DEAR DR. BLONZ: I have been diagnosed with macular degeneration. Upon searching for help, I found that eating pistachio nuts and Brazil nuts is recommended to stave off the expected decline of my sight. Although I don't care for either of those, my question is: How much and how often should I eat these two nuts? I read that three Brazil nuts daily are recommended but have no information on the quantity of pistachios. Any information from you will be appreciated. My ophthalmologist hasn't talked to me about what to eat. -- J.G., via email

DEAR J.G.: While they can provide healthful benefits to any diet, there are no exceptional powers in pistachios or Brazil nuts per se as regards macular degeneration. However, I do have a couple of resources for you. First is an article on age-related blindness (b.link/bay43); next is a link to the American Macular Degeneration Foundation that provides material about macular degeneration, but also has information about a cookbook focused on this issue (macular.org/good-food).

DEAR DR. BLONZ: About a year ago I was introduced to Hawaiian black salt. While I am not a heavy salt user, I like the taste and texture. One of the ingredients is activated charcoal. Is it OK to eat activated charcoal? -- R.L., San Ramon, California

DEAR R.L.: Activated charcoal is specially processed to increase the size of the pores on its surface, which effectively increases the total surface area. This type of charcoal has a greater ability to bond with and hold on to certain substances on its surface. It is used commercially in water filters because it attracts and holds heavy metals and unwanted minerals and odors. The activated charcoal itself is not absorbed; it travels down the gastrointestinal tract and is eliminated. Taking in significant amounts of activated charcoal can make certain substances consumed at the same time unavailable for absorption. However, given the small amount that would be consumed in a salt, plus the issue of whether the charcoal in the salt is, indeed, “activated,” makes this less of an issue. On the cautious side, it would be prudent to not use this salt in or around the time you are taking medications. I must admit that I am skeptical that your salt has actual “activated” charcoal. One reason is that activated charcoal does not taste that great, and can affect the flavors of other items you are eating. Hawaii has amazing black-sand beaches, and I would predict that this is plain charcoal present in the regions where the salt was harvested.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: We would appreciate some information regarding the subject of naturally appearing arsenic. I have heard reports on the radio and elsewhere regarding natural arsenic in fruit juices. Could you please give some perspective and guidance on this issue as it affects children? -- P.M., via email

DEAR P.M.: The adage “the dose makes the poison” definitely applies, but with children, it’s a dose in relation to a smaller body in the process of growth. A cup of juice is the liquid extract of several pieces of fruit. For example, a child will not typically consume four apples at a sitting, but an 8-ounce glass of apple juice typically contains the fluids extracted from three to five medium apples. The whole fruit contains pulp, fiber and skin, but juice does not come with all the good stuff in the whole fruit. Added concerns are the sweetness and attraction of a sweet liquid that gets consumed like water, not to mention the potential negative impact on developing teeth. Children also have a smaller body size, which makes the concentrations higher; a greater risk in growing bodies. Bottom line, more of any heavy metal contaminant, such as arsenic, will be taken in with a volume of fruit juice than a similar volume consumed as whole fruit. I would monitor the sites of juice manufacturers you are considering to see if they are taking steps to reduce the arsenic levels in their products. You can push this forward by writing to them to express your concerns. More on arsenic in apple juice at b.link/arsenic48.

DEAR DR. BLONZ: I am doing the best I can with a big change in diet and activity but want to know what controls how much cholesterol the body manufactures. How can it manufacture more cholesterol than it gets in food? -- S.T., Charlotte, North Carolina

DEAR S.T.: Even if there were no cholesterol in your diet, your body would need to continue making it. This is because cholesterol is an essential structural element in every cell of the body. In addition, cholesterol is a raw material for a number of hormones, including estrogen and testosterone. Most of the cholesterol in the body is manufactured in the liver. When cholesterol is present in the foods we eat, the liver is programmed to make less. There are also genetic conditions in which the body makes way more cholesterol than it needs, but these tend to be rare. More common is the condition in which the body is forced to cope with an unbalanced diet that's light on the plant-based component, such as whole grains, fresh fruits and vegetables, but heavy on the rest. More on that debit side are stress-filled, unhealthful lifestyles with poor sleep habits. All these negatives contribute to blood cholesterol levels that are inconsistent with an interest in health.

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.

DEAR DR. BLONZ: I recently had heart bypass surgery after blockages were found in my coronary arteries. I am looking for my own brand of a healthy lifestyle to make sure that this is my last visit to an operating table. One natural component is diet, and I have read all these handouts and websites about fats. I have read that the oils in certain cold-water fish are beneficial. One of my favorite foods has become sardines because they are easily available in the supermarket. I looked at the label of the brand I buy, and I have determined that I have been having 11 grams total fat, 2 grams saturated fat and 131 milligrams cholesterol. Given my history, should I discontinue eating sardines? -- M.M., Tulsa, Oklahoma

DEAR M.M.: There is no need to stop eating sardines if you enjoy them. The totals you cite are for a 3.5-ounce tin. According to my nutrient database, aside from its 11 grams of fat, one tin of sardines also contains about 23 grams of protein and 350 milligrams of calcium, along with other nutrients. Sardines have a moderate fat content, and they do contain the heart-healthy fats EPA and DHA, collectively known as the omega-3s. The key to a healthy diet, however, is variety and moderation. You could be eating a variety of fish, not only sardines, but the emphasis should be that your meals include whole foods, such as fruits, vegetables and fiber-rich grains. Combine this with the non-food essential element -- a daily serving of physical activity -- and you'll be on the road to the healthy lifestyle you seek. I don’t know how recently you went through your bypass, so proceed with caution, taking into account the advisories of your physician. Consider also enlisting the guidance of a trainer with expertise in this area as you weave this important aspect of healthful living into your daily life.

DEAR DR. BLONZ: This is to help settle an office argument. Does the extra virgin vs. virgin grade of an olive oil reflect the fatty-acid proportion as well as other health values? -- F.S., Tucson, Arizona

DEAR F.S.: A couple of things to consider here. First, the main fatty acid in all types of olive oil is oleic acid, which is a monounsaturated fatty acid. The grade of an olive oil reflects the level of “acidity,” which indicates the level of free fatty acids, those not attached to a triglyceride in the oil. Higher grades of olive oil have only a small amount of free fat. Extra-virgin olive oil must have no more than 0.8 percent acidity. Virgin olive oil can have no more than 2 percent acidity. This means that, as a general rule, all grades of olive oil will have comparable proportions of monounsaturated, saturated and polyunsaturated fatty acids. When considering potential health attributes, I favor the extra-virgin olive oil (EVOO). This is the first oil out during the pressing of the olives. EVOO has higher levels of the olive’s protective assets, the main one being the plant polyphenols that are there to protect the olive and its seed. Research evidence suggests that these substances can be beneficial for us as well (see b.link/olive30).

Send questions to: “On Nutrition,” Ed Blonz, c/o Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to questions@blonz.com. Due to the volume of mail, personal replies cannot be provided.