Are You Getting Your Ds?
IC columnist Dr. Mukund Acharya discusses the essential role of Vitamin D for bone, immune system, muscle, and brain health, and how sunlight, diet, age, and certain conditions affect its levels.
Rickets
I first heard about rickets in elementary school, and recall seeing children stricken with this condition in the late 1950s. “It’s a painful illness that affects the bones,” I was told, “it makes them soft and weak, and leads to deformities like bowed legs. You need Vitamin D to prevent it. Make sure you get plenty of sunlight or drink cod liver oil!” This connection between sunlight and Vitamin D stuck in my mind.
A little history
During a 17th-century rickets epidemic, observers correlated an increase in its incidence with a lack of sunlight. By the early 1800s, cod liver oil was recognized as an effective treatment for this affliction. In 1922, the American biochemist Elmer McCollum isolated the specific nutrient in cod liver oil responsible for rickets’ curative properties and gave it the name Vitamin D. McCollum’s pioneering work laid the foundation for an understanding of Vitamin D’s role in bone health. A public-health campaign in the mid-20th century to eliminate rickets advocated for increased sun exposure and the fortification of milk and other foods with Vitamin D and other essential nutrients.
Vitamin D – some science
Vitamins are organic compounds, essential nutrients that our bodies need in small amounts to function properly. They play vital roles in our growth and development and help maintain our overall health.
We now know a lot about the role and importance of Vitamin D for bone health and other bodily functions. One of its primary roles is to absorb from our intestines the calcium needed to harden our bones and keep them strong and healthy. Having the right amount of Vitamin D, calcium, and phosphorus is essential for bone health. Vitamin D is a fat-soluble vitamin that comes in two main forms: Vitamin D2 (Ergocalciferol) and Vitamin D3 (Cholecalciferol). Vitamin D2 is naturally present in some foods, and is added to so-called fortified foods like milk, orange juice, and cereals. Vitamin D3, also known as the ‘sunshine vitamin,’ is produced when our skin is exposed to ultraviolet-B rays in sunlight, triggering a process of vitamin D synthesis in the body. It is also found in animal-based foods like oily fish, eggs, and liver. Both forms are also available as over-the-counter dietary supplements.
Both forms of Vitamin D are converted by our liver and kidneys – working in sequence – into the hormonal form, called calcitrol, which regulates our calcium levels and bone health. Some recent research suggests that Vitamin D3 may be more effective than D2 at raising blood Vitamin D levels and maintaining those levels longer.
What else does Vitamin D do for health?
In addition to enabling the absorption of the calcium needed for building and maintaining strong bones, Vitamin D has other functions. It supports our immune system by helping to regulate immune-cell activity. It promotes the production of some cells that act as a natural defense against various pathogens, including bacteria, fungi, and viruses, and other kinds of cells that regulate the body’s immune response. It plays a crucial role in maintaining and improving muscle function, helping to repair muscle damage and regeneration.
It is also important for brain health, influencing brain development and function, and potentially protecting against cognitive decline and neuropsychiatric disorders. Some research indicates a potential link between low levels of Vitamin D and colon cancer. Laboratory studies have shown that Vitamin D can inhibit the development of tumors and slow the growth of existing tumors, including those from the breast, ovary, colon, prostate, and the brain. Research is ongoing to further understand and verify these links between Vitamin D and cancer. Other research has found that long-term use of vitamin D supplements may lower the risk of multiple sclerosis.
Are you getting the Vitamin D you need?
Sunscreen, protective clothing, limited exposure to sunlight, dark skin, and age may prevent you from getting enough vitamin D from the sun. Where you live, the availability of sunlight, the color of your skin, your habits and lifestyle, your dietary habits, and your age are all important factors in determining whether or not you are getting enough of it. People with conditions that affect how the body absorbs fat, such as ulcerative colitis and Crohn’s disease, also may not get enough vitamin D. The recommended daily amount (RDA) for adults under 70 years is 600 IU, or 15 micrograms (mcg). About 1 in 1000 adults in the US suffer from the adult form of rickets or bone softening, called Osteomalacia. A much higher number: 12.6% of adults over 50 have osteoporosis. You should make sure you are getting the Vitamin D your body needs.
Seniors, take heed
Older adults especially should note the importance of Vitamin D as a nutrient for optimal health. As we age, our skin is unable to synthesize vitamin D as efficiently as it did in our younger years. Older adults are also more likely to spend time indoors and away from the sun. As a result, they are more likely to suffer from Vitamin D deficiency, requiring supplementary sources of this nutrient. The RDA of vitamin D for adults over 70 is 800 IU, a 33% increase over that for younger adults.
A cautionary note
While Vitamin D supplements are generally considered safe, do not begin using them (or any other kind of supplements) before consulting your physician. A simple blood test can check your levels of Vitamin D. Supplements are known to interact with and reduce the efficacy of cholesterol-lowering and blood-pressure medications, among others.
Too much Vitamin D can cause toxicity, with some unpleasant side effects for all adults, regardless of age. The tolerable upper limit is set at 4000 IU per day.
Let the sunshine in, eat the right foods, and take supplements only if you need to. Don’t forget your D’s!