The 3 Core Nutrient Deficiencies According to a Functional Medicine Expert
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Original Article found in Well & Good
by Michele Ross  January 29, 2023

Feel like you’re not functioning at 100 percent despite your best efforts? Even if you adhere to a well-balanced diet, minimize stress whenever possible, and prioritize movement regularly—essentially, checking off the basics in a standard wellness toolkit—there’s a chance that certain things may be outside of your control. For instance, you can still lack certain vitamins and minerals necessary to support the mind and body to the fullest due to genetics, preexisting conditions, lifestyle, and so on. (BTW, our hectic modern lifestyles aren’t doing us any favors, either.)

With these points in mind, Will Cole, IFMCP, DNM, DC—leading functional medicine specialist, author of the forthcoming book Gut Feelings, and NOW wellness expert—says there are a few very common nutrient deficiencies worth keeping tabs on. Keep reading to see what those are exactly, with actionable FYIs to ensure your levels are (or will soon reach) where they need to be.

Why are nutrient deficiencies all too common?

Cole gets right into things, stating that the most common nutrient deficiencies he witnesses most often in his practice are magnesium, vitamin D, and vitamin K. “With the development of agriculture and modern farming practices, our soil has drastically dropped in nutrient density,” he says. “This directly impacts the nutrient levels in our foods, particularly with magnesium-rich crops like kale.”

Moreover, a 2017 study published in Frontiers in Behavioral Neuroscience found that western diets high in saturated fat and added sugar aren’t only linked to gut issues like intestinal permeability, but also neuroinflammation and cognitive dysfunction. In short, while our food choices certainly dictate how healthful our diets may be, we need to be even more diligent these days to ensure that we also make up for losses beyond our control.

3 common nutrient deficiencies and how to correct them

Below, Cole outlines the ins and outs of the nutrient deficiencies he sees most often, why each nutrient is so important, and how much you should aim to get daily.


“Magnesium is the fourth most abundant mineral in your body and is involved in over 300 biochemical reactions,” Cole says. “It plays a role in your sleep, cognitive function, and so much more.” Additional worthy benefits of magnesium include its potential to help with anxiety, convert food into energy, and promote healthy estrogen levels… yet as many as 75 percent of Americans aren’t getting enough of this all-important mineral.

So how much magnesium actually counts as enough? Cole says that daily needs will vary from one person to the next when it comes to any nutrient insufficiency. However, he notes that 350 milligrams of magnesium per day is a general target worth aiming for. (Magnesium recommendations can also vary based on your gender and age, as well as if you’re pregnant or lactating.) To rev up your intake through whole foods, prioritize the likes of nuts and seeds (pumpkin, chia, cashews), almonds, spinach, and black beans.

Vitamin D

“Vitamin D is so important to pay attention to, as it’s the one nutrient required by every single cell of your body. But it's also one of the most common nutrient deficiencies in our society,” Cole says. In fact, research estimates that as many as one billion people globally have inadequate vitamin D levels, which can lead to issues including but not limited to weakened bones, compromised immunity, and depression.

Cole advises getting between 2,000 and 6,000 IU of vitamin D per day, though it can be a bit tricky to reach these levels. While exposure to sunlight can boost our vitamin D status (hence its nickname, the sunshine vitamin), extenuating factors like how close to the equator you live and what season it is will impact how much of it you’ll get. (At the same time, we also need to take care not to spend too much time in the sun in order to minimize damage from UV rays.)

Plus, vitamin D doesn’t exist naturally in many foods, which also poses a unique challenge to getting enough of it through diet alone. With that in mind, the best food sources of vitamin D include eggs (the yolks in particular), salmon, tuna, mushrooms, milk, and fortified cereals—so eat up if these items are compatible with your personal dietary plan.

Vitamin K

Last on the functional medicine expert’s list of common nutrient deficiencies is vitamin K. While it’s especially important to support proper blood clotting, vitamin K also offers benefits for your bones, heart, and brain.

According to Cole, we should aim for 100 to 200 micrograms of vitamin K2 per day. The best food sources of K2 include natto, as well as grass-fed meat, dairy, and eggs. While you’re at it, eating more foods that contain vitamin K1—including broccoli, spinach, and kale—won’t hurt either. Cole adds that if you’re open to taking supplements (and your doctor signs off on it), one that contains both K2 and D3 is a great option. “I often recommend taking vitamin K2 and D3—a more bioavailable form of vitamin D—together, as they are both fat-soluble and can help enhance each other's bioavailability,” he says. “I formulated NOW’s D3-K2 to harness the power of this vitamin synergy.”

The takeaway

Of course, a food-first approach remains the gold standard to boost your intake of diverse nutrients—but there are exceptions. “While I believe food is foundational, sometimes you do need a little extra support when it comes to overcoming nutrient deficiencies,” says Cole. If you’re feeling off and you suspect your nutritional status isn’t where it should be, he advises getting lab work done with a trusted health professional. From there, they’ll be able to determine if dietary changes and supplementation—including the precise dosage that’s best for you—are necessary. “I always recommend a whole-foods based diet in conjunction with supplements,” Cole concludes… with one final caveat. “[But] no matter how many supplements you take, you can't supplement your way out of a poor diet.”




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