Grass-fed vs. grain-fed beef
Q. Is grass-fed beef included in the recommended limit on red meat consumption?
A. Yes. The most recent recommendations based on a research-grounded, peer-reviewed report on how diet can influence cancer risk advise no more than 18 ounces per week of red meat. That includes beef, pork, lamb and goat.
Nutrient content of grass-fed beef does differ in several ways from grain-fed beef: It tends to be lower in saturated fat and slightly higher in omega-3 fat and conjugated linoleic acid (CLA), the latter two both considered healthy types of fat. Content of some vitamins and minerals differ, and interesting discussion is underway about possible environmental differences.
The population studies that form part of the basis for the recommended limit on meat consumption don't differentiate between people consuming grass- or grain-fed beef, and it is likely that grain-fed beef is by far most represented. However, the report only makes recommendations supported by biological evidence of how a cancer link works.
A switch from grain- to grass-fed beef does not resolve concerns about red meat, such as the high amount of heme iron found in red meat. Regardless of your choice, for now it makes sense to keep all the red meat you eat within the recommended 18-ounce per week limit.
Q. Can you explain how to check the vitamin A content information on food and supplement labels against recommended amounts, since they seem to be listed in different units?
A. It can be confusing! When the current vitamin A recommendations were released in 2001, we switched from a system that referred to International Units (IU) to one that uses micrograms of Retinol Activity Equivalents (RAEs). Vitamin A from animal sources, such as milk, meat and eggs, is well-absorbed in the body in the form of retinol. Beta-carotene, which comes from plant sources, is another form of vitamin A. When vitamin A comes from retinol, the current recommended amounts translate to 2330 IU for women and 3000 IU for men.
Nutrition Labels also express vitamin A as %DV (percent of Daily Value), which tries to show what proportion of the amount recommended in a healthy adult diet is in one serving. But the DV for vitamin A is based on the old, higher recommendations: 5000 IU. The 2001 recommendations for vitamin A were lowered because research linked excess amounts of retinol with bone weakening.
So when it comes to vitamin A, don't aim for 100% DV. You will meet current recommendations when foods and supplements add up to about 60% DV.
Some food and supplement labels do separate vitamin A into its sources: retinol and beta-carotene. Although the studies linking bone weakening relate to retinol, studies have found high levels of beta-carotene from supplements - not food - also raise health concerns for some populations.
Q. Is it true that coffee blocks calcium absorption?
A. Caffeine-containing coffee does seem to slightly decrease absorption of calcium, but the effect amounts to about 2 milligrams to 5 milligrams (mg) less calcium for each six-ounce cup of coffee. The recommended amount of calcium for adults (ages 19 to 50) is 1,000 mg daily, so even multiple cups of coffee add up to relatively small amounts.
You may have heard of this effect from past studies that linked coffee consumption to lower calcium levels and weaker bone strength. These studies were few and relatively short-term. More recent studies show past findings were often more about coffee-drinkers getting less calcium, rather than a sign of any biological effect of the coffee itself.
• Karen Collins, registered dietitian, writes this column for the American Institute for Cancer Research. To submit a question, please write to Ask the Nutritionist, c/o the Daily Herald, 1759 R St., N. W., Washington, D.C. 20009. Questions will not be responded to personally.