Archive 2007 2008 2009 2010

Q: Does adding milk to cocoa neutralize cocoa’s healthy compounds?

A: It’s unclear how much of an effect milk has on the absorption of cocoa flavonoids, the antioxidants in chocolate that have been linked to decreased risk of heart disease and other potential benefits; studies have been inconsistent. But you may not be getting much benefit to begin with, since most cocoa is treated with alkali ("Dutched" or "Dutch style"), a process that reduces the flavonoids.

A small study in Nature in 2003 found that when people consumed dark chocolate along with a glass of milk they had no rise in blood antioxidants, compared to eating dark chocolate alone; it was hypothesized that milk proteins bind to the flavonoids in cocoa, limiting their absorption. And a new study in the American Journal of Clinical Nutrition found reduced flavonoid absorption when people drank cocoa made with milk versus cocoa made with water.

Still, other studies have found no effect of milk on cocoa flavonoid absorption and no difference in blood antioxidant levels. One even hinted at a possible benefit of adding milk to cocoa.

Our advice: The health benefits of cocoa and chocolate are far from certain, while those of milk are known. So keep adding low-fat or nonfat milk to your cocoa as a good source of calcium and protein. To get more flavonoids, look for "natural" (not "Dutched") cocoa powder.

Q: I keep hearing that we should eat less red meat. Is lamb a red meat? How does it compare to other meats, nutritionally and environmentally?

A: Lamb is a "red meat" because it’s high in myoglobin, a protein in muscle that turns red when combined with oxygen. The same is true of beef, pork, veal, and game meats. Poultry and fish, the so-called "white meats," have less myoglobin.

The problem with red meat is that it is usually high in saturated fat. But this varies quite a bit. In fact, some cuts of lamb, beef, and pork are leaner than some higher-fat poultry (chicken wings or thighs, for instance, or duck). All meat contains about the same amount of cholesterol. On the plus side, red meat contains more iron and zinc.

If you like lamb, choose leaner cuts such as those from the leg and loin, and trim all visible fat. The American Lamb Board has been marketing lamb as "lean," claiming it has only 175 calories and 8 grams of fat (3 grams saturated) in 3 ounces cooked. But this is an average of all cuts and is misleading. Many lamb cuts, including some rib and shoulder cuts, have more than 250 calories and 15 grams of fat in 3 ounces; a few cuts have more than 300 calories and 25 grams of fat. And 3 ounces is a small portion.

As for the environment: All meat production is more energy-intensive and polluting than growing plant foods, especially when done in industrial feedlot operations—and nothing, perhaps, is worse than beef. Much lamb is pasture-raised in small operations, but it is increasingly being grain-finished in factory feedlots. And about half the lamb we eat is shipped all the way from New Zealand or Australia, which, even if production there is efficient, still adds to carbon emissions. You can try to find local pasture-raised lamb, but the best step to take for both your health and the environment is to eat less meat overall.

Q: Can exercise cause varicose veins?

A: Low-impact, moderate exercise, especially walking and swimming, may help prevent varicose veins and ease symptoms if you have them. It gently stimulates circulation, without increasing pressure on the legs. However, strenuous cycling or high-impact exercise such as running may make varicose veins worse. Talk with your doctor about the right exercise program for you.

Q: What are METs? I see them listed on the monitors on some cardio machines at my gym.

A: METs, short for metabolic equivalents, are a measure of the intensity of physical activity. One MET is the equivalent of resting metabolic rate—the rate at which the average person burns calories when at rest. At 2 METs, you’re working at twice your resting metabolic rate. In general, 3 to 6 METs is considered moderate exercise, depending on your age. Activities with METs higher than 6 include singles tennis, jogging, cycling (more than 10 miles per hour), and cross-country skiing.

Scientists often use METs to evaluate and compare the health benefits of various types and intensities of exercise. METs are also the units used in exercise stress tests to estimate a peak "exercise capacity"—that is, the maximum level of exercise a person can do. People with higher exercise capacity tend to live longer.

Q: I’ve heard that some high-calcium vegetables, such as dark leafy greens, contain oxalic acid or phytates, which keep calcium from being absorbed. How can I counteract this?

A: Oxalates and phytates, sometimes called anti-nutrients, can indeed interfere with the absorption of calcium, iron, and other minerals. Oxalates are highest in certain dark leafy greens such as spinach and beet greens; kale and turnip greens have less. Phytates are found in whole grains, nuts, seeds, and legumes.

Keep in mind that your body can use only a portion of the nutrients you eat, and that many factors influence absorption, including the presence of other nutrients. This is the principle of bioavailability. Foods high in oxalates are often the same foods that are high in iron or calcium. Though some of the mineral is chemically bound by oxalates, much of it still gets through and is absorbed.

With phytates, it’s a similar story. Whole grains are higher in phytates than refined white flour, but the mineral content of whole grains is also higher. In breads, leavening counteracts phytates and increases bioavailability, and so does fermentation, as with sourdough.

If you want to avoid high-oxalate greens, eat kale instead of spinach or beet greens, for instance. But the best way to get calcium and other minerals is simply to eat a varied diet, including dark greens. You’ll still probably need supplements to reach the 1,200 milligrams of calcium a day recommended for people over 50, plus 800 to 1,000 IU of vitamin D to help your body absorb calcium.

Note: People who form calcium oxalate kidney stones may have to limit their intake of oxalates.

UC Berkeley Wellness Letter, October 2009