Discussion beyond the article:
Vitamins are also considered dietary supplements. Have students use resources such as textbooks, library books, encyclopedias or the internet to learn more about vitamins. Assign a particular vitamin to a pair of students, and ask them to research the set of questions about their vitamin. Then, give the pair time to present their findings to the rest of the class. If time allows, ask the class to create a reference sheet about vitamins they can share with other students, their family members or other members of the local community.

As an introduction to the research and discussion, you may want to briefly present the general information about vitamins and vitamin types included on the reference sheet below. This sheet also contains information about specific types of vitamins that can be assigned to students. You may want to also review how vitamins’ molecular structure relates to being water-soluble or fat-soluble, so students will be able to predict their vitamin type based on the known molecular structure.

Approximate time required: One or two 45-minute class periods, depending on how you modify the research and discussion.  

Reference sheet for teachers:

What are vitamins?

Vitamins are assorted biomolecules that the human body needs. Vitamins are made by plants, fungi, bacteria or other critters, and they work their way up the food chain until we consume them. Some, such as vitamin D, are even made by the human body.

The structures of vitamins don’t have much in common with each other, except that they don’t really fall into the other major categories of biomolecules (nucleic acids, proteins, lipids, carbohydrates and porphyrins). Look up the chemical structures of all vitamins on PubChem, an open chemistry database by the National Institutes of Health.

Type of vitamins:

Fat-soluble vitamins
Some vitamins are hydrophobic, or readily soluble in fat but not water. We might classify these vitamins as lipids, except unlike normal lipids (phospholipids, sterols, fatty acids, triglycerides, etc.), the human body cannot make all of the fat-soluble vitamins. Because fat-soluble vitamins can accumulate in body fat and are difficult to dissolve in water and eliminate in urine, they can last a long time.

Some major fat-soluble vitamins to assign include:

• Vitamin A (retinol) can be derived from certain plants such as carrots, sweet potato, pumpkin, spinach, kale or fats from animals that have previously ingested such plants. Retinol and its related forms, retinal and retinoic acid, are essential components of the eyes’ light-detecting rhodopsin molecules, and of some DNA-regulating transcription factors in cell nuclei. Vitamin A helps to maintain healthy teeth, bones, mucus membranes and skin. Lack of dietary vitamin A can cause blindness. Excessive vitamin A can cause liver damage or birth defects.
• Vitamin D (cholecalciferol) can be made from cholesterol in human skin cells that are exposed to sunlight. Vitamin D can also be derived from certain mushrooms, alfalfa, fats or eggs from animals that have previously ingested such foods. Milk that has been fortified with vitamin D is also a common source. Vitamin D acts on the intestine and bones to maintain sufficient levels of calcium and phosphorus in the body. Insufficient vitamin D can cause bone demineralization and deformation (called rickets in children or osteomalacia in adults). Very high levels of vitamin D can cause nausea or kidney stones.
• Vitamin E (tocopherol) is found in vegetable oils (canola oil, palm oil, olive oil, etc.). Vitamin E prevents free oxygen radicals — molecules that contain chemically reactive oxygen — from damaging cells. Too little vitamin E can increase oxidative damage in cells, especially red blood cells and neurons. Vitamin E also helps produce red blood cells. Very high levels of vitamin E can act as an anticoagulant to interfere with proper blood clotting.
• Vitamin K (phylloquinone) can be obtained by eating leafy green vegetables such as spinach, collard greens, broccoli and Brussels sprouts. Vitamin K is also made by the bacteria that naturally live inside the human gastrointestinal tract. Vitamin K is used as a coenzyme to modify a number of proteins in the human body, most of which play key roles in blood clotting. Too little vitamin K can hinder blood clotting and too much can potentially harm red blood cells.

Water-soluble vitamins
Other vitamins are hydrophilic, or readily soluble in water but not fat. The more polar the chemical structure of a vitamin, the more hydrophilic, or water-soluble, the vitamin is. Thus water-soluble vitamins are not stored in body fat and are readily eliminated in urine. As a result, one can quickly become deficient in these vitamins if they are not consumed regularly.

In general, these water-soluble vitamins are essential for:

1. Synthesis of biomolecules such as amino acids and nucleotides.
2. Metabolism to produce energy by breaking down fats and sugars.

Therefore, the effects of water-soluble vitamin deficiencies are most pronounced in:

1. Rapidly-dividing cells that have energetic metabolisms and need lots of biomolecules such as bone marrow, mucous membranes, skin cells and developing embryos.
2. Neurons in the central or peripheral nervous system that require a steady, energetic metabolism.

Some major water-soluble vitamins include:

• Vitamin B₁ (thiamine) can be derived from whole grains, legumes, nuts, or fungi, or from animal products (e.g., animal liver or chicken eggs). It is a precursor for thiamine pyrophosphate (TPP), a coenzyme essential for preparing sugars for the energy-producing citric acid cycle. Vitamin B₁ helps to convert carbohydrates into energy and regulate heart function and nerve cells. Thiamine deficiency can damage the central nervous system, which is most dependent on consistent energy production from sugars. This condition is called beriberi and manifests as tingling sensations, poor coordination and heartbeat irregularities.
• Vitamin B₂ (riboflavin) is found in leafy vegetables, legumes and animal products (milk, eggs, liver, etc.). Vitamin B₂ helps promote production of red blood cells and optimize the function of other B-type vitamins. Vitamin B₂ deficiency can cause anemia and inflammation of mucous membranes, but a wide variety of processed food ingredients in developed countries are fortified with extra riboflavin.
• Vitamin B₃ (niacin) can be derived from grains, cereal, nuts, milk and meat. It is an essential precursor of nicotinamide adenine dinucleotide (NAD⁺ or NADH) and nicotinamide adenine dinucleotide phosphate (NADP⁺ or NADPH), two major electron and proton transport proteins. Vitamin B₃ helps maintain healthy skin and nerves, and can lower cholesterol. Vitamin B₃ deficiency can cause mental confusion and damage to the skin and gastrointestinal membranes.
• Vitamin B₅ (pantothenic acid) is found in a wide variety of plant- and animal-derived foods such as avocado, mushrooms and organ meats. Vitamin B₅ helps metabolize foods and produce hormones and cholesterol. Because Vitamin B₅ is so widespread, deficiency is very uncommon except in cases of starvation. Its absence from metabolic pathways appear to decrease energy production and cause loss of skin sensation.
• Vitamin B₆ (pyridoxine) is also found in a wide variety of plant- and animal-derived foods. Vitamin B₆ helps produce red blood cells, maintain brain function and mediate protein function in the body. Vitamin B₆ is the only major water-soluble vitamin with significant toxicity, and even then only at very high doses, where it can cause neurosensory damage. Insufficient vitamin B₆ can cause dermatitis, anemia and central nervous system impairment.
• Vitamin B₇ or H (biotin) is found in a wide variety of plant- and animal-derived foods and is also produced by bacteria in the human gastrointestinal tract. Vitamin B₇ helps metabolize protein and carbohydrates, and produce cholesterol and hormones. Vitamin B₇ deficiency is not common, but if a person did run low on the vitamin, it wouldn’t be good for their skin and central nervous system.
• Vitamin B₉ or M (folic acid or folate) is most plentiful in leafy green vegetables. It is a precursor of tetrahydrofolate (THF), a coenzyme essential for amino acid and nucleotide synthesis. Vitamin B₉ helps the brain function properly. Vitamin B₉ deficiency can cause anemia and birth defects, so supplemental folic acid is especially recommended for women who are pregnant or may become pregnant.
• Vitamin C (ascorbic acid) is abundant in many fruits and leafy green vegetables. It is an essential cofactor for a number of enzymes, including those involved in collagen synthesis, and may prevent cellular damage. Vitamin C is an antioxidant and helps promote healthy teeth and gums, absorption of iron and wound healing. Vitamin C deficiency is called scurvy, a condition where inadequate collagen synthesis causes damage to the gums, mucous membranes and skin.
• Vitamin B₁₂ (cobalamin) is made by intestinal bacteria in farm animals and accumulates in meats, eggs and dairy products. Vitamin B₁₂ is essential for the normal function of some enzymes that help control the brain, and also helps from red blood cells and maintain the central nervous system. Vitamin B₁₂ deficiency causes anemia and damage to the central nervous system.