Dear Doctor: How should chocolate be processed to preserve its healthful properties? I've read that a non-alkalizing process is better than an alkalizing process, but I don't understand the difference.

Dear Reader: Ever since studies revealed that chocolate can convey health benefits, a certain segment of the population (hello, fellow chocolate lovers) has been doing a happy dance. Researchers have found that biologically active compounds in chocolate, known as flavonoids, can lower cholesterol, prevent memory decline and reduce the risk of developing heart disease. (Cocoa is also a good source of potassium, magnesium and phosphorus.) But while the headlines simplified the findings to just plain "chocolate," the facts of the matter are a bit more complex.

Chocolate is the end product of a multistep process that begins with the colorful, podlike fruit of the cacao tree. Farmers harvest the cacao pods and separate the seeds from the fleshy (one reference we read used the word "mucilaginous") white pulp via a multiweek process of fermentation and drying. The seeds are then roasted and ground into chocolate liquor, a thick liquid comprised of cocoa butter and cocoa solids. From there, it's up to each manufacturer how this liquid will be manipulated, and how much sugar and other ingredients will be added to create the final product that we call chocolate.

Which brings us back to those flavonoids. They are a class of plant nutrient contained in most fruit and vegetables. Not only do they give our fresh food those bright colors, they're also powerful antioxidants that help boost the immune system and act as anti-inflammatories. One of the subgroups of flavonoids are flavanols, which are found in grapes, apples, berries, tea, red wine and -- here's why they're important to this discussion -- cocoa. And like many micronutrients, they can be damaged during cooking or processing.

Cocoa is naturally acidic, which can give the natural products a rough edge. Natural cocoa powder is basically a cocoa bean concentrate. It's light brown, slightly fruity and has a penetrating and bitter flavor. To take the edge off that bitterness, some manufacturers treat the cocoa with an alkalizing agent. Cocoa that has been alkalized is also known as Dutch-process.

This type of processing makes the cocoa powder darker, decreases the bitterness, and makes it smell and taste more "chocolatey." However, it does have a negative effect on flavanol levels. In some analyses, cocoa that had been alkalized had half of the amount of flavanols as did natural cocoa. So, if your chocolate intake is specifically for its health effects, then natural cocoas are the way to go.

Whether alkalized or not, pure cocoa is extremely bitter. To make it palatable, chocolate products are highly processed. In addition to fermenting, roasting and alkalization, all of which can reduce flavanol levels, cocoa is combined with sugar, fat and various milk products. The result are foods whose fat and sugar levels may outweigh whatever advantages the flavanols would confer.

Bottom line? Despite its purported health benefits, chocolate is not a food group. (Sorry, chocoholics.) Instead, think of it as a condiment. Go for the darker, less processed varieties, and just enjoy a square or two at a time.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I've been diagnosed with polycythemia vera, which I understand is very rare. I'm currently being treated with phlebotomies. Please explain this diagnosis and what science has learned about it.

Dear Reader: To understand polycythemia vera (PV), you must first understand how bone marrow works. For starters, the marrow is full of stem cells that eventually become red blood cells (which carry oxygen), platelets (which help the blood to clot) and white blood cells (which fight infection). Initially, however, the stem cells become either lymphoid cells (which develop into lymphocytes, a specific type of white blood cell) or myeloid cells (which develop into red blood cells, platelets or white blood cells that are not lymphocytes). PV occurs when the myeloid cells reproduce preferentially, producing more of their type of cells.

This causes a significant elevation in the number of red blood cells and, to a lesser degree, platelets and white blood cells. The origin of this proliferation is linked to a mutation in the JAK2 gene, which is only occasionally linked to a genetic susceptibility within families. More often than not, it's a random mutation.

The greatest complications of PV are due to the increased concentration of red blood cells and platelets within the blood stream. This increases the risk of blood clots, which can lead to strokes, heart attacks and a sudden loss of blood flow to other organs or to the extremities. About 16 percent of people with PV develop an arterial thrombosis, or blood clot in an artery. About 7 percent develop blood clots in the veins, which can lead to clots in the legs or lungs or in the vein to the liver and spleen.

Speaking of the spleen, 36 percent of people with PV develop an enlarged spleen. Because this organ stores red blood cells and filters out old ones, the high concentration of red blood cells mean that these cells become sequestered in the spleen, causing it to enlarge and compress surrounding structures.

One of the more irritating symptoms of PV is itching, which worsens with exposure to warm water. A more troublesome symptom is a burning sensation in the hands or feet due to alterations of blood flow in the small blood vessels in the feet or hands. This condition, called erythromelalgia, affects 29 percent of patients.

Once a practitioner is clued into the possibility of PV, he or she may order a bone marrow biopsy as well as further blood work, including checking for the mutation in the JAK2 gene.

Phlebotomy is often necessary to lower the red blood cell count, which significantly decreases the risk of blood clots. Low-dose aspirin (81 milligrams) can provide benefit too, not only by reducing the chance of clotting, but by reducing the itching of PV. And, for people over 60, or those with a history of clots, the medication hydroxyurea can help by lowering the red and white blood cell and platelet counts.

As you mention, PV is rare, occurring in 1 out of every 50,000 people per year on average. Although the condition can be life-threatening -- for all the reasons explained above -- the phlebotomies (inconvenient though they are) can help keep the disease under control.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My blood test results always include levels of HDL and LDL cholesterol, but what about lipoprotein(a)? Don't high levels triple the risk of a heart attack or stroke at an early age? If so, shouldn't doctors test for it?

Dear Reader: The short answer is: for some people, yes.

The longer answer starts with some background: Lipoprotein(a) is a type of blood protein similar to the low-density lipoprotein (LDL) commonly measured in a cholesterol test. Because its structure resembles that of the proteins plasminogen and tissue plasminogen activator (TPA), which are involved in the breakdown of blood clots, lipoprotein(a) competes with those proteins and decreases their ability to break down clots. In other words, lipoprotein(a) boosts the blood's clotting ability. This could potentially aid wound healing and repair of tissues, but no specific need for lipoprotein(a) has been found.

The big concern with lipoprotein(a) is its potential to encourage clot formation within the arteries, raising the risk of heart attacks and strokes. A 2009 study in the Journal of the American Medical Association reviewed the results of 36 studies assessing the role of lipoprotein(a) and vascular disease in a total of 126,634 people. The authors found that, with every 3.5-fold increase in the level of lipoprotein(a), there was a 13 percent relative increase in coronary heart events and a 10 percent increase in stroke rate. The authors concluded that the high lipoprotein(a) levels were an independent risk factor for heart attacks and strokes, but not as strong a risk factor as other cholesterol markers.

However, very high levels of lipoprotein(a) are a significant risk factor for coronary heart disease, as illustrated in an Italian population study. The 2014 study measured lipoprotein(a) in 826 people and then followed them for 15 years. Those with lipoprotein(a) levels greater than 45 mg/dl -- totaling 20 percent of the study group -- had 2.3 times greater odds of stroke or coronary heart disease compared to those with lower levels.

As for why some people have higher lipoprotein(a) levels than others, the answer is in our genes. Variations of lipoprotein(a) levels appear to be related to a part of a gene called apo(a). Two different variations in this gene can cause elevation of lipoprotein(a). A grouped analysis found that people with one of the variations had 50 percent greater odds of coronary heart disease, while those who had both variations had 2.5 times greater odds.

So, to answer your question: If you have a family history of early heart disease, your doctor should consider checking your lipoprotein(a) level, especially if you have no other risk factors. People who have had a heart attack without any other risk factors also should have their levels checked.

As for lowering the lipoprotein(a) level, niacin can do this at high doses (2 to 4 grams per day), as can cholesterol-lowering PCSK9 inhibitors. Note, however, that no studies thus far have assessed the benefits of doing so.

Instead, people with very high levels of lipoprotein(a) may find greater benefit in significantly lowering their overall cholesterol with statins. Statins won't lower the lipoprotein(a) level itself, but they provide greater health-related bang for the buck. Lastly, because elevated lipoprotein(a) levels increase the risk of clot formation in the arteries, people at high risk may also find it prudent to take aspirin as a blood thinner.

In summary, for most people, overall cardiovascular health should be the focus in reducing the risk of heart attack and stroke, not lipoprotein(a).

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)