Following a winter during which it’s seemed like everyone’s always coming down with something at any given moment, we’re likely looking at a banner year for early spring colds. Milder weather is perfect for the reproduction of rhinoviruses and coronaviruses (responsible for the common cold), while fluctuations in temperature and air pressure tax our bodies, making us more vulnerable to illness. We know that everything we do and are exposed to has effects on the strength of our immune response, and that we benefit from adequate rest, ways of alleviating stress, regular exercise, moderation of certain vices, and a nutritious diet. When it comes to the latter, what can we eat and drink to help keep us from getting sick, or to speed recovery?
Strictly, no food can be considered as medicine. That designation is restricted to pharmaceuticals and other products approved by the FDA and backed by accepted scientific studies. It’s true that very little such research has been performed on the relation between specific foods and human immune response. It’s also clear that real food promotes fundamental good health in ways unmatched by extracts or compounds manufactured in a laboratory. It’s ironic that the latter are much more acceptable to our dominant form of scientific thinking, which often favors removing an element from its complex context and reducing whatever’s under study to its simplest factors. Nonetheless, we’ll meet our legal and cultural obligation by emphasizing that no food or drink discussed here is recommended for the treatment or prevention of any illness. We’ll restrict ourselves to reporting anecdotally on longstanding traditional uses of some foods, and on the quantity and quality of the nutrients which, it’s accepted, are essential or beneficial when it comes to keeping us well.
IMMUNE NEEDS
For optimal functioning, the human immune system requires a suite of nutrients. Most fundamentally, though (just as we’re always advised when we get sick) we need plenty of fluids. Water transports nutrients from the digestive system into the bloodstream, where they’re circulated throughout the body. It’s also the main component of lymphatic fluid, which carries the white blood cells that fight infections. Finally, it protects mucous membranes, allowing them to work as barriers against hostile microbes.
We all know about vitamin C. It makes the immune system more efficient by encouraging the production of white blood cells and protecting them from damage. We can’t produce vitamin C without consuming it, and we have to get it from food (or, ineffectively by comparison, supplements). Interestingly, it turns out that no studies have successfully shown that taking vitamin C can shorten a cold—but all of them confirm its vital role in immunity.
While our bodies do make vitamin D in response to sun exposure, our stores dwindle by the end of a winter. Among other things, vitamin D boosts the production of antimicrobial compounds by immune cells, strengthening our ability to fight infections while regulating that activity. Vitamin E, another essential antioxidant, also aids in the rapid production of T cells, which shut down viral reproduction in the immune system’s first response to an infection.
The standout role of zinc in immunity stems from its necessity for basic cellular functioning throughout the body, including proper DNA replication and cell division. It’s essential for the production of some of our most important immune cells, and also highly important in maintaining acquired immunity–that is, the way our body learns to fight off very specific pathogens (in contrast to innate immune response, which doesn’t make distinctions between invaders, and isn’t as supple in its response to newcomers).
Finally, protein is important for good immune function. Dietary proteins (especially glutamine) are the material for antibodies, cells in the blood which identify and attach to pathogens. Once “tagged” by antibodies, these pathogens get “noticed” by the immune cells which deactivate and consume them, then get rid of residual waste.
Of course, plenty of other nutrients provide general support for the body, and thus indirectly boost immunity. There’s no single, most important factor here. Humans are complex systems. Fortunately, the plants and animals we eat are too.
ORANGE JUICE AND CHICKEN SOUP
The traditional recommendations have something to them. Citrus fruits are, of course, a generous and delicious source of vitamin C. Many vegetables have at least as much C, and often more—as is the case with sweet bell and hot chili peppers. Chilies are also high in vitamin E, and capsaicin, which gives them their heat, is a widely-studied, powerful antioxidant. Less often noted are a number of green veggies that also surpass oranges when it comes to vitamin C. A serving of broccoli, for instance, contains more than twice the recommended daily allowance (RDA). Then there are wild plants, typically much more nutrient-dense than almost all their cultivated cousins. Ramps, or wild leeks, show up on Co-op shelves and farmers’ market stands starting near the end of the spring cold season; they’re very high in vitamin C and other nutrients. The leaves of common violets are a powerhouse, boasting a massive amount of this vitamin, among others; lamb’s quarters are a good source as well, while garlic mustard (considered a particularly nefarious invasive plant) outshines most foods in this respect. Vitamin C is water-soluble, which means that its content is reduced by boiling or steaming. Light cooking minimizes this loss, while breaking down the cell walls of plants and making its nutrients more bioavailable than when eaten raw.
In addition to the minerals released from vegetables by long, slow simmering, chicken soup offers high quantities of the protein glutamine. Poultry—especially dark meat—is also rich in zinc. Warm and easily digestible soup also comforts us, lowering stress to promote wellness.
Glutamine and zinc go together in a number of other animal foods as well, like shellfish, beef and lamb (grass-fed red meats being significantly more nutrient-dense than grain-fed). They’re also both found in cooked dry beans, though the zinc there is less bioavailable (absorbable). Whole eggs (especially the yolks) are good sources of a wide array of nutrients, including glutamine and vitamin D. Red cabbage and parsley both provide fair quantities of glutamine as well—and both make great additions to a soup!
NUTS, FISH, AND SHROOMS
Plants put a lot into reproduction, making their seeds wonderfully nutrient-dense food for animals, ourselves included. Many nuts offer high amounts of vitamin E, among other nutrients, valuable fiber and healthy fats. The caveat with nuts and seeds is that most of them also contain phytates, and often (particularly when it comes to almonds and brazil nuts) oxalates—two “antinutrients” that bind to minerals, making them unusable. These compounds, made to ensure the survival of some of a plant’s seeds, can be reduced by soaking and cooking—or we can simply eat them in moderation. Sunflower seeds and walnuts are less risky, while avocados provide a lot of E without the antinutrients, and with its own beneficial oils.
There aren’t a vast number of food sources of vitamin D. Fatty fish boasts a lot of it, along with valuable omega 3s and plenty of other nutrients. Liver is another “superfood”(countless natural foods are superfoods) that contains decent quantities of D. Intriguingly, it’s been shown that mushrooms, when grown outdoors or exposed to ultraviolet light, produce a significant amount of this vitamin, making them the only known non-animal source. Shiitake mushrooms produce more sub-types of vitamin D than most other edible fungi, and have been considered a valuable medicinal mushroom in Asia for a very long time.
ANTIOXIDANTS AND ANTI-INFLAMMATORIES
Our bodies produce quantities and varieties of free radicals as a by-product of turning food into energy (and more in response to various forms of stress and exposure to toxins). Free radicals “steal” electrons from other molecules. This can change the structure of cells, alter DNA, and cause other forms of damage that can lead to chronic health conditions, including increased vulnerability to infections. There are countless “antioxidants,” some produced by the body and some derived from our food, that neutralize free radicals by “donating” electrons without thereby turning into free radicals themselves.
Technically, “antioxidant” doesn’t name a substance, but a way a substance can behave. A compound might behave as an antioxidant when it’s consumed in a whole fruit that also contains other antioxidants, but not in isolation, where it might even act like a free radical. This is why, though it’s generally accepted that antioxidants support immunity, studies have generally failed to show it—they’ve been based on extracts and supplements, which turn out to be largely ineffective.
All the vitamins mentioned as essential for immune health are considered antioxidants. Many high-antioxidant foods are also anti-inflammatory, meaning they regulate the immune system to prevent situations in which the body effectively attacks itself, unable to shut off an immune response. Ginger and turmeric are thought to boast particularly powerful anti-inflammatory properties.
Resveratrol and anthocyanins, compounds found especially in dark blue, purple, and red berries, have been studied extensively for their antioxidant and anti-inflammatory effects. Promising research has been done on the additional ability of a compound in elderberries to prevent reproduction of the flu virus, supporting the use of elderberry syrup in folk medicine. Traditional elderberry syrup also contains raw (unpasteurized) honey, which is thought to offer potent antiviral and antimicrobial effects. Green tea has also been studied for its possible antioxidant and stress-reducing compounds. Basically, most edible plants boast some antioxidant properties, though some are more potent than others.
While it’s not known whether garlic will shorten the duration of a cold, some studies have suggested that eating it before you get sick can reduce the likelihood of infection. This is attributable to allicin, the compound responsible for its distinctive aroma. Allicin is produced when garlic is crushed or chopped, allowing two separate compounds to react with and transform one another. Allicin has an initial oxidative (cell-damaging) effect—but it subsequently increases production of glutathione, the body’s main innate antioxidant, by a significant amount; the by-products of this process are themselves potent antioxidants as well. Allicin is found in lower amounts in ramps (wild leeks), onions and cultivated leeks. In addition, all these plants from the allium genus are considered to be beneficial to our digestive systems.
GUT FOOD
Seventy percent of our immune cells are in the gastrointestinal tract, and the functioning of our immunity is dependent upon intricate interactions with the microbes that live in our gut. Essentially, if our native bacteria aren’t fed well, our immune system doesn’t function at its peak. Prebiotics are forms of dietary fiber that we can’t digest directly, but which are ideal food for gut microbes. They’re found in plant foods; in addition to the alliums, dandelion greens, beans and sunchokes (Jerusalem artichokes) are particularly high in prebiotic fiber, though they’re found in many plant foods.
The jury is still out on whether and when probiotic bacteria can survive the journey through our digestive system and take up residence in the gut. On the other hand, it’s clear that lacto-fermentatio—the transformation of foods by lactic acid bacteria and other microbes—makes many essential nutrients more available to our bodies. A good kimchi, with the nutritional benefits of fermented cabbage and the addition of garlic, ginger and hot pepper, seems like a great component of an immune-supportive diet—as do glutamine-rich yogurt and other fermented foods.
VARIETY
It’s the spice of health. As should be clear, there’s no magic bullet when it comes to eating for immune support. Drinking plenty of water, eating mostly unprocessed foods and including a lot of plants of all kinds is probably the best dietary strategy if we want to remain well—and we can be confident that whole foods are more likely to support immunity than supplements. In addition to incontestable nutritional benefits, a diverse natural diet also seems likely to provide stronger placebo effects—which, even when factually erroneous, are still effects. Switch it up and enjoy the tasty aspect of the task of self-care!
