Ah, winter. Like it or loathe it, there’s no denying, it’s heading our way. For those of us in the Northern Hemisphere, sunlight will soon be in short supply. Not great news for our bodies which need sunlight to help us produce our own vitamin D supplies, but an annual reminder to ramp up your stockpiles. With less light and consequently less vitamin D in our systems comes increased vulnerability to just about every bug that crosses our paths and a less-than-optimal immune system that may not quite be up to the challenge should opportunistic pathogens start to take you down. How to fortify yourself through the winter so your body’s ready to fight back? Focus on vitamin D and keep your tank topped up. Here are a few tips on how to do that and why you should:

Vitamin D in a nutshell.

If you think of your skin as a big solar panel that converts waves of ultraviolet light into health-protecting vitamins and immunity-boosting energy, you start to understand just how important sunlight is. Your skin needs and wants exposure to sunlight – done thoughtfully and safely, of course – as sunlight is the primary way your body makes vitamin D.

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Despite the name, vitamin D is not quite a vitamin per se. It’s actually a steroid with hormone-like abilities, helping to regulate the functions of hundreds of genes and assist with the production of hundreds more enzymes and other proteins that are crucial for maintaining health. What else does vitamin D do for you? Think bone-building, inflammation control, regulating neurological and cardiovascular function, fighting depression and helping protect against several types of cancer. It also helps improve our cells’ sensitivity to insulin and enhances muscle strength. In short, it’s powerful stuff.

Chances are you’re seriously short on vitamin D.

It’s estimated that close to half of all American adults are deficient in Vitamin D and more than fifty percent of children ages 1 to 5 and 70% of children ages 6 to 11 have a vitamin D deficiency. Worldwide, it’s estimated that the epidemic of vitamin D deficiency affects one billion people, and in my practice roughly 80% of patients whose vitamin D levels I check come up deficient – and odds are you too are part of the deficient majority.

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So what’s at play here? Though a number of things are undermining our levels (more on that later), one very common thread is our way-too-indoorsy lifestyles, which have robbed us of a lot of opportunities for sunlight to trigger vitamin D production. The short daylight hours of winter make matters worse.

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What else short-changes our vitamin D levels? A number of common factors, like being over 50 years old; excess body fat; gut issues; and even skin tone. For the older set, aging skin doesn’t produce D as efficiently as it did back in the day. Carrying around excess weight also impedes the body’s ability to produce it. And for those with darker skin, roughly 3 -5 times more sun exposure is needed to get the same amount of vitamin D as someone with a lighter complexion. Another underminer? Poor gut health and/or gastric bypass surgery, either of which can hinder vitamin D absorption.

Vitamin D deficiency goes hand-in-hand with lowered immunity.

Think falling short is no big deal? Think again. A 2020 Spanish study published in Journal of Clinical Endocrinology & Metabolism found that more than 80% of those hospitalized with Covid-19 had low vitamin D levels. Though it’s not quite a magic bullet, vitamin D can help to boost your immune system and help thwart the potentially lethal ‘cytokine storm,’ when the inflammatory system goes haywire and damages vital organs. What’s more, a statistical analysis of patient data from hospitals across Asia, Europe, UK and US also found a strong correlation between low vitamin D levels and hyperactive immune responses. So, the take-away here is that the vexing, still-circulating COVID 19 virus can still trigger major trouble – one more reason to keep your tank topped.  

A ‘normal’ vitamin D level can still fall quite short.

To get your levels checked, ideally, twice a year, your doctor can do a quick blood draw, or you can use a high-quality at-home test. Most docs will be looking for a reading of a serum 25(OH) D level greater than 20 ng/ml, but if optimal health is your goal, this number is on the way-too-low end. Vitamin D levels in the 50 to 70 ng/ml is a good place to land, and even up to 80 ng/ml for a truly optimal level.

Dig into platefuls of D’s.

Most of us don’t eat enough vitamin D, in part because it’s not that easy to do. Turns out few foods are naturally D-rich, and by some estimates, just 10% of our D’s come for the food we eat, so it’s important to know which ones deliver the biggest payload. Which foods make the list? Among the biggies, according to Harvard’s T. H. Chan School of Public Health: the skin of preferably wild (not farmed) fatty fish, and fish liver oils. Beyond the skin and oils, also making the cut are wild mackerel, salmon, halibut, tuna, sardines and herring. Organic, grass fed eggs, cheese and beef liver as well as wild shiitake and wild morel mushrooms are also good sources to work into your dietary rotation. Although fortified milk and orange juice also contain some vitamin D, you’d have to drink huge quantities each day to get close to what your body needs, and I certainly don’t recommend doing that!

Supplement your vitamin D levels to a better place.

Supplementation can help get those levels up when daily sunlight is not available. The key, however, is to do it with your doctor’s OK to make sure you’re not interfering with any meds you might be on, such as statins, corticosteroids, or seizure medications, or conditions like kidney disease.

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With the medical go-ahead, it’s OK to supplement with the good stuff. Buying the right kind, D3, aka cholecalciferol, is also essential as it’s the type of vitamin D your body produces in response to sun exposure, whereas D2 supplements, aka ergocalciferol, are a synthetic form. Don’t be fooled.

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Also look for a D3 supplement that’s combined with vitamin K2, and take it with a meal that includes some healthy fat because vitamin D is fat-soluble and requires some fat to be absorbed.

Know when to walk it back.

Most people need anywhere between 2,000 and 10,000 units per day depending on their blood levels; higher doses should only be taken under doctor’s supervision. How to know if you may be over-doing it? Keep an eye out for symptoms like a metallic taste in the mouth, increased thirst, itchy skin, muscle aches and pains, urinary frequency, nausea, and diarrhea and/or constipation – any and all can be signs that your D3 dose may be too high, so again, take a conservative approach, and, as you work with your health care practitioner, keep these guidelines in mind:

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• For levels in the 45 ng/ml range: For general maintenance, 2,000-4,000 IU daily should cover it, depending on your age, weight, how much time you spend outdoors, where you live, etc.
• For levels in the 30-45 ng/ml range: Under a doctor’s supervision, boost levels with 5,000 IU of vitamin D3 a day for three months, and then recheck blood levels, and adjust accordingly.
• For levels below 30 ng/ml: Increase levels with up to 10,000 IU of vitamin D3 a day under a doctor’s supervision – and have your blood levels re-checked after 3 months. Once levels are optimized, most people can dial it down to a maintenance dose of 2,000 – 4,000 IU a day.