Q: What is the difference between cream cheese and Neufcha tel cheese?

A:They are quite similar, except that Neufcha tel is lower in fat and higher in moisture. Both are unripened cheeses made from a mixture of milk and cream. Processing begins with the addition of lactic-acid starter and sometimes milk-clotting enzymes. Once the cheese has coagulated, it is warmed, stirred and drained. The resulting curd is then chilled, salted and worked some more. Last, one of several whey mixtures is added to adjust the final moisture content. According to federal Standards of Identity, stabilizers may be added to prevent moisture from separating from the cheese.

The differences in fat content in these two kinds of cheese do show up in calorie count. An ounce of cream cheese contains 99 calories, nearly all of them from 10 grams of fat (the cheese would contain only two grams of protein). The same amount of Neufcha tel has 74 calories and less than 7 grams of fat. Neither of these cheeses, by the way, is a particularly good source of calcium.

Q: In answering a recent question, you commented that there are many reasons to doubt the value of hair analysis. Could you please tell me what they are?

A: We can cite several grounds for believing that hair analysis is not a valid technique to identify bodily nutrient excesses or deficiencies, and why it should not be used as the basis for recommending nutritional supplements.

Perhaps most fundamental is that the use of a single diagnostic tool such as hair analysis violates the basic principle of competent medical practice in which laboratory tests are only part of the patient profile (and which the physician always remembers are subject to error). Physical findings and patient history must be taken into account in making a diagnosis.

Beyond that, as pointed out more than 10 years ago in a statement by the American Medical Association Committee on Cutaneous Health, "the state of the health of the body may be entirely unrelated to the chemical condition of the hair." For most elements, no correlation has been established between hair composition and other known indicators of nutritional status. In fact, hair nutrient levels can be affected by numerous commonly used substances, including shampoos, bleaches and dyes. There is no way to determine the source of minerals found in hair samples.

An important problem in interpreting results is that minerals in hair vary in individuals according to personal factors, including age and sex as well as the color, diameter and rate of hair growth, and by season and local geography. And because the hair grows slowly, even that closest to the scalp may not be useful for diagnostic purposes.

Finally, most commercial laboratories have not validated their analytical techniques against a reference standard. And some of the methods used to prepare samples can introduce errors.

Q: I recall reading in your column recently that the ingredients other than peanuts that are allowed in peanut butter were quantitatively unimportant. Then I saw a television program that seemed to suggest that if one is interested in eating more polyunsaturates, it is better to buy the old-fashioned variety that contains only peanuts. Can you please straighten this out?

A: Partially hydrogenated oil is added to peanut butter to help maintain the homogenous mixture and easy spreadability many people prefer. Under the legal "recipe," or Standard of Identity, for peanut butter, the total weight of allowable ingredients other than peanuts, including seasonings, stabilizers and shortening, cannot exceed 10 percent of the finished product. Translated into household terms, that is just 1.6 grams, or about 1/4 teaspoon per tablespoon of spread, for all of these ingredients.

In short, when viewed in the context of your total diet and compared with a myriad of other choices that affect the type of fat you consume, whether the peanut butter you choose has partially hydrogenated shortening added to it is unlikely to have an important effect on the fatty-acid composition of your diet.