Everyone knows healthy foods give us energy and satisfy our hunger. But you may not realize that the foods we eat supply us with essential vitamins and minerals our body can't produce on its own — and without them, we wouldn't be able to properly function.

The good news is humans don't need large doses of vitamins and minerals to stay healthy, and most people can get what they require from their regular daily meals. Still, some may struggle to maintain a well-rounded diet, and others may deal with impaired absorption from certain medical conditions. Supplements can help make up the difference, acting as an insurance policy against vitamin deficiency.

Vitamin and Mineral ABCs

Vitamins and minerals are micronutrients — elements in food that don't provide calories but are essential for building and repairing cells. Our bodies don't produce the majority of minerals or vitamins we need, so we have to get them from food or supplements.

Live plants and animals produce vitamins, and your body needs 13 essential vitamins to thrive: A, C, D, E, K and eight different B-complex vitamins. Vitamins are either water-soluble or fat-soluble. Water-soluble vitamins (like vitamin C and the B complex vitamins) dissolve in water, and the body cannot store them, so it releases any excess amounts in urine. Vitamins A, E, D and K are fat-soluble vitamins. The body absorbs these best with dietary fat and can store them in its own fat reserves until they become necessary.

Minerals (like calcium, iodine, iron, magnesium, phosphorus, potassium, sodium and zinc) come directly from the earth. Plants absorb these elements directly from the soil, and then animals, and humans, in turn, get them from the food they consume.

Vitamin and Mineral Deficiencies: What to Look For

Vitamin D Deficiency

The body requires vitamin D to properly absorb calcium and phosphorus, which are critical to bone density. A lack of vitamin D can lead to osteoporosis and bone fractures. In severe cases, vitamin D deficiency can lead to bowed legs (a complication called osteomalacia or rickets). Vitamin D deficiency typically doesn't cause symptoms, but some may experience vague signs, such as muscle and bone pain, a "pins and needles" sensation in the hands or feet, muscle weakness in the upper arms or thighs, a waddling gait, muscle twitches, tremors or spasms. However, keep in mind that these signs could be a symptom of other conditions, as well.

Unlike other vitamins, vitamin D can be produced by the human body. When you spend time outdoors, your skin converts the sun's ultraviolet (UV) radiation into vitamin D. Individuals with a darker skin pigment take longer to produce vitamin D than those with a lighter complexion. This is because higher melanin levels provide more protection from UV rays, but the tradeoff is slower vitamin D production.

Those who live in certain climates may also have difficulty producing enough vitamin D if the weather or temperature keeps them indoors most of the time. They can fill that gap with excellent sources of dietary vitamin D, such as egg yolks, fatty fish like salmon, beef liver and items fortified with vitamin D (like cereal, orange juice and dairy products). Vitamin D supplements may be beneficial for people who cannot eat enough foods with vitamin D or who have a medical condition that makes vitamin D absorption difficult, such as inflammatory bowel disease, celiac disease or a resection of the small intestine.

Vitamin B12 Deficiency

Vitamin B12 plays a role in red blood cell production and nervous system health. Chronic digestive conditions like Crohn's disease and celiac disease prevent the absorption of vitamin B12. Individuals who've had weight loss surgeries, such as gastric bypass, may also be unable to absorb enough vitamin B12. Because vitamin B12 is critical to forming new red blood cells, a vitamin B12 deficiency can lead to anemia. Vitamin B12 deficiency can also cause nervous system problems like weakness, numbness or tingling.

Animal-based foods like beef, liver, chicken and fish contain high amounts of vitamin B12, as do dairy products. Plants do not produce large amounts of vitamin B12, so those who follow a vegetarian or vegan diet may lack vitamin B12, but they should consider breakfast cereals, plant-based milk, bread products and nutritional yeast fortified with vitamin B12.

Oral vitamin B12 supplements can help raise vitamin B12 levels, but in severe cases, vitamin B12 injections may be needed. If your vitamin B12 deficiency is due to an absorption issue, you may need to supplement throughout your life.

Vitamin C Deficiency

Vitamin C, also known as ascorbic acid, is best known as a star player in immune health. Vitamin C plays a role in forming skin, collagen, bones, teeth and connective tissues. It also helps with wound healing, the formation of scars and the absorption of iron. It's also a powerful antioxidant that blocks damage caused by free radicals — byproducts of metabolism that can lead to cell damage, aging and cancer. Some symptoms of vitamin C deficiency include fatigue, gum bleeding and joint pain. A severe deficiency in vitamin C can lead to a condition called scurvy.

Vitamin C is plentiful in most fruits and green leafy vegetables, so deficiency is uncommon in developed countries with ready access to fresh, frozen or canned produce. Vitamin C supplements are popular during cold and flu season when people want to avoid getting sick. Many supplements contain much more than the recommended daily allowance of vitamin C. Because vitamin C is water-soluble, your body will not store the extra vitamin C you do not need.

If you take a vitamin C supplement, do not exceed the recommended dosage on the label. Also, be cautious about combining multiple over-the-counter supplements or remedies containing extra vitamin C. Consuming over 2,000 mg daily can lead to upset stomach, diarrhea or kidney stones.

Iron Deficiency

Iron is a building block of hemoglobin, the molecule on red blood cells that transports oxygen to your body's tissues. A lack of iron can lead to iron deficiency anemia. Signs and symptoms of iron deficiency anemia resemble anemia from other causes: pale skin, tiredness, a fast heart rate, brittle nails and, sometimes, a craving for ice. If lab tests indicate anemia, your healthcare provider can confirm that iron deficiency is the cause with additional blood tests.

Slow blood loss over time can also lead to iron deficiency anemia. Individuals with chronic gastrointestinal issues and women who experience heavy menstrual bleeding, are pregnant, have recently given birth or are breastfeeding are at particularly high risk for iron deficiency anemia.

Iron in foods comes in two forms: heme and non-heme iron. Heme iron comes from animal sources like poultry and seafood. Animal products may contain some non-heme iron if the animal consumes it from plants like grass. Non-heme sources of iron are plant-based, such as whole grains, leafy greens, legumes, nuts, seeds and whole grains. Because the body less readily absorbs non-heme iron, vegetarian diets could benefit from including plant-based foods fortified with iron or iron supplements.

Vitamin A Deficiency

Vitamin A maintains healthy eyes, skin and mucous membranes. A vitamin A deficiency can cause vision loss, night blindness, dry skin, more frequent respiratory infections and growth delay in children. Green, orange and yellow fruits and vegetables have high levels of vitamin A, as do dairy products, salmon and eggs.

Who Is at Risk?

Most vitamin and mineral deficiencies are caused by too little of the vitamin or mineral in the diet or a medical condition that prevents the body from absorbing enough of it. Certain groups, like those with chronic medical conditions, the elderly and pregnant women, are at higher risk and are more likely to benefit from multivitamin supplements.

A vitamin deficiency may have no signs or symptoms, so speak with your healthcare provider if you are concerned or at risk. Regular check-ups and blood tests can help identify deficiencies early.

The American College of Obstetrics and Gynecology recommends that pregnant women supplement with vitamin B9 (also called folic acid or folate) to prevent neural tube defects, as well as congenital abnormalities of the brain and spinal cord. Most prenatal vitamins provide the recommended daily allowance of folic acid for a pregnant woman.

If you enjoy drinking alcoholic beverages, you should know that alcohol interferes with absorption of thiamine (vitamin B1), vitamin B12, folic acid and zinc. Consequently, it's best to drink in moderation.

If a medical condition puts you at a higher risk for a nutrient deficiency, ask your doctor to suggest dietary changes and find out if supplements are a good idea. Your physician should check your levels routinely if you have a known deficiency to determine if you need supplements. Keep in mind that many over-the-counter dietary supplements can interfere with prescription drugs. Ask your pharmacist to check for potential interactions with all your medications.

Remember: Your Body Craves Variety

Each food has a unique nutrient profile, so choosing a variety of foods throughout the week will give your body the most comprehensive range of nutrients. Keep your diet rich in fruits, vegetables, lean proteins and whole grains.

Inadequate vitamin intake often goes unnoticed until vitamin deficiency symptoms indicate that it's time to recalibrate. You may want to consider vitamin supplements if you can't get enough vitamins through your diet, but talk to your doctor first and then perhaps your local pharmacist, as well. Or, ask for a referral to a registered dietitian — a licensed healthcare professional with the credentials to make dietary and nutritional recommendations to those with chronic health conditions.

These articles are intended for informational purposes only and are not a substitute for professional medical advice, diagnosis, or treatment and are not intended to treat or cure any disease. Never disregard professional medical advice or delay in seeking it because of something you have read in these articles. Advances in medicine may cause this information to become outdated, invalid, or subject to debate. Professional opinions and interpretations of scientific literature may vary. Consult your healthcare professional before making changes to your diet, exercise or medication regimen.