When cauliflower is boiled, it loses a percentage of all nutrients except vitamin B-12 because they leach into the cooking water. Minerals hold up to heat and water better than vitamins, but boiling still decreases all mineral content by 5 to 10 percent.Steamed cauliflower retains 100 percent of all minerals.Youâll pour 10 to 20 percent of most vitamins down the drain when you boil cauliflower.inerals hold up to heat and water better than vitamins, but boiling still decreases all mineral content by 5 to 10 percent. Steamed cauliflower retains 100 percent of all minerals. Youâll pour 10 to 20 percent of most vitamins down the drain when you boil cauliflower.