Many nutritional studies correlate food intake with health outcomes, but don't attempt to track the way in which the food was prepared. Understanding how different food preparations and combinations affect absorption and availability of beneficial nutrients is important. Recently, more research has been devoted to studying the specific bioavailability of foods after they are prepared by common methods. Knowing how to prepare foods can make a big difference in nutritional and health effects.
For example, to test the carotenoid content of red peppers, a group of researchers subjected peppers to one or two common food processing techniques: boiling for 10 minutes in water, or freezing for 4 months.1They then tested how well the compounds of interest were absorbed into intestinal mucosal cells through an in vitro simulation of digestion.1 They found that boiling decreased bioavailability of xanthophylls, while carotenoid bioavailability was increased by freezing.
Another set of researchers heated 115 foods deemed to have anti-inflammatory properties and looked at what beneficial compounds remained after cooking.2They found that English Breakfast tea leaves, onions, oregano, oyster mushrooms, red sweet potatos, lime zest, honey-brown mushrooms, button mushrooms, cinnamon, and cloves had the highest levels of anti-inflammatory compounds remaining after cooking.2 Another group examined the absorption and effects of whole turmeric versus curcumin alone in rats. They found that the complex compounds present in whole turmeric have stronger and somewhat different anti-inflammatory effects than curcumin alone.3
Other studies have shown that flavonoids vary dramatically in speed of absorption and total bioavailability, and that combining these phytonutrients with other foods greatly impacts both qualities.4 For instance, catechins from green tea are more bioavailable when consumed with steamed rice.4 An avocado added to a meal increases human blood levels of vitamin A from tomatoes and carrots compared with eating the same foods without avocado.5Thus, eating combinations of foods that assist absorption can be very powerful. But the company that a phytonutrient keeps is not the only variable that impacts bioavailability; other factors include the intestinal microflora4 and the chemical form of the food compound.1
For these reasons, it is best to consume whole foods and combinations of diverse foods, as well as chosing food preparation techniques that improve absorption and bioavailability, support the microbiome, as these factors are likely to be just as important as genetic variations in influencing each individual’s response to dietary and nutritional treatment.
- Pugliese A, O'Callaghan Y, Tundis R, et al. In vitro investigation of the bioaccessibility of carotenoids from raw, frozen and boiled red chili peppers (Capsicum annuum). Eur J Nutr. 2014;53(2):501-10.
- Gunawardena D, Shanmugam K, Low M, et al. Determination of anti-inflammatory activities of standardised preparations of plant- and mushroom-based foods. Eur J Nutr. 2014 Feb;53(1):335-43.
- Martin RC, Aiyer HS, Malik D, Li Y. Effect on pro-inflammatory and antioxidant genes and bioavailable distribution of whole turmeric vs curcumin: similar root but different effects. Food Chem Toxicol. 2012;50(2):227-231. doi:10.1016/j.fct.2011.10.070.
- Thilakarathna SH, Rupasinghe HPV. Flavonoid bioavailability and attempts for bioavailability enhancement. Nutrients. 2013;5(9):3367-3387. doi:10.3390/nu5093367.
- Kopec RE, Cooperstone JL, Schweiggert RM, et al. Avocado consumption enhances human postprandial provitamin A absorption and conversion from a novel high-β-carotene tomato sauce and from carrots. J Nutri. 2014;144(8):1158-1166. doi:10.3945/jn.113.187674.