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Q. Is grass-fed beef a good source of omega-3 fats? How does it compare to salmon?

A: There’s no real comparison. Grass-fed beef often has more of these heart-healthy fats than conventional beef, but the amount in any kind of beef is minimal compared to salmon or other fatty fish.

Grass-fed cattle are raised exclusively on grass (or hay) after weaning, not grain-finished in a feedlot, like most cattle in the U.S. are. The beef produced is leaner than conventional beef, yet its fat tends to have a higher proportion of omega-3s. In contrast, when cattle are fed grains at the end of their lives, their omega-3 stores rapidly decline.

The amount of omega-3s in beef varies depending on the cow’s diet, breed, the cut of meat, and other factors. But according to several analyses, a 3.5-ounce serving of grass-fed steak has about 80 milligrams of total omega-3s, on average—twice as much as in conventional beef. While that may sound impressive, the same-size piece of salmon has 1,000 to 2,000 milligrams of omega-3s.

Moreover, the type of omega-3s in grass-fed beef is predominantly alpha-linolenic acid (ALA), which is different from the types in fish (EPA and DHA). ALA may have some health benefits of its own, and our bodies convert small amounts of it into EPA and DHA—but it can’t replace the omega-3s from fish. And other foods, such as flaxseeds, walnuts, and canola oil, are better sources of ALA than grass-fed beef.

Better reasons to eat grass-fed beef than for its omega-3s: Grass-fed cattle are raised without antibiotics. And when pastures are well managed, beef production is less energy-intensive, less polluting, and more humane than feedlot operations.

Q: Why do antiperspirant labels advise people with kidney disease to talk to their doctor before using?

A: The FDA requires the labeling because antiperspirants contain small amounts of aluminum, which could be a potential problem for people with impaired kidney functioning, if the metal is absorbed. The warning does not apply to healthy people, whose kidneys are able to process aluminum more efficiently. As the main active ingredient in antiperspirants, aluminum temporarily plugs up sweat ducts to reduce perspiration.

Keep in mind that the warning may be overly cautious, since it’s not known if aluminum is even absorbed through the skin in significant amounts. Moreover, aluminum is widespread in water, air, soil, and food—and one study estimated that exposure to aluminum from antiperspirants is only 2.5% of what we typically get from food in a day. Buffered aspirin and some antacids also contain aluminum, and people with kidney disease should use them with caution as well.

Aluminum in antiperspirants does not cause kidney disease (or breast cancer or Alzheimer’s disease, though myths persist). But if you already have kidney disease, ask your doctor if you should avoid antiperspirants. Deodorants have no aluminum, but they lack the antiperspirant effect and merely help prevent odors.

Q: When I cook poultry, the meat around the bones sometimes has a pink tinge, even when cooked through. Is it safe to eat?

A: Yes. What you see is pigment from bone marrow, which can leach out as the meat is cooked, producing a pink, gray, or brownish tinge. This happens more often in poultry that has been frozen and defrosted before cooking, and is most common in smaller birds (broilers and fryers). Juices that run clear rather than pink are an indication that poultry is cooked.

Q: Are sebaceous cysts dangerous? Should I have them removed? How are they different from lipomas?

A: These lumps just beneath the skin, properly called epidermal cysts, are common and harmless. The most important thing is to check with a doctor to make sure they are cysts, and not something more serious.

Typically on the head, neck, or torso, the cysts are firm, round, and movable, and grow slowly, sometimes to an inch or more in diameter. They’re usually caused by injury to a hair follicle or some other damage to the skin. They are filled with fat and keratin, a greasy, cheeselike substance.

If a cyst is very visible or becomes infected, or if you are bothered by it for any other reason, it can be surgically removed. This is a simple procedure, but usually requires stitches. If it is simply drained, it will probably grow back.

Lipomas can look like large cysts, but are benign fatty tumors. They seem to run in families and also grow slowly; they can occur inside the body as well. A doctor will often be able to tell you whether you have a cyst or lipoma by its look and feel. Lipomas don’t need to be removed unless they are unsightly or uncomfortable.

Q: Can biotin help my brittle nails?

A: Many people claim it does, and some doctors recommend large doses of this B vitamin to treat brittle nails. But the evidence for this is slim. Biotin plays a role in energy production, protein synthesis, growth of skin, hair, and nails, and other body processes.

In a small Swiss study in the Journal of the American Academy of Dermatology in 1990, women with brittle nails who took biotin for several months had a 25% increase in nail thickness, reduced nail splitting, and improved nail structure, as seen under a special microscope. A few other old reports also hint at nail improvement with biotin, but they were small, too, and poorly designed—and there have been no follow-up studies. Still, the idea of biotin therapy for brittle nails is not so farfetched. It comes out of veterinary medicine, which uses high doses to correct hoof abnormalities in horses and pigs—and nails are similar in composition to hooves.

According to the National Academy of Sciences, an “Adequate Intake” of biotin for adults is 30 micrograms a day. Biotin is found in a variety of foods, including soybeans, nuts, cereals, dairy, bananas, and sardines. Eggs are one of the best sources, though eating raw egg whites regularly can actually cause biotin deficiency. Multivitamins usually contain 30 to 300 micrograms (300 micrograms is the Daily Value, the recommended intake used on food and supplement labels). The amount commonly recommended for brittle nails is a lot higher (2,500 to 3,000 micrograms a day).

Keep in mind: Brittle nails are often caused by dryness from winter weather, hot water, and detergents, as well as over-manicuring, artificial nails, and other nail products. They can also just be a normal part of aging. But if you have very brittle nails, talk to your doctor, since they are sometimes associated with fungal infections or a medical condition such as thyroid disease.

UC Berkeley Wellness Letter, June 2009