"The Scarborough Fair Trial": effects of increased vegetables, herbs and fruit on adiponectin levels in postmenopausal women

Abstract

Background: Increased vegetables/fruit may reduce bone loss at midlife by provision of micronutrients for bone formation, buffer precursors to reduce potential renal acid load (PRAL) and anti-inflammatory phytochemicals. Adiponectin is an anti-inflammatory marker positively associated with both increased bone loss and increased fracture risk as well as Mediterranean and plant based diets. Objective: To assess effects of increased intake of vegetables/herbs and fruit on adiponectin levels and urinary calcium excretion in three groups of post menopausal women. Design: Two intervention groups (A,B) of healthy, postmenopausal women (N=50) increased intake of vegetables/herbs and fruit to ≥9 servings/day (three months) with one group selecting from a specific range containing phytochemicals attributed with lowering bone resorption. A control group (C) (N=43) consumed their usual diet. Primary outcome variables included adiponectin and urinary electrolytes (calcium and potassium). PRAL was determined from three day diet diaries. Outcomes Urinary potassium excretion (mmol/day) increased in groups A and B (86, 85) but also C (104, P>0.05), however calcium excretion reduced in A and B (-26,-24%) compared to C group (2%, P<0.05). Groups A and B had lowered estimated PRAL (-17,-22mEq/day) compared to C (-1.6mEq/day, P<0.001). Adiponectin levels were modulated downward in all three groups. Adiponectin reduced the most in intervention group women with osteoporosis and significant osteopenia compared to women with normal bone mineral density (P<0.003) There were no significant differences between the two intervention groups in adiponectin or calcium excretion. Conclusion: Calcium excretion decreased in intervention groups with lowered PRAL. Decreased levels of adiponectin and increased urinary potassium excretion were seen in all three groups. The reduction in adiponectin differs from previous observational research showing increased levels associated with plant based diets and may reflect a more positive environment for bone maintenance at midlife. Trial No: ACTRN 12611000763943 Source of funding: Hawke’s Bay Medical Research Foundation (HBMRF) AMGEN, (Osteoporosis Australia, Glaxo Smith Kline Australian and NZ Bone Mineral Society) Massey University Research Fund (MURF)