How A Balanced Diet Keeps Infections Away
In these unprecedented times of COVID19 pandemic, people are increasingly seeking information on importance of healthy food to regulate immunity, keep viral/other infections (communicable diseases)at bay.
As for diet, diversity and variety are key factors. There are specific nutrients and food which help maintain optimal immune function and good health. Vitamins A, E and D - the three fat soluble vitamins; C & B vitamins, and minerals such as zinc, selenium, iron, copper etc. and phytonutrients, amino acids, fatty acids help check uncontrolled proliferation of immune cells that may cause more harm than good to the body, and also help protect us against viral infections. These nutrients are critical for the function of T cells, B cells, killer cells, macrophages, neutrophils/granulocytes that are involved in the killing and elimination of infectious microbes.
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These nutrients and phytonutrients play other important roles too. For instance, vitamin A maintains structure and function of the mucosal epithelial cells of the respiratory tract and enhances mucosal immunity (critical for prevention of respiratory infection), vitamin E, beta-carotene (precursor of vitamin A), vitamins C & B, Zinc, Selenium act as potent antioxidants and reduce oxidative stress in the body.
Some locally available foods that are rich sources of the above-mentioned nutrients are:
•Papaya, guava, apple, grapes, mango and many other fruits: are rich in beta carotene (precursor of Vitamin A), Vitamin C, Potassium, B vitamins and folate which help in overall maintenance of health and immunity
•Citrus fruits like oranges, tangerines, lemons, sweet lime, goose berries, and Red bell pepper are good source of Vitamin C
•Green Leafy Vegetables are rich sources of beta carotene (precursor of Vitamin A), vitamins C and E, anti-oxidants and fibre
•All seasonal Vegetables and spices are rich sources of multiple micronutrients and antioxidants that aid in immune function, regulate gut microbiota and reduce inflammation
•Curd is a source of many nutrients, improves gut health by regulating gut bacteria; aids immune function and reduces inflammation
•Legumes (chickpea, green gram, black gram, lentils, and beans) provide many nutrients including iron and Zinc
•Millets are good sources of multiple micronutrients and fibre
•Meat and poultry provide many nutrients including iron, zinc and essential amino acids
•Fish are rich sources of protein, vitamin A, Vitamin E and essential fatty acids
These nutrients are usually present in a good balanced diet. But there two important points to be noted: One, though deficiency of one or more of these nutrients can increase the frequency and severity of infections, supplementing them among healthy population doe not confer any additional benefit; and two, some of these nutrients in excess can increase susceptibility to infections.
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Here are some useful dietary and lifestyle guidelines to follow:
Micronutrients (vitamins and minerals) and phytonutrients that are primarily available in fruits, vegetables, greens, nuts, and whole grains play a crucial role in helping ensure optimal immune function. These nutrients also
•Enhance both native and adaptive immune function and prevent infections,
•Regulate immune function, keep inflammation under control and prevent tissue damage,
•Aid immune memory formation that helps prevent reinfection with the same pathogen,
•Help clear/scavenge oxidant species (toxins) that are produced in large quantities in the body during infection and immune response, and
•Increase beneficial probiotic bacteria in the intestine, regulate gut microbiota, maintain intestinal integrity and thereby reduce transmission of toxins from the intestine to the blood
Therefore, ensure substantial servings of fresh fruits and vegetables (as much as 450 to 500gm per day per person) and opt for whole grains. These can be easily drawn from what is locally produced, seasonal, available and accessible.
Limit consumption of highly processed foods, avoid fruit juices & carbonated drinks - these are high in fat, salt and sugar, and poor in nutrients like vitamins, minerals, phytonutrients
Consuming meat, poultry and eggs is not risky, but you must wash your hands thoroughly after handling raw meat, eggs or even vegetables. Thoroughly cooked meat/ poultry may be included in moderation.
Avoid too much fat (no more than 30 gm/person/day, preferably from more than 2 varieties of oils), salt (no more than 5gm/person/day), and sugar (which is just calories with no nutrients, keep it to bare minimum)
Maintain ideal body weight (less than 18.5 BMI is undernourished, and more than 25 is overweight for Indians). Being underweight or overweight/obese – impairs immunity and increases inflammation
Moderate physical activity/yoga will reduce stress and build immunity.
Keep your body hydrated with adequate water intake for good immune response to any infection
Smoking & alcohol adversely affect immunity and increase the risk and severity of infections, hence must be avoided
Tips for those suffering from diabetes and other chronic illnesses:
Most infections can be prevented by practicing good personal hygiene such as washing hands before preparing or eating food; washing hands after cleaning vegetables or meat; stroking pets/animals; covering mouth with a tissue or cloth while coughing or sneezing. People with diabetes or other chronic illnesses should continue their regular medication and prescribed healthy dietary patterns along with adequate physical activity and keep themselves stress free. Diabetics and patients with chronic kidney disease and hypertension are more vulnerable to infections and should strictly follow social distancing and hand hygiene.
For more information, please check My Plate For The Day designed by the National Institute of Nutrition, which depicts 8 different kinds of foods to be consumed in a day, to obtain different vitamins, minerals and phytonutrients required for optimal health and immunity.
(The author is the Director of ICMR-National Institute of Nutrition)