March is National Nutrition Month, so I thought it might be a good idea to look at the link between nutrition and our immune systems. After all, immunity is a big topic right now. Vaccines against COVID-19 are rolling out around the world, offering a glimmer of hope that the pandemic can be tamed. This article is not intended to suggest that you can fight COVID-19 by diet alone, but rather to share information about how the immune system can be impacted by nutrition.
What is the immune system?
Our immune system is a network of intricate stages and pathways in the body, which protects us against harmful microbes as well as certain diseases. It recognizes foreign invaders (pathogens) like bacteria, viruses, and parasites and takes immediate action.
The first line of defense is a set of protective barriers in the body, such as:
- Skin that keeps out the majority of pathogens
- Mucus that traps pathogens
- Stomach acid that destroys pathogens
- Enzymes in our sweat and tears that help create anti-bacterial compounds
- Immune system cells that attack all foreign cells entering the body
A breakdown in any of these barriers could result in pathogens entering the body.
The body is able to acquire immunity (called “adaptive immunity”) by learning to recognize a pathogen and creating antibodies to destroy it. Certain white blood cells are responsible for making the antibodies, and others clean up after the pathogen is destroyed. Adaptive immunity works for some pathogens, but not all. For example, you may develop immunity to the measles but not the common cold.
What is role does nutrition play in the immune system?
If you have ever loaded up on vitamin C when you have a cold, or fed your sick child chicken noodle soup, you have an idea that there is a link between nutrition and immunity.
An American Journal of Clinical Nutrition article cited nutrition as a critical determinant of immune responses. Malnutrition was said to be the most common cause of immunodeficiency worldwide. Deficiency of just a single nutrient can impair the body’s ability to generate an immune response. Most of the nutrients are vitamins and minerals, but low protein intake can also result in reduced immunity.
The following is a list of nutrients that help boost the immune system, as well as some dietary sources.
| Nutrient | Dietary Sources |
| Copper | Liver, crabs, cashews |
| Folic Acid | Beef, liver, black-eyed peas, spinach, asparagus |
| Iron | Oysters, white beans, spinach, meat (especially red meat) |
| Vitamin A | Retinol (liver, dairy, fish), carotenoids (sweet potatoes, carrots, spinach) |
| Vitamin C | Tomatoes, citrus fruit, sweet peppers, broccoli, kiwi fruit |
| Vitamin E | Sunflower seeds and oil, almonds, safflower oil, peanut butter |
| Vitamin B-6 | Chicken, cereals, bananas, pork loin, potatoes with skin |
| Vitamin D | Sunlight, fish oil, milk |
| Protein | Meat, dairy, tofu, nuts, seeds |
| Selenium | Brazil nuts, sardines, ham |
| Zinc | Oysters, beef shank, turkey (dark meat), crab, chickpeas |
For most people, it is best to get nutrients from whole foods, but supplements may be necessary at times. Talk to your healthcare professional if you have any dietary restrictions, digestive problems or food allergies.
Herbal supplements
Several herbal supplements have been suggested to boost immune function. Echinacea has been shown to destroy influenza viruses in cell studies, but research in humans is inconclusive. Garlic has been shown in some studies to reduce occurrences of the common cold. Catechins, found in green tea, may have some effect on replication of flu and cold viruses and boost immune activity. In all cases, more research is needed.
Other considerations
In addition to getting sufficient nutrients, there are other things that you can do to boost your immune system.
- Avoid processed foods
- Exercise regularly
- Get plenty of sleep
- Do not smoke
- Keep alcohol to a minimum
Sources: Harvard School of Public Health https://www.hsph.harvard.edu/nutritionsource/nutrition-and-immunity/
American Journal of Clinical Nutrition
Healthline www.healthline.com