The effects of vitamin K-rich green leafy vegetables on bone metabolism: A 4-week randomised controlled trial in middle-aged and older individuals
Marc Sim,
Joshua R. Lewis,
Richard L. Prince,
Itamar Levinger,
Tara C. Brennan-Speranza,
Claire Palmer,
Catherine P. Bondonno,
Nicola P. Bondonno,
Amanda Devine,
Natalie C. Ward,
Elizabeth Byrnes,
Carl J. Schultz,
Richard Woodman,
Kevin Croft,
Jonathan M. Hodgson,
Lauren C. Blekkenhorst
Affiliations
Marc Sim
School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia; Medical School, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia; Corresponding author at: School of Medical and Health Sciences, Edith Cowan University, Joondalup 6027, Western Australia, Australia.
Joshua R. Lewis
School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia; Medical School, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia; Centre for Kidney Research, Children's Hospital at Westmead, School of Public Health, Sydney Medical School, The University of Sydney, Sydney, NSW, Australia
Richard L. Prince
Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, WA, Australia; Medical School, Sir Charles Gardner Unit, The University Western Australia, Perth, WA, Australia
Itamar Levinger
Institute for Health and Sport (iHeS), Victoria University, Melbourne, VIC, Australia; Australian Institute for Musculoskeletal Science (AIMSS), University of Melbourne and Western Health, St Albans, VIC, Australia
Tara C. Brennan-Speranza
Department of Physiology, Bosch Institute for Medical Research, University of Sydney, Sydney, Australia
Claire Palmer
School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia; School of Biomedical Science, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia
Catherine P. Bondonno
School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia; Medical School, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia
Nicola P. Bondonno
School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia; Medical School, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia
Amanda Devine
School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia
Natalie C. Ward
Medical School, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia; School of Public Health & Curtin Health Innovation Research Institute, Curtin University, Perth, WA, Australia
Elizabeth Byrnes
Department of Clinical Biochemistry, PathWest Laboratory Medicine, Queen Elizabeth II Medical Centre, Perth, Australia
Carl J. Schultz
Medical School, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia; Department of Cardiology, Royal Perth Hospital, WA, Australia
Richard Woodman
Flinders Centre for Epidemiology and Biostatistics, Flinders University, Adelaide, SA, Australia
Kevin Croft
School of Biomedical Science, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia
Jonathan M. Hodgson
School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia; Medical School, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia
Lauren C. Blekkenhorst
School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia; Medical School, Royal Perth Hospital Unit, The University Western Australia, Perth, WA, Australia
Background: High vegetable intake is associated with beneficial effects on bone. However, the mechanisms remain uncertain. Green leafy vegetables are a rich source of vitamin K1, which is known to have large effects on osteoblasts and osteocalcin (OC) metabolism. Objective: To examine the effects of consumption of two to three extra serves of green leafy vegetables daily on bone metabolism. Methods: Thirty individuals (mean age 61.8 ± 9.9 years, 67% male) completed three experimental phases in a randomised controlled crossover design, each lasting four weeks, with a washout period of four weeks between phases (clinical trial registration: ACTRN12615000194561). The three experimental phases were: (i) increased dietary vitamin K1 by consuming green leafy vegetables (H-K; ~200 g/d containing 164.3 [99.5–384.7] μg/d of vitamin K1); (ii) low vitamin K1 by consuming vitamin K1-poor vegetables (L-K; ~200 g/d containing 9.4 [7.7–11.6] μg/d of vitamin K1); and (iii) control (CON) where participants consumed an energy-matched non-vegetable control. OC forms, total OC (tOC), carboxylated OC (cOC) and undercarboxylated OC (ucOC), were measured in serum pre- and post-intervention for each experimental phase using a sandwich-electrochemiluminescence immunoassay. Results: Pre-intervention tOC, ucOC and ucOC:tOC levels were similar between phases (P > .05). Following H-K, but not L-K, tOC, ucOC and ucOC:tOC levels were significantly lower compared to pre-intervention levels (P ≤ .001) and compared to CON (~14%, 31% and 19%, respectively, all P < .05), while cOC remained unchanged. Conclusions: In middle-aged healthy men and women, an easily achieved increase in dietary intake of vitamin K1-rich green leafy vegetables substantially reduces serum tOC and ucOC suggesting increased entry of OC into bone matrix, where it may improve the material property of bone. In conjunction with previous epidemiological and randomised controlled trial data, these findings suggest that interventions to increase vegetable intake over extended periods should include bone end points including fracture risk.
