Using Nutrition to Help Perceive and Combat Flu

Byron J. Richards, Board Certified Clinical Nutritionist

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Using Nutrition to Help Perceive and Combat Flu
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The flu is a subject of concern for many Americans each year. Your immune system is perfectly capable of mounting a highly effective response against any never-before-seen virus. This article explains how your immune system does this, what nutrients can help, what forms of stress handicap this capability, and how to help prevent the cytokine storm that would be associated with a severe flu episode.

Perception 101

Various foot soldiers of your immune system, called innate immunity, come into contact with any viral invader. During this front line scuffle the invader is broken down into pieces. The invader's unique look, called an antigen, is then presented to cells of your higher powered, cell mediated immune response, called adaptive immunity. The perception part of your immune system's operation is based on antigen presentation.

You have three main types of antigen presenting immune cells: macrophages, B lymphocytes, and dendritic cells. Macrophages and B lymphocytes can only present antigens to memory related immune cells. Therefore, they do not initially help your higher powered forces respond to a new type of virus, such as the current swine flu.

This is the main reason why previous experience has some advantages. It is also why the vaccination theory has some utility. If your immune system has experience with a previous exposure, then a greater number and type of immune cells can participate in the initial immune response. This increases the potential for a more robust immune response.

Dendritic cells are the most important antigen presenting immune cells. This is especially true when the invader is a new variety. Dentritic cells present antigen to naive T cells, the type of T cells that activate the higher powered immune response when it is a new type of invader.

Dendritic cells are in your skin and on the inner part of the mucosal linings of your nose, lungs, stomach, and intestines. They constantly take samples of whatever you come into contact with.

If they recognize a viral enemy, they help call ground troops to the scene for immediate front line action (innate immunity). They present the antigen of the enemy to your higher powered immune response (adaptive immunity) so that you can mount a highly aggressive immune response targeted for the specific enemy.

Most of this dendritic cell activity takes place on barriers that separate your internal body from the outside world. When your immune system is working well, the virus does not breech these barriers and enter your body. You do not feel sick, even though you may be mounting an immune response.

During a typical flu season, there is an extremely high probability that you will be exposed to the flu. The odds of whether or not you actually get sick depends in part on how well your dendritic cells do their job.

You don't have to actually get sick or be vaccinated in order to develop a memory enhanced immune response for a future flu encounter. If your immune system is successfully defending you from exposure to any current flu, which will be the case for many, then your memory related immune cells will become “trained” and be prepared for the same invader in future years.

Dendritic cells are also on patrol in your blood. These cells are in an “immature” state. They constantly nibble on whatever is around them, taking small samples to see if anything is foreign. If they do identify a foreign flu invader then they rapidly mature into active dendritic cells, and the battle is on. When there is less likelihood of an invader, this is part of the way your immune system carries out patrols without having an aggressive immune response going on at the same time.

Think of it this way: Your borders are lined with well-armed soldiers who have "shoot to kill" instructions if a viral enemy is identified. Dendritic cells on the borders are always on high alert. This is called mucosal immunity.

Dendritic cells in your circulation are like a friendly police officer. They constantly mingle and brush shoulders with the crowd while routinely checking identification. Even though these internal dendritic cells are in a more relaxed or casual state while on patrol they are capable of springing into deadly action and coordinating an all-out attack on the invader and anything that looks like that invader.

The fundamental nutritional concerns relating to dendritic cells are whether or not you have enough of them and if you can you readily make more when needed. These concerns are similar for all types of immune cells needed at a time of battle, as you actually manufacture immune troops on demand once a battle is taking place.

The most important calorie needed for any type of immune response is protein. Without adequate dietary protein many aspects of the immune response are seriously handicapped. The production of new immune cells requires protein as the raw material for formation. Whey protein1, in particular, is an excellent immune support food.

You also need the energy to support the immune cell production line. If you are fatigued, or worn down then you can assume that your ability to make immune cells will be adversely effected. Conversely, any dietary supplement that improves your energy will by definition support the energy intense requirements of a vigorous and effective immune response. This assumes that the dietary supplement isn't based on stimulants and your energy level isn't based primarily on caffeine intake.

Because your immune system must make numerous cells rapidly, the ability of DNA to replicate at an optimal pace is vital. This function requires folic acid2 (operating synergistically with immune-boosting B123). The lack of folic acid4 is known to reduce the immune response.

You also need iron to form immune troops5. Low iron has been proven to reduce the efficient immune response of dendritic cells6 (as well as other immune cells). Iron supplements should only be of the best quality (such as iron glycinate), otherwise too much iron in a free state in your gut (from cheap supplements and prescription iron) can disturb your digestive tract and make bacterial infections grow.

Basic nutrient deficiencies are common in the elderly, young children, vegetarians, menstruating women (especially if blood flow is heavy), andthose who eat junk food diets. Deficiencies are also seen during high stress, and with frequent exercise. It is widely acknowledged that a number of nutrients7 are required for healthy immune system function.

Immune System Tolerance

Just about everything dendritic cells do in the process of coordinating an effective immune response is HIGHLY INFLAMMATORY BY DESIGN. This is important to understand, as excess inflammation, even low-grade excess inflammation, sets the stage for early onset of just about every disease of aging. So here we have the opposite situation, your immune system uses inflammation as a tool to help combat the enemy.

Note that anti-inflammatory nutrients do not interfere with this process; rather they tend to make it work better. On the other hand, anti-inflammatory drugs can be a major problem – especially the TNFa-blocking drugs8 now in common use for arthritis.

Dendritic cells deal with inflammation as the nature of their job, just as a cook works over open flames to broil food. Success depends in part on being able to handle a lot of heat without getting burned. A severe infection will test the boiling point. Your dendritic cells must have a mechanism for dealing with massive numbers of invaders; i.e., zillions of antigens.

If such a mechanism is not functioning then inflammation overload can take place in an attempt to respond to the infection. A severe case of overload is known as a cytokine storm. This would be like having a deep fat fryer catch fire in a kitchen and possibly burn the whole restaurant down. However, even if excess inflammation isn't so severe, it can have serious consequences to the quality of your immune response.

The ability to handle or tolerate a high level of inflammatory demand is vital to maintain an efficient immune response under pressure. Scientists have spent considerable energy trying to figure out how your dendritic cells do this. They were surprised to find out that two vitamins9 are required for dendritic cell immune system tolerance, vitamin A10 and vitamin D11. Yes, without adequate supply of these two nutrients your immune system can overheat and meltdown in the process of trying to do its work.

Furthermore, vitamin D12 is also needed for dendritic cells to properly present their antigens to the adaptive immune system, a critical step in mounting a high powered, flu specific immune response.

When you stop and realize that 70% of the children in the U.S. are known to be vitamin D deficient and that children are a group at risk for potentially severe flu, you have to wonder why our government isn't telling parents to have their kids take some extra vitamin D, and be sure they have adequate vitamin A to reduce the risk of contracting a severe bout of flu.

I recommend 1,200 IU of vitamin D for children under age 6, and 2,500 IU of vitamin D for everyone older than 6. More may be needed by some people, especially if they are under high stress or suffer from other forms of excessive inflammation such as chronic pain or an autoimmune problem.

Lactoferrin, an important component of mother's milk, boosts many aspects of immunity13 and specifically helps dendritic cells to have better tolerance for inflammation14 while at the same time helps them present antigen more efficiently. It is obvious that supporting immune tolerance is vital in times of infection. It is not surprising that the survival of the human race depended on having lactoferrin in mother's milk, a tool that could be used in case there was not adequate vitamin A or D available in the mother's diet.

Dendritic cells also require antioxidants; vitamin C15, vitamin E16, and NAC (N-acetyl-cysteine17) in particular, allow you to sustain an immune battle and not have too much inflammation18 that tilts in the direction of a cytokine storm. It has now been demonstrated that dendritic cells head in the direction of inflammation once there is too much free radical damage. The only solution for this free radical damage is antioxidants. Antioxidants also power and protect the weapons your immune system uses to shoot “free radical bullets” at the enemy. The longer the battle the more weapons you need.

New science shows that your dendritic cell team is involved with the initial identification of an invader. It is also a central communication network in your immune response. For an optimal immune response to occur it must be maintained in a high state of function during the entire infection.

Thus, we need vitamin A, vitamin D, and possibly lactoferrin for basic immune system function. We must also enough antioxidants especially vitamin C and NAC, so that the free radical damage that naturally occurs during battle is minimized. Nothing replaces adequate nutrition.19 It's absolutely vital for an optimal immune response and reduced risk of a serious bout of flu or a life threatening cytokine storm.

Superior Dendritic Cell Fitness

Dendritic cells are not only involved in an efficient immune response, they can also be directly involved in many inflammatory problems20 associated with poor health. In other words, they can already be all worked up and generally unfit for high performance duty.

The immune system cytokine known as TNFa (tumor necrosis factor alpha21) is the primary signal that arouses dendritic cells and calls them into a higher state of pro-inflammatory activity. Many of your front line immune troops release TNFa when an invader is encountered, which is all part of a system of healthy function to get your immune system ready to defend you.

Unfortunately, these very same immune cells required for a vigorous immune response are also involved in general inflammatory wear and tear of any kind. This means that under stress, especially excessive stress that results in wear and tear, the level of TNFa will rise and consequently activate dendritic cells.

Too much fat also produces TNFa and adds to the systemic TNFa load, in turn activating dendritic cells from obesity. This is why obesity is a risk factor for flu.

The bottom line is that if you are already in some type of inflammatory state, then your dendritic cells are already inappropriately aroused and likely inefficient, especially if your issues tend to be ongoing. A pre-existing state of poor health is a significant disadvantage to a healthy immune response.

Zinc is a vital nutrient for reducing inappropriate inflammation22 within immune cells and restoring their efficiency. Adequate zinc23 is also needed just to make sure healthy immune cells are ready when they go into battle. Furthermore, zinc is required within dendritic cells24 so that they can maintain optimum function and natural balance (homeostasis) under stress.

Any nutrition that helps you lose weight or helps you improve some aspect of inflammatory wear and tear will consequently promote better baseline fitness in your dendritic cell team. This is why anti-inflammatory nutrients like quercetin25 have been found to be highly effective at helping combat and prevent the flu, as well as assist with weight loss. Quercetin can even boost the antioxidant defense system in the lungs following flu exposure, providing a specific boost to help the lungs stay healthy in the face of an attack.

Your digestive tract is especially important in this context. Too many hostile bacteria or yeast can wreak havoc with your immune system and dendritic cell function. This is why friendly flora (acidophilus) have been shown to help condition and tone your digestive dendritic cells26 as well as help reduce the number and severity of winter bug infections. Friendly flora also assists in the repair of your digestive tract lining and helps your gut recover from stress within it.

Lactoferrin has been proven to strengthen the digestive “barrier” wall, while enhancing the immune response against bacteria and viruses27. The amino acid glutamine28, also high in mother's milk, is the primary amino acid needed to form the protein structure of your digestive lining as well as help front line troops perform better in your gut. Lactoferrin was recently shown to have broad anti-influenza activity against all major flu types including H3N2 (the 2013 type).

First milk colostrum is also known to enhance digestive stability while reducing digestive and respiratory infections. It contains lactoferrin and has many other strategies to enhance immune function.

An overgrowth of Candida albicans is especially problematic to your dendritic cells. Hostile Candida actually sends a signal to your dendritic cells telling them not to do anything in terms of mounting an immune response for a specific enemy (simply leaving dendritic cells in an inflammatory funk). Lactoferrin has been shown to inhibit Candida signals while boosting front line troop response.

Remember, any flu first incubates in your digestive tract before it moves to your respiratory system. If your digestive tract is out of whack then it is more likely to be a friendly Petri dish as opposed to having a super front-line immune troop operation.

Yet another example of the concept of dendritic cell fitness is that of interferon29. This highly inflammatory immune system molecule is vital for a competent immune response that will kill a viral invader. Scientists have just discovered that you need a low level amount of interferon present in dendritic cells that are basically at rest, as a form of fitness, so that they can spring into action when needed. Having some interferon present seems to be the military equivalent of noncombat readiness training for dendritic cell troops. Vitamin C is needed for healthy interferon production. Bovine colostrum has been shown to enhance interferon status.

In many ways, fighting a nasty viral flu infection is like going for a 10 mile run. Even if you make it to the end you may have dealt with so many antigens that your dendritic cell team is in a state of wear and tear, leaving your defenses down for another infection30 to come along, such as a secondary bacterial infection or a flare-up of the previous infection. Research shows that such a depleted immune system struggles to make TNFa to activate the key dendritic cell response to efficiently fight the next infection. In fact, your immune system can now be so tired of looking at antigens that it has trouble recognizing new ones. Even if your immune system has a memory of them your battle field may be so strewn with antigen debris that spotting the invader is like trying to find a needle in a haystack. This is why so many people either relapse or get a new infection, especially if they try to push themselves too soon following the flu or other bug. You must fully recover from an infection before pushing your body too hard.


Basic nutrition can make a profound difference in fighting the flu. Generally improved nutrition in our country would reduce the spread and severity of any seasonal flu, reduce the severity of flu symptoms, and reduce the overall number of flu cases.

Whether or not you get a flu vaccine is your choice (I'm no fan, as outlined in my article, The Narrow Scope of Flu Vaccine Usefulness). Regardless of whether you do or don't get a flu vaccine, nutrition is profoundly beneficial to help your immune system perform in a time of need.

An idea as simple as making immune cells is of extreme importance and requires protein, iron, folic acid, and B12.

Dendritic cells are vital players in the response to any flu challenge and especially when the type of flu coming around has not been seen before. Dendritic cells must function under very high stress, and so need the ability to tolerate excessive antigen presentation and inflammation.

The key nutrients that allow this are vitamin D and vitamin A; lactoferrin can also be used. Quercetin works synergistically in this picture to reduce inflammation involving front line troops. Many other nutrients have anti-inflammatory properties that would lend support to better balance within this vital system.

Improving the efficient function of immune cells is vital. Zinc and vitamin C head the list, and are supported by the entire antioxidant network (NAC, vitamin E, etc).

Managing stress, improving digestion, reducing any inflammatory health problem (not with immune suppressing or toxic drugs), and losing weight healthfully are all extremely beneficial toward creating the likelihood for a healthier immune response in a time of need.

Originally published 11/21/2010

Referenced Studies

  1. ^ Whey Protein for General Immune Support  Br J Nutr.   Pérez-Cano FJ, Marín-Gallén S, Castell M, Rodríguez-Palmero M, Rivero M, Franch A, Castellote C.
  2. ^ Folic Acid Needed for Immune Cell Replication  Prog Food Nutr Sci.   Dhur A, Galan P, Hercberg S
  3. ^ B12 Supports a Healthy Immune Response  Clin Exp Immunol.   Tamura J, Kubota K, Murakami H, Sawamura M, Matsushima T, Tamura T, Saitoh T, Kurabayshi H, Naruse T.
  4. ^ Low Folic Acid Linked to Poor Immune Response  Am J Med.  Youinou PY, Garre MA, Menez JF, Boles JM, Morin JF, Pennec Y, Miossec PJ, Morin PP, Le Menn G.
  5. ^ Quality Iron Needed for Immunity   Br J Nutr.  Muñoz C, Rios E, Olivos J, Brunser O, Olivares M.
  6. ^ Iron is Needed to Help Produce Dendritic Cells  Br J Haematol.   Kramer JL, Baltathakis I, Alcantara OS, Boldt DH.
  7. ^ Nutrients are Essential for a Proper Immune Response   Br J Nutr.   Maggini S, Wintergerst ES, Beveridge S, Hornig DH
  8. ^ TNFa Drugs Disrupt Dendritic Cell Networks  J Immunol.  Anolik JH, Ravikumar R, Barnard J, Owen T, Almudevar A, Milner EC, Miller CH, Dutcher PO, Hadley JA, Sanz I.
  9. ^ Vitamins A and D Vital to Dendritic Cell Immune Function   Nat Immunol.  Sigmundsdottir H, Butcher EC.
  10. ^ Vitamin A is Required to Prevent Excessive Immune Response  Mucosal Immunol.  Strober W.
  11. ^ Vitamin D Prevents Dendritic Cells from Overheating  J Immunol.  Széles L, Keresztes G, Töröcsik D, Balajthy Z, Krenács L, Póliska S, Steinmeyer A, Zuegel U, Pruenster M, Rot A, Nagy L.
  12. ^ Vitamin D Needed for Dendritic Cells to Alert Adaptive Immune Cells  Journal of Immunology  Enioutina EY, Bareyan D, Daynes RA.
  13. ^ Lactoferrin is a Potent Immune Support Nutrient  Biochimie.  Puddu P, Valenti P, Gessani S
  14. ^ better tolerance for inflammation    
  15. ^ Vitamins C and E Support Immune System Tolerance  J Immunol.  Tan PH, Sagoo P, Chan C, Yates JB, Campbell J, Beutelspacher SC, Foxwell BM, Lombardi G, George AJ
  16. ^ Vitamin E Helps Age-Related Immune Function  Journal of Nutrition  Melissa G. Marko, Hoan-Jen E. Pang, Zhihong Ren, Angelo Azzi, Brigitte T. Huber, Stephen C. Bunnell and Simin Nikbin Meydani.
  17. ^ NAC Lowers TNFa to Reduce Excess Inflammation in Immune Response  Int Immunopharmacol.   Victor VM, Rocha M, De la Fuente M.
  18. ^ NAC Reduces Excessive Immune Response to Strong Challenge  J Invest Dermatol  Bruchhausen S, Zahn S, Valk E, Knop J, Becker D.
  19. ^ Front Line Troops Must Have Vitamins and Minerals for Healthy Function  J Infect Dis.  Erickson KL, Medina EA, Hubbard NE
  20. ^ Dendritic Cells - Friend or Foe  Eur J Dermatol.  Adler HS, Steinbrink K
  21. ^ TNFa Signalling is key to Ramping Up Your Immune Response  Am J Physiol Renal Physiol  Iqbal J, Zaidi M.
  22. ^ Zinc Reduces Inappropriate Immune-Related Inflammation in the Elderly  Rejuvenation Res.   Kahmann L, Uciechowski P, Warmuth S, Plümäkers B, Gressner AM, Malavolta M, Mocchegiani E, Rink L.
  23. ^ Zinc and Immunity  Journal of Leukocyte Biology.  Tolunay B. Aydemir, Juan P. Liuzzi, Steve McClellan, and Robert J. Cousins.
  24. ^ Zinc is Needed for Healthy Dendritic Cell Function  Nat Immunol.  Kitamura H, Morikawa H, Kamon H, Iguchi M, Hojyo S, Fukada T, Yamashita S, Kaisho T, Akira S, Murakami M, Hirano T
  25. ^ Quercetin Prevents Inflammatory Signal Release from Mast Cells  Br J Pharmacol.  Kandere-Grzybowska K, Kempuraj D, Cao J, Cetrulo CL, Theoharides TC.
  26. ^ Friendly Flora and Dendritic Immune Cells  World J Gastroenterol.  Latvala S, Pietila TE, Veckman V, Kekkonen RA, Tynkkynen S, Korpela R, Julkunen I.
  27. ^ Lactoferrin is Part of the Foundation of Natural Immune Defense Against Bacterial & Viral Infection  Cell Mol Life Sci.   Valenti P, Antonini G.
  28. ^ Glutamine Enhances Digestive Immunity  Journal of Nutrition  Marcelo Macedo Rogero, Julio Tirapegui, Marco Aurélio Ramirez Vinolo, Maria Carolina Borges, Inar Alves de Castro, Ivanir Santana de Oliveira Pires and Primavera Borelli.
  29. ^ Beta-Interferon Needed for a Healthy Immune Response  J Immunol.  1.Zietara N, Łyszkiewicz M, Gekara N, Puchałka J, Dos Santos VA, Hunt CR, Pandita TK, Lienenklaus S, Weiss S.
  30. ^ Flu Can Knock Out important Immune Function  Journal of Leukocyte Biology,  Meredith L. Heltzer, Susan E. Coffin, Kelly Maurer, Asen Bagashev, Zhe Zhang, Jordan S. Orange, and Kathleen E. Sullivan.

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