Vitamin D Facts: Everything You Need to Know

By Tiffany Tseng. May 7th 2016

Vitamin D is important for the maintenance of a healthy body because it helps maximize the absorption and utilization of calcium, an important mineral that our bodies need. When paired with calcium, vitamin D helps regulate bone remodeling and growth, ensuring healthy, strong bones. Vitamin D can also help protect older adults from osteoporosis, which is characterized by bone loss due to aging. Furthermore, this nutrient boosts the immune system and reduces inflammation within the body, thus warding off future medical conditions. It also plays a vital role in cell growth, neuromuscular functions and protein encoding. Studies have shown that a regular, healthy vitamin D intake can also serve as an antidepressant and make people feel generally happier.

Sources of Vitamin D

Vitamin D can be naturally found in few sources of food, but thanks to modern technology, the nutrient has become readily available in fortified foods that normally have low amounts of D. The best sources of naturally occurring vitamin D are cold water fish that are oily and fatty. These fish, high in omega fatty acids, include salmon, tuna, cod, sardines and mackerel. Fish liver oils are another good source of vitamin D. Small amounts of the nutrient can also be found in beef liver, cheeses, egg yolks and mushrooms. Commonly, vitamin D-fortified foods include whole milk, orange juice, margarine and breakfast cereals. It is important to look at the label and nutrition facts to verify the presence of vitamin D. Since vitamin D-fortified foods are often found in dairy products, lactose intolerant or vegan individuals should keep an eye on their diets to ensure adequate intake of the nutrient.

Sun exposure is another method of obtaining vitamin D, as our bodies can create our own sources of the nutrient upon exposure to UV rays. However, it is difficult to gauge exactly how much sun exposure can generate sufficient vitamin D, as overexposure can be harmful to the body as well. UV rays are also known to trigger free radicals, which can lead to skin cancer if left unchecked. It has been suggested by some vitamin D researchers that approximately 5 to 30 minutes of sun exposure between 10 a.m. and 3 p.m. at least twice a week to the face, arms, legs or back can usually lead to sufficient vitamin D synthesis. Exposed areas of the body cannot be covered by sunscreen, as the SPF factor blocks UV rays and can hinder vitamin D synthesis reaction. For individuals living in cloudy areas lacking in sunlight, it is important to gain the recommended vitamin D via other means.

Dietary supplements are also an excellent way of obtaining vitamin D. They are generally offered in two formats, vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). These two forms of D only differ in their chemical side-chain structure and how they are synthesized, but are equally effective upon ingestion.

Side Effects

Since vitamin D is a fat-soluble substance, it can stay in the body for several days. Thus, vitamin D poisoning is possible if an individual overdoses over a period of a few months. Symptoms of vitamin D overdose include dehydration, vomiting, decreased appetite, irritability, constipation and fatigue. If left unaddressed, vitamin D poisoning can lead to anorexia, over-calcification of the bones and internal organs, kidney stones and hypertension (high blood pressure). However, it is important to note that vitamin D poisoning usually only occurs with excessive intake of dietary supplements because naturally occurring foods and sun exposure simply has too little vitamin D to become toxic over time.

Vitamin D deficiency occurs when an individual does not have adequate absorption of the nutrient, or when the kidneys cannot convert the nutrient to an active form. The classic cases of such deficiency are two medical conditions, rickets and osteomalacia. Rickets, a disease characterized by a failure of mineralization of bone tissues, can result in abnormal, soft bones and skeletal deformities, and are most commonly found in children. Fortunately, it can be easily reversed by ingesting as little as 1 to 3 teaspoons of cod liver oil a day. With the help of fortified foods today, rickets are almost rendered obsolete in the United States. Osteomalacia, characterized by soft and weak bones, is usually present in adults but can also be treated with a treatment of an intense regimen of vitamin D under the care of a physician. A lack of vitamin D has also been linked to depression.

Daily Dosage Recommendations

The recommended dietary allowances for vitamin D show a daily intake of the nutrient to help maintain healthy bone health and calcium metabolism in healthy individuals. For infants under 12 months, the recommended intake is 400 IU (10 mcg). For individuals under 70 years old, the recommended intake is 600 IU (15 mcg). For individuals over 70 years old, the intake increases to 800 IU (20 mcg). If you are someone who has a pre-existing medical condition or other medical concerns, it is best to seek a healthcare professional for your recommended dietary allowance for vitamin D to be sure it does not interact negatively with your condition or medication.

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