society and the media still struggle with sexuality in older persons; the topic is treated differently when compared with discussions on sexuality in the young and is considered taboo by many.
Chapter 10: Sex and Intimacy
Sex is good for us. Just being physically close with another human increases brain levels of the ‘cuddle hormone’, making us feel happy and safe. Oxytocin is secreted by the posterior lobe of the pituitary gland, a pea-sized structure at the base of the brain. Oxytocin is known as the ‘cuddle hormone’ or the ‘love hormone’ because it is released when people snuggle up or bond socially. If oxytocin is administered to virgin rats, all of a sudden they begin acting like mothers, collecting all the pups and building nests. Prairie voles are monogamous mammals but if oxytocin in the vole’s brain is blocked, they become uninterested in their mates. This hormone promotes extensive additional brain activity, including empathy and trust. In one study, couples who worked on art projects together, rather than alone, boosted levels of the hormone and injected more empathy into their relationship. People on oxytocin have been shown to be more willing to entrust someone with their money than those on placebo. And oxytocin not only increases monetary trust; people on the drug were 44 times more trusting with privacy and confidential information than those on placebo.