There are many things people can live without, but adequate food is not one of them. As food prices increase and finances become more uncertain, ensuring that purchased food meets nutrient needs becomes more challenging. Essential nutrients in food are required for multiple functions in every cell in the body to maintain a healthy life. As the COVID-19 pandemic continues, ongoing stress may be affecting your immune system, leaving you more vulnerable to illness.

Question: Which nutrients and foods help to maintain or improve the immune system?

Answer: To maintain immune health, dietary protein and at least seven vitamins (A, D, C, E, B6, B12 and folate) and five minerals (copper, iron, magnesium, selenium, and zinc) are needed in adequate amounts.

Fruits and vegetables are promoted for health. However, these foods are good sources for only four critical immune vitamins and minerals. Therefore, a variety of whole and fortified foods or dietary supplements is needed to meet these vitamin and mineral needs.

With food costs increasing, it is becoming more challenging to consume adequate protein. Lean animal protein foods provide high concentrations of many of the critical nutrients needed by the immune system. Plant protein sources are less expensive and can be an essential component of meeting immune system nutrient needs.

Q: What plant foods are good protein sources for maintaining a healthy immune system?

A: Lentils and beans can be an inexpensive source of protein, especially when purchased dry and prepared at home. However, these legumes also contain fiber and other natural substances that inhibit the absorption of minerals needed for immune system health.

Tofu is a high-protein plant food that costs significantly less than most animal protein foods and can be incorporated into many types of dishes. When frozen and thawed, tofu takes on an entirely different texture that is somewhat like meat. Soft tofu takes on the characteristics of ground meat, and firm tofu can be cut into stew-cut pieces. When combined with small amounts of meat, these tofu forms take on the flavors of the meat and spices used in a recipe.

Q: Are there potential downsides to using beans and other legumes as primary protein foods in the diet?

A: Many of these foods contain naturally occurring substances (goitrogens) that decrease iodine absorption and can interfere with normal thyroid function. Adding a small amount of iodized salt can help maintain a healthy iodine supply for thyroid function and metabolism. Keep in mind that sea salt has very little iodine due to the natural evaporation of iodine.

As we often have stressed, keep a wide variety of food in the diet. Variety is important to meeting nutrient needs and enjoying food!

Alan Titchenal, Ph.D., C.N.S., and Joannie Dobbs, Ph.D., C.N.S., are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. Dobbs also works with University Health Services.