Vitamin D and Liver Disease

From HCV Advocate

HEALTHWISE: Vitamin D and the Liver
—Lucinda K. Porter, RN

Vitamin D is frequently in the news, presenting interesting, but conflicting information. At the recent Liver Meeting sponsored by the AASLD, there were at least two posters about vitamin D and chronic hepatitis C virus (HCV) infection. On November 30, 2010, the Institute of Medicine of the National Academies (IOM) released its vitamin D consensus report. This month’s Healthwise discusses vitamin D—what it is, why we need it, how much we need, how to get enough, and what those of us with hepatitis C need to know about this supplement.

The liver is essential for the production of vitamin D. A prohormone (precursor to a hormone), vitamin D is activated first by the liver; then by the kidneys. Vitamin D enters the body two ways—via sunlight or by consuming it. When exposed to sunlight’s ultraviolet B (UVB) rays, the skin manufactures vitamin D and the bloodstream transports D to the liver. If consumed by way of food or dietary supplements, vitamin D is circulated to the liver for activation.

The best-known disease associated with vitamin D deficiency is rickets, a condition that causes softening and deformity of the bones. During the industrial era in northern United States and Europe, children working in factories lacked sunlight, making them susceptible to rickets. Scientist discovered the link between vitamin D and rickets, and beginning in the 1930’s, children were given a daily dose of cod liver oil. Fortifying milk with vitamin D dramatically reduced rickets in the U.S. Children were quite happy to drink milk rather than smelly fish oil.

If you scan the news, it looks like vitamin D is a wonder supplement, suggesting that vitamin D does more than just protect the bones. There are reports linking vitamin D to muscle tissue, inflammation, and the immune system. Lab, animal, and epidemiological data suggest a possible link between low vitamin D levels, cancer, diabetes, high blood pressure, cardiovascular disease, multiple sclerosis, gum disease, rheumatoid arthritis, and osteoarthritis.

Since the vitamin D research is confusing, the governments of the U.S. and Canada asked the IOM to clarify the issue. In its report “Dietary Reference Intakes for Calcium and Vitamin D,” the IOM thoroughly reviewed all available research and made the following conclusions:

Vitamin D is vital to bone health, but has not been proven to have any other healthy benefits.

The current recommended daily allowance for vitamin D (RDA) needs to be increased.

More vitamin D is not better. The total daily vitamin D intake for adults and children over age 9 should not exceed 4000 International Units (IU) per day. The totals for infants and children under age 9 are less and vary according to age.
Although the IOM’s report is exhaustive, it is not necessarily perfect. The IOM based its recommendations on a literature review, rather than the gold-standard randomized, double-blind, placebo study. Other researchers are voicing their objections about the IOM’s report, stating that the report is not conclusive and should not make across the board recommended daily allowances that don’t take geography into consideration.

What we do know is that older adults with insufficient vitamin D are at risk for osteopenia (bone thinning) and osteoporosis (bone loss), which may lead to fractures and other complications. With age, the skin’s ability to utilize sun as a source of vitamin D is compromised. Adequate supplementation is the best insurance policy.

Vitamin D and Liver Disease

People with liver disease are susceptible to vitamin D deficiency according to an article titled “Prevalence of Vitamin D Deficiency in Chronic Liver Disease” (Digestive Diseases and Science, September 2010). In this study, researchers Arteh, Narra, and Nair from the University of Tennessee Health Science Center in Memphis, TN looked at 118 patients: 43 with HCV cirrhosis, 57 non-cirrhotic patients with HCV, and 18 patients who had cirrhosis from a cause other than HCV. Arteh and colleagues found that 92% of patients with chronic liver disease had vitamin D deficiency. One-third of these had severe vitamin D deficiency; African American females had the highest risk.

Looking further at the role of vitamin D and liver disease, a team of researchers presented a poster at the 2010 Liver Meeting. In “Vitamin D Metabolites Inhibit Replication of the Hepatitis C Virus” by Gutierrez et al. presented laboratory data showing vitamin D’s ability to inhibit HCV replication. More research is needed to understand the relationship of vitamin D, liver cells and HCV.

Also at the 2010 Liver Meeting, Mouch and Assy presented a poster titled “Vitamin D Supplementation Improves Viral Response in Chronic Hepatitis C Genotype 2/3 Patients Treated with Peg Interferon Alpha and Ribavirin.” This small study looked at 40 HCV patients with genotypes 2 and 3. Baseline levels of vitamin D were measured, before treating all subjects with standard HCV medications. Half of the subjects were also given 1000 to 4000 IU/day of vitamin D, depending on their baseline vitamin D levels.

Despite the fact that the vitamin D group had higher body mass and viral loads, those who took additional vitamin D had better treatment outcomes. It was also noted that those who had lower vitamin D levels at baseline were more likely not to respond to HCV treatment.

Taking Vitamin D

Your medical provider can order a simple blood test to see if you are getting sufficient vitamin D. The IOM recommends that vitamin D levels should be above 20 nanograms per milliliter of blood.

Although we get most of our vitamins from food, vitamin D is more readily obtained from the sun and supplementation. It is naturally available in a few foods, such as fatty fish (salmon, sardines, and mackerel), fish liver and beef liver. Fortified foods are the highest source of dietary vitamin D for those living in the U.S.

Sun exposure is a good source of vitamin D, but it is a not a perfect source. First, there is not enough UV energy in the winter above 42 degrees north latitude (above Boston or the northern border of California). People living in much of Canada and Alaska have less than 6 months of sufficient UV energy from the sun to produce sufficient vitamin D. Second, UV is a potential carcinogen and most experts suggest avoiding direct sunlight or using sunscreen.

In ideal circumstances, 5 to 30 minutes of sun exposure to the arms, and legs or face three times weekly in sunny weather (between 10 AM and 3 PM) will yield sufficient vitamin D. However, darker skin, older age, obesity and other factors may interfere with obtaining adequate D levels. Sunscreen, a necessary protection from skin cancer, melanoma, and interferon-related photosensitivity reduces vitamin D exposure.

Certain medications may interfere with production of vitamin D. The most common of these are anti-seizure medications such Dilantin, weight loss drugs such as Xenical and Alli, the cholesterol-lowering medication cholestyramine and steroids, such as Prednisone.

The best way to insure sufficient vitamin D intake is with dietary supplements. The IOM recommends 600 IU/day for children and adults ages 1 to 70. The RDA for adults over age 71 is 800 IU/day of vitamin D. Keep in mind that if you get vitamin D from the sun and fortified foods, you may already be getting sufficient vitamin D. Do not take more vitamin D than your medical provider recommends.

Excess Vitamin D

Vitamins are classified as water-soluble (dissolves in water) or fat-soluble (dissolves in fat). Water soluble vitamins B and C are eliminated from the body fairly quickly. Fat-soluble vitamins A, D, E and K are stored in the liver. Therefore, it is possible to have excess fat-soluble vitamins stored in the liver, particularly vitamin A.

Excess vitamin D is rare as the amount that produces toxicity is quite high. Adults taking 50,000 IU/day for several months can reach toxic levels. The symptoms of vitamin D toxicity are nausea, vomiting, loss of appetite, excessive urination, excessive thirst, weakness, nervousness, itching, and eventually kidney failure. The IOM advises no more than 4000 IU/day for adults and children over age 9.

Now that the winter months are shortening the amount of sun we are exposed to, take a moment to assess your vitamin D intake. If you have liver disease, such as hepatitis C, are over age 70, or have any factors that may interfere with your body’s production of vitamin D, talk to your medical provider about a blood test to measure the levels. Getting enough vitamin D is a simple, relatively inexpensive way of protecting your health.

References:

Institute of Medicine of the National Academies, Dietary Reference Intakes for Calcium and Vitamin D
www.iom.edu/Reports/2010/
Dietary-Reference-Intakes-for-Calcium
-and-Vitamin-D/Report-Brief.aspx

Linus Pauling Institute at Oregon State University
http://lpi.oregonstate.edu/infocenter
/vitamins/vitaminD

National Institutes of Health’s Office of Dietary Supplements
http://ods.od.nih.gov/factsheets/vitamind