Study under review: Vitamin K-induced effects on body fat and weight: results from a 3-year vitamin K2 intervention study
Obesity rates in the United States are now in excess of 36% and obesity remains one of the leading risk factors for heart disease, stroke, and diabetes. While weight gain and the rise in obesity affects all age groups, the increase in weight amongst middle-aged and postmenopausal women is of particular note. In 2002, women aged 50 to 59 years old were, on average, approximately 23 pounds heavier than they were in 1960. This compares to roughly 17 pounds for women aged 40-49 years old and 9 pounds for women over 60. Therefore, interventions that address weight gain in middle-aged, postmenopausal women are of specific importance for tempering the rise in obesity rates.
Hormonal changes that occur during menopause (e.g.,decreases in estrogen) have been shown to alter bone metabolism, resulting in lower bone mineral content in postmenopausal women. It has been hypothesized that changes in the metabolism of the bone-related protein osteocalcin may be responsible for at least some of the weight gain observed in postmenopausal women due to its potential role in energy metabolism.
Osteocalcin is a protein found in bone tissue and is secreted by osteoblasts. Osteocalcin’s function is regulated by a process known as carboxylation, the chemical process of adding a carboxyl group to an amino acid. The metabolic (i.e. fat and glucose) roles of osteocalcin are largely dependent on its carboxylation status, which is shown in Figure 1 and largely regulated by vitamin K. This is why it has been hypothesized that vitamin K, which acts as a carboxylating molecule, might be largely responsible for maintaining adequate levels of carboxylated osteocalcin and therefore maintaining normal fat metabolism in postmenopausal women. In small intervention studies, supplementation of vitamin K has been shown to increase osteocalcin carboxylation and decrease levels of decarboxylated osteocalcin. Therefore, the purpose of this study was to test the hypothesis that long term supplementation of vitamin K would result in lower body fat, or influence fat distribution.
Postmenopausal women are a high-risk group for both weight gain and decreases in bone mass. A bone-related protein, osteocalcin, may be a key regulator of fat and glucose metabolism and its function is regulated by its carboxylation status. Vitamin K supplementation has previously been shown to improve osteocalcin carboxylation. The study under review therefore sought to test whether vitamin K supplementation would improve fat and glucose metabolism and reduce body fat accumulation in postmenopausal women.
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Other Articles in Issue #38 (December 2017)
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