Last updated: 23 ก.ค. 2564 | 457 จำนวนผู้เข้าชม |
What is Vitamin D?
Vitamins are organic compounds required in the human diet in small amounts. An organic compound is generally any chemical compound that contains carbon. In order for an organic compound to be considered a vitamin, a lack of the compound in the diet must result in symptoms of deficiency.
Vitamin D is a fat-soluble vitamin that can be obtained through dietary means or synthesized in the skin upon exposure to sunlight. Cholecalciferol or vitamin D3, the form of vitamin D formed in the skin, is a potent and active form of the vitamin. Ergocalciferol or vitamin D2 is a vitamin D analog formed in plants, mushrooms and yeasts during photosynthesis. While vitamin D2 is sometimes used in food fortification, Nature’s Bounty® Vitamin D3 provides the active form.
Why Supplement with Vitamin D?
National survey data show that American’s vitamin D intakes do not meet their dietary requirements for optimal health so much so that the 2015-2020 Dietary Guidelines for Americans identified vitamin D as a nutrient of public health concern. Insufficient intakes of calcium and vitamin D are more pronounced in women than in men. If you’re not getting enough vitamin D every day, you may not be able to adequately absorb calcium from the foods you eat, and your body will have to take calcium from your bones.
Natural food sources of vitamin D are limited and include cod liver oil, liver and some fatty fish such as mackerel, salmon, and sardines. Egg yolks from hens that have been fed vitamin D and mushrooms that have been exposed to sun or UV light also provide vitamin D. In the US, milk is fortified with vitamin D but not all products that have been made from milk, such as cheese, contain vitamin D so it is important to check the label. Some cereals, bread, fruit juices, and non-dairy milks may also be fortified.
Even though our bodies are able to synthesize vitamin D, many of us are falling short in getting enough of this important nutrient. Residents of northern climates may have inadequate exposure to sunlight in order to produce sufficient vitamin D, especially during the winter months. You can use your shadow as a general predictor of vitamin D synthesis. When you are shorter than your shadow, the intensity of the sun is not enough to stimulate the production of vitamin D.Atmospheric conditions such as air pollution and the presence of clouds can also have a major impact on the intensity of UVB radiation that reaches the ground.
Even in ideal conditions, actions we take to protect our skin from the potentially harmful rays of the sun can be affecting our vitamin D status. Limiting sun exposure and wearing protective clothing such as hats and long sleeves inhibits the body’s natural production of vitamin D. Even the application of sunscreen will reduce vitamin D synthesis. When used as directed, a sunscreen graded SPF-10 will block 90% of UVB radiation reaching the skin. UVB radiation is needed in order to stimulate endogenous production of vitamin D. Aging is yet another factor that can affect vitamin D status since the skin produces vitamin D less efficiently as we age. Vitamin D absorption may also decrease with age, making vitamin D supplementation especially beneficial for older individuals.
What Are the Benefits of Vitamin D?
Vitamin D is perhaps most well-known for its role in bone health.† It helps develop strong bones and teeth by enhancing the absorption of calcium and phosphorus.† Vitamin D also helps the kidneys re-absorb calcium that otherwise would have been excreted.† A scientific study showed that older adults who consumed 5000 IU of vitamin D plus small amounts of calcium daily were able to maintain healthy bone density measures.† In the study vitamin D and 320 mg elemental calcium were administered in the form of fortified bread.
Vitamin D also helps support a healthy immune system.† Vitamin D may assist the immune system by helping to regulate T- and B-lymphocytes (T cells and B cells).