source("http://192.38.117.59/~linearpredictors/datafiles/readVitaminD.R")

women <- subset(vitaminD, category == 2)
       
model <- lm(log10(vitd) ~ country + bmi + country:log10(vitdintake) -1 ,
            data = women)

## Effect of vitamin D intake
print(b <- confint(model))

## Effect of doubling the intake 
2^model$coef[6:9]

## and confidence intervals obtained by transformation of CI for b
2^b[6:9,]