Epidemiological research shows that high-quality diets are associated with a lower risk of getting sick. Eating well may also be associated with how bad that sickness gets. Or the research suggesting that key nutrients may help manage symptoms of an infection.
In this article, I translate the science of diet and immune function so you know what to eat, when to eat it, and how to provide the right nutrients for your immune system to function optimally.
The first 5 are foods that you can add to your diet year-round to promote healthy immune function. The last 5 are foods and foods used as supplements that have a long history of use in traditional medicine and have gained a positive track record in modern-day clinical research too.
1. Green Leafy Veggies
It’s hard to overstate how powerful green leafy vegetables are for your immune system.
First, they are one of the most concentrated sources of natural nitrates, which are converted to nitric oxide, the molecule responsible for stopping infections in their tracks.
Next, green leafy veggies are important sources of vitamin C, a critical antioxidant for immune function.
The numerous other vitamins and minerals, from vitamin A to zinc, make green leafy vegetables a foundational piece of any effective immune-boosting diet. To learn new ways of getting your greens, check out our ratings for top organic meal delivery services and start cooking healthier!
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2. Acerola Cherries
Acerola cherries may be tart, but they are the most concentrated natural source of vitamin C available, according to USDA data.
Pooling the results from multiple studies, regular vitamin C supplementation does not affect how often you get sick, but may slightly decrease how bad a sickness gets.
If you choose natural forms of vitamin C, you may get even more benefits. The natural antioxidant polyphenols in acerola cherries and other berries and fruits may also have a positive effect on immune function.
Other great sources of vitamin c include kiwis, red and orange bell peppers, citrus fruits, and green veggies.
3. Fiber for a healthy microbiome
Most people don’t realize that your gut health plays a huge role in your immune response.
Immune cells in your digestive system are the front line against pathogens that enter through your food and drink. The balance of healthy and unhealthy bacteria in your gut also plays a role in fending off invaders.
Unfortunately, gut health is an afterthought for most people. The average American gets less than half of the USDA recommendation for daily fiber intake: 25 grams for women, 38 grams for men.
Aside from taking a fiber supplement — which has been shown in mouse research to decrease chronic (“bad”) immune inflammation — optimize your immune function with fiber from fruit, vegetables, and whole grains.
The list of nutrients in the liver reads like the ingredients label for an immune-boosting supplement.
Rich with all essential minerals, and every vitamin save for vitamin C, liver is the natural multivitamin that few people eat. It may be the most nutrient-dense food on the planet, which is vital for an immune system ramping up to fight off an infection.
If you’re new to liver or never really liked it, try sneaking it into other meals or dressing it up with barbecue sauce, marinade, or hot sauce. Liver and onions is a popular dish for a reason — the combination helps cut the multivitamin taste.
There is no plant-based alternative to liver, but nutritional yeast combined with a diet of plant-based whole foods provides a high concentration of the same nutrients.
Oysters are one of the richest sources of both copper and zinc which are essential for the immune response, especially during the initial stages of an infection. Oysters are also a great source of omega-3 fatty acids, which may be linked to lower rates of infection and less severe sickness in children.
When you look at the differences between studies that show zinc supplementation works and the ones that show otherwise, the timing of zinc matters.
6. Vitamin D
More than 70% of Americans do not get enough vitamin D for health, even though it plays a critical role in regulating immune function.
The sunshine vitamin is hard to come by in your food. Fish liver oil — which is also renowned for its omega-3 fatty acid content — is the most concentrated food source of vitamin D. Fish, irradiated mushrooms, and fortified milk and OJ are some of the only other substantial sources.
Aside from getting it in supplements, most of your vitamin D is made in response to sun exposure.
Pro tip: Exercise outside in the sun when you can, limiting your sun exposure to 20 minutes to 90 minutes 3 times weekly depending on the color (melanin content) of your skin— you’ll get the benefits of vitamin D combined with the immune-boosting benefits (e.g. increased glutathione, increased nitric oxide) of exercise.
Fish oil, fish (particularly sardines, salmon, and low-mercury tuna), or a vegan omega-3 supplement are important sources of omega-3 fatty acids.
Omega-3s are commonly known as anti-inflammatory nutrients. Supplementing with the equivalent of 1 tsp of fish liver oil was shown in a study published in the Journal of Pediatrics to decrease how often kids get a cold and the severity.
Fish liver oil is also the best dietary source of vitamin D. So if you’re not able to get enough sunshine for your vitamin D needs, talk to your healthcare provider and find a supplement that works for you
Elderberry has a reputation for its immune-boosting properties for a reason. Study after study shows a small, but positive advantage for people who supplement with elderberry as soon as cold symptoms start.
Many of the benefits of elderberries are shared by other superfood berries, so eat the rainbow!
Aronia berries, cranberries, goji berries, acai berries, and tart cherries are each full of polyphenol antioxidants called catechins and anthocyanins that may help boost your immune response to infections.
Ginseng is known for its positive effects on boosting the immune system’s reaction to infections, besides its other heart- and brain-healthy effects.
Though not a typical food, you can find it in the tea or bulk section of natural food stores. It’s also a common addition to functional food energy drinks.
An analysis of five studies showed that regular ginseng supplementation lowered people’s risk of getting a cold by a full 25%.
In two of the studies analyzed, colds were 6 days shorter among people taking ginseng. That’s the kind of cold I want to have!
Crushed garlic may be the single most potent food to boost your immune response.
High-quality clinical research shows that the equivalent of a couple of cloves of crushed garlic every day for 3 months can reduce the severity of cold and flu symptoms by over half.
Unfortunately, the odor imparted by this immune booster is undeniable. And that’s only half of it! Taking raw, crushed garlic is sure to feel like a kick in the stomach and has led to more than one person losing their lunch, so to speak.
If your morning routine doesn’t include nausea and gut pain, then try a garlic supplement that provides 180 mg of allicin, the dose of the major active ingredient seen in research studies.
Specific foods can improve your immune system, decrease the risk of getting sick, and limit how bad an infection gets.
Making the switch to a healthy diet can be difficult without help, but these top-rated prepared meal delivery services will make healthy meal planning a breeze.
Incorporate these to get the immune-boosting benefits seen in research:
- Garlic, crushed
- Elderberry or other polyphenol-rich super berries
- Fish liver oil (vitamin D and omega-3 fatty acids)
- Oysters and liver (concentrated sources of zinc, copper, and other nutrients)
- Acerola cherries and other sources of vitamin C
- Fiber and a healthy microbiome
- Green leafy veggies (for the spread of nutrients they provide, especially nitrates and vitamin C)