The kids are going back to school, and this time of year usually brings with it a wave of viral infection. Most of them have had a couple of months off, some have gone to camp, gone on vacation, or to visit family. School is where they all congregate to share the “souvenir” viruses and bacteria they picked up in all those places. Then they bring those souvenirs home to parents and siblings.

Rather than waiting until you or your child catches a virus this fall to explore immune support supplements, we suggest building a strong defense now. Take a critical look at your nutritional preparedness for cold and flu season. Bolster your immune system with powerful vitamins and nutrients to fend off viral intruders before they take a toll on your mental and physical health.

Cold and Flu vs. Mind and Body

We all know that a cold virus can bring on much more than just physical symptoms. Even if you could take away the excess mucus, body aches, and chills, getting sick can leave you feeling depressed and helpless, or anxious and overwhelmed. Of course, the seasonal shift alone can bring on a low mood– no virus necessary. There are multidirectional connections between the brain and body, and more and more, the world of functional medicine is uncovering the links between complete nutrition and physical and mental health. A healthy gut and balanced diet can help to keep your body moving, your mind at peace, and the immune system firing on all cylinders. 

Your body’s immune system has two lines of defense against pathogenic threats. The first is your innate immune system: physical barriers like skin, hair, and mucous membranes, chemical defenses like digestive acids and enzymes, inflammation, and killer cells sent to an infection site to disable and break down anything foreign. The second line of defense is the adaptive immune system, which builds antibodies to target specific invaders that you’ve been exposed to in the past. All of these elements require specific nutritional building blocks from the diet. Without proper nutrition, the body struggles to defend itself and is more likely to succumb to illness, cellular damage, and associated symptoms.

Gut Health for Immunity and Mood

The gut is an important barrier between the circulation and anything ingested. The types of microorganisms living in the gut can have an effect on whether pathogens invade via intestinal absorption to multiply in the body. “Probiotics” are yeasts and bacterial species that benefit the human host when their populations dominate the available adhesion sites in the gastrointestinal tract. Probiotics can increase the activity of macrophages and natural killer cells, modulate the secretion of antibodies and cytokines, enhance the gut epithelial barrier, support healthy levels of mucus secretion, and contribute to the competitive exclusion of other, pathogenic bacteria [1]. Probiotics can also affect the secretion and receptor activity of mood-modulating signals such as serotonin, dopamine, and GABA by gut cells [2].

When the health of your gut is compromised, not only can unwanted pathogens move into the bloodstream more freely, but your body may also have trouble digesting and absorbing the micronutrients (vitamins and minerals) needed to properly fight back. Restoring health to the gut is a first step in supporting your immune system, mood, and overall health. Taking a daily probiotic supplement like BioMaintenance™ Shelf Stable Probiotic can help restore balance to the microbiome. A prebiotic supplement like BioMaintenance™ Prebiotic + Fiber feeds the beneficial microbial species and can optimize the transit time of digested material for maximized nutrient absorption.

Nutrients for Immunity and Mood


Antioxidants are a great start for optimizing your health as we enter cold and flu season. Antioxidants not only clear out the free radicals that cause oxidative damage to cells, but they can also help rebuild and repair the damage that has previously occurred. If your cells aren’t busy fighting oxidative stress, more energy can be spent fending off a viral invasion. You can get a diverse and plentiful dose of antioxidants by eating a rainbow of brightly colored fruits and vegetables or by taking a multivitamin/mineral supplement with vitamins such as A and C. 

Vitamin D

Vitamin D is another micronutrient that has been extensively studied for its cold-fighting and mood-boosting properties. While vitamin D is not technically essential if you are getting proper sun exposure, wintertime darkness often leads to insufficiencies. Supplementary vitamin D has been shown to stimulate the innate immune system, induce autophagy (clearing out damaged cells) in response to both bacterial and viral infections, and reduce the risk of more serious acute respiratory tract infections [3]. Almost all cells in the immune system (except B cells) have vitamin D receptors, providing evidence that vitamin D is an important mediator of immune response [4]. 


Zinc has direct effects on innate and adaptive immune functions and acts as a cofactor for more than 300 enzymes [5]. Unbound zinc ions have even demonstrated a direct antiviral effect on rhinovirus (common cold) replication [4]. 

All of these vitamins, in combination with research-backed herbal extracts, Sambucus (elderberry) and Andrographis, are available in the potent supplement, Acute Immune Boost, from Metabolic Maintenance. 

B Vitamins

Folate (B-9), B-6, and B-12 are a powerful trio. All three are required in their activated forms for methylation to take place in our cells. Methylation is a chemical process necessary for numerous physiological functions, including the proper production of neurotransmitters (such as serotonin) that modulate mood, and the proliferation of new cells (such as immune cells). Clinical studies have demonstrated that vitamin B-6 deficiency impairs lymphocyte maturation and growth, antibody production, and T cell activity [4]. Folate deficiency has been shown to negatively impact immunity, reduce resistance to infections, and lead to a depressed mood, fatigue, and feelings of anxiety [4,6,7]. B-12 is required for folate metabolism, and so can cause a secondary folate deficiency if levels are low. B-12 is also a modulatory agent for cellular immunity and contributes to lymphocyte production and natural killer cell activity [4]. While all of these vitamins can be found in foods like red meat and dark leafy greens, consumers should be wary of supplements and fortified foods containing “folic acid” (the synthetic form of folate). A significant amount of the population cannot activate this form of folate efficiently, due to genetic differences [7]. These individuals sometimes express symptoms of a folate deficiency even when consuming recommended amounts of folic acid. 

Luckily, L-methylfolate, the activated form of folate that participates in methylation, can now be taken as a supplement. This form of folate is more bioavailable than folate in food and can be used by anyone, regardless of genetic variability [7]. Metabolic Maintenance® offers L-methylfolate supplements in a range of dosing options, with or without complementary cofactors and B-vitamins, under the label of our sister company, MethylPro®.


  1. La Fata, Giorgio, Peter Weber, and M. Hasan Mohajeri. “Probiotics and the gut immune system: indirect regulation.” Probiotics and antimicrobial proteins 10.1 (2018): 11-21.
  2. De Vadder, Filipe, et al. “Gut microbiota regulates maturation of the adult enteric nervous system via enteric serotonin networks.” Proceedings of the National Academy of Sciences 115.25 (2018): 6458-6463.
  3. Martineau, Adrian R., et al. “Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data.” bmj 356 (2017).
  4. Maggini, Silvia, et al. “Selected vitamins and trace elements support immune function by strengthening epithelial barriers and cellular and humoral immune responses.” British Journal of Nutrition 98.S1 (2007): S29-S35.
  5. Rink, Lothar. “Zinc and the immune system.” Proceedings of the Nutrition Society 59.4 (2000): 541-552.
  6. Coppen, Alec, and Christina Bolander-Gouaille. “Treatment of depression: time to consider folic acid and vitamin B12.” Journal of psychopharmacology 19.1 (2005): 59-65.
  7. NIH. “Folate”. National Institutes for Health Office of Dietary Supplements – Fact Sheet for Health Professionals. Accessed October 13, 2020.