Other Trace Minerals: Videos & Practice Problems

Zinc, abbreviated as Zn, is a vital trace mineral that plays numerous roles in the body, primarily as a cofactor for over 300 enzymes. These enzymes are crucial for various biochemical reactions, making zinc essential for numerous bodily functions. Its enzymatic role is complemented by its structural function, as zinc stabilizes certain proteins, some of which are involved in regulating gene expression. This regulatory function is particularly important during fetal development, ensuring that the correct genes are activated at the appropriate times.

In addition to its enzymatic and structural roles, zinc may also contribute to immune function. Some studies suggest that zinc supplementation could reduce the duration of the common cold, although this area remains somewhat controversial with mixed evidence.

The Recommended Dietary Allowance (RDA) for zinc for adults aged 19 to 50 is between 8 to 11 milligrams per day. Good dietary sources of zinc include fish, meat, and particularly oysters, which are considered one of the best sources. Other sources include whole grains, enriched grains, and leavened bread, which is bread that has been allowed to rise due to yeast fermentation. This is significant because leavened bread contains fewer phytates, compounds that can inhibit zinc absorption.

Non-heme iron, found in plant foods, can compete with zinc for absorption in the gut, meaning excessive intake of non-heme iron can limit zinc absorption and vice versa. Additionally, high fiber intake and phytates can also hinder zinc absorption, particularly in diets rich in unleavened bread, which contains more phytates. While zinc deficiency is rare in developed countries, it can occur in populations consuming large amounts of unleavened bread, leading to symptoms such as growth delays, delayed sexual maturation, reduced appetite, and increased susceptibility to infections.

On the other hand, excessive zinc intake, often from supplements, can lead to toxicity, although this is also uncommon. Symptoms of zinc toxicity include gastrointestinal upset, headaches, weakened immune function, and interference with iron absorption. Therefore, it is crucial to avoid over-supplementation, especially for individuals relying on non-heme iron sources, such as vegetarians and vegans.

Overall, obtaining sufficient zinc through a balanced diet is generally not a concern, and the primary dietary advice is to avoid excessive supplementation.

Selenium, abbreviated as Se, is a trace mineral essential for various bodily functions, primarily acting as a cofactor for numerous enzymes. These enzymes play diverse roles in cellular processes, making it challenging to pinpoint selenium's exact contributions. Notably, selenium is crucial for the production of thyroid hormones, which also require iodine. Additionally, selenium functions as an antioxidant and supports immune health, with adequate intake linked to a reduced risk of certain cancers. However, exceeding the recommended intake does not further decrease cancer risk, highlighting the importance of obtaining sufficient selenium without overconsumption.

The recommended dietary allowance (RDA) for selenium for individuals over 19 years old is 55 micrograms, a relatively small amount. Selenium is present in all food groups, but its concentration varies based on soil content where the food is grown. Regions such as Michigan, Florida, and the Desert Southwest in the United States have lower selenium levels, affecting the selenium content in local plants and animals. Fortunately, deficiencies are rare in modern diets, which typically include a variety of foods sourced from different regions.

In cases where selenium deficiency occurs, often in subsistence farming communities in selenium-poor areas, it can lead to impaired thyroid function or conditions like Keshan disease, a heart disorder named after a region in China with low selenium levels. Conversely, excessive selenium intake can lead to toxicity, known as selenosis, primarily from over-supplementation. Symptoms of selenosis include brittle nails, hair loss, skin rashes, nausea, vomiting, and potential liver damage.

In summary, as long as individuals consume a diverse diet with foods from various regions, there is generally no need to worry about selenium intake. Maintaining a balanced diet is key to ensuring adequate selenium levels without the risk of deficiency or toxicity.

Trace minerals play a crucial role in various bodily functions, and among them, manganese (Mn), chromium (Cr), and molybdenum (Mo) are often considered lesser trace minerals. This designation does not imply that they are less important, but rather that they are needed in smaller amounts and may not require as much detailed knowledge.

Manganese is essential for daily intake, with recommendations ranging from 1.8 to 2.3 milligrams. It serves primarily as a cofactor for numerous enzymes, particularly those involved in metabolism. It is important to distinguish manganese from magnesium, as both act as enzyme cofactors, but magnesium is a major mineral and an important electrolyte. Good dietary sources of manganese include mollusks, nuts, and whole grains like oatmeal. While manganese deficiency is rare, excessive intake can lead to toxicity, although this typically occurs only with significant over-supplementation or in specific industrial settings.

Chromium, required in microgram amounts (25 to 35 micrograms), enhances insulin function, which is vital for glucose regulation and storage. It is generally obtained from a varied diet, although specific food sources are not well-studied. Deficiency in chromium is uncommon and primarily observed in individuals on long-term intravenous feeding without proper supplementation. Notably, chromium has not been associated with toxicity.

Molybdenum, another trace mineral, has a recommended intake of at least 45 micrograms. It acts as a cofactor for several enzymes, particularly those involved in the metabolism of sulfur-containing amino acids. Molybdenum can be found in milk, dairy products, beans, whole grains, and nuts. Similar to manganese and chromium, deficiencies in molybdenum are rare, and the risk of toxicity is low, typically only arising from excessive supplementation.

In summary, while manganese, chromium, and molybdenum are required in smaller quantities compared to other minerals, they play significant roles in metabolic processes and enzyme function, making them essential components of a balanced diet.