Vitamin A, also known as retinol, is essential to the formation of visual purple in the retina, which allows vision in dim light. It helps your eyes adjust to light changes when you come in from outside and also helps keep your eyes, skin and mucous membranes moist. Vitamin A mostly comes from animal foods, but some plant-based foods supply beta-carotene, which your body then converts into Vitamin A. Vitamin A deficiency is rare in the United States, but it can cause night blindness, eye inflammation, diarrhea and other problems. Overconsumption of vitamin A can cause nausea, irritability and blurred vision in its mild form.
Iron is an essential mineral needed for the manufacture of haemoglobin, the part of red blood cells that helps carry oxygen from the lungs to the muscles and other organs. When iron levels are low, red blood cells can’t carry enough oxygen to the body’s tissues, causing fatigue. When haemoglobin levels are low, anaemia occurs.
There are two types of iron: haem iron (from animal sources) and non-haem iron (from plant sources). The body absorbs haem iron much more easily than non-haem iron, which is why vegetarians are at greater risk of iron-deficiency anaemia.
Vitamin D, ‘the sunshine vitamin’, is a fat-soluble nutrient that is found not only in natural foods, but is also manufactured by the body when the skin is exposed to ultraviolet (UV) rays from the sun. And, it may come as a surprise to many to know that this single vitamin has the potential to not only strengthen our bones and teeth, but is also known to protect against cancer, TB, diabetes, arthritis, the flu and even the common cold. It’s ironic however, that despite accessibility to the outdoors, most people aren’t getting sufficient quantities. Variations in blood concentrations can result through seasonal conditions, where cold weather protective clothing and the sun’s angle in the winter sky limit the amount ultraviolet light that actually reaches the skin. Additionally, skin color and dietary intake, through balanced nutrition or vitamin supplements all affect vitamin D levels in the body.