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  • Taylor Richter, RDN, LD

Nutrient Deficiencies: Uncovering the Top 5 - Vitamin B6, B12, C, D, and Iron

It's a startling fact: A staggering 31 percent of Americans are at risk for a nutrient deficiency that could undermine their overall well-being. It might be hard to believe, considering the abundance of food options available 24/7, but the truth is, many of us aren't getting the nutrition we need.

Is it worth worrying about a potential shortage of one or two vitamins or minerals? Absolutely. The reason is crystal clear: vitamins and minerals are the linchpins of optimal health. While a deficiency might not trigger immediate symptoms, it exposes you to the potential for serious diseases that can wreak havoc on your brain, heart, blood, immune system, metabolism, bones, and mental well-being, among other vital systems. The absence of just a single nutrient can disrupt the delicate equilibrium necessary for your well-being and overall vitality. What makes it even more fascinating is that most nutrients aren't single-taskers; they perform a multitude of crucial roles within the body.

How would you even know if you’re at risk for a nutrient deficiency? It’s not always obvious. Sometimes symptoms aren’t apparent and sometimes they’re very vague or non-specific. For example, fatigue, irritability, aches and pains, decreased immune function, and heart palpitations can be signs of many things, including a nutrient deficiency. This article goes over the five most commonly deficient nutrients, some of the more obvious symptoms, and foods that are high in each so you can get enough.

Vitamin B6

Vitamin B6 stands as the most prevalent nutrient deficiency in the United States, and its significance cannot be overstated. This vitamin plays a pivotal role in the health of your blood, brain, and metabolism. It spearheads the production of hemoglobin, the essential component responsible for carrying oxygen through your bloodstream. Moreover, Vitamin B6 helps maintain the crucial balance of homocysteine levels, a factor intertwined with heart disease.

It also plays a crucial part in crafting neurotransmitters, the messengers that enable nerve cells to communicate seamlessly. As if that weren't enough, Vitamin B6 wears many hats, actively engaging in over 100 enzyme reactions, most of which fuel your metabolic processes.

A significant deficiency in Vitamin B6 can manifest as depression, confusion, convulsions, or even a specific form of anemia known as microcytic anemia. However, even milder deficiencies carry significant risks, including an elevated vulnerability to heart disease and Alzheimer's. These wide-ranging health effects are why Vitamin B6 is so essential for health.

Vitamin B6 is found in all food groups. People who eat high-fiber cereals tend to have higher levels of the vitamin because cereals are often fortified with it. Vitamin B6 is also found in high quantities in potatoes, non-citrus fruits (e.g., bananas), and various animal-based foods such as poultry, fish, and organ meats.

Vitamin B12

Similar to Vitamin B6, Vitamin B12 plays a vital role in maintaining the health of both your blood and brain. It is essential for the production of healthy red blood cells and the formation of the protective coating around nerve cells, known as myelin, which is crucial for their optimal functioning.

Vitamin B12 can be a bit difficult to absorb from your food. To enhance its absorption, it's essential to have sufficient stomach acid and digestive enzymes. This is because the vitamin strongly attaches to the proteins in food, and stomach acid and enzymes aid in breaking these bonds, freeing the vitamin for your body to utilize.

A deficiency in Vitamin B12 can be caused by a condition known as pernicious anemia. Pernicious anemia is an autoimmune disorder that affects the stomach's ability to absorb Vitamin B12. A deficiency can lead to another type of anemia called megaloblastic anemia. In addition, low levels of Vitamin B12 can result in neurological damage due to impaired myelination of nerve cells.

Vitamin B12 is not naturally present in most plant-based foods, with some exceptions like nutritional yeast products. It is naturally found in dairy products, eggs, fish, poultry, and meat, especially in clams, beef liver, trout, and salmon. Many breakfast cereals are fortified with Vitamin B12.

When you are consuming Vitamin B12 supplements or foods enriched with this vitamin, the role of stomach acid and digestive enzymes becomes less critical compared to direct absorption from natural foods. This is because Vitamin B12 added to foods and supplements is not tightly bound to their proteins, making it significantly more easily absorbed by the body.

Vitamin C

Vitamin C plays a pivotal role in several bodily functions, including wound healing through the synthesis of collagen, neurotransmitter production, metabolic processes, and the effective operation of the immune system. Vitamin C acts as an antioxidant to reduce the damage caused by free radicals that can worsen several diseases such as certain cancers and heart disease. Vitamin C also helps your body absorb the essential mineral iron, which is one of the top five nutrient deficiencies also included in this article.

Collagen is a vital component of connective tissue and this describes some of the symptoms of its deficiency disease, scurvy. Symptoms of scurvy include weak connective tissue such as bleeding gums, wounds that won’t heal, and even the loss of teeth.

You can get Vitamin C from many fruits and vegetables. Ones particularly high in Vitamin C include bell peppers and oranges. Other good sources of the vitamin include kiwi, broccoli, strawberries, Brussels sprouts, tomatoes, cantaloupe, cabbage, and cauliflower. Vitamin C is not naturally present in grains, but some breakfast cereals are fortified with it.

Vitamin D

Vitamin D, also known as the “sunshine vitamin,” is very important for your bones. It promotes the absorption of the mineral calcium. When your body has enough calcium, it can maintain normal bone mineralization and prevent problems in the muscles that lead to cramps and spasms. Getting enough Vitamin D and calcium can also help protect against osteoporosis. In addition to all of these bone and muscle impacts, Vitamin D helps to reduce inflammation and modulate both immune function and sugar metabolism.

Without enough Vitamin D bones can become thin, brittle, or misshapen. Vitamin D prevents these issues known as rickets (in children) and osteomalacia (in adults).

Your skin makes Vitamin D when it’s exposed to the ultraviolet rays of the sun and very few foods naturally contain it. The few Vitamin D-rich foods include fatty fish and fish liver oils (e.g., salmon, trout, cod liver oil). Other foods that naturally contain small amounts of Vitamin D include egg yolks, beef liver, and cheddar cheese. Some mushrooms can contain Vitamin D—particularly those exposed to UV light.

Most of the dietary Vitamin D that people in the US get is from fortified foods and beverages. These include some dairy products (mainly milk), certain plant milks (e.g., soy, almond, or oat milks), various breakfast cereals, and a few types of orange juice. Be sure to look at the nutrition labels to see if and how much Vitamin D is in each serving of the food or beverage.


Iron is a mineral needed for maintaining healthy blood, ensuring the continuous transportation of oxygen throughout your body day in and day out. This function is facilitated by hemoglobin, a compound present in your red blood cells. Additionally, iron plays a supportive role in muscle and connective tissue health, similar to the roles of Vitamin D and Vitamin C, respectively. Adequate iron levels are imperative for physical growth, neurological development, hormone production, and cellular function.

A deficiency in iron is commonly referred to as anemia, a condition particularly prevalent among menstruating women.

While most iron resides in the blood, there are also reserves stored in the liver, spleen, bone marrow, and muscles. Iron deficiency progresses gradually, starting from depleting these reserves (mild iron deficiency), then reducing the number of red blood cells (marginal iron deficiency), before culminating in full-blown iron deficiency anemia.

Iron is naturally present in foods in two forms: heme and nonheme. Animal-based foods contain the more readily absorbed heme form, whereas plant-based foods contain nonheme iron. This is where Vitamin C becomes crucial. Vitamin C aids the absorption of nonheme iron from plant sources. Therefore, if plants constitute a significant portion of your iron intake, it's important to combine iron-rich plants with Vitamin C-rich plants in the same meal.

Some of the best sources of plant-based, or nonheme iron, include fortified cereals, white beans, dark chocolate, lentils, spinach, and tofu.

Meat, poultry, and fish, shellfish, and beef liver are excellent sources of highly absorbable heme iron, and when eaten along with plant-based sources of iron, they can help enhance absorption of nonheme iron.

Final Thoughts

Approximately one-third of people in the US are vulnerable to at least one nutrient deficiency, with Vitamin B6 being the most common shortfall. Deficiencies in vitamins B12, C, D, and the mineral iron are also prevalent. These nutrients are indispensable for overall well-being, and a deficiency in any of them can have significant repercussions.

Ensuring a balanced, nutrient-rich diet with a diverse range of foods is vital for achieving and maintaining good health.

Never start a new supplement or assume you have a nutrient deficiency without speaking to a medical professional.

If you're experiencing symptoms or simply feel off and are seeking inspiration on how to achieve your health goals through proper nutrition, consider scheduling a complimentary curiosity call to see if working with a dietitian at the Functional Kitchen is right for you!


Bird, J. K., Murphy, R. A., Ciappio, E. D., & McBurney, M. I. (2017). Risk of Deficiency in Multiple Concurrent Micronutrients in Children and Adults in the United States. Nutrients, 9(7), 655.

National Institutes of Health Office of Dietary Supplements. (2020, February 28). Iron fact sheet for health professionals.

National Institutes of Health Office of Dietary Supplements. (2020, February 4). Vitamin B6 fact sheet for health professionals.

National Institutes of Health Office of Dietary Supplements. (2020, March 30). Vitamin B12 fact sheet for health professionals.

National Institutes of Health Office of Dietary Supplements. (2020, February 27). Vitamin C fact sheet for health professionals.

National Institutes of Health Office of Dietary Supplements. (2020, October 9). Vitamin D fact sheet for health professionals.

Oregon State University. Micronutrient Information Center, Linus Pauling Institute. (2016 May). Iron.


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