November 21st, 2019

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Title:
Twinning and Higher Intake of Dairy Products
Authors:  Daniel A. Goldstein, M.D., David F. Kowalczyk, V.M.D., Ph.D., John L. Vicini, Ph.D., Fran C. Buonomo, Ph.D., and Donna R. Farmer, Ph.D.
  To the Editors:
We have read with interest the paper by Dr. Steinman1 suggesting that an increase in twinning is associated with higher intake of dairy products, perhaps as a result of increased levels of insulin-like growth factor-1 (IGF-1) in milk following the introduction of recombinant bovine somatotropin (rbST) to enhance milk production. It does not appear that a dose-response analysis for IGF-1 was performed. When such an analysis is considered, we believe that any effect of milk on circulating IGF-1 is clearly negligible and that the rbST hypothesis is highly unlikely.
The impact of milk consumption on circulating IGF-1 levels in women is believed to be negligible based upon the poor absorption of this protein from the gastrointestinal tract and upon confirmatory animal studies.2 Storm et al3 demonstrated that four 8-oz glasses of milk daily for 2 years produced no alteration in circulating IGF-1 levels in adult women.
Keywords:  insulin like growth factor-1, twinning, bovine somatotropin
   
   
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