Mom Was Right: Eat Your Broccoli and eat at least some of it raw. Why?Two studies published this year help us both understand how one of the important molecules we obtain from broccoli (and other Brassica vegetables like kale and all those listed on the right side of this blog) helps optimize our health and also how to maximize the level in our body.
(1) The first study (Oral sulforaphane increases Phase II antioxidant enzymes in the human upper airway. Clin Immunol. 2009 Mar;130(3):244-51. Riedl MA, Saxon A, Diaz-Sanchez D) found that the molecule sulforaphane increases enzymes that cut inflammation in our respiratory system that have been linked to increased risk of allergic rhinits, asthma, and chronic obstructive pulmonary disease (COPD). This was a human study that used varying doses of broccoli sprouts or alfalfa sprouts to test responses of various enzymes involved in these processes. The broccoli sprouts showed significant increase (~2-3 fold increase over baseline levels) in these detoxifying enzymes while the alfalfa sprouts showed no response.
(2) The second study (Bioavailability and kinetics of sulforaphane in humans after consumption of cooked versus raw broccoli, J Agric Food Chem. 2008 Nov 26;56(22):10505-9. Vermeulen M, Klöpping-Ketelaars IW, van den Berg R, Vaes WH) aimed to determine the bio-availability and kinetics (how fast it is metabolized) of sulforaphane from raw and cooked broccoli.
When consuming 200 grams of raw or cooked broccoli (approx 1/2 pound) with a warm meal, this study shows that consumption of raw broccoli results in faster absorption, higher bio-availability (37% versus 3.4%), and higher peak plasma amounts of sulforaphane, compared to cooked broccoli.
I will still consume some cooked broccoli (quickly stir-fried or very lightly steamed, in each case so the broccoli is still crunchy), but these studies add to data from other studies that at least some of these vegetables that we consume should be raw (and chewed well since that is a necessary step in the release of the sulforaphane molecule, thus developing maximum levels of sulforaphane to be absorbed into our body).
However, variety, variety, variety are still key for both types of foods to eat and preparation methods. It is well accepted that some nutrients or phytochemicals are better absorbed after cooking (lycopene from tomatoes is one example) because the cooking process breaks down the plant's cell walls, thus releasing the intra-cellular molecules to be more available for absorption.
At the very least, be sure to eat the decorative kale leaves that may come on your plate in a restaurant!
Where kale (along with broccoli and all other Brassica vegetables) are more than decoration on my plate!
Diana Dyer, MS, RD