1. Iron deficiency
Iron is an essential mineral.
It’s a large component of red blood cells, in which it binds with hemoglobin and transports oxygen to your cells.
The two types of dietary iron are:
Heme iron. This type of iron is very well absorbed. It’s only found in animal foods, with red meat containing particularly high amounts.
Non-heme iron. This type, found in both animal and plant foods, is more common. It is not absorbed as easily as heme iron.
Iron deficiency is one of the most common nutrient deficiencies in the world, affecting more than 25% of people worldwide (1, 2).
This number rises to 47% in preschool children. Unless they’re given iron-rich or iron-fortified foods, they are very likely to lack iron.
Around 30% of menstruating women may be deficient as well due to monthly blood loss, and up to 42% of young, pregnant women may be deficient as well.
Additionally, vegetarians and vegans have an increased risk of deficiency because they consume only non-heme iron, which is not absorbed as well as heme iron (3, 4).
The most common consequence of iron deficiency is anemia, in which the number of your red blood cells and your blood’s ability to carry oxygen drops.
Symptoms usually include tiredness, weakness, a weakened immune system, and impaired brain function (5, 6).
The best dietary sources of heme iron include (7):
- Red meat. 85 grams (3 ounces) of ground beef provide almost 30% of the Daily Value (DV).
- Organ meat. 81 grams of liver gives more than 50% of the DV.
- Shellfish. Clams, mussels, and oysters are excellent sources of heme iron, with 85 grams (3 ounces) of cooked oysters packing roughly 50% of the DV.
- Canned sardines. 106 grams (3,75 ounce) can offer 34% of the DV.
The best dietary sources of non-heme iron include:
- Beans. 85 grams (Half a cup) of cooked kidney beans provides 33% of the DV.
- Seeds. Pumpkin, sesame, and squash seeds are good sources of non-heme iron. 28 grams (one ounce) of roasted pumpkin or squash seeds contains 11% of the DV.
- Dark, leafy greens. Broccoli, kale, and spinach are rich in iron. 28 grams (one ounce) of fresh kale provides 5.5% of the DV.
However, you should never supplement with iron unless you truly need it. Too much iron can be very harmful.
Notably, vitamin C can enhance the absorption of iron. Eating vitamin-C-rich foods like oranges, kale, and bell peppers alongside iron-rich foods can help maximize your iron absorption.
2. Vitamin D deficiency
Vitamin D is a fat-soluble vitamin that functions like a steroid hormone in your body.
It travels through your bloodstream and into cells, telling them to turn genes on or off. Almost every cell in your body has a receptor for vitamin D.
Vitamin D is produced from cholesterol in your skin upon exposure to sunlight. Thus, people who live far from the equator are likely to be deficient unless their dietary intake is adequate or they supplement with vitamin D (8, 9).
In the United States, about 42% of people may be deficient in this vitamin. This number rises to 74% in older adults and 82% in people with dark skin since their skin produces less vitamin D in response to sunlight (10, 11).
Vitamin D deficiency is not usually obvious, as its symptoms are subtle nd may develop over years or decades (12, 13).
Adults who are deficient in vitamin D may experience muscle weakness, bone loss, and an increased risk of fractures. In children, it may cause growth delays and soft bones (rickets) (14, 15, 16).
Also, vitamin D deficiency may play a role in reduced immune function and an increased risk of cancer (17).
While very few foods contain significant amounts of this vitamin, the best dietary sources are (18):
- Cod liver oil. A single tablespoon (15 ml) packs 227% of the DV.
- Fatty fish. Salmon, mackerel, sardines, and trout are rich in vitamin D. 85-gram (3 ounce) serving of cooked salmon provides 75% of the DV.
- Egg yolks. One large egg yolk contains 7% of the DV.
People who are deficient may want to take a supplement or increase their sun exposure. It is hard to get sufficient ammount through diet alone.
3. Vitamin B12 deficiency
Vitamin B12, also known as cobalamin, is a water-soluble vitamin.
It is essential for blood formation, as well as brain and nerve function.
Every cell in your body needs B12 to function normally, but your body is unable to produce it. Therefore, you must get it from food or supplements.
B12 is only found in sufficient amounts in animal foods, although certain types of seaweed may provide small quantities. Therefore, people who do not eat animal products are at an increased risk of deficiency.
Studies indicate that up to 80–90% of vegetarians and vegans may be deficient in vitamin B12 (19, 20).
More than 20% of older adults may also be deficient in this vitamin since absorption decreases with age (21, 22, 23).
B12 absorption is more complex than that of other vitamins because it’s aided by a protein known as intrinsic factor. Some people are lacking in this protein and may thus need B12 injections or higher doses of supplements.
One common symptom of vitamin b12 deficiency is megaloblastic anemia, which is a blood disorder that enlarges your red blood cells.
Other symptoms include impaired brain function and elevated homocysteine levels, which is a risk factor for several diseases (24, 25).
Dietary sources of vitamin B12 include (7):
- Shellfish. Clams and oysters are rich in vitamin B12. 85-gram (3 ounce) portion of cooked clams provides
1,400% of the DV.
- Organ meat. 60-gram (2 ounce) slice of liver packs more than 1,000% of the DV.
- Meat. 170-gram (6 ounce) beef steak offers 150% the DV.
- Eggs. One whole egg provides about 6% of the DV.
- Milk products. One cup (240 ml) of whole milk contains about 18% of the DV.
Vitamin B12 isn’t considered harmful in larger amounts because it’s often poorly absorbed and easily excreted.
4. Calcium deficiency
Calcium is essential for every cell in your body. It mineralizes bones and teeth, especially during times of rapid growth. It is also very important for bone maintenance.
Additionally, calcium serves as a signaling molecule. Without it, your heart, muscles, and nerves would not be able to function.
The calcium concentration in your blood is tightly regulated, and any excess is stored in bones. If your intake is lacking, your bones will release calcium.
That is why the most common symptom of calcium deficiency is osteoporosis, characterized by softer and more fragile bones.
One survey in the United States found that fewer than 15% of teenage girls, fewer than 10% of women over 50, and fewer than 22% of teenage boys and men over 50 met the recommended calcium intake (26).
Although supplementing increased these numbers slightly, most people were still not getting enough calcium.
Symptoms of more severe dietary calcium deficiency include soft bones (rickets) in children and osteoporosis, especially in older adults (27, 28).
Dietary sources of calcium include (7):
- Boned fish. One can (92 grams) of sardines contains 44% of the DV.
- Dairy products. 240 ml (one cup) of milk provides 35% of the DV.
- Dark green vegetables. Kale, spinach, bok choy, and broccoli are rich in calcium. 28 grams (1 ounce) of fresh kale offers 5.6% of the DV.
The effectiveness and safety of calcium supplements have been somewhat debated in the last few years.
Some studies demonstrate an increased risk of heart disease in people taking calcium supplements, although other studies have found no effects (29, 30, 31).
While it’s best to get calcium from food rather than supplements, these supplements seem to benefit people who are not getting enough in their diet (32).
5. Magnesium deficiency
Magnesium is a key mineral in your body.
Essential for bone and teeth structure, it’s also involved in more than 300 enzyme reactions (33).
Close to 70% of the US population under 71, and about 80% over 71 years old consume less than the required amount of magnesium. (34).
Low intake and blood levels of magnesium are associated with several conditions, including type 2 diabetes, metabolic syndrome, heart disease, and osteoporosis (35).
Low levels are particularly common among hospitalized patients. Some studies find that 9–65% of them are deficient (36, 37, 38).
Deficiency may be caused by disease, drug use, reduced digestive function, or inadequate magnesium intake (39).
The main symptoms of severe magnesium deficiency include abnormal heart rhythm, muscle cramps, restless leg syndrome, fatigue, and migraines (40, 41, 42).
More subtle, long-term symptoms that you may not notice include insulin resistance and high blood pressure.
Dietary sources of magnesium include (7):
- Whole grains. 170 grams (one cup) of oats contains 74% of the DV.
- Nuts. 20 almonds pack 17% of the DV.
- Dark chocolate. 30 grams (one ounce) of dark chocolate offers 15% of the DV.
- Dark green, leafy vegetables. 30 grams (one ounce) of raw spinach provides 6% of the DV.