Vitamin D Deficiency and the Prevention of Heart Disease
- Created on Thursday, 09 June 2016 18:40
This is an article about Vitamin D deficiency and its role in heart disease by a leading cardiologist. Note the statistics on Vitamin D deficiency among Blacks and Hispanics, and that's because of their darker skin. She advises that one shouldn't take more than 4,000 IUs without a doctor's approval, but the Vitamin D Foundation, which is run by a doctor, recommends 5000 IUs daily for most people. However, this time of year (summer) if you get plenty of sun, as I do, you should cut back. What I do is take 5000 IUs of Vitamin D3 every day for most of the year, but in June, July, and August, I cut back to 5000 IUs every other day. Dr. Cinque
The author: Dr. Erin Michos, a preventive cardiologist and researcher at Johns Hopkins, has been studying the potential impact of vitamin D and cardiovascular health for over 10 years. Ironically, at her last annual checkup, Michos -- an avid outdoor runner -- was shocked to learn that she, too, was vitamin D deficient with a blood level of only 15 nanograms per milliliter. Should she take a vitamin D supplement for her heart health? In this piece, Michos and her internal medicine colleague Samuel Kim discuss the "sunshine" vitamin.
Vitamin D: Does it Even Matter?
Vitamin D is a hormone that helps control calcium levels in your body, which is ultimately important for your overall bone health. Vitamin D is produced in the skin from exposure to ultraviolet B rays in sunlight or taken in from food or dietary supplements. However, only limited food sources contain vitamin D, such as fatty fish, cod liver oil, eggs, milk, cereal and bread.
It's well-known that vitamin D is important for bone health. Very low levels of vitamin D can cause low levels of calcium in your blood, which can increase your risk of bone fractures, tingling and numbness sensation, and muscle weakness.
Recent research, including many of the studies that Michos conducted, has found that the sunshine vitamin may also be linked to other health conditions, like an increased risk of heart disease, stroke, diabetes, high blood pressure, abnormal cholesterol levels, erectile dysfunction and obesity.
Still, most of these observational studies do not prove a cause and effect because they don't involve intervention to correct low vitamin D levels. Having a low vitamin D level may simply be a risk marker indicating an individual is less healthy from other causes. Further research needs to be conducted to see if treating vitamin D deficiency through vitamin D supplementation can impact vascular disease outcomes. Fortunately, randomized clinical trials to answer this question are ongoing.
Who Becomes Vitamin D Deficient?
There are three major groups of people who develop vitamin D deficiency:
1. People who do not get enough vitamin D either through diet or sunlight exposure. Inadequate sunlight exposure is a problem for many people, especially darker-skinned individuals, those who use sunscreen for skin cancer protection and those who live in sun-limited areas in northern parts of the U.S.
2. Patients with kidney and liver diseases can have low vitamin D levels because they have decreased levels of important proteins that metabolize vitamin D.
3. Patients with bowel diseases, such as celiac disease, Crohn's disease and cystic fibrosis, or who have had any surgery that removes or reconnects the intestines or stomach cannot readily absorb vitamin D.
Who Should Get Tested?
In general, routine testing of vitamin D is currently not recommended except for people with kidney diseases, bowel diseases and a higher risk of osteoporosis, including previous bone fractures and low calcium levels.
When testing for vitamin D deficiency, physicians order the blood test for 25-hydroxyvitamin D concentration. This is the form of vitamin D that is the best measure of vitamin D stores in the body.
There is some controversy though about what is considered a normal amount of vitamin D in a blood test. The Institute of Medicine says that blood levels of 25-hydroxyvitamin D greater than 20 nanograms per milliliter should be adequate. However, many experts, including the Endocrine Society, advocate for levels greater than 30 nanograms per milliliter.
Because of the widespread use of sunscreen and more time spent indoors, particularly for occupational work, vitamin D deficiency is actually quite common. In the U.S. alone, the National Health and Nutrition Examination Survey found that over 40 percent of the American population was deficient in vitamin D (levels less than 20 nanograms per milliliter), with the highest rates seen in African-Americans (82 percent) and Hispanics (69 percent).
How Do You Treat Vitamin D Deficiency?
Vitamin D can be obtained from diet, but food sources generally have small quantities. In the absence of adequate sunlight exposure, it can be difficult to get enough vitamin D from diet alone. As a reference, 1 cup of milk (8 ounces) is roughly equal to about 100 International Units of vitamin D. For individuals with fair skin, 15 to 30 minutes of midday sun exposure during the summer months can give you close to 5,000 IU a day -- the equivalent of drinking 50 glasses of milk! Dark-skinned individuals and the elderly may produce less vitamin D in response to sunlight.
Prolonged peak sunlight exposure is not recommended for patients with a higher risk of skin cancer, especially individuals who are fair-skinned. Vitamin D from tanning beds is also not recommended given the high risk of skin cancer development.
In addition to diet and sunlight, you can get vitamin D from supplements. Vitamin D supplements come in either D2 (ergocalciferol) or D3 (cholecalciferol) forms. We generally recommend D3, since this is the form that is naturally produced in the body by sunlight, but either supplementation is reasonable. Most supplements at lower doses can be purchased over the counter without a prescription.
It is not completely clear what the ideal vitamin D intake goals should be for each individual. The U.S. Preventive Services Task Force recommends that all adults should intake at least 600 to 800 IU daily. The National Osteoporosis Foundation recommends somewhere between 800 to 1,000 IU daily for adults over age 50.
For patients with vitamin D deficiency, the guidelines recommend an initial treatment with a 50,000 IU vitamin D booster pill -- which normally requires a doctor's prescription -- once a week for eight weeks, then transitioning to a once-a-day supplementation between 1,500 and 2,000 IU. Patients on seizure medications, steroids, antifungals and HIV antiviral medications are often recommended to take two to three times more vitamin D because these medications can increase vitamin D metabolism. Personalized vitamin D treatments can be discussed with your doctor.
[See: The 12 Best Diets for Your Heart.]
What Are the Side Effects of Vitamin D Supplements?
In general, the side effects from vitamin D supplements are uncommon and relatively benign. However, high doses could lead to high calcium or phosphorous levels, increased thirst, a metallic taste in the mouth, tiredness, constipation and kidney stones. Although vitamin D toxicity is rare, it's not recommended to take more than 4,000 IU a day, unless a doctor is also monitoring your blood levels.
So What Does All This Mean for Me?
Vitamin D deficiency is common in the U.S., especially because many of us stay indoors and do not eat vitamin D-rich foods. There are reasonably good data to support the use of vitamin D supplementation by patients with a higher risk of osteoporosis. However, the benefit of supplementation in the normal aging population remains unclear.
Although there are more data to suggest that vitamin D deficiency may increase the risk of heart diseases, high blood pressure and obesity, it is not unclear at this time if and how vitamin D treatment will improve the development or progression of these diseases. More research is needed. Also, vitamin D treatment may only benefit those with deficiency, not individuals who already have adequate levels from sunlight and diet.
Back to our case about the author: Despite her physical activity levels, perhaps it isn't so surprising that Michos ended up vitamin D deficient. She eats a largely vegetarian/vegan diet, does most of her outdoor physical activity in the early morning, avidly uses sunscreen in the summer and lives in the northern part of the U.S. -- all known risk factors for deficiency.
In the end, Michos decided take a vitamin D supplement for her bone health, particularly because of her family history of osteoporosis. But at this time, despite her own research, she cannot recommend vitamin D for the sole purpose of preventing heart and related vascular diseases. As mentioned, there are several large randomized clinical trials ongoing now to test whether vitamin D treatment can reduce the risk of heart disease, cancer, diabetes and death. Hopefully, the results of these trials will inform future recommendations to patients.
Dr. Erin Michos is a cardiologist and associate professor of medicine at the Johns Hopkins University School of Medicine with a joint appointment in epidemiology at the Johns Hopkins Bloomberg School of Public Health. She is the associate director of preventive cardiology for the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease. Her research interests focus on general preventive cardiology, cardiovascular health in women, vitamin D and management of lipid disorders.