6 Eating Habits That Weaken Your Immune System Health

Keeping your immune system strong is one of the most important and impactful things you can do to stay active and energetic. But bolstering immunity is a two-sided coin: It's about choosing foods that help support immune function and limiting foods and behaviors that can weaken immunity.

Here are six habits to be mindful of as you work on boosting your body's defenses.

Men and woman eating donuts

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Drinking Alcohol and Immune Health

A glass of wine here and there has been shown to have some health benefits. But excessive alcohol consumption, even short-term, can alter your immune system.

Researchers have noted that there's been a long-observed relationship between excessive alcohol intake and a weakened immune response. The effect includes an increased susceptibility to pneumonia and a greater likelihood of developing acute respiratory stress syndrome (ARDS)—factors that could potentially impact COVID-19 outcomes.

Other outcomes observed involve an increased risk of sepsis (infection in the blood), a higher incidence of postoperative complications, poor wound healing, and a slower and less complete recovery from infections.

Excessive drinking includes both binge drinking and heavy drinking. Binge drinking is defined as four or more drinks during a single occasion for females, and five or more for males. Heavy drinking means consuming eight or more drinks per week for females and 15 or more for males.

If you find yourself drinking too much, cut back to a moderate amount of no more than one drink per day for females or two for males.

And if you think you may need help regarding alcohol, there are several ways to seek professional services from home. This includes counseling via the Substance Abuse and Mental Health Services Administration national helpline: 1-800-662-HELP (1-800-662-4357).

Going Overboard With Salt

You may associate excess sodium with problems like fluid retention and high blood pressure. But research also shows that too much salt in the diet can lead to abnormal changes in immune responses that could cause inflammation.

Also, too much salt can change the way immune cells work.

Researchers found that when the kidneys excrete excess sodium, a domino effect occurs that reduces the body's ability to fight bacterial infections. While the body has many compensatory mechanisms that may still prevent sickness, a long-term high salt diet is not recommended.

The recommended daily maximum for sodium intake is under 2,300 milligrams per day for a healthy adult, but it's estimated that the actual average intake of sodium for adults in the U.S. is 3,440 milligrams per day.

About 70% of Americans' sodium consumption comes from restaurants, prepackaged, and processed foods. So the best way to curb your intake of sodium is to limit highly processed products:

  • Canned soups and chili
  • Smoked, cured, and deli meats
  • Snack foods (like chips, popcorn, pretzels, snack mixes, and crackers)
  • Frozen pizza
  • Frozen entrees

Check the milligrams (mg) of sodium per serving on nutrition facts labels and choose products that are lower in sodium.

As for salting your food, one teaspoon of table salt has 2,300 milligrams of sodium. If you use salt sparingly to season fresh food, you can still remain under the recommended cap. And you can use alternatives to replace or reduce the amount of salt you use, including:

  • Fresh garlic or garlic powder
  • Onion powder
  • Citrus juices
  • Salt-free seasonings
  • Dried spices and fresh herbs

Consuming Excess Sugar

Cutting back on added sugar is a smart idea for a number of reasons, including good mental health. It could also be beneficial for immune support.

One study found that after an overnight fast, humans fed 100 grams of sugar experienced a reduction in the ability of immune cells to get rid of bacteria. The greatest effects were found between one and two hours later but lingered for up to five hours.

This doesn't mean you have to nix sugar completely, but avoiding an ongoing surplus or short-term overindulgence is a worthwhile goal.

The American Heart Association recommends limiting added sugar—the kind added to foods by you or a manufacturer—to no more than six teaspoons worth per day for females and nine for males.

One teaspoon equals four grams of added sugar, so that's 24 and 36 grams of added sugar respectively for females and males daily.

If you're prone to stress-eating sugary goodies, test out some alternative coping mechanisms to help reduce the need to eat your feelings. Some examples include:

  • Reaching out to loved ones
  • Practicing meditation
  • Going for a walk or doing other indoor or outdoor activity
  • Even playing a video game

Overdoing Caffeine Intake

Coffee and tea are health-protective, due to their high levels of antioxidants, which can help reduce inflammation. However, too much caffeine can interfere with sleep, and that result can increase inflammation and compromise immunity.

To best support immune function, replace caffeinated drinks that don't have nutrients or are made with sugar or artificial sweeteners—like soda and energy drinks and limit caffeinated coffee and teas to just a couple of cups per day. Instead, choose decaffeinated beverages like:

  • Plain water
  • No-calorie flavored carbonated water
  • Water infused with limes, lemons, cucumber, strawberries, oranges, or other fruits
  • Decaffeinated coffee and tea or herbal tea
  • Milk or plant-based milk alternatives

When you do enjoy coffee and tea, be sure to stop caffeine intake at least six hours before bedtime to prevent sleep interference.

Skimping on Fiber

Fiber supports good digestive health and helps to shift the makeup of gut bacteria in ways that enhance both immunity and mood.

Research shows that a higher intake of dietary fiber and prebiotics supports healthier immune function, including protection against viruses. Adequate fiber also promotes more and better sleep.

Yet just 5% of Americans consume the recommended daily fiber goal of at least 25 grams per day for females and 38 grams for males.

The best way to upgrade your fiber intake is to eat more whole foods, including:

  • Vegetables: fresh, frozen, or low-sodium canned
  • Fruit: fresh, frozen, canned, or dried
  • Whole grains: whole grain bread, cereals, and pasta; oats; brown, red, or wild rice; quinoa
  • Pulses: beans, lentils, peas, and chickpeas
  • Nuts and seeds

Trade lower-fiber processed foods for fiber-rich unprocessed foods. Try these ideas:

  • Swap sugary cereal for oatmeal topped with fruit and nuts
  • Exchange white rice for brown or wild
  • Replace fiberless meat with beans or lentils
  • Trade traditional pasta for pasta made from pulses (black bean, chickpea, lentil)
  • Exchange packaged snacks, like cookies and chips, with a combination of fruit and nuts or veggies with hummus or guacamole

Not Eating Enough Green Veggies

Aiming for the recommended four to five cups of fruits and vegetables daily provides numerous health benefits, but green veggies may be particularly helpful for immunity.

These plants provide key nutrients known to help immune function, including vitamins A and C, plus folate. Greens also offer bioactive compounds that release a chemical signal that may optimize immunity in the gut, the location of 70 to 80% of immune cells.

For the most benefit, zero in specifically on green veggies in the cruciferous family, which include:

  • Kale
  • Collard greens
  • Broccoli
  • Bok choy
  • Cabbage
  • Brussels sprouts

Incorporate at least three cups per week—either raw, like kale salad, vinegary slaw, and fresh broccoli florets with dip—or steamed, sautéed, oven-roasted, and stir-fried versions.

A Quick Review

Shifting these six foods and habits into healthier choices can give your immunity a boost year-round.

Start with a couple of changes—like adding more green vegetables and decreasing foods and drinks with added sugar—then gradually add more healthy habits as the first changes become more routine.

Keep in mind that making small food and lifestyle changes over time can lead to healthy results long-term.

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Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Castaldo L, Narváez A, Izzo L, et al. Red Wine Consumption and Cardiovascular HealthMolecules. 2019;24(19):3626. Published 2019 Oct 8. doi:10.3390/molecules24193626

  2. Sarkar D, Jung MK, Wang HJ. Alcohol and the Immune SystemAlcohol Res. 2015;37(2):153-155.PMC4590612

  3. Centers for Disease Control and Prevention. Alcohol use and your health.

  4. Substance Abuse and Mental Health Services Administration. SAMHSA's national helpline.

  5. Afsar B, Kuwabara M, Ortiz A, et al. Salt intake and immunity. Hypertension. 2018;72(1):19-23.doi:10.1161/HYPERTENSIONAHA.118.11128

  6. Jobin K, Stumpf NE, Schwab S, et al. A high-salt diet compromises antibacterial neutrophil responses through hormonal perturbation. Sci Transl Med. 2020;12(536):eaay3850.doi:10.1126/scitranslmed.aay3850

  7. Centers for Disease Control and Prevention. Salt.

  8. U.S. Department of Agriculture. Dietary Guidelines for Americans 2020-2025.

  9. Centers for Disease Control and Prevention. The role of sodium in your food.

  10. Lim SY, Kim EJ, Kim A, Lee HJ, Choi HJ, Yang SJ. Nutritional factors affecting mental healthClin Nutr Res. 2016;5(3):143. doi:10.7762/cnr.2016.5.3.143

  11. Kris-Etherton PM, Petersen KS, Hibbeln JR, et al. Nutrition and behavioral health disorders: depression and anxietyNutrition Reviews. 2021;79(3):247-260. doi:10.1093/nutrit/nuaa025

  12. Sanchez A, Reeser JL, Lau HS, et al. Role of sugars in human neutrophilic phagocytosis. The American Journal of Clinical Nutrition. 1973;26(11):1180-1184.doi:10.1093/ajcn/26.11.1180

  13. American Heart Association. Added sugars.

  14. Rico-Rosillo MG, Vega-Robledo GB. Sueño y sistema immune [Sleep and immune system]Rev Alerg Mex. 2018;65(2):160-170. doi:10.29262/ram.v65i2.359

  15. Besedovsky L, Lange T, Haack M. The Sleep-Immune Crosstalk in Health and DiseasePhysiol Rev. 2019;99(3):1325-1380. doi:10.1152/physrev.00010.2018

  16. Trompette A, Gollwitzer ES, Pattaroni C, et al. Dietary fiber confers protection against flu by shaping ly6c− patrolling monocyte hematopoiesis and cd8+ t cell metabolism. Immunity. 2018;48(5):992-1005.e8.doi:https://www.doi.org/10.1016/j.immuni.2018.04.022

  17. St-Onge MP, Roberts A, Shechter A, Choudhury AR. Fiber and saturated fat are associated with sleep arousals and slow wave sleep. Journal of Clinical Sleep Medicine. 2016;12(01):19-24.doi:10.5664/jcsm.5384

  18. Quagliani D, Felt-Gunderson P. Closing America's Fiber Intake Gap: Communication Strategies From a Food and Fiber SummitAm J Lifestyle Med. 2016;11(1):80-85. Published 2016 Jul 7. doi:10.1177/1559827615588079

  19. Li Y, Innocentin S, Withers DR, et al. Exogenous stimuli maintain intraepithelial lymphocytes via aryl hydrocarbon receptor activationCell. 2011;147(3):629-640. doi:10.1016/j.cell.2011.09.025

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