Inflammaging, foods and the brain

During this week, we’ve discussed unhealthy or pathological eating behaviours – from eating disorders, such as anorexia, orthorexia and bulimia to the effects on the brain and on the body of nutritional deficits and of diets too rich in fructose. In this lecture, too, we will talk about the relationship between nutrition and health, but we will focus on the role of inflammation in ageing, and on a few foods that could help slowing it. The key notion of this lecture is “inflammaging”. Inflammaging is the idea that as we get older there is a state of constant activation of our immune system and, as a consequence, the inflammation markers in our body increase.

This status of persistent low-grade inflammation has been linked with many age-related diseases, such as parkinson’s disease, depression, cognitive decline, and metabolic diseases such as type 2 diabetes. Since the early 2000’s scientists have studied the causes of this inflammatory state, and it seems that an excess of nutrients such as fats and glucose and the imbalance of the bacterial equilibrium in our gut can play a role in this process. The role of a healthy bacterial population in our gut – or gut microbiota – is a fascinating topic on its own, and is the subject of other lectures in this mooc.

Chronic, diffuse inflammation states are marked by an increase of some specific molecular signals , called interleukins, and these molecules can cross the blood-brain barrier in different ways once in the brain, they interfere with numerous brain functions – for instance, by disrupting the availability of serotonin a neurotransmitter involved in functions such as feeding regulation, mood and sleeping. At the same time, interleukins can cause neurotoxicity and cell death in the brain by increasing the level of another neurotransmitter, glutamate. What this means is that our diets can be a cause of a chronic inflammation state in our body, and inflammation can, in turn, affect the functioning of our brains, Causing symptoms such as fatigue, cognitive impairment, depressed mood and sleep disturbances.

The inflammatory state can also directly affect the hypothalamus – a structure that is involved in the regulation of appetite and bodily weight. This could lead to increased weight, which will cause more inflammatory response and make it harder to break the inflammaging downwards spiral. Is there anything we can do to avoid slipping further down the spiral? One early approach was to test anti-inflammatory drugs, such as aspirin. Even if the results of studies in men are mixed, it seems that these drugs can lower the inflammatory state and therefore, in theory, reduce the probability of illnesses such as diabetes or neurodegenerative diseases.

This approach, however, requires people to stay on a weekly (or daily!) Drug regimen for many years, with the associated monetary costs and health risks due to side effects. A similar argument can be made for dietary supplements, such as vitamins, antioxidants and fish oil. Fish oil is rich in omega-3 fatty acids, a type of fat that has been the subject of extensive scientific research. There is some evidence that sufficient dosages of omega-3 decrease the inflammation state in the body, but the results specific to inflammaging are still scarce.

Therefore, as omega-3s can be found in a number of foods, a tastier – and sometimes cheaper – alternative to supplementation comes from walnuts, flax and chia seeds and, of course, from seafood and fatty fish. This is one of the reasons why these foods are often mentioned as healthy additions to our diets, especially when substituting less healthy foods. Whole grains, fruit and vegetables are also linked to a decreased inflammatory state, likely because of their content in term of antioxidants and vitamins, And because of the beneficial effects of dietary fibre on our gut bacteria. Similar results apply to curcumin, a molecule contained in tùrmeric and also in ginger.

Curcumin is a potent anti-inflammatory when tested on cell cultures, but in clinical tests its effectiveness seems to be much lower. due to its potential relevance, studies on curcumin and on its combination with other molecules, such as piperine, are still ongoing. In conclusion, there are a lot of specific molecules and foods that can potentially decrease inflammation and prevent age-related illnesses, but in many cases we don’t have robust evidence of their efficacy in humans. On the other hand, a healthy diet will contain omega-3 from vegetable and animal sources; prebiotics from some fruits and vegetables; probiotics from yogurt, kefir and fermented vegetables such as kimchi.

no single element is an antidote to ageing and illnesses, but a healthy, tasty and varied diet can be the first line of defence against inflammation and its consequences.