The Best Foods and Nutrients for Immunity

Fighting Disease, Infections & COVID-19 for the Long Haul

As of April 5, 2020, 11:20 P.M. (ET), there are at least 336,775 cases and 9,606 deaths related to the COVID-19 virus in the U.S. (REUTERS). The immune system protects the body against foreign pathogens. Pathogens are bacteria, viruses, or other microorganisms that can cause disease. The immune system helps to control inflammation, which is a mechanism of action of the SARS-2-COVID virus. Your immune system is your defense mechanism against infections, and the immune system is easily affected by nutrition and exercise activities (Allaire et al., 2016). Eating well and staying in shape are critical pillars to help you stay fit for defense against an infectious fight. In fact, your level of nutrition and exercise status may determine who wins the battle.

Stay battle ready by maintaining a healthy, well-balanced diet as the first step to supporting immunity (Bresnahan KA, et al. 2014). I have made a list of key nutrients to incorporate as a part of a well-balanced diet to help improve your nutrition and immune status. I have also included some potential nutrition supplements to consider and insights into exercise for optimal immune health.

Foods and Immunity:

Garlic - Typically praised for its vibrant flavor in dishes, garlic is an allium vegetable that has been shown to enhance the immune system and reduce the risk of colds and other infections. These effects come from improving the ability of white blood cells (lymphocytes) to fight invaders and by increasing the production of T cells (T lymphocytes). Garlic will not, however, reduce the duration of a disease or the severity of the symptoms; it is more of a preventive nutrient to incorporate into your diet daily.

Vitamin C - Vitamin C, also known as ascorbic acid, is a water-soluble essential vitamin. It is necessary for collagen synthesis, hormone, and neurotransmitter synthesis and acts as an antioxidant. Vitamin C is greatest known for preventing the deadly condition known as scurvy, which was first described by ancient Greeks, Egyptians, and Romans. Vitamin C protects the body from free radical damage as an antioxidant and helps maintain the immune system. It also aids in the absorption of non-heme iron foods, which can be found in dark-green leafy vegetables. Vitamin C has also been shown to scavenge reactive molecules in white blood cells, in the lung, and the stomach mucosa (Food and Nutrition Board, Institute of Medicine, 2000).

Vitamin C is very popular as a cure-all supplement, particularly when we think of someone getting sick. It is estimated that 35% of adults take multivitamin supplements (which typically contain vitamin C) based on an NHANES data survey from 1999-2000. Does supplemental vitamin C reduce the chances that you will catch a cold? No - a Cochrane Database Systematic Review found that vitamin C does not prevent colds, but does moderately reduce the duration and severity of cold symptoms (Douglas RM., 2007).

Food sources of vitamin C: broccoli, brussel sprouts, cantaloupe, citrus fruits and juices, kiwifruit, peppers, strawberries, and tomatoes. Adult men need 90 mg per day and women need 75 mg per day.

Vitamin D - Vitamin D is a fat-soluble vitamin known as cholecalciferol. Vitamin D is known for its role in supporting calcium absorption. Vitamin D also plays other roles in the body, such as supporting immune function and reducing inflammation. Many cells have a vitamin D receptor. There is evidence that vitamin D can have a modest reduction in the risk for respiratory tract infections, especially when vitamin D levels are very low (Rees JR, et al., 2013). There is also some evidence for a modest reduction in pneumonia and influenza, though more research is needed to be more conclusive.

Food sources of vitamin D: eggs, fish, fish liver oil, fortified cereals, fortified dairy products, fortified margarine, fortified orange juice, and fortified soy milk. The recommended daily allowance for vitamin D is 400-800 IU/day; however, this has been suggested as too low for adults. For moderate supplementation 1,000-2,000 IU of vitamin D3 is suggested.

Fish oil (omega-3 fatty acids) - Omega-3 fatty acids are essential fatty acids made up of alpha-linolenic acid (Eicosapentaenoic acid, EPA and Docosahexaenoic Acid, DHA). Omega-3 fatty acids antagonize or suppress arachidonic acid (omega-6, pro-inflammatory fatty acids) as an anti-inflammatory agent. Omega-3 fatty acids produce specialized pro-resolving mediators (SPMs) that play a role in activating multiple immune cell types.

Food sources of omega-3 fatty acids: salmon, herring, sardines, mackerel, trout, oysters, sea bass, shrimp, lobster, tuna, cod, olive oil, almonds, and avocado. It is recommended to consume at least 250 mg of DHA and EPA combined, The American Heart Association recommends 1g daily; to obtain the benefits of SPMs, take >2.5g of EPA and DHA per day.

Fiber - Fiber, as in non-digestible parts of fruits, vegetables, and cereals, is an important energy source for healthy bacteria of the gut. Over 70% of our immunity is in our gastrointestinal system. Fruits, vegetables, and cereals provide specific nutrients for the gut, which are fermented into short-chain fatty acids. It is important to feed the gut with these foods to maintain gut integrity and immunity, which in turn helps reduce bacterial translocation. These food particles act as a source of energy to fuel the defense cells of the gastrointestinal tract. The GI tract becomes more susceptible to disease when the diet is overabundant in foods void of fruits, vegetables, and cereals such as high fat, high animal protein diet with very little to no fruits and vegetables. Interestingly, these short-chain fatty acids are distributed throughout the blood and, thereby, may also prevent pathogens outside the gut (Venter C., et al. 2020). A long-term, fiber-rich diet (from fruits, vegetables, and cereals) has been shown to improve lung function and to lower the risk for COPD (Keranis E., 2010 and Szmidt M.K., 2019). Following a Mediterranean diet (30 g fiber/day) has been associated with a lower risk for type-2 diabetes and patients at risk for cardiovascular disease (Estruch, et al.. 2013, Jones et al., 2011 and Del Chierico et al., 2014). Aim for the recommended intake of 25-31 grams of fiber per day or even higher. Assess for how many non-starchy vegetables, fruits, and whole-grain carbohydrate foods you have consumed in a day to gauge your total fiber intake.

Zinc - Zinc is an essential mineral often taken in many cold lozenges and some over-the-counter drugs sold as a cold remedy. Zinc is involved in several cellular and metabolic pathways and acts as a driver for over 100 enzymes. Zinc plays a role in immune function, protein synthesis, wound healing, DNA synthesis, and cell division. Unlike some other vitamins or minerals, zinc is required in the diet to maintain a steady state because the body is unable to store zinc. If you have a zinc deficiency it could severely depress immune function, which is why eating food sources of zinc is very important. Zinc deficiency impairs macrophage and neutrophil functions. More recently, a Cochrane review concluded that “zinc (lozenges or syrup) is beneficial in reducing the duration and severity of the common cold in healthy people when taken within 24 hours of the onset of symptoms” (Singh M and Das RR, 2011). Similar to vitamin C, zinc acetate lozenge (13.3 mg zinc) taken every 2-3 hours has been affiliated with reducing the duration of cold symptoms such as cough, nasal discharge and muscle aches (Prasad et al., 2008). Stop supplementing after one week at the disappearance of symptoms. High doses of zinc over time can irritate the GI tract. Do not take zinc as a regular supplement unless using when you have a cold, as it can cause copper deficiency and issues with the liver and kidneys.

Food sources: Beans and peas, beef, dairy products, fortified cereals, nuts, poultry, seafood, and whole grains

Protein - This macronutrient is necessary to support the immune system by providing specific amino acids such as leucine, arginine, and glutamine. Proteins help build antibodies and play an important role in healing and recovery. When you are sick or fighting an infection, it is important to maintain protein homeostasis (balance) through the ingestion of protein foods or supplements. Otherwise, your body will begin to break down protein for a fuel source. This is particularly important because with muscle loss comes increased risk for complications such as infections (no amino acids for the fight increases bacterial translocation and invasion), spontaneous pressure injuries, poor wound healing, pneumonia and even mortality (Demling RH, 2009). Include protein-rich foods in your diet at breakfast, lunch, and dinner. Obtaining foods rich in branched-chain amino acids are important, as they are a precursor to glutamine which plays a pivotal role in immune function. I have designed all of my meal plans to obtain high-quality protein foods at each meal - Mediterranean, Muscle Building, Vegan, Weight Loss, and Ketogenic.

Glutamine - Glutamine is a conditionally essential amino acid; however, under conditions of stress, injury and infection, glutamine can become essential to support the immune system. What I find incredibly interesting is that glutamine can act as a respiratory (breathing) fuel and it can enhance the function of stimulated immune cells (Newsholme, 2001). Long-distance runners could be at risk for developing upper respiratory tract infections (lots of running and breathing, high use of glutamine as a fuel source) and thus, 5g of glutamine after an endurance run has been suggested to reduce the risk for an upper respiratory tract infection (Castell and Newsholme, 1998).

Glutamine is the most abundant amino acid in the body. It plays an essential role in protein synthesis for all cell types. Some bodybuilders and athletes take glutamine as a muscle-building supplement; however, studies show that glutamine is not effective as a muscle-building supplement (Candow et al., 2001). Glutamine plays a fundamental role in the metabolism of immune cells. When the immune system is activated, glutamine acts as a main source of energy to support the production of glutathione, which is an antioxidant capable of preventing cellular damage (Johnson et al., 2016). Glutamine can be found in foods such as meats and eggs. Glutamine may be of benefit in supplemental forms for vegans, vegetarians with low dairy intake, or during prolonged endurance exercise. If not consumed adequately from foods, a dose of 5g/d is recommended or 0.75g/kg/d.

Arginine - Arginine is an amino acid in foods that contain protein. It is known as a conditionally essential amino acid, similar to glutamine. A healthy, well-balanced diet provides about 4-5 grams per day. I would not recommend arginine as a supplement for athletes to take if looking for an enhancement in workouts or to induce the “pump.” Under stress, trauma, injury and illness, arginine is more readily used to support metabolic processes, especially relating to immune function with T-cells. Arginine may be needed as a supplement during times of physiological stress (not mental stress).

Immunity and Supplements:

When considering the use of supplements for immunity, you have to be very cautious, particularly due to the risk of drug-nutrient interactions.

Pelargonium sidoides - a plant that contains compounds that can prevent bacteria from attaching to the throat and lungs. It is suggested to take at the onset of illness characterized by dry and hoarse coughing. Pelargonium sidoides can reduce the severity of the symptoms and the duration of the disease. It has not been associated with preventing infections from occurring in the first place, so I wouldn’t start taking this prophylactically as a preventive measure. However, I would focus on the foods mentioned above in this article as preventive measures to adhere to for a lifetime to potentially help prevent future infections and disease. This supplement has primarily been utilized to treat acute bronchitis, while there is less evidence showing that it could treat the common cold. Most studies utilized Pelargonium sidoides (EPs 7630), as it has been suggested that you can also use raw powder. Take 1 ml (about 1/4 teaspoon) three times per day before meals for 3 mL per day. For EPs 7630 hydroalcoholic extract, take 1 teaspoon three times per day before meals for a total of 13.5 mL per day. For the raw powder, take 720 mg three times per day before meals.

Echinacea Purpurea -This is one of the first supplements marketed as an immune-boosting supplement. Taken year-round or during periods of likely illness may reduce the risk of catching a cold. It is not like vitamin C or zinc where it may reduce the duration of a cold; however, it may reduce the risk of complications such as pneumonia. This supplement has many potential pharmaceutical/drug interactions, so if you are taking medications, talk to your doctor first to see if it is appropriate, particularly with immunosuppressive drugs. Take three times per day at 300-500 mg of the powder or 2.5-10 mL of the tincture.

Elderberries - these are berries with a long history of medicinal use in Native America, Mediterranean, and ancient Egyptian cultures. Elderberries have been associated with antiviral properties and notably with the inhibition of influenza. Supplementation has been suggested at the onset of the first symptoms to reduce infection severity and duration. Some people have tried preparing elderberries themselves, but I wouldn’t recommend it. They have to be properly cooked, and if they are not, they can be toxic due to the cyanide content. The bark, root, and leaves of the elder tree should never be part of supplementation. Use the lozenges or capsules and take 700-900 mg per day, split into 3 or 4 doses 300mg times three. To supplement syrup, take 1 teaspoon (5 mL) four times a day.

N-acetylcysteine (NAC) - this compound is a mucolytic and reduces the viscosity of mucus, making it easier to cough out. This supplement also replenishes the cell’s supply of the antioxidant glutathione. NAC has been indicated to hinder some lung diseases. It has been particularly implicated in reducing the number of chronic obstructive pulmonary disease (COPD) exacerbations to a small extent. Take 600 mg of NAC twice a day with or without food. Higher doses do not seem to be more effective, whereas lower doses do not seem to be effective at all.

Exercise and Immunity:

Moderate exercise can help strengthen the immune system. An acute bout of exercise can increase the total number of leucocytes (a white blood cell that counteracts foreign substances) in the blood (Batatinha HAP et al., 2019). The intensity and duration of exercise influence your immunity positively or negatively. If you run for prolonged periods, such as with a marathon race or cycling for 2 hours or more, your immune cells decline. An acute bout of high-intensity interval exercise decreases glutamine levels for example, which is why 5g of supplemental glutamine is suggested post-workout to help reduce the risk for upper respiratory tract infections. Also, working out in a state of low carbohydrate intake for a few days or exercising with low glycogen (stored glucose/carbohydrate) can lead to a decrease in T-cells. This is why for athletes, like basketball players, it’s important to follow a diet with adequate carbohydrate intake to keep your muscle and immune cells fueled.

It is important to get regular exercise to increase the total number of leucocytes. Aim for 30-45 minutes of activity three-five times per week. When working out for prolonged periods or when doing high-intensity exercises, be sure to fuel properly before, during and after exercise to counter the potential decline in immunity. Request a personal one-on-one consult for more specifics as to how to incorporate these principles around nutrition, supplementation, and exercise into your daily routine for optimal health and immunity.

This article is a general-health document for adults 18 or over. Its aim is strictly for educational purposes. It does not constitute medical advice. Please consult a medical or health professional before you begin any exercise-, nutrition-, or supplementation-related program, or if you have questions about your health. If you decide to follow any of the activities or take the supplements above, you are then doing so on your free will, and you knowingly and voluntarily accept the risk.

Sleep and Immunity:

Sleep is at the very bottom of the list because I wanted to save the best for last! Without adequate sleep, it could impair your recovery from exercise, lead to hormonal imbalances and increased appetite, which could lead to overindulgence and selection of empty calorie foods, in turn potentially leading to immunity deficient intake and a higher risk for acute and chronic conditions. According to the National Sleep Foundation, the amount of sleep that you need depends on your age, lifestyle, and health. Generally, most adults need 7-9 hours of sleep each night. You can utilize the new InsideTracker Immunity, Stress and Sleep test to find out more about your current sleep patterns and how sleep, diet and exercise play a role in your immunity and overall health.

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