Catherine Conlon: Diet is crucial to our ability to fight Covid-19 and other diseases

Reducing salt, sugar and saturated fat across the board would improve the diet of the entire population.

As I navigate middle age, no longer young but not yet old, I am aware of friends and colleagues succumbing to the early stage of the bell curve of disease, accidents and even death — the beginnings of the process of disintegration.

An understanding, never spoken that the news of a stroke, a surprise death, a tumour, or Alzheimer’s diagnosis will not be the last. 

The body is beginning to creak and protest, and I wonder how much of this is age and how much is self-inflicted.

Professor Cliona O’Farrelly, chairwoman of comparative immunology at Trinity College Dublin, suggested in the Irish Examiner recently that the Covpandemic is "teaching us how to live better". 

"I often wonder if the entire nation lost a stone would Omicron have less effect in the autumn?" she wrote.

What is the association between diet and inflammation and how can this affect our immunity?

The role of the food industry in obesity and Covid-19 was considered in an editorial in the British Medical Journal in June 2020.

It argued that the food industry shares the blame, not only for the obesity pandemic but also for the severity of Covid-19 and its devastating consequences. 

The editorial urged food industries to immediately stop promoting and governments to force reformulation of unhealthy food and drinks.

"Reducing salt, sugar and saturated fat across the board would improve the diet of the entire population and bring even greater benefits for people who are most socially deprived," the editorial concludes.

"The toll of morbidity and mortality from Covid-19 has made this more apparent and more urgent than ever."

Fast food

The link between Covid-19 and fast-food consumption was examined in a review in International Journal of Food Properties in 2021. The review found that diets high in refined carbohydrates and saturated fats contribute to the prevalence of obesity and type-2 diabetes and these disorders increase the risk for severe Covid-19 morbidity and mortality.

Fast food consumption activates the intrinsic immune system and impairs adaptive immunity, leading to chronic inflammation and impaired host defence against viruses.

It is becoming increasingly apparent that one of the best ways to reduce inflammation is not in the medicine cupboard but in the fridge.

A recent blog article from Harvard Health Publishing in November 2021 states that following an anti-inflammatory diet can help to fight inflammation.

Dr Frank Hu, professor of nutrition and epidemiology in the Department of Nutrition at the Harvard School of Public Health, suggests that one of the most powerful tools to combat inflammation comes from the local grocery store.

"Many experimental studies have shown that components of food or beverages may have an anti-inflammatory effect," he said.

Foods that cause inflammation are generally the ones that are considered bad for our health, including fizzy drinks and refined carbohydrates, as well as processed meats, chips, and other fried foods.

Anti-inflammatory diets

The Mediterranean diet, which is high in fruits, vegetables, nuts, wholegrains, fish, and healthy oils is an eating plan that closely follows the tenets of anti-inflammatory eating.

Most research that focuses on foods that are associated with low-level inflammation are linked to Western-type dietary patterns high in processed meats, saturated fat, refined sugars, salt, and white flour while being low in fibre, nutrients, and phytochemicals.

These diets also tend to be calorie-dense with a high glycaemic load, with the potential for blood sugar surges, insulin resistance, and excess weight gain. The evidence shows that these diets are associated with increased blood markers of inflammation.

Low-level inflammation can lead to a build-up of fatty acids in fat tissue and other tissues, promoted by a high-fat or high-sugar diet. 

This build-up of fatty acids can send signals to immune cells that produce inflammation.

Inflammation in the pancreas can lead to insulin resistance and diabetes. This means that the combination of carrying extra fat (obesity) and eating a diet high in saturated fat and refined sugars increases the risk of cell damage because of increased immune cell activity.

Dietary patterns that are anti-inflammatory are rich in wholegrains, fruits, vegetables, legumes, nuts, seafood, and olive oil.

The goal of an anti-inflammatory diet is to eliminate pro-inflammatory foods and replace them with nutritionally adequate foods that are high in anti-inflammation compounds.

For example, avoiding refined flour, excess salt from precooked foods and sugary drinks and increasing fruit, vegetable and wholegrain intake are among common recommendations.

What does this look like in practice?

• Drinking water instead of sugar-sweetened or fizzy drinks.
• Increasing fibre intake with wholegrains, fruit, and vegetables.
• Eating fatty fish such as sardines or salmon twice a week.
• Eating more nuts, seeds, and olive oil.

For me a good rule of thumb is half of every meal or snack should be fruit and/or vegetables. Replacing cereal and toast with fruit and yogurt and toast. Replacing a chicken sandwich and yogurt with a salad or homemade soup and some wholegrain bread. Replacing two biscuits and a coffee with one biscuit and a banana or an orange. Never ever drinking fizzy drinks.

Half of your plate should be loaded with fruit and/or vegetables.

The portion plate from Karl Henry — available in retail stores — is divided into three sections, half for salad and vegetables, one quarter for protein and one quarter for carbohydrate. 

With meal suggestions on the plate, it is a good guide to keeping healthy lunches and dinners very easy.

Amber Charles in a special feature for Honest Nutrition in March 2022 takes an in-depth look at the evidence that an anti-inflammatory diet can reduce markers of inflammation in the diet as well as risk of chronic conditions.

Researchers suggest that risk of heart disease is reduced by lowering inflammation in blood vessel walls and maintaining their health and resilience. 

Less severe symptoms of chronic conditions such as muscle pain, swollen joints, itchy skin, tiredness, and mood swings are further potential health benefits as well as the potential to reduce fatigue brought on by chronic conditions.

We have a better understanding now of how pro-inflammatory food is causing increased propensity to chronic disease including heart disease, type-2 diabetes, and cancer, as well as an impaired immune response to Covid-19.

Legislation

The Government can support individual efforts to eat an anti-inflammatory diet with legislation to enact the Public Health (Obesity) Act it committed to in June 2020.

This legislation would include restricting the marketing of unhealthy food to children.

Other measures include taxes on foods high in fat and sugar that would incentivise reformulation to healthier products.

A tax on unhealthy foods along with subsidies on healthy foods would shift consumption towards a healthier diet, making a real impact on obesity, chronic disease as well as morbidity and mortality from Covid 19.

This policy would be particularly influential among low-income groups as the cost-of-living spirals.

All of this would shift the culture away from junk food that has been destroying our health and wellbeing for decades. The profit-driven global market has had its own way for too long.

A Public Health (Obesity) Act is an opportunity to forge policy that is robust, underpinned by science and with the prospect of Covid- 19 continuing staying with us for the near future, badly needed.

Dr Catherine Conlon is senior medical officer in the Department of Public Health, St Finbarr’s Hospital, Cork and former Director of Human Health and Nutrition, safefood. All views are author’s own.