Cold weather is here and so are colds, flus and other immune insults. Fortunately, there is a lot we can do to keep our bodies fortified and protected – and much of it can be found at your local supermarket. While it’s true that almost every whole food makes a positive nutritional contribution that aids and supports the immune system, most processed foods have had their important and health-bestowing nutrients manufactured out, and thus negatively impact immunity. They may also undermine immunity by increasing systemic inflammation, disturbing hormone balance and increasing oxidative stress.
Let’s focus on some whole foods and specific nutrients that can help fortify your body and, thus, your immunity. I love this quote from my teacher Laura Knoff to address what nutrients you need and when: “You need everything all the time.” So, don’t wait until cold and flu season hits or until you start feeling run down; the tips, foods and nutrients listed below are necessary all year long!
Vitamin C is essential for protecting the body from free radicals and toxins as well as for supporting your body’s stress response. Too much stress can lead to poor immune health. Vitamin C also maintains the health of the structural components of the body (the blood vessels, tendons, ligaments and more) by supporting collagen synthesis. The basic structure and the integrity of our cells is our first line of defense against infection.
Additionally, vitamin C supports the thymus, one of our body’s main immune organs, which has been shown to stimulate both the production and function of leukocytes (white blood cells). Neutrophils (a type of white blood cell), which attack foreign bacteria and viruses, are also stimulated by vitamin C (LPI, 2009).
Food sources of vitamin C include sprouts, bell peppers, citrus, cruciferous vegetables, kiwi, spinach, apples and berries. Most fresh fruits and vegetables will contribute to your vitamin C intake.
Vitamin A is commonly referred to as the anti-infection vitamin in nutrition circles because it is required for normal functioning of the immune system. The skin and mucosal cells (cells that line the airways, digestive tract and urinary tract) function as a barrier and form the body's first line of defense against infection. Retinol (one of the active forms of vitamin A) and its metabolites are required to maintain the integrity and function of these cells. Vitamin A and retinoic acid (another active form of vitamin A) play a central role in the development and differentiation of white blood cells, such as lymphocytes. Activation of T-lymphocytes, the major regulatory cells of the immune system, also appears to require vitamin A (LPI, 2007).
Liver, cod liver oil, egg yolks, butter from grass-fed cows, shellfish and organ meats contain significant amounts of vitamin A. Leafy greens and other fruits and vegetables contain carotenoids (vitamin A precursors), which are best absorbed when consumed with fat, as vitamin A is a fat-soluble vitamin.
Vitamin D is, in fact, not a vitamin but a pro-hormone that we can obtain from both the sunlight and some foods. It is known to enhance immune function, and deficiency of vitamin D increases the risk of developing infections. Studies suggest that vitamin D supplementation can prevent infections among the general population (Gaby, 2009). Vitamin D is a crucial immune system regulator and an important nutrient for preventing or managing conditions of either hypo- or hyper-immunity, including colds and flu, asthma, autoimmune diseases, inflammation and cancer. It can be particularly effective in helping to reduce the incidence and severity of winter colds and flus – by activating proteins that have antibacterial and antiviral actions in the body. Vitamin D is also essential for antibody production (Bauman, 2011).
Cod liver oil, some mushrooms, sardines, and fortified milk, yogurt and orange juice (but watch the sugar!) are all dietary sources of vitamin D.
Do get your vitamin D3 levels tested the next time you visit your doctor to see where you stand and to determine if extra supplementation is needed.
Stay tuned for Part 2, in which I will share more information about foods and nutrients that boost your immune system.
Linus Pauling Institute (LPI) (2009). Vitamin C, Micronutrient information Center. Retrieved from Linus Pauling Institute, Oregon State University: http://lpi.oregonstate.edu/infocenter/vitamins/vitaminC/
Amanda is a nutritionist with a holistic attitude about health. She graduated from the George Washington University School of Public Health and Health Services, with a Bachelor of Science in Exercise Science and a pre-med concentration. To further round out her holistic beliefs, she studied with some of the world’s top public health professionals and obtained her Master’s degree in Public Health Nutrition, with a concentration in Health Promotion, at The London School of Hygiene and Tropical Medicine. Additionally, Amanda completed a program in Holistic Nutrition at Bauman College in Berkeley, California. She is a Certified Nutrition Consultant and works with individuals (adults and children) and companies in the Bay Area. Amanda is also the in-house nutritionist at the Village Doctor in Woodside. Contact her for one-on-one nutrition counseling; together you will create an actionable plan individualized for your needs and lifestyle.