Seasonal Eating: The Micronutrients that Matter in Winter

Our ancestors never had access to ripe strawberries in December or juicy oranges in July—they had to make do with the fruits and vegetables harvested in that season. This way of eating has immense benefits for our health, as the micronutrients found in seasonal produce actually provide nutritional value that our bodies tend to be depleted of at that particular time of year. From vitamin C-loaded citrus fruit to squash rich in vitamin A, focusing on eating in-season produce is a wonderful way to support nutrient status and immune health all winter long.

Seasonal Eating 101

Seasonal eating is the practice of consuming foods—typically fruits and vegetables—that are harvested during certain seasons. This approach is cyclical in nature, eating produce only during specific times of the year when they are at peak freshness and availability in your local region. 

Different fruits, vegetables, and herbs have varying growing parameters influenced by sunlight, climate, temperature, and soil fluctuations. Because of these seasonal differences, some produce grows during the warmer months, while other fruits and veggies are better suited for chilly, damp, low-sun conditions.

Seasonal eating and local eating have recently gained popularity—so much so that some people now classify themselves as “locavores”—but in reality, these practices are steeped in tradition and have been used by our ancestors for centuries. 

Nutrients You Need in the Winter

While we need these nutrients year-round, the winter season is rife with increased illness, meaning our immune systems need extra support. 

• Vitamin C. Everyone knows that vitamin C is the superstar micronutrient when it comes to immunity. Vitamin C is an essential component of the immune system, as it heals wounds and infections, provides antioxidant activity, and helps to make collagen—a protein we need to grow bones, cartilage, blood vessels, skin, gums, and teeth. Research shows that people with high physical stress have a 52% reduced risk of developing a cold when taking vitamin C regularly.

• Vitamin D. Vitamin D plays a role in innate and adaptive immune responses—and most people get far less sun exposure in the winter months, meaning vitamin D levels can become subpar. This fat-soluble vitamin enhances the production of antimicrobial compounds, upregulates the production of other defensive immune cells, and strengthens the physical barrier function of epithelial cells. Additionally, vitamin D modulates the adaptive immune system by helping to synthesize T cells and reducing the secretion of pro-inflammatory cytokines.

• Vitamin A. This vitamin and its precursors (most notably beta-carotene) are essential for maintaining mucosal surfaces in the respiratory and gastrointestinal tracts, which act as first lines of defense against pathogens by physically preventing their entry into the body. Vitamin A also enhances immune cell function, modulates inflammation, and supports the production of antibodies. 

• Magnesium. This mineral has more of an indirect role in immunity, contributing to antioxidant defenses that neutralize free radicals and oxidative stress. Magnesium also regulates inflammatory pathways and helps to modulate stress and sleep—two crucial areas of health that impact immune function. 

• B Vitamins. While all B vitamins are vital for health, three are essential for immune function: B6, B9 (folate), and B12. These vitamins are involved with producing and activating immune cells, synthesizing antibodies to fight off pathogens, and creating red blood cells. 

• Zinc. Along with vitamin C, zinc is another well-known nutrient we need in the winter to support immunity. Zinc is a mineral needed for the development and proper functioning of many immune cells, including neutrophils, natural killer cells, macrophages, and T-lymphocytes. It also promotes antioxidant enzymes and maintains the integrity of the skin and mucous membranes, like vitamin A.

• Probiotics. While probiotics are not a micronutrient, these healthy bacteria are vital to consume in every season—but especially in the winter, when our immune systems are fighting increasing amounts of pathogens. A more robust gut microbiome—which is influenced by the probiotic-rich foods we consume—leads to lower inflammation, a stronger gut barrier to prevent pathogens or toxins from entering the bloodstream, and enhanced functioning of immune cells like natural killer cells, T cells, and B cells. 

How Seasonal Eating Can Support Wintertime Nutrient Status 

With higher amounts of stress, reduced sunlight exposure, more time spent indoors, and lifestyle changes like increased sugar and alcohol intake, it’s no wonder that more and more people get sick during the colder months—but filling your plate with winter-dominant produce may help to bolster your immunity and prevent some of these illnesses. 

Fruits and vegetables that are in season during winter include avocados, beets, Brussels sprouts, cabbage, carrots, celery, grapefruit, kale, leeks, lemons, limes, onions, oranges, pears, pomegranate, potatoes, rutabagas, Swiss chard, turnips, and winter squash.

Notably, winter produce is rife with citrus fruits, dark leafy greens, and root vegetables, which are particularly rich in some of the vitamins and nutrients we need more of in the winter—let’s take a closer look.  

• Cabbage: This cruciferous vegetable is loaded with vitamin C—just one leaf contains 14% of your daily needs. While many cultures eat boiled cabbage or cabbage stews during the winter, others utilize the fermented forms of cabbage known as sauerkraut or kimchi, which are some of the best sources of dietary probiotics. 
• Citrus fruits (oranges, grapefruit, lemons, and limes): As far back as the 1500s, sailors recognized the value of lemons and limes for immune health as they shielded themselves against the dreaded scurvy. Now, we know that citrus fruits—which are in season during the winter months—are some of the best sources of vitamin C and antioxidants that support immunity. Oranges have the greatest vitamin C levels, followed by grapefruit, lemons, and limes. Citrus fruits also contain vitamin B9 (folate) and plentiful antioxidants, including hesperidin, naringin, and flavonols. 
• Dark leafy greens (kale and Swiss chard): Leafy greens like kale and Swiss chard are loaded with vitamins A, B6, C, K, folate, fiber, manganese, and antioxidants known as carotenoids. Notably, kale has four times the amount of vitamin C than spinach, and Swiss chard contains alpha-lipoic acid, an antioxidant that supports healthy glucose metabolism and fights oxidative stress. 
• Potatoes: The humble potato does much more than simply mash into everyone’s favorite side dish—it also contains vitamins C and B6. One medium potato contains 30% of your daily needs for vitamin C and 10% of the recommended intake for vitamin B6.
• Pomegranate: In addition to being a beautiful addition to any dish, pomegranate seeds are rich in vitamin C, folate, and antioxidants that support immune health. Specifically, pomegranate contains ellagic acid—a compound with antiviral, antibacterial, and antioxidant properties. 

• Squash and sweet potato: Lastly, winter squashes and sweet potatoes are important sources of vitamin A (in the form of beta-carotene) and vitamin B6. Winter squashes include acorn, butternut, delicata, and spaghetti squash—and their yellow-orange colors are indicative of their beta-carotene content that benefits immunity. 

Key Takeaways: 

Seasonal eating can be challenging to take on—especially if you are used to eating your favorite fruits or veggies year-round. However, it doesn’t have to be an all-or-nothing approach. Rather, try incorporating just a few seasonal fruits or vegetables into your meal planning this week and increase from there. Eating seasonally in the winter can help provide your body with the nutrients it tends to be depleted in or needs more of—especially ones that impact a winter-weakened immune system. It’s no coincidence that winter produce provides more of these nutrients in this season’s harvest—after all, Mother Nature always knows best. 

References: 

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