DEAR DR. BLONZ: There have been a number of articles lately questioning the wisdom of taking vitamin and mineral supplements. And although it seems to be at cross-purposes, I have also read about the benefits of wheatgrass juice. The product literature states the body will absorb about 90 percent of the nutrients from wheatgrass, which is much more than other foods or pills. Is there any truth to this? Is this food a better source of nutrients than others? -- M.S., Spokane, Wash.
DEAR M.S.: There is no evidence I am aware of that the nutrients in wheatgrass are absorbed more efficiently than those from other whole foods. If by "questioning the wisdom of taking vitamin supplements" you mean questioning the wisdom of relying on supplements to provide all that the body needs, that is certainly something I am in agreement with. I have never recommended supplements as a primary source for nutrients. There is no basis to believe that a lousy diet can be made "healthful" through supplements. With few exceptions, preparing, eating and enjoying whole foods will always be superior. The exceptions might be when there are elevated or specific needs for certain nutrients.
As regards that rate of absorption for the nutrients in wheatgrass versus those in vitamin or mineral supplements, we need to assume that they are constructed so that they will be in solution by the time they reach the absorptive surfaces of the small intestines. Taking a supplement at mealtime aids this process. Supplement manufacturers should provide data to affirm that their products dissolve. In general, there should be a comparable rate of absorption between the vitamins or minerals in foods, and those coming from dissolved supplements. There are exceptions. The absorption of naturally occurring folate in foods turns out to be less efficient than that of the synthetic folate found in fortified foods and supplements. Vitamins tend to be more bioavailable, but minerals are not always efficiently absorbed.
The form a nutrient is in, and the presence or lack of key food components, can affect absorption. For example, calcium is more efficiently absorbed from milk or milk products primarily because the lactose in the milk enhances calcium uptake. The form of iron found in meat, known as heme iron, is more efficiently absorbed than the iron found in fruits and vegetables. Non-heme iron absorption is enhanced in an acid environment, such as that found in citrus juices or tomato sauce. Please don't fret over every last bit of absorption. It does, however, strengthen the argument for variety.
As for wheatgrass juice, it's definitely an acquired taste. Depending on how much is consumed, it can be a source of certain nutrients and it does contain phytochemicals, but I question any acclaim for it being "magical." If you are taking or considering this product, or a similar powdered whole food supplement, I encourage you to visit consumerlab.com to see their recent report on contaminants found in some of these products (tinyurl.com/l3yzswy).
Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to firstname.lastname@example.org. Due to the volume of mail, personal replies cannot be provided.