9 Most-Common Nutrient Deficiencies

Most of the nutrients we need are easy to get from a balanced, whole-food-based diet. However, there are a few nutrients that are essential for good health that, sometimes, can be hard to get from food alone.

1. Iron Deficiency

This is extremely common (affecting more than 25% of people worldwide) and can cause anemia. It is even more common in preschool-aged children, vegetarians and vegans, and menstruating or pregnant women.


Iron is important because it is the main component of red blood cells and it helps transport oxygen to cells. When you don’t have enough iron, the quantity of red blood cells decreases and the blood’s ability to carry oxygen throughout the body goes down.

The common symptoms of iron deficiency are

  • Tiredness
  • Weakness
  • Low energy
  • A weakened immune system

There are two types of dietary iron:

  • Heme iron: This type of iron is very well absorbed by the body, but it is only found in animal foods, particularly in red meat.
  • Non-heme iron: This type of iron is found in both animal and plant foods, but it’s not absorbed as easily as heme iron by the body.

The Best Dietary Sources

Of heme iron,

  • Red meat
  • Shellfish
  • Canned sardines

Of non-heme iron,

  • Beans
  • Seeds
  • Broccoli
  • Kale
  • Spinach

Vitamin C helps increase the absorption of iron as well.


2. Iodine Deficiency

Iodine is an essential mineral for normal thyroid function and the production of thyroid hormones. These hormones are involved in many processes in the body, including growth and metabolic rate.

Iodine deficiency affects nearly 33% of the world’s population. The most common symptom of this deficiency is goiter.


The Best Dietary Sources

  • Seaweed
  • Fish
  • Dairy
  • Eggs

Many countries have also added iodine to salt to help reduce the severity of the deficiency.

3. Vitamin D Deficiency

Vitamin D is one of the most important vitamins in the body. It works like a steroid hormone, telling cells to turn genes on or off.


Vitamin D is produced in the skin when it’s exposed to sunlight, so people who live in less-sunny areas are highly likely to be deficient. People with dark skin are more likely to be deficient as well, since their skin produces less vitamin D in response to sunlight.

Symptoms of the deficiency include the following:

  • Muscle weakness
  • Bone loss
  • Reduced immune function
  • Increased risk of cancer

The Best Dietary Sources

Very few foods contain enough amounts of Vitamin D. The best sources are

  • Cod liver oil
  • Fatty fish
  • Egg yolks
  • Supplements

4. Vitamin B12 Deficiency

Vitamin B12 is used in the body for blood formation and brain and nerve function. The body can’t produce vitamin B12 on its own, so it’s important to get enough from food or supplements. People who don’t eat animal products are at an increased risk of deficiency (e.g., vegetarians and vegans).

Some symptoms of the deficiency are

  • Impaired brain function
  • Megaloblastic anemia

The Best Dietary Sources

  • Shellfish
  • Organ meat
  • Meat
  • Eggs
  • Milk products

5. Calcium Deficiency

Calcium plays a critical role in the body. It’s especially important for the maintenance and growth of bone and teeth in the body. It also plays a signaling role in the body, which helps all of our muscles and nerves to function properly.

The most common symptom of calcium deficiency is osteoporosis, characterized by softer and more fragile bones.

The Best Dietary Sources

  • Boned fish
  • Dairy products
  • Dark green vegetables like kale, spinach, bok choy, and broccoli

6. Potassium Deficiency

Potassium helps the kidneys, heart, and other organs to work properly. The most common causes of this deficiency are stomach flu (diarrhea/vomiting), antibiotics, or chronic conditions like eating disorders or kidney disease.

The most common symptoms include

  • Weight loss
  • Muscle weakness
  • Constipation
  • In severe cases, abnormal heart rhythm

The Best Dietary Sources

  • Bananas
  • Whole grains
  • Milk
  • Vegetables
  • Beans
  • Peas

7. Folate Deficiency

Folate, or folic acid, is a particularly important vitamin for women of childbearing age, which is why prenatal vitamins contain such a hefty dose. A folate deficiency can cause a decrease in the total number of cells and large red blood cells as well as neural tube defects in an unborn child.

Symptoms of folate deficiency include

  • Fatigue
  • Gray hair and poor growth

The Best Dietary Sources

Supplements are an easy way to get enough folate in your diet, but other food sources include:

  • Fortified cereals
  • Beans
  • Lentils
  • Leafy greens
  • Oranges

8. Vitamin A Deficiency

Vitamin A helps form and maintain healthy skin, eyes, teeth, bones, and cell membranes. Vitamin A deficiency is more common in developing countries than in developed countries (most people in developed countries don’t have to worry about this deficiency).

Vitamin A deficiency is the world’s leading cause of blindness. It can also suppress immune function and increase mortality.

The Best Dietary Sources

  • Organ meat
  • Fish liver oil
  • Sweet potatoes
  • Carrots
  • Dark leafy vegetables

9. Magnesium Deficiency

Magnesium is essential for bone and teeth structure and enzyme reactions in the body. Almost half of the US population is estimated to be deficient in magnesium.

Symptoms of low magnesium intake are

  • Abnormal heart rhythm
  • Muscle cramps
  • Restless leg syndrome
  • Fatigue
  • Migraines

The Best Dietary Sources

  • Whole grains
  • Nuts
  • Dark chocolate
  • Green leafy vegetables

Overall, it is possible to be deficient in any nutrient, but these are the most common by far. The best way to prevent a deficiency is to eat a balanced, whole-food diet that includes nutrient-dense foods. If you are deficient, consider a supplement or eating more of the foods listed above.