Vitamins are organic substances essential to human life that come in both food and dietary supplement forms.
Thiamine, riboflavin, niacin and folate provide your cells with energy they require for proper functioning and are also vital in wound healing, blood cell production and much more.
Vitamin A
Vitamin A is an essential fat-soluble vitamin essential for eye and immune health. It works to maintain the health of epithelial tissues lining respiratory and digestive tracts as well as immune defense systems, providing first-line protection from infection. Furthermore, Vitamin A promotes T lymphocyte development – essential immune cells responsible for fighting infection while producing retinoic acid (RA), an important signaling molecule which stimulates and modulates other immune responses.
Vitamin A deficiency is quite uncommon in the US but may occur if you suffer from conditions that interfere with digestion and absorption, such as celiac disease, Crohn’s disease or cirrhosis. Mild vitamin A deficiencies can cause fatigue while severe forms may even result in blindness and even death due to infections.
Diets that meet or exceed the recommended daily amount (900 micrograms or more) of preformed vitamin A can get their recommended daily amount through foods and supplements containing retinol or its precursors, like b-carotene. Most multivitamins and breakfast cereals are fortified with retinol; fruit, vegetables and some supplements contain b-carotene or lutein and zeaxanthin fortification.
Vitamin D
Vitamin D is a fat-soluble vitamin produced in our bodies through sun exposure and can be found in limited food sources. Once in tissues, vitamin D converts to its active form 1,25(OH)2D for use in modulating processes such as bone mineralization and the immune system.
Large observational studies have linked low vitamin D status (as measured by serum 25(OH)D levels or diet intakes) with an increased risk of cardiovascular disease (CVD), such as ischemic stroke, coronary heart disease and cardiac arrhythmias. Other research indicates that higher vitamin D status can help with better glucose homeostasis among people living with type 2 diabetes reducing both their risks of developing it or dying from it altogether.
The Institute of Medicine issued a 2010 recommendation that daily vitamin D intake be increased, but research is ongoing on what amount is optimal. Some clinical trials have demonstrated that taking 2,000 International Units/day could help prevent scurvy while increasing blood levels of 25(OH)D.
Vitamin E
Vitamin E is a fat-soluble antioxidant and the only vitamin in our bodies capable of protecting cells against free radical damage caused by free radicals. As such, it plays an integral part in photoprotection and preventing free radical-induced damage to skin.
Vitamin E can be found both in foods and supplements. While it exists in four tocotrienol forms and eight tocopherol forms, only the a-tocopherol form is widely present in blood and tissues as it preferentially binds to an a-tocopherol transfer protein and lipoproteins that transport it outside the liver.
Observational studies have reported an inverse association between vitamin E intake and heart disease risk; however, randomized controlled trials do not support this correlation (reviewed here). Higher doses of supplemental vitamin E appear to help improve insulin action and endothelial function in those living with type 2 diabetes (89), although high-dose supplements should be used with caution due to possible increases in prostate cancer risks (121). (121). (121). (121). (121). (121).
Vitamin K
Vitamin K is essential in maintaining normal blood clotting and bone metabolism processes in our bodies, and also prevents arterial calcification that could potentially lead to heart disease.
Phylloquinone (vitamin K1) and menaquinones are the two main forms of vitamin K found in food sources; plants generally provide more phylloquinone while animal products and fermented food contain menaquinones. Bacteria in the intestinal tract convert phylloquinone to menaquinones.
Studies have linked higher intakes of vitamin K with improved episodic memory in older adults, as it acts as an essential cofactor in gamma-carboxylation of osteocalcin, one of the key proteins for bone metabolism.
Vitamin K can be obtained without a valid prescription from multivitamin/mineral supplements and single nutrient pills, usually at lower dosage levels. Because it interacts with anticoagulant medicines such as warfarin, it’s essential that adequate levels of vitamin K be ingested daily through diet.
