Vitamins and minerals
Vitamins and minerals are a large class of micronutrients, most of which are considered essential as they act synergistically to perform hundreds of roles in the body. Read on for an overview of the role these nutrients play in the body along with some tips to make sure you meet your needs.
Vitamins are usually classified into two groups based on their solubilities: the fat-soluble vitamins A, D, E and K and the water-soluble vitamins B-complex and C.
Fat-soluble vitamins vs. Water-soluble vitamins
While water-soluble vitamins are able to ‘slip into the bloodstream’, fat-soluble vitamins need fat and bile (produced by the liver) for their absorption. Once absorbed, they enter the lymph before entering the bloodstream, coupled with a protein. Another difference between these two types of vitamins is that water-soluble vitamins are not stored in appreciable amounts in the body and most of the ‘extras’ are excreted in the urine. This is not the case for fat-soluble vitamins which are stored in the liver and fat tissues and released whenever needed by the body.
Vitamin A: This antioxidant vitamin does much more than fight free radicals and improve your night vision. It also helps maintain a healthy immune system by stimulating the production and activity of white blood cells; and controls cell growth (including bone remodelling) and division.
Sources: Preformed vitamin A (retinol) can only be found in animal foods, either in storage areas like the liver, in the fat of milk and eggs and in cod and halibut oils. Plant foods contain provitamin A carotenoids, especially dark green leafy vegetables and yellow-orange fruits and vegetables.
Although it’s possible to get too little vitamin A, it’s easy to get too much retinol from supplements — this may cause vomiting, headaches, nail fragility, liver disease and increases risks of hip fracture by interfering with vitamin D’s functions.
Vitamin D: Known as calciferol, vitamin D maintains calcium and phosphorus homeostasis, which — in a nut-shell — helps maintain strong bones.
Sources: There are few dietary sources of vitamin D and these include mushrooms, fortified dairy products and breakfast cereals as well as fatty fish such as salmon and tuna. Vitamin D can be produced by the body via modest exposure to sunlight, hence its other name the ‘sunshine vitamin’.
People who are scarcely exposed to sunlight are at risk of vitamin D deficiency which increases risks for fractures, heart disease, certain cancers and multiple sclerosis. Pregnant women who are deficient in vitamin D have higher risk of gestational diabetes mellitus.
Vitamin E: This antioxidant vitamin has been shown to protect against some types of cancer and to reduce risks of heart disease. Moreover, when consumed together with foods rich in vitamin C, beta-carotene and zinc, vitamin E appears to offer some protection against the development of advanced age-related macular degeneration1.
Sources: The two classes of biologically active vitamin E — tocopherols and tocotrienols — are synthesized only by plants. Hence, plant products, especially the oils, are the best sources.
Vitamin K: This vitamin plays an essential role in blood clotting and in bone formation. The best sources are green leafy vegetables.
Vitamin B-complex: This ‘complex’ includes thiamine (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), pantothenic acid (B5), pyridoxamine (vitamin B6), biotin (vitamin B7), folate (vitamin B9) and cobalamin (vitamin B12).
Most of the B-vitamins act as coenzymes that help release energy from food. For instance, vitamins B1, B2, B3, B5 and B7 are involved in energy production while vitamins B6, B9 and B12 metabolize amino acids and assist cell growth.
Folate is especially important prior to and during pregnancy since a deficiency of this B-vitamin has been linked to spina bifida and anencephaly.
Vitamin C: Known as ascorbic acid, this vitamin is a potent antioxidant that strengthens the immune system and helps prevent infections. Vitamin C is also needed for the production of collagen, a tissue needed for healthy bones, teeth, gums, and blood vessels
Sources: Citrus fruits, broccoli and other dark green vegetables, bell peppers.
Calcium: This mineral does not only help maintain strong bones and teeth; it is also involved in blood clotting, transmission of ions across cell membranes and in required in nerve transmission. This mineral has also been linked to weight loss.
Sources: Dairy products, sardines, salmon, fortified cereals, some green leafy vegetables like broccoli, kale, collards and turnip greens.
Iron: Essential for the formation of haemoglobin and oxygen transport, iron also increases resistance to infections; functions as part of enzymes involved in tissue respiration and collagen synthesis.
Sources: Animal foods, legumes, whole grains, dark green vegetables.
Iodine: This mineral helps prevent thyroid enlargement and regulates cellular oxidation and growth.
Sources: Seafood and iodized salt.
Zinc: Zinc is a component of many enzyme systems and the hormone insulin. It is also essential in wound healing.
Sources: Seafood and other animal products, legumes, whole grains.
Chromium: This mineral is required for normal glucose metabolism.
Sources: Meat, whole-grains, broccoli.
Magnesium: Magnesium is involved in nerve impulse transmission and muscle contraction. This mineral is also required in energy-producing processes in the body.
Sources: Whole grains, legumes, green vegetables.
Selenium: This antioxidant is associated with fat metabolism and vitamin E. It is also required in tissue respiration and in wound healing.
Sources: Whole grains and animal products.
Potassium: This well-known mineral is essential for normal cardiac function and also helps regulate acid-base equilibrium.
Sources: Fruits especially bananas; potatoes; animal products.
There are many more trace-minerals — the ones mentioned here are the most important ones. Don’t worry too much about the micronutrient amount of your meals: focus on variety and make sure your plate is always colourful to ensure an intake of various vitamins and minerals.
1. A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Arch Ophthalmol. 2001;119:1417-36.