Vitamins are chemically active agents that are required in small quantities for our health and growth. They facilitate or control vital chemical reactions. As they cannot be manufactured by the body, we must rely on outside sources to supply them.

Vitamins A, D, E, and K dissolve in fat – hence the term fat-soluble – and can be stored in adipose tissue or the liver. The body can leverage these repositories to address any short-term deficiencies.

We associate Vitamin A with healthy vision. It also plays a role in protein digestion, gene transcription, cell differentiation (i.e., telling cells what to become), epithelial cell development, bone metabolism, and blood development. It also serves as an antioxidant, protecting the body against free radicals and pollutants. Of the three forms of Vitamin A – retinol, retinal, and retinoic acid – retinoic acid is the most bioavailable. Vitamin A rich vegetables include sweet potatoes, spinach, kale, collard greens, and carrots. Egg yolks, organ meats, shellfish, and cod liver oil are good resources for meat-eaters. While we need sufficient Vitamin A for optimal health, an excess can be toxic. Laxatives, fat substitutes, and cholesterol-lowering drugs may interfere with absorption.

Vitamin D is most closely associated with healthy bone and teeth mineralization. It also regulates the amount of calcium that circulates in the blood. We generate Vitamin D out of cholesterol in the presence of sunlight. Synthesis depends on the amount of direct sunlight we experience, the level of melatonin in our skin, our use of sun screen, our clothing, and the time of day when exposure occurs. While sun exposure is not toxic with respect to our Vitamin D manufacturing operation, it may engender skin-related problems – notably burns, cancer, and premature signs of aging. Therefore, for those of us with sensitive skin or living in dark or overcast climates, Vitamin D supplementation might make sense. Blood tests can reveal whether or not the body has what it needs.

Vitamin E serves as an antioxidant to stabilize cell membranes and prevent oxidation by free radicals. It helps protect against mutation in our DNA and staves off heart disease by thwarting LDL oxidation. It has 8 different forms (called tocopherols), and each form serves a slightly different function. Dietary sources of Vitamin E include butter, organ meats, oils, nuts, seeds, and dark leafy greens. Preparation and timing matter. Roasted almonds lose 80% of their Vitamin E; oils lose their Vitamin E over time. Vitamin E deficiency in the U.S. is rare. While Vitamin E supplementation used to be quite popular, its efficacy has been called into question in recent years.

Vitamin K is the master coagulator. It promotes blood clotting and the formation of proteins necessary for bone health. Plant-based sources of Vitamin K include kale, spinach, cabbage, broccoli, asparagus, brussels sprouts, and miso. Levels may be threatened when taking antibiotics as they kill the bacteria necessary to activate Vitamin K. Persons on anticoagulant drugs may also need to monitor their vitamin K intake to ensure they have sufficient resources for appropriate blood clotting.

Check with your doctor or a trusted government resource to determine the recommended daily allotment of these vitamins based on your age and overall health. Let your doctor know about any supplements that you take regularly. Make sure to consume sufficient dietary fat to give these vitamins the means for proper absorption.