DEAR DR. BLONZ: I continue to read that we should not mix carbohydrates and proteins together. Is this the current thought among scientists? -- S.W., Portland, Oregon
DEAR S.W.: The idea that you should not mix carbohydrate foods with protein foods makes little scientific sense, and it runs contrary to the way the human digestive system is designed.
The foods we consume are systematically broken down until their component parts are suitable for absorption. It begins before any food is even consumed: Just thinking about eating and being exposed to the aromas, sights and sounds of food primes the digestive system for the meal to come. These sensory experiences, often referred to as the cephalic phase of digestion, stimulate the secretion of saliva (hence the term "mouth-watering"), along with other secretions important for digestion. Once some food has been eaten, the action of chewing keeps this going, while physically breaking apart the food from large to smaller pieces.
With the physical breakdown of the food come chemical treatments, featuring an enzyme in saliva and stomach acid designed to denature protein and break down complex compounds. Then comes exposure to a series of digestive enzymes, which are chemical compounds, each designed to disassemble a specific chemical bond holding protein, fats or carbohydrates together. This is all done in a sequential, "assembly line" arrangement; all digestible nutrients get attention before arriving in the areas of the small intestine where nutrients are absorbed.
The mixing of foods is not an issue at any stage of this process. Consider that many healthy, whole foods are combinations of protein, fats and carbohydrates. After you digest the above, I trust you will realize that this particular misinformation contains no "nutrients" you need to absorb.
DEAR DR. BLONZ: Why is palmitate an ingredient in powdered milk? -- M.L., Vancouver, British Columbia
DEAR M.L.: Palmitate is connected to palmitic acid, a saturated fatty acid. It is found in a number of foods, but the name comes from its primary source: palm oil.
Palmitic acid becomes "palmitate" when combined with another compound. In milk, vitamin A (or retinol) is combined with palmitic acid. The resulting compound can be called "vitamin A palmitate" or "retinol palmitate," or the milk product can list vitamin A and palmitate as separate ingredients. You can also see palmitate in other compounds, such as "ascorbyl palmitate," which is a combination of palmitic acid and vitamin C (ascorbic acid).
The amount of palmitate added to powdered milk is negligible. It is only there as an "escort" for the small amount of vitamin A added to the product. It helps to appreciate that palmitate is not a foreign substance to the human body: In fact, palmitic acid makes up about 25 percent of the fats found in breast milk. It's also present in human lung surfactant, a substance that coats the inside of our lung surfaces and allows us to breathe.
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