How brain fog, fatigue, and more can signal that you have one of the 5 most common vitamin deficiencies

• Some of the most common nutrient deficiencies are B6, B12, D, iron, and calcium.
• If you're deficient in vitamin B12 you might experience irritability, fatigue, and canker sores.
• An iron deficiency can cause fatigue, depression, brain fog, and muscle cramps.

The typical American diet generally consists of processed foods rather than nutrient-dense options like fruits and vegetables. 

This is great for convenience, but can put you at risk of vitamin and mineral deficiencies that may jeopardize your physical and mental health, says Lahana Vigliano, a board-certified clinical nutritionist and owner of Nutrivu Wellness. 

Rates of vitamin deficiencies in the US vary based on race, gender, and socioeconomic status. But, in general, 31% of Americans are thought to be at risk of at least one vitamin deficiency. 

Here's a look at the most common vitamin deficiencies among the general population, how much you should consume of these vitamins each day, and the best food sources to meet your recommended daily intake. 

1. Vitamin B6

Vitamin B6 supports many functions in the body, including the immune system, the heart, and the brain. Vitamin B6 also helps your body convert food to energy. 

Symptoms of a vitamin B6 deficiency include:

• Skin rashes
• Tongue swelling
• Depression
• Seizures
• Fatigue
• Cracked lips
• Weakened immune system 

Here's how much vitamin B6 you need each day: 

Our bodies do not store vitamin B6, so it's crucial to eat a little B6 each day, says Stephanie Taylor, RD, clinical nutrition manager at Providence St. Joseph Hospital.

Good sources of vitamin B6 include:

• Salmon: 3 ounces contains 0.6 mg of vitamin B6 (35% DV)
• Chicken breast: 3 ounces contains 0.5 mg (29% DV)
• Spinach: 1 cup contains 0.2 mg (15% DV)
• Bananas: 1 medium-size banana contains 0.4 mg (31% DV)

2. Vitamin B12

Vitamin B12 plays a number of roles, including:

• Aiding in the creation of red blood cells, which helps carry oxygen throughout the body to vital organs and tissue.
• Helping the body maintain appropriate levels of an amino acid known as homocysteine, which reduces the risk of cardiovascular events like heart attack and stroke.

Symptoms of a vitamin B12 deficiency include:

• Irritability
• Fatigue
• A yellow tinge to the skin
• Canker sores
• Sore and swollen tongue
• Difficulty with balance
• Numbness and tingling in hands and feet

Here's how much B12  you need each day: 

The (RDI) of vitamin B12 in adults would be covered by two eggs for breakfast and a serving of red meat for dinner, Gladd says. 

Other sources of vitamin B12 include:

• Salmon: 3 ounces contains 4.8 mcg of vitamin B12 (200% DV)
• Tuna: 3 ounces contains 2.5 mcg (104% DV)
• Milk: 1 cup of 2% milk contains 1.3 mcg (54% DV)

3. Vitamin D

Vitamin D plays an essential role in bone health, Gladd says. A deficiency of vitamin D may increase your risk of fractures and can lead to a condition known as osteomalacia which is a softening of the bones that can cause pain and muscle weakness. 

Vitamin D also helps support the immune system, and you may become sick more often if you are deficient in it. 

Symptoms of a vitamin D deficiency include:

• Fatigue
• Muscle weakness
• Back pain
• Bone pain
• Frequent colds or respiratory infections 

Here's how much vitamin D you need each day:

Vitamin D is produced by the body naturally when skin is exposed to ultraviolet rays from the sun, so spending at least 15 minutes outside a day is the best way to get your daily intake of vitamin D, Vigliano says.

You can also get vitamin D from foods like:

• Trout: 3 ounces contains 16.2 mcg of vitamin D (81% DV)
• Salmon: 3 ounces contains 14.2 mcg (71% DV)
• Mushrooms: 1/2 cup of white mushrooms contains 9.2 mcg (46% DV)

4. Iron

Iron helps your body produce hemoglobin, the part of red blood cells responsible for transporting oxygen to vital organ and tissue.

Iron deficiency is the most common cause of anemia, or a lack of healthy red blood cells. In fact, a diagnosis of anemia is usually how an iron deficiency is identified, Gladd says. 

However, it is possible to have low iron and not be anemic, Gladd says, so it's important to look at iron levels directly and not only hemoglobin levels when diagnosing iron deficiencies.

Symptoms of an iron deficiency include:

• Fatigue
• A depressed mood
• Brain fog
• Muscle cramps

Here's how much iron you need each day:

The body absorbs iron from animal sources, like beef, chicken, and eggs better than it absorbs iron from plant sources, Gladd says. However, you can still get your daily intake of iron even if you don't eat animal products. 

Good sources of iron include:

• White beans: 1 cup contains 8 mg of iron (44% DV)
• Lentils: 1/2 cup contained 3 mg (17% DV)
• Spinach: 1/2 cup contains 3 mg (17% DV)
• Beef liver: 3 ounces contains 5 mg (28% DV)

5. Calcium

Calcium's main claim to fame is that it helps maintain strong bones, Gladd says. Therefore, a calcium deficiency can result in weak and brittle bones, aka osteoporosis, which increases the risk of fractures and breaks. 

However, calcium also plays a key role in supporting nerve and muscle function, including the heart. Because of this, other symptoms of a calcium deficiency can include:

• Cramps
• Muscle aches and pains
• Muscle spasms  
• Irregular heartbeats
• Osteoporosis (a condition in which the bones become weak or brittle)

Here's how much calcium you need each day:

The RDI for calcium in adults is 1,000 mg a day. For women over the age of 51, the recommendation is increased to 1,200 mg a day. 

Good sources of calcium include:

• Milk: 1 cup of nonfat milk contains 299 mg (23% DV)
• Yogurt: 8 ounces of plain, low-fat yogurt contains 415 mg (32% DV)
• Tofu: 1/2 cup contains 253 mg (19% DV) 

Insider's takeaway

About 31% of the US population is thought to be at risk of at least one vitamin deficiency.

The most common vitamin deficiencies among the general population are:

• Vitamin B6
• Vitamin B12
• Vitamin D
• Iron
• Calcium

To get the recommended daily amounts of these key vitamins, Taylor recommends eating a variety of foods ranging in different colors and nutrients. 

If you find it difficult to include different types of foods in your meals, try seeking out new recipes or cooking methods that encourage you to use new ingredients and increase the diversity of your diet.