DEAR DR. BLONZ: Should there be any concerns about eating baked potato peelings? I wash and prick holes in my potatoes, then put them in a sandwich bag with a little water and cook them in the microwave. The resulting peel is soft and I enjoy the taste, often seasoning it with garlic or onion, salt and pepper. -- S.T., Redding, Calif.

DEAR S.T.: The vitamins, minerals and fiber in a potato come primarily from the flesh. Although not a nutrition powerhouse, the peel does contain a small amount of iron and fiber, and it provides a good contrast to the smooth texture of the flesh. There's absolutely nothing unsafe about eating potato peels provided they are clean, free from sprouts and have no greenish discolorations.

The green aspect is particularly important as potatoes can produce solanine, a bitter-tasting toxin that affects the nervous system. Solanine is produced when the potato is exposed to sunlight or allowed to sprout. It is most concentrated in the sprout, but it's also present in potatoes having a greenish tint to the skin. The solanine itself isn't green, but when that color is present, it indicates that the sprouting process has begun. You can slow the production of solanine by storing your potatoes in a cool, dark place. Carefully cut away all sprouts and green portions before cooking. And discard any potatoes that taste bitter.

Regarding your plastic bag cooking technique, I trust you have already read the carton or checked with the manufacturer to verify that the product is safe for microwave use. All plastic bags are not the same, and a number of brands will melt in the microwave.

DEAR DR. BLONZ: Is it all right to combine fruits and vegetables together in blended drinks for breakfast, lunch or dinner? -- B.H., San Diego, Calif.

DEAR B.H.: Yes, but from a taste perspective, it helps to do some experimenting to see which combinations work best.

DEAR DR. BLONZ: How much fiber and fat is in an avocado? Also, what is the minimum amount of saturated fat that a person should have in his or her diet? -- R.M., Oakland, Calif.

DEAR R.M.: There are many avocado varieties on the market, each having different qualities of flavor and texture. There tend to be generic differences, however, between the varieties grown in California and Florida. Florida avocados tend to be larger in size, with less fat, protein and slightly more carbohydrates than a comparable serving of California avocado. A 100-gram (3.5-ounce) portion of a California avocado will contain 6.8 grams of fiber, and 167 calories from 2 grams of protein, 8.6 grams of carbohydrate and 2.1 grams of saturated fat, 9.8 grams of monounsaturated fat, and 1.8 grams of polyunsaturated fat.

That same 100-gram portion of a Florida avocado contains 5.6 grams of fiber and 120 calories from 2.2 grams of protein, 7.8 grams of carbohydrate and 2 grams of saturated fat, 5.5 grams of monounsaturated fat, and 1.7 grams of polyunsaturated fat.

As for your second question, the human body has no minimum requirement for saturated fat.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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: My hairstylist recommended I get a biotin supplement to help strengthen my hair. I would like some insight as to whether this makes sense, and if so, why I hadn't heard of this until now. -- V.H., Oakland, Calif.

DEAR S.F.: Biotin is a vitamin that plays a role in the metabolism and synthesis of fats, amino acids and carbohydrates. As such, it is important that we have this nutrient in our diet. Biotin, however, is only needed in small amounts, and deficiencies are rare. An adequate intake of biotin for adults is 30 micrograms per day (one microgram is one millionth of a gram). Symptoms of a biotin deficiency include hair loss and skin rashes, but if there's no deficiency to start with, there is no evidence that taking amounts above normal body requirements can solve hair, skin or nail problems.

Foods that contain biotin include organ meat, oatmeal, egg yolks, milk, soybeans, peanuts, whole grains, fruits and vegetables. It is also known that biotin can be synthesized by the bacteria that live in our large intestine, though it's unclear how much of this biotin we actually absorb.

While we are on this topic, here is an interesting side note about biotin and eggs. While egg yolks are a good source of biotin, there is a compound in raw egg whites, called avidin, that prevents biotin from being absorbed. Biotin deficiencies have been found in individuals who consume large quantities of raw egg whites. Perhaps this was nature's way of keeping the fox out of the hen house.

DEAR DR. BLONZ: Can vitamin K creams help remove spider veins? -- C.S., Berkeley, Calif.

DEAR C.S.: Spider veins are small red blood vessels usually found on the legs near the skin surface. They fan out from a small branch of a blood vessel near the surface. Treatment involves locating and disrupting the blood supply. Spider veins are not a sign of poor health in and of themselves, but they can be a source of embarrassment.

Vitamin K plays a role in blood coagulation (clotting), and current treatments of spider veins involve coagulation, or blocking the blood flow to the visible vessels. One medical technique uses a laser to "photo-coagulate" the master vessel feeding the veins, while another uses a saline injection to bring about the desired blockage.

The idea that an externally applied vitamin K cream might clear up spider veins seems straightforward, but there is little in the way of evidence to support this use. It is also not advisable to take vitamin K by mouth in the hopes that it can eliminate spider veins. As a caution, individuals with a blood-clotting disorder, or those taking anticoagulants, should speak with their physician before using any product containing vitamin K.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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 have a question about eating oatmeal uncooked. I've been doing it lately, mainly due to time constraints, but also to avoid the heat of cooking because the air conditioning in our house struggles on hot summer days. Of course, oatmeal is more pleasing cooked, but beyond that, are there any health or nutritional concerns associated with eating it uncooked? -- C.M. Walnut Creek, Calif.

DEAR C.M.: Bypassing the high-heat cooking step places a greater onus on cleanliness, but assuming all is wholesome, it is definitely OK. I would advise a good chew and sufficient fluid with your "meal."

If you know you are going to be eating them uncooked, opt for rolled oats, or even a muesli-type trail mix that contains uncooked rolled oats. Quick oats, which are sliced and diced even more finely, are another option. All of these have an increased surface area, which decreases cooking time; if consumed uncooked, this also makes it easier for the body to access the grain's nutrients.

It is possible that switching to uncooked oats might give rise to a bit more gas production until your body adapts, since the whole grain might not be digested as efficiently. This leaves some components to end up as food for the flora that normally reside in the large intestine.

DEAR DR. BLONZ: Do you think it's safe to drink straight, pure vinegar? How many ounces per sitting or per day is it safe or advisable to imbibe? I'm asking because I'm one of those who can drink straight vinegar and not gag, and I'm willing to do so if it's good for my health. So what are the main claimed health benefits of drinking vinegar? -- D.S., San Francisco

DEAR D.S.: Vinegar is safe, but it has no nutrients or phytochemicals of note. One possible benefit of vinegar is described in studies reporting that about 2 tablespoons (one ounce) at mealtime was associated with a decreased glycemic index of a food. Glycemic index is the rate at which a food causes the blood sugar level to rise.

The first study, in the December 2005 issue of the Journal of the American Dietetic Association, also reported the same effect when peanut butter was included instead of the vinegar, and these effects were only found with a meal that was high in easily absorbed sugars and starches. Another small study in the November 2007 issue of Diabetes Care reported that 2 tablespoons of apple cider vinegar taken at bedtime by subjects with type-2 diabetes had a favorable effect on their blood glucose levels during the day. Next, there is a study in the May 2009 issue of Diabetes Research and Clinical Practice that looked at the mealtime consumption of vinegar and measured hemoglobin HbA1c, which is a measure of the average blood-glucose value over an extended period of time. The daily consumption of 2 tablespoons of vinegar over 12 weeks was associated with a small but significant decrease in the HbA1c value. Body weight did not vary.

There is a definite theme here, but be aware that the Web is loaded with reports proclaiming special abilities of vinegar to break down fatty deposits, mucus and phlegm and provide help with weight loss. There is no evidence for any of these, and there's also no evidence of benefit from drinking greater amounts.

Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 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.