Bioavailability: Using the Food We Eat In the Body We Have (Part Two)
October 30, 2018
By Mary Brighton, M.S., RDN
“It has been shown as proof positive that carefully prepared chocolate is as healthful a food as it is pleasant; that it is nourishing and easily digested... that it is above all helpful to people who must do a great deal of mental work.” Jean Anthelme Brillat-Savarin Physiology of Taste, 1825
Welcome to Part Two
Bioavailability: Using the Food We Eat in the Body We Have – How the Preparation of Food and Combining Nutrients Can Influence the Bioavailability of Food.
Part One is about the importance of digestion and absorption to obtain and use nutrients in the foods we eat - the bioavailability of food (click here to read Part One). In this sense ‘bioavailability’ refers to the degree nutrients are available based on a person’s digestion and absorption mechanisms. But did you know that the nutrients in our meals can also have varying degrees of bioavailability depending on how food is prepared, whether eaten raw or combined with other foods? For example, vitamins and minerals in leafy greens like spinach, chard and kale are more or less bioavailable depending on whether they are eaten cooked or raw. In some instances, cooking ‘transforms’ that food so we obtain more from it. Cooking can also destroy key nutrients, especially when high heat is involved. What is the general rule? As Michael Pollan says, “Eat food. Not too much. Mostly Plants.”
And I will add “Food needs to taste good to be enjoyed.” Variety, creativity, freshness and using a combination of different preparation and ingredients can increase the nutrition and pleasure we get from our meals.
If you are not sure what methods are the best, read my top 10 tips on food preparation and ingredient combinations, and then call for an appointment at 732-994-7855. I like to talk about our “Food is Medicine” philosophy and how to get the most nutrition from every bite you eat.
My Top Ten Ways to Get the Most Nutrients from Your Food:
Don’t boil or overcook any vegetable. High heat destroys water-soluble vitamins especially those in green vegetables. In
general, steaming is the preferred method of cooking vegetables.
Eat locally sourced produce. Fruits and vegetables begin to lose their nutrients when they are separated from their soil or root nutrient source soon after harvest. Buy local, eat quickly.
Match vitamin C foods like citrus and tomatoes with iron-rich plant foods like lentils and other legumes. When these ‘friends’ are together in the same meal, iron is better absorbed. This tip is especially important for vegetarians who rely on non-heme plant sources like lentils and other legumes for iron.
Soak dried beans before cooking. Beans contain phytic acid which is considered a beneficial anti-nutrient because phytic acids functions both as an antioxidant, but it also limits absorption of key minerals like iron and zinc. My advice: soak beans 12-36 hours in water, rinse them at least once to remove phytic acid. Keep your diet diverse, eat a variety of plants, nuts and grains in a plant forward eating plan. For vegetarians who need iron from legumes, soaking beans is an important step to maintaining adequate iron stores.
Store food correctly. Heat, light and oxygen destroy nutrients. Eat produce quickly or store in refrigerator. Keep food away from direct sunlight and enjoy cut fruit as you cut it, as soon as the fruit is exposed to oxygen it starts to lose vitamins.
Crushing, cutting or chopping vegetables maximizes nutrient bioavailability and release beneficial compounds. Some micro and phytonutrients are liberated by the physical act of damage to the cell walls of plants. Allium foods like garlic and onion emit protective compounds and help micronutrient bioavailability when they are broken by a knife or mortar. The physical act of chewing food also helps to increase the bioavailability because the food is broken down and is better digested.
Cook tomatoes. Tomatoes contain lycopene, a carotenoid and powerful antioxidant that protects against degenerative disease. Cooked tomatoes contain significant
more lycopene than raw tomatoes. By adding a healthy fat like olive oil to tomatoes lycopene is even more bioavailable because of pairing ‘like with like’ and better absorption thru the small intestinal barrier.
Pairing like with like increases bioavailability. Fat is unique because it is carried differently thru the intestinal wall than proteins or carbohydrates. Fat soluble vitamins and phytonutrients like carotenoids and lycopene, need ‘like with like’ to increase bioavailability. Fat must be present for the fat soluble vitamins and phytonutrients to be absorbed and carried thru the body in the lymph system. As an example, a green salad topped with tomatoes and carrots needs a healthy fat salad dressing to use the phytonutrients present in the salad.
Cooking or citric acid denatures proteins. Heat or acid denatures (breaks apart) proteins, rearranging them and allowing them to unfold. The exposed protein chains are more easily digested and bioavailable than raw proteins.
Chose frozen vegetables and fruits as an alternate for fresh. In non-growing seasons or just to have on hand for a quick meal, frozen vegetables are a viable go-to meal option because they are frozen quickly after harvest and retain much of their nutrients.
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