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Hydrogenated Oils Affect Amount of Vitamin K Available to Bone

Hydrogenation of plant oils decreases the amount of vitamin K available to bone in consumers using food products containing the oils.

Hydrogenation reduces the role such oils might otherwise play in "improving the consequences of an already low-to-average phylloquinone intake in certain subgroups of the adult population," United States researchers suggest.

They say available data indicate that more than half of younger US adults do not meet the current guidelines governing adequate intake of the nutrient.

Investigators are therefore concerned that "some individuals are at risk of increased bone turnover when consuming low-phylloquinone diets.

"Although children have phylloquinone intakes that are reportedly greater than the recommended adequate intakes for their respective age groups, children also consume foods with a 1:2 ratio of dihydrophylloquinone to phylloquinone," they explain.

During hydrogenation of phylloquinone-rich oils, phylloquinone is converted to dihydrophylloquinone.

Researchers from Tufts University in Boston, Massachusetts and Yale University in New Haven, Connecticut point out that in the US use of hydrogenated oil is ubiquitous in the food supply.

They also say that low vitamin K nutrition has been proposed as a modifiable risk factor for osteoporosis.

"At least three vitamin K-dependent proteins have been identified in bone or cartilage, including osteocalcin, which is one of the most abundant non-collagenous proteins in bone.

"Most of the evidence supporting a role for vitamin K in age-related bone loss is based on reported associations between bone mineral density or the bone fracture rate and biological markers of vitamin K status."

Investigators note the "proposed role of poor vitamin K status as a risk factor for osteoporosis would be strengthened if controlled changes in dietary vitamin K were shown to influence bone metabolism."

In a randomised, crossover study, 15 young adults in a metabolic unit were fed a phylloquinone-restricted diet for 15 days. They then crossed over to 10 days of repletion with either phylloquinone or dihydrophylloquinone.

The researchers report: "There was an increase and subsequent decrease in measures of bone formation and resorption after dietary phylloquinone restriction and repletion.

"In comparison with phylloquinone, dihydrophylloquinone was less absorbed and had no measurable biological effect on measures of bone formation and resorption."
American Journal of Clinical Nutrition, 2001; 74: 783-790. "Effects of a hydrogenated form of vitamin K on bone formation and resorption"

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