There's a lot of buzz about the liver in the nutrition world and the role it plays in so many areas of health — the number of liver cleanse and liver detox programs and supplements on the market is evidence of that.
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Vitamin deficiencies can cause myriad problems, so it's important to eat a well-balanced diet to improve liver function, but there's currently no sound scientific proof that any vitamins for the liver play a well-defined role in preventing or treating diseases.
Love Your Liver
Weighing in at over 3 pounds and the approximate size of a football, your liver is the second largest organ in your body, second only to the skin. According to Michigan Health, the liver contains as much as 13 percent of the body's blood supply, and it also plays a major role in digestion.
Responsible for over 500 jobs that maintain your health, the liver is arguably the hardest working organ in the body. Key among the liver's functions are:
- Filtering all ingested substances — food, alcohol, medications — for nutrients and toxins, storing nutrients or sending them out into the bloodstream and getting rid of toxic substances through urine or stool.
- Regulating energy by removing sugar from the blood and storing it as glycogen, then converting that glycogen to glucose. When blood sugar decreases, the liver releases some stored glucose into the bloodstream for use by cells.
- Breaking down fats, making cholesterol, converting excess protein and carbohydrate and storing them for later use and producing bile, by which waste products and toxins are carried out of the body.
- Supplying blood during fetal development and recycling blood in adult bodies. It also breaks down damaged and old blood cells and aids in releasing plasma proteins that are crucial for blood to clot.
Liver injury and disease can have profound effects on overall health, so keeping your liver in tip-top shape is critical. A few vitamin deficiencies have been implicated in diseases of the liver, although their exact roles aren't fully understood.
Read more: The 10 Best Supplements
Vitamin D and NAFLD
Known as the sunshine vitamin, vitamin D is a fat-soluble vitamin synthesized by the skin when exposed to UV rays from the sun. It's also found naturally in some foods, added to others and available in supplement form. But vitamin D in any form is biologically inactive and it must be converted first by the liver and then by the kidneys into a form the body can use.
According to a review published in the journal Nutrients in September 2017, vitamin D deficiency occurs in epidemic proportions in industrialized countries due to lack of sun exposure and inadequate dietary intake. Also common — occurring in over 70 percent of people with type 2 diabetes, metabolic syndrome and obesity — is non-alcoholic fatty liver disease (NAFLD).
This condition is characterized by a buildup of fats in the liver that is unrelated to alcohol use. The disease may progress to nonalcoholic steatohepatitis, a more serious condition marked by liver inflammation and potentially permanent liver damage.
Although study results are controversial, reports the Nutrients review, there is evidence that vitamin D deficiency contributes to the development and progression of NAFLD, and that high-dose supplementation can help treat liver damage caused by NAFLD and nonalcoholic steatohepatitis. According to another review published in Nutrients in April 2018, vitamin D deficiency is more common in NAFLD patients compared to healthy individuals.
Vitamin D affects the production of adipokines — peptides secreted by fat tissue that regulate crucial biological processes — as well as inflammation in fat cells. Low-serum vitamin D levels have been associated with a higher concentration of adiponectins, which are fat cell hormones that promote inflammation.
Because fat cell dysregulation features prominently in NAFLD, and because fat cells respond to vitamin D, the review authors conclude that the nutrient plays a plausible role in the development, progression and treatment of the disease.
Antioxidant Vitamin E
Another fat-soluble nutrient, vitamin E is a powerful antioxidant that can protect cells from free radical damage. Free radicals are molecules with one or more unpaired electrons that may play a role in the development of cardiovascular disease and cancer, according to the National Institutes of Health. Research shows that vitamin E may also play an important role in the development and progression of NAFLD.
According to a review published in the journal Antioxidants in January 2018, vitamin E's antioxidant activity has been shown to lower levels of oxidative stress in NAFLD. Authors of the review state that the development of NAFLD is not fully understood, but that oxidative stress appears to greatly contribute to the liver cell damage seen in the disease.
Other Vitamins for Liver Health
Additional roles of vitamins C, B12 and folate in the promotion and protection against liver diseases have been highlighted in scientific research. A review published in Nutrients in December 2014 suggests that vitamin C deficiency may also be implicated in the development of NAFLD and non-alcoholic steatohepatitis.
Like vitamin E, vitamin C is an antioxidant nutrient that can combat oxidative damage from free radicals. Also like vitamin E, deficiency of vitamin C has been shown to be more prevalent in NAFLD patients.
Deficiencies in the water-soluble vitamins B12 and folate were correlated with severity of non-alcoholic steatohepatitis in a study published in Nutrients in April 2018. Another study published in the journal Yonago Acto Medica in March 2017 found that falsely elevated levels of B12 were associated with increased severity and poor prognosis in patients with chronic viral liver disease.
The researchers hypothesize that the false high blood levels may have been due to decreased storage of the nutrient in the liver, caused by the liver releasing too much into the blood. Because B12 has a liver-protective effect, low levels in the liver exacerbated liver damage.
Should You Take a Supplement?
All of the reviews and studies cited here emphasize that vitamin therapy still cannot be confidently recommended for the prevention or treatment of liver diseases until more large-scale, controlled trials have been undertaken. Unless your doctor has recommended a vitamin supplement to treat a particular condition, don't bank on any beneficial effects.
High-dose vitamin supplements often rank up there with liver cleanses and liver detox supplements to improve liver function — there's not enough evidence to show that they offer any additional benefits unless there is an outstanding deficiency. When taken in excess amounts, some vitamins can even cause liver damage.
The National Institute of Health's LiverTox database reports that excessive intakes of vitamin A and the B vitamin niacin can be particularly harmful. Liver injury can occur when these vitamins are taken in high doses — 100 to 400 times the recommended daily intake (RDI) of niacin, which is 14 to 16 milligrams per day, and 10 times the RDI for vitamin A, which is 700 to 900 micrograms daily.
That said, it is important to get enough of these nutrients from your diet. Deficiency can cause not only potential liver damage and disease, but also a host of other health problems. Generally, eating a well-balanced diet including plenty of fresh fruits and vegetables, lean meats, low-fat dairy, whole grains and healthy fats can provide all the liver-protective nutrients you need.
If your lifestyle is such that vitamin D deficiency may be an issue, consult your doctor to see if you should take a supplement and at what dose.
- Michigan Health: "What Does the Liver Do, and How Do I Keep Mine Healthy?"
- NIH: "Vitamin D"
- Nutrients: "Vitamin D Supplementation and Non-Alcoholic Fatty Liver Disease: Present and Future"
- Mayo Clinic: "Nonalcoholic Fatty Liver Disease"
- Nutrients: "Vitamin D and the Liver—Correlation or Cause?"
- Trends in Pharmacological Sciences: "Adipokines in Health and Disease"
- NIH: "Vitamin E"
- Antioxidants: "Vitamin E as a Treatment for Nonalcoholic Fatty Liver Disease: Reality or Myth?"
- Nutrients: "Does Vitamin C Deficiency Promote Fatty Liver Disease Development?"
- Nutrients: "Folate and B12 Levels Correlate With Histological Severity in NASH Patients"
- Yonago Acto Medica: "Falsely Elevated Serum Vitamin B12 Levels Were Associated With the Severity and Prognosis of Chronic Viral Liver Disease"
- LiverTox: "Vitamin A"
- LiverTox: "Vitamin B and Water Soluble Vitamins"
- National Academy of Medicine: "Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes, Vitamins"