Nutrition Science and Everyday Application - beta v 0.1

442 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
capacity for fat-soluble vitamins increases the risk for toxicity. While toxic levels are typically
only achieved through vitamin supplements, if large quantities of fat-soluble vitamins are
consumed, either through foods or supplements, vitamin levels can build up in the liver and
fatty tissues, leading to symptoms of toxicity.
There is limited storage capacity in the body for water-soluble vitamins, thus making
it important to consume these vitamins on a daily basis. Deficiency of water-soluble vitamins
is more common than fat-soluble vitamin deficiency because of this lack of storage. That also
means toxicity of water-soluble vitamins is rare. Because of their solubility in water, intake
of these vitamins in amounts above what is needed by the body can, to some extent, be
excreted in the urine, leading to a lower risk of toxicity. Similar to fat-soluble vitamins, a toxic
intake of water-soluble vitamins is not common through food sources, but is most frequently
seen due to supplement use.
Characteristics of Fat-Soluble Vitamins
Protect cell membranes from free radical damage; act within the cell’s
nucleus to influence gene expression
Absorbed into lymph with fats from foods
Large storage capacity in fatty tissues
Do not need to be consumed daily to prevent deficiency (may take
months to develop)
Toxicity is more likely
Characteristics of Water-Soluble
Vitamins
Act in the cytosol of cells or in
extracellular fluids such as blood
Absorbed directly into blood
Little to no storage capacity
Need to be consumed regularly to
prevent deficiency
Toxicity is rare
Table 8.1. Characteristics of fat-soluble and water-soluble vitamins.
MINERALS
Similarly to vitamins, minerals are micronutrients that are essential to human health and can
be obtained in our diet from different types of food. Minerals are abundant in our everyday
lives. From the soil in your front yard to the jewelry you wear on your body, we interact with
minerals constantly. Minerals are inorganic elements in their simplest form, originating from
the Earth. They can’t be broken down or used as an energy source, but like vitamins, serve
essential functions based on their individual characteristics. Living organisms can’t make
minerals, so the minerals our bodies need must come from the diet. Plants obtain minerals
from the soil they grow in. Humans obtain minerals from eating plants, as well as indirectly
from eating animal products (because the animal consumed minerals in the plants it ate). We
also get minerals from the water we drink. The mineral content of soil and water varies from
place to place, so the mineral composition of foods and water differs based on geographic
location. 2