When what you see isn't what you get

The subject today, ladies and gentlemen, is bioavailability. Please don’t let your eyes glaze over…this is important stuff. It’s importance was made clear to me over the past couple of weeks as people have become increasingly interested in the nutrient lutein. This member of the carotenoid family has been linked to a reduced risk of age-related macular degeneration—an eye disease that seems to be increasing at an unusual rate (I have a theory as to why that is, but we’ll discuss it later). Men are similarly interested in getting more of a substance called lycopene to reduce their risk of prostate cancer, and the upshot of all this nutrient interest is that folks are turning to pills! Bad move.

As you may be tired of hearing from me by now, nutrients are almost always better absorbed—or bioavailable—from food (the two possible exceptions are folic acid and Vitamin D). In a study at Tufts University Dr. Elizabeth Johnson gave her research subjects 6 milligrams of lutein a day, either from a supplement or from a third of a cup of spinach or from eggs. Everyone on the study had nine days of receiving each form of the lutein. At the end of the study it was found that the lutein was much more available to the body from both the eggs and the spinach than from the supplements. What I found particularly interesting about the study was that the spinach caused an increased blood level of lutein that was 40 percent higher than from the supplements, but the eggs had a 300 percent greater impact. What’s interesting about this is that most health professionals recommend spinach as a source of lutein because it contains way more of the stuff than does an egg…but the bioavailability of lutein from the egg is significantly greater.

Still with me? OK…here’s my theory as to why we’re seeing an increased incidence of age-related macular degeneration: in the first place people have been scared away from eating eggs because of an invalid concern about their cholesterol content, and then, to add insult to injury, they’ve been encouraged to consume lots of vegetable oil, which is rich in linoleic acid…and that’s been associated with macular degeneration! So then, in a nutshell: less egg consumption plus more vegetable oil intake equals increased age-related macular degeneration. My theory aside, if you’re looking to increase your lutein intake, you’re much better off with food than with pills. And food, of course, is a lot less expensive than supplements.

The same can be said for lycopene. The very best source of this substance is processed tomatoes. It’s not that fresh tomatoes aren’t good, or don’t contain lycopene, they do. When tomatoes are processed, however, the cell walls are ruptured and the lycopene becomes much more available to the body. It turns out that we can even say something good about ketchup…so if someone is forcing you to eat French-fries, you can comfort yourself that they’re just vehicles for your ketchup! Tomato sauce and tomato puree are other good examples of processed tomatoes and might explain the lower incidence of prostate cancer among Italian men.

Bioavailability is a particular issue where calcium fortification is concerned. You might recall me explaining in an earlier column that the amount of calcium a body receives from a particular food depends on both the absolute amount of calcium that food contains and the degree or percent bioavailability of the calcium from that food. So, for example, milk contains approximately 300 milligrams of calcium per 250 mL and has a bioavailability of 32%. Broccoli, on the other hand has a bioavailability of 50 %, but only 38 milligrams of calcium per half cup serving…so the body gets more calcium from the milk. With fortified beverages, whether soy or orange juice, no standards have been established to ensure a uniform, high quality of fortification, so the consumer may very well be misled in terms of the calcium benefit the beverage is presumed to give. Unfortunately I can’t give you any guidelines or cite superior brand names since studies have shown that the bioavailability can vary even from the same product. Of course, the fortification process is simply adding a supplement to a food, similar to your taking a pill separate from food. It seems that there are substances in foods that naturally contain calcium that help the body to absorb it more readily.
The bottom line, then, is that what you see isn’t necessarily what you get. Just because a pill claims to contain x amount of a substance doesn’t mean that all of that substance will make its way to your body. It’s been true since the Garden of Eden, where there were no supplements and food was truly natural, the best way to get all the nutrients you need is by eating real, wholesome food…not by relying on a pill out of a bottle