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5 Most Common Nutrient Deficiencies Explained

Even if you are super health-conscious, busy schedules and the demands of modern life can make it hard to get all the nutrients you need from diet alone. Many people take a multivitamin to “be on the safe side” because they hear that the soil our food is grown in is no longer nutrient-dense or worry that their diet isn’t as healthy or diverse as it should be. The reality is that for most people, if your diet is varied and filled with a rainbow of fruits and vegetables, and you are healthy and absorbing nutrients well from your gastrointestinal tract, you probably don’t need the extra vitamins and minerals.


Nutrient Deficiency Symptoms

While each nutrient can have their own distinct set of symptoms, there are some that carry across almost all deficiencies. These include:

• General lethargy, tiredness, aches, and pains

• Increased anxiety and restlessness

• Brittle hair and nails

• Irritability

• Depression

• Brain fog

• Acne

While this is not an exhaustive list, it’s also important not to pass off these symptoms as normal parts of life. Instead, they are often clues that something deeper is going on in the body.

Top 5 Nutrient Deficiencies

Here’s a look at the most common nutrient deficiencies that contribute to everything from fatigue and migraines to hormonal imbalances, what a deficiency means for your overall health, and how you can address them.

1. Vitamin D

Vitamin D gets top billing because almost every single person we see at Parsley Health is deficient in this vitamin. Understanding what a vitamin D deficiency is, and what part of your lifestyle are contributing, can help you resolve symptoms.


Vitamin D deficiency symptoms

Some symptoms unique to vitamin D deficiency include:

• Low immunity and getting sick often

• High blood pressure

• Low bone mineral density

Vitamin D deficiency causes

While it’s true that we can get Vitamin D from the sun, most of us wear clothing that covers most of our bodies, use sunscreen, and spend the majority of our time indoors. Since sunlight on exposed skin is the primary way our bodies produce vitamin D, we simply don’t get enough.

Recommended levels of Vitamin D

You’d think the answer would be straightforward, but it’s most definitely not. In 2011 the Endocrine Society issued a report recommending a vitamin D level of 30ng/mL, and because of inconsistencies with testing, suggested aiming for a level of 40-60ng/mL. But then some top doctors in the field said the minimal level should be decreased to 12.5ng/mL because only 6% of Americans have levels below that. In other words, they suggested we just lower the bar for what is considered deficient, and then we won’t have so many people low in vitamin D.


Some of the studies of vitamin D and risk for various cancers, cardiovascular disease, certain autoimmune diseases, falls and depression suggest that you need a level somewhere between 40-60ng/mL. At Parsley Health we aim for levels slightly above that, 50-70ng/mL which is also well below any risk for vitamin D toxicity. We also have our own Vitamin D optimized for maximum absorption.

2. Magnesium

Magnesium comes next not only because people are frequently deficient in it, but also because its value in wellness is often underappreciated.

Magnesium deficiency symptoms

Some of the most common symptoms of magnesium deficiency include:

• Kidney and liver damage

• Migraine headaches

• Restless leg syndrome

• Worsened PMS symptoms

• Osteoporosis

• Cavities

• Impotence


Magnesium deficiency causes

With less nutrients from soil, which have become depleted of nutrients, and chemical processing taking nutrients out of foods, its becoming harder and harder to reach recommended magnesium levels from your diet alone. Grains, for example, a good source of magnesium, lose most of their magnesium content when they are refined. Medications can also impact magnesium levels: antacids decrease absorption and diuretics increase urinary excretion.

Recommended magnesium levels

Magnesium’s most crucial role is in helping with brain, heart, and muscle function, but it’s also involved in the synthesis of DNA, RNA, and proteins, and is a critical factor in at least 600-800 enzymatic reactions. According to the National Institute of Health, recommended daily allowances range from 400-420 mg for adult men and 310-320 mg for adult women.

3. Iodine

If magnesium is underappreciated, iodine is downright ignored. Ever since iodine was added to table salt, people in developed countries have stopped giving this mineral its due attention.

• Iodine deficiency symptoms

• Swelling in the neck

• Dry, flaky skin

• Sudden weight gain

• Changes in heart rate

• Irregular periods


Iodine deficiency causes

Iodine is used by the thyroid, stomach lining, and mammary glands to produce hormones that are essential for so many functions in your body. But as important as it is, it’s not naturally made by the body, meaning you need to get all necessary iodine from your diet—which many struggle with. Foods like seaweed salad, a sprinkle of dulse on your greens, or some kombu in your soup can be good sources of this element.

Recommended Iodine Levels

Iodine is one of those Goldilocks nutrients—you have to be careful you don’t get too much or too little. If you are severely deficient you could develop hypothyroidism, but even modest deficiencies may be problematic.

Although iodine deficiency is much less common in developed countries, it is still an issue, with about 10% of the population in the Americas and 52% of Europeans deficient. In the US, 15% of women of reproductive age are deficient. What qualifies as adequate is questionable, as the US RDA is 150mcg/day, while in Japan the typical intake is 1000-3000mcg/day.

4. Vitamin B12

Vitamin B12 plays a role in everything from making DNA to regulating brain function, but like iodine, it’s not made in the body, making deficiencies common.

Vitamin B12 Deficiency Symptoms

• Pale Skin

• Constipation

• Diarrhea

• Gas

• Numbness or tingling

Common Causes of Vitamin B12 Deficiency

Vitamin B12 is abundant in animal food but practically non-existent in plant foods. That’s why we expect our vegan members to have low levels of this nutrient and need to take a supplement. However, what’s surprising is that many people who eat animal protein on a daily basis are also low in vitamin B12.


For those who don’t follow a vegan diet, common causes of this deficiency include:

Low stomach acidity: Stomach acid is needed to separate B12 from the food protein it is attached to when swallowed. Of course, acid-blocking medications decrease stomach acidity, and it often decreases simply in the course of aging.

Pernicious anemia: This is an autoimmune disease that interferes with the absorption of vitamin B12.

Small intestinal bacterial overgrowth (SIBO): The bugs that mistakenly take up residence in the upper part of the small intestines in SIBO consume some of the B12, so less reaches the lower part of the small intestines (ileum) where B12 gets absorbed into the bloodstream.

Metformin: This is the most common medication used to treat type 2 diabetes and can interfere with B12 absorption into the bloodstream. MTHFR mutation: There are genetic variations in this gene that don’t affect B12 absorption but can affect its utilization in the cells.

Recommended Vitamin B12 Levels

As is true for most nutrients, assessing what is a sufficient level is not as straightforward as we’d like it to be. It is clear that people with blood levels of B12 150pg/mL are deficient, but plenty of people with levels higher than that still have inadequate stores of B12, so a level between 150-400 pg/mL is considered borderline.

5. Iron

Of all the nutrients in this list, iron is the most straightforward, but still so many fail to reach the recommended amount.

Iron deficiency symptoms

Some symptoms unique to an iron deficiency include:

• Fatigue

• Dizziness and headaches

• Sensitivity to temperature

• Shortness of breath

• Chest pain

Iron deficiency causes

Iron comes from both plant and animal food. Plant sources of iron (called non-heme iron), such as leafy greens, legumes, nuts and seeds, are not as easily absorbed as the animal sources (heme iron). So vegetarians and vegans are at higher risk for iron deficiency than omnivores. In addition, menstruating women, especially those with heavy periods, can have low iron stores.

Recommended daily levels and iron deficiency anemia

A minimum level of ferritin is somewhere between 12-20ng/mL. Levels less than that often lead to iron deficiency anemia, with its associated symptoms, including fatigue, weakness and cold extremities. But even levels that aren’t low enough to cause anemia can still cause other problems, such as restless leg syndrome, hair loss, brittle or spooning of the nails, loss of sense of smell, and hypothyroidism.

Fortunately, it is easy to increase your iron levels either by eating red meat (ideally organic and grass fed) or taking an iron supplement. And if necessary, intravenous iron replacement is also an option.