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Micronutrients and food sources: Part 5 of 7-Vitamins

This is post 5 in a seven-part series about the nutrients that our body needs to function optimally. We covered the macronutrients and are now into the micronutrients. As a reminder, macronutrients are the nutrients we need in large quantities, whereas, micronutrients are the nutrients we need in smaller quantities. Vitamins and minerals are micronutrients. Today the spotlight is on vitamins. This is a quick overview of the different types of vitamins, what they do and what foods to find them in.


Vitamin History

In the mid-1800s a mysterious condition that caused numbness in the extremities, weakness in the legs and difficulty walking was becoming more prevalent. Scientists thought it was blood contamination or some type of bacteria, until 1897 when Christiaan Eijkman noticed these same symptoms improved in chickens when their diet was switched from polished rice to unpolished rice. He postulated that there was an important compound in the unpolished rice that was vital to life. Polished rice was refined white rice and had it’s outer layer removed, while the unpolished rice, similar to brown rice today, did not have it’s outer layer removed.

In 1912, Casimir Funk named this new compound “vitamine” after “vita” which means life and “amine” from  the structure of the compound he found in unpolished rice, later named thiamine or vitamin B1. Thiamine deficiency results in a disease called Beriberi, which meant that this “vitamine” was essential to life. The “e” was dropped and vitamine became vitamin.

Fat Soluble vs Water Soluble Vitamins

There are two categories of vitamins, fat-soluble and water-soluble. The solubility of the vitamin impacts the absorption, transport, storage, and bioavailability of that vitamin.

 Fat-soluble: A, D, E, K

  • Found in fats and oils of foods
  • Require fat for absorption
  • Stored in the liver or in fatty tissues
  • Some can build up to toxic concentrations

Water-soluble: B vitamins, vitamin C

  • Absorbed directly into blood stream
  • Most are not stored to any great extent
  • Excess excreted in urine
  • Lower risk of toxicity than fat-soluble vitamins

Vitamin Functions and Food Sources

Vitamin A

Vitamin A is not a single vitamin, but a group of compounds that are categorized as retinoids and carotenoids. 

Functions: aiding in vision, growth of skin, bones and teeth and has an important role in the immune response. 

Food Sources of Vitamin A

  • Animal sources (retinoids): beef liver, cod liver oil, eggs, butter and whole milk.
  • Plant sources (carotenoids): cantaloupe, pumpkin, mango, carrot, kale and butternut squash.

Vitamin D

Vitamin D is known as the “sunshine vitamin” because we were designed to obtain this vitamin from the sun. The active form of Vitamin D is a hormone.

Functions: regulates blood calcium and phosphorus levels, although many new functions have recently been discovered. Almost every cell in the body has a vitamin D receptor, which means that Vitamin D is important in most of the systems in our body.

Food Sources of Vitamin D

Unfortunately, there are not many good sources of vitamin D.  yogurt, fortified milk, tuna fish and fatty fish all contain vitamin D, but do not give us all that we need. 

Vitamin D From the Sun

During the winter months, the skin makes very little vitamin D from the sun, unless you live below latitudes of 37 degrees. This means that everyone who lives above the 37th parallel is not receiving enough vitamin D from the sun during the winter months (this includes all of us here in NC)

Vitamin E

Vitamin E is not one vitamin, but a group vitamin, included several forms of tocopherol and tocotrienol.

Functions: The main role of Vitamin E in the body is as an antioxidant. An antioxidant defends the body against oxidative damage. Oxidative damage is caused by free radicals. A free radical is a molecule which is produced by normal metabolism. In short, that damage can lead to a series of events (domino effect) that can cause chronic diseases, such as cancer. This is why we don’t want free radicals roaming our body inflicting damage! Antioxidants combine with free radicals, and in a sense, neutralize them so that they cannot cause damage.

Food Sources of Vitamin E: Vitamin E is widespread in foods, mostly occurring in fruits and vegetables and whole grains. Olive is a good source of vitamin E and cold pressed EVOO (extra virgin olive oil) is a good source. 

Vitamin K

Functions: There are two types of vitamin K, vitamin K1 and vitamin K2. Vitamin K1 (phylloquinone) is important in blood clotting. The main function of vitamin K2 is important for regulating calcium levels in the bones and blood, essentially it directs calcium from out blood to go to our bones and not our soft tissues like arteries and muscles. Without Vitamin K2, there is a greater risk for heart disease and osteoporosis.

Food Sources of Vitamin K

  • Vitamin K1 is found in: leafy greens like kale, swiss chard, spinach and broccoli.
  • Vitamin K2 sources are more difficult to find. Vitamin K2 is found in animal foods: dutch hard cheeses, egg yolk, pate, pasture butter (from grass fed cows).

Vitamin C

Vitamin C is a water-soluble vitamin and non-toxic from food.
Functions: collagen production, restoring vitamin E to its active form, immunity, antioxidant, boosting non-heme iron (found in plant foods) absorption. Although vitamin C plays a role in immunity, research suggests that vitamin C does not prevent the common cold, but it may reduce symptoms.

Food Sources of Vitamin C: Citrus fruits are a good source of vitamin C, but in addition to oranges, grapefruits, and limes, vitamin C is abundant in a variety of fruits and vegetables, including kiwis, strawberries, tomatoes, red pepper, broccoli, potatoes and spinach.

B-Vitamins Overview

Functions: The B-vitamins work together. All of them act as part of coenzymes and they play a direct or indirect role in energy metabolism.  Coenzymes assist enzymes in reactions. B-vitamins work in every cell, in every organ of the body to help create energy, but, vitamins do NOT provide energy.

An enzyme is a protein, a specific type of protein that will speed up a reaction, often called a catalyst. B-vitamins work together as a group, as coenzymes, facilitating necessary reactions in the body. 

Thiamin Sources: Thiamin is widespread in food. Thiamin sources include lentils, brown rice, wheat germ and spinach. Animal sources include beef and pork. Many processed foods, particularly grains, are fortified with thiamin.

Riboflavin Sources: Riboflavin naturally occurs in a wide variety of foods, particularly animal foods like milk, yogurt, cheese, eggs and meat. Riboflavin is also found in cereal grains and legumes.

Niacin Sources: The main food sources of niacin are animal foods, but it is also found in some plant food including: chicken, tuna, turkey, salmon, beef, peanuts, cereal grains, lentils, lima beans

Vitamin B6 (Pyridoxine) Sources: found in plant and animal sources including salmon, potato, turkey, avocado, chicken, cooked spinach, bananas, and dried plums.

Folate Sources: Folate is derived from the Latin word folium, which means leaf. When you think of folate, think of dark leafy greens, such as spinach and kale. Other good sources include beef liver, lentils, asparagus, avocado, garbanzo beans, lima beans, and pinto beans.

Vitamin B12 Sources: Vitamin B12 only occurs in animal foods. Good sources include clams, mussels, crab, beef, pork, tuna, turkey, cheese, egg, and milk.

Impact of Preparation and Storage on Vitamin Content of Foods

Although food may initially contain many vitamins, some can be destroyed by inappropriate storage or cooking.

Oxygen exposure – destroys antioxidants (Vitamin C & E)

  • Vitamin C is in fruits and vegetables. Close juice containers tightly and place fruits and vegetables in airtight containers.
  • Vitamin is in nuts and oils. Make sure oils and sliced nuts are in air tight containers.

Vitamin degradation – this occurs after fruits and vegetables have been harvested. Keeping them chilled or eat soon after harvest to ensure a higher amount of vitamins.
Vitamin & Mineral leaching – water soluble vitamins (& minerals) will be attracted to water, so when fruits and vegetables are soaked or cooked in water, many vitamins & minerals leach into the water.

  • Wash fruits and vegetables just before cutting them
  • Don’t soak vegetables
  • Steam vegetables instead of boiling
  • If you need to boil, bring water to boil first, then boil vegetables and remove quickly

Heat destroys some vitamins – thiamin, folate, vitamin C are easily destroyed by heat. Extreme heat can destroy more vitamins. Minerals are generally not affected by heat.

  • Eat some raw fruits and vegetables daily
  • Cook vegetables until they are tender, don’t overcook
  • Avoid cooking with very high heat

UV light destroys some vitamins – riboflavin is the most susceptible to UV light. Riboflavin is found in milk products and in grains.

  • Don’t drink milk in clear glass containers unless it is noted that the glass is UV protected
  • Make sure grains are stored in opaque containers.

Stay healthy!
Lisa Robinson-Mihiar, RDN, LD
ClubWorx Dietitian

Have a question you want Lisa to answer on the blog? Send your questions and ideas to Lisa at lrobinson (at)

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