Maintaining a healthy immune system is top of our to-do list as the Northern Hemisphere heads into flu season during the second year of a global pandemic. But what does your immune system need to function at its best? And how do those needs fit into a Keto or low-carb lifestyle?
Today we’re going to break down the key micronutrients that keep your immune system humming and the best places to find them in Keto-friendly foods.
The Effect of Keto on Your Immune System
Before we get into specific foods, it’s worth noting that there’s evidence that a Ketogenic, or low-carb diet can boost your immune system by decreasing inflammation in your body. Our staff nutritionist Tony has written a deep dive into that science here: How To Support Your Immune System With Keto.
From Macro to Micro
If you’re a Carb Manager user, you’ll be used to tracking your macronutrient ratios. Macros are the big building blocks that provide our energy: carbohydrates, fats and protein. On a Keto diet, we are primarily focused on healthy fats to provide this fuel.
But equally important to our health are the micronutrients – the vitamins and minerals that keep everything in working order and allow our bodies to process and use the energy we get from our macros.
We rely on these crucial vitamins and minerals to do everything from building bones and transferring nutrients across cell membranes, to regulating the pH of our blood and contracting and relaxing our muscles.
Micronutrients for Immune System Function
Micronutrients don’t work in isolation. All the essential micronutrients work together in synergy within your body – which is why it’s best to get your vitamins and minerals from whole food sources instead of supplements when you can. That said, we know from research that some vitamins and minerals are more critical than others to the proper functioning of your immune system.
- Vitamins A, C, D, E, B6, B12 and folate
- Minerals zinc, iron, copper, selenium and magnesium
- Unsaturated fatty acids, particularly omega-3 and omega-9s.[*][*][*][*]
Next, let’s talk about the best places to find these nutrients when you’re eating Keto or low carb.
Our Top Keto-Friendly Superfoods for Immune Health
Superfoods are foods that are considered to be especially dense in nutrients or health-promoting compounds. Today, we’re using it to mean the everyday foods that pack the biggest bang for your low-carb buck in the immune-supporting vitamins and minerals listed above.
1. Leafy greens
Leafy greens, including spinach, lettuce, kale, collard greens, arugula and chard, are very low in carbs but pack a massive nutritional punch. They’re full of vitamin C, vitamin A, vitamin E, zinc, magnesium, iron and antioxidants. If you can’t be bothered to chew your way through the 2–4 cups of vegetables the USDA recommends you eat each day,[*] you can blend them into your morning smoothie and drink them instead.
2. Cruciferous vegetables
The cruciferous vegetable family includes low-carb MVP cauliflower, as well as broccoli, cabbage, kale, collard greens and Brussels sprouts. A half-cup serving of any of these vitamin-packed veggies has loads of vitamin C, folate and antioxidants – and only 1 to 3 grams of net carbs.
To preserve the micronutrient content, only gently cook or steam cruciferous vegetables – or better yet, try them raw. They’re delicious shredded into a salad or slaw.
3. Red bell peppers
Pop quiz: what’s the best source of cold-busting superstar vitamin C? If you said oranges or citrus fruits, you’re wrong – believe it or not, it’s red bell peppers.
A medium orange has 12g net carbs and 77% of your daily vitamin C requirement (based on the FDA's Percent Daily Value) – whereas a medium red bell pepper has 169% of your vitamin C and only 5g net carbs. The bell pepper also has more vitamin A, vitamin B6, folate, magnesium, zinc and iron.
4. Fish and shellfish
Fatty fish like cod, salmon, sardines and anchovies are full of inflammation-reducing omega-3 fatty acids. Salmon is also one of the few good food sources of vitamin D, and both salmon and tuna are packed with zinc.
However, if you really want to supercharge your minerals-per-serving, opt for shellfish – oysters have more zinc per serving than any other food. Shellfish (including oysters, crab, lobster, mussels and scallops) are also packed with iron, magnesium, B vitamins, copper and selenium.
5. Chicken soup
There’s a reason why we eat chicken soup when we’re sick. Three ounces of skinless chicken thigh has 22% of the Daily Value for vitamin B6. It also contains 58% of your B12 and 37% of the Daily Value for zinc.
Meanwhile, the soup broth (specifically bone broth, made by simmering chicken bones in water) is full of gelatin, collagen and amino acids like glutamine. These support the health of your gut lining, where 70% of your immune system is located.
Chicken Soup also gets bonus points because you can add almost everything on this list into it to supercharge the benefits – just be sure to use low-carb noodles to keep it Keto.
Avocados are a good source of vitamins E and B6, copper and magnesium. They’re also second only to asparagus as a food source of glutathione, the “master antioxidant” that plays a major role in regulating your immune system.
The good fats in avocado also increase the absorption of the fat-soluble vitamins (A, D, E and K).
7. Nuts and seeds
Vitamin E deficiency has been associated with an increased incidence of infectious disease and cancer.[*] As a fat-soluble vitamin, vitamin E needs to be combined with fat in order for your body to absorb and digest it. Nature to the rescue – nuts and seeds like almonds, walnuts and sunflower seeds are great sources of both good fats and vitamin E.
Nuts and seeds are also good sources of selenium (especially Brazil nuts), zinc (especially pumpkin seeds), copper, B6 and magnesium. And, as a bonus, walnuts have also been shown to improve the body’s response to stress.[*]
8. Fermented food
A healthy gut microbiome makes for a healthy immune system, and fermented foods are full of good probiotic bacteria. Probiotics have been found to reduce the incidence and severity of colds in children, as well as resulting in fewer prescriptions for antibiotics.[*]
Unsweetened Greek yogurt is a great source of protein, as well as the mineral selenium and vitamin B12. A tablespoon of sauerkraut has 0g net carbs and only 3 calories but can contain up to 10 billion good gut bugs, as well as iron, magnesium, copper, folate, vitamin B6 and vitamin C.
Mushrooms are one of the best vegetarian sources of vitamin D, as well as being a great source of selenium and B vitamins. Studies have also found that eating mushrooms can boost immunity and reduce inflammation[*] and that certain types of mushrooms (including shiitake and chaga) may even have an antiviral effect.[*]
Eggs really are a complete food. Two eggs (make sure you include the yolk) will make a significant dent in your daily requirement for every nutrient on our list – including 11% of your vitamin D, which can be hard to get enough of when the sun isn’t shining.
11. Olive oil
The polyunsaturated fats in olive oil have been found to have a beneficial effect on the immune system.[*] Extra virgin olive oil is also full of polyphenols and antioxidants that provide antimicrobial and antiviral properties, which have the potential to protect against coronary heart disease and cancer.[*]
And adding olive oil to your salad isn’t just delicious and satiating – it also helps your body absorb the vitamins in your food.[*]
By the way, it’s a myth that you shouldn’t cook with olive oil. A 2018 study showed that the antioxidants in extra virgin olive oil allow it to remain stable even when heated to high temperatures[*] – so fry away, friends.
A clove of garlic will add 1g of carbs to your dinner but make it taste three times more delicious. That’s science. It’s also science that a compound called allicin is what gives garlic its powerful odor and taste. Allicin appears to enhance the functioning of the immune system[*] and may have antibacterial, antifungal and antiviral properties.[*]
One study also showed that supplementing garlic for 12 weeks reduced the incidence of colds among the participants by 63%.[*]
Tracking your Micronutrients in Carb Manager
Not sure if you’re getting everything your immune system needs to thrive? If you have Carb Manager Premium, you can check your daily micronutrient intake against the Dietary Reference Intake (DRI) by going to Settings > Goal Settings > Micronutrients and selecting “Enable DRI”.
To view your micronutrient intakes, select “In-Depth Details” – your micronutrient intakes are under “Supplemental” in “My Nutritional Facts.”
Note: If you’re interested in tracking your micronutrient intake, try to stick to Common Foods when logging your meals – Member Foods will not usually have micronutrient quantities listed.