Writing in the journal Redox Biology, the team’s findings likely help to explain why these patients, who have low vitamin C levels, are at high-risk for liver dysfunction and liver injury seen in Non-alcoholic fatty liver disease (NAFLD).
“Vitamin C actually protects vitamin E, so when you have lipid peroxidation, vitamin E is used up and vitamin C can regenerate it," said Maret Traber, review team member and professor at the Oregon State University (OSU) College of Public Health and Human Sciences.
"If you don't have the vitamin C, the vitamin E gets lost and then you lose both of those antioxidants and end up in this vicious cycle of depleting your antioxidant protection."
Easing blood endotoxin levels
The review points to improved vitamin C status as an approach to alleviate endotoxemia—the presence of endotoxins in the blood—and its consequent pro-inflammatory responses that may trigger insulin resistance and related metabolic disorders.
Along with colleagues from The University of Iowa, the end-goal is to translate vitamin C benefits into novel dietary strategies to help reduce the growing public health burden of MetS while also providing investigators new tools to evaluate gut-liver functions.
Data drawn from National Health and Nutrition Examination Survey (NHANES) indicate that obese adults have 5 − 12% lower micronutrient intakes along with a higher prevalence of nutrient inadequacy compared with normal weight adults.
In particular, vitamin C intakes are poor among the obese with 8% of women and 13% of men having circulating concentrations indicative of vitamin C deficiency.
Despite the general recognition that nutritional status in MetS is compromised, nutrition and medical professionals do not advise antioxidant supplement use because of a lack of scientific evidence demonstrating health benefits.
The review also points towards the gut microbiota composition as an important factor in the disease’s onset.
The Mediterranean influence
In one study, beneficial changes in gut bacteria composition were observed in MetS patients, who consumed a Mediterranean diet for two years.
At baseline, the abundance in MetS of Bacteroides, Eubacterium and Lactobacillus genera was higher than in non-MetS controls patients.
Following long-term consumption of Mediterranean diet, the populations of P. distasonis, B. thetaiotaomicron, F. prausnitzii, B. adolescentis and B. longum were restored in MetS as compared with the microbiota composition in MetS persons assigned to a low-fat diet.
Moreover, decreased lipopolysaccharide (LPS) levels and cardiac event-free survival were linked to adherence to the Mediterranean diet, especially in those who ate fruits and legumes, important sources of vitamins C and E, respectively.
“What these findings are really saying to people as we move out of the rich-food holiday season and into January is eat your fruits and vegetables," said Dr Traber.
"Eat five to 10 servings a day and then you'll get the fibre, you'll get the vitamin C, and you'll really protect your gut with all of those good things."
The team also pointed towards vitamin supplementation as a way to improve liver health citing vitamin E supplementation in persons with nonalcoholic steatohepatitis (NASH).
Source: Redox Biology
Published online: doi.org/10.1016/j.redox.2018.101091
“The Relationship Between Vitamin C Status, the GUT-Liver Axis, and Metabolic Syndrome.”
Authors: Maret Traber, Garry Buettner, Richard Bruno