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.
Summary: Iron deficiency is very common, especially among young women, children, and vegetarians. It may cause anaemia, fatigue, a weakened immune system, and impaired brain function.
2. Iodine deficiency
Iodine is an essential mineral for normal thyroid function and the production of thyroid hormones. Thyroid hormones are involved in many bodily processes, such as growth, brain development, and bone maintenance. They also regulate your metabolic rate. Iodine deficiency is one of the most common nutrient deficiencies, affecting nearly a third of the world's population.
Summary: Iodine is one of the most common nutrient deficiencies in the world. It may cause enlargement of the thyroid gland. Severe iodine deficiency can cause mental retardation and developmental abnormalities in children.
3. 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.
Summary: Vitamin D deficiency is very common. Symptoms include muscle weakness, bone loss, an increased risk of fractures, and — in children — soft bones. It is very difficult to get sufficient amounts from your diet alone.
4. Vitamin B12 deficiency (see also related posts below)
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. More than 20% of older adults may also be deficient in this vitamin since absorption decreases with age.
Summary: Vitamin B12 deficiency is very common, especially in vegetarians, vegans, and older adults. The most common symptoms include blood disorders, impaired brain function, and elevated homocysteine levels.
5. 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 signalling 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. Symptoms of more severe dietary calcium deficiency include soft bones (rickets) in children and osteoporosis, especially in older adults.
Summary: Low calcium intake is very common, especially in women of all ages and older adults. The main symptom of calcium deficiency is an increased risk of osteoporosis later in life.
6. Vitamin A deficiency
Vitamin A is an essential fat-soluble vitamin. It helps form and maintain healthy skin, teeth, bones, and cell membranes. Furthermore, it produces eye pigments, which are necessary for vision. There are two different types of dietary vitamin A - Preformed vitamin A. This type of vitamin A is found in animal products like meat, fish, poultry, and dairy. Pro-vitamin A. This type is found in plant-based foods like fruits and vegetables. Beta carotene, which your body turns into vitamin A, is the most common form.
Summary: Vitamin A deficiency is very common in many developing countries. It may cause eye damage and blindness, as well as suppress immune function and increase mortality among women and children.
7. 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. Almost half of the U.S. population consumes less than the required amount of magnesium. Low intake and blood levels of magnesium are associated with several conditions, including type 2 diabetes, metabolic syndrome, heart disease, and osteoporosis. The main symptoms of severe magnesium deficiency include abnormal heart rhythm, muscle cramps, restless leg syndrome, fatigue, and migraines. More subtle, long-term symptoms that you may not notice include insulin resistance and high blood pressure.
Summary: Magnesium deficiency is common in Western countries, and low intake is associated with many health conditions and diseases.
The bottom line
It is possible to be deficient in almost every nutrient. That said, the deficiencies listed above are by far the most common. Children, young women, older adults, vegetarians, and vegans seem to be at the highest risk of several deficiencies. The best way to prevent deficiency is to eat a balanced diet that includes whole, nutrient-dense foods. However, supplements may be necessary for those who can’t obtain enough from diet alone."
It appears to be most effective in helping with weight loss and thus reducing insulin resistance. This effect is not maintained at the same rate after the initial period of weight loss and treatment, but many patients, including those not overweight at diagnosis, continue to take it for the cardiovascular protection it is said to afford.