Dear Doctor: After a mammogram, I was told I have dense breast tissue and that instead of a regular mammogram, I need to start getting a 3D mammogram. Why would that be? What exactly is dense breast tissue, anyway?

Dear Reader: A woman’s breasts are made up of several different types of tissues. There are glandular tissues, which produce, store and deliver milk; connective tissues, which support the breast and help give it shape; and fatty tissues, which make up the rest of the breast. Fatty tissues help protect and support the glandular tissues, and they play a role in breast size. Breasts have no muscles, but they do also contain blood vessels, lymph vessels and lymph nodes.

Dense breast tissue is indicated when your mammogram reveals a high proportion of connective and glandular tissue, and a lower amount of fatty tissue. Up to half of all women are considered to have dense breast tissue. Unlike fatty tissue, which appears as dark and transparent on a mammogram, dense tissue reads as solid white. So do the tumors that mammograms are used to identify. As a result, the presence of a high proportion of dense breast tissue can make it easier for cancers and other potential problems to go undetected.

Like regular mammograms, the 3D mammogram is an image of the breast obtained using low-dose X-rays. The procedure for the 3D mammogram is also the same. You stand in front of the imaging machine, and your breast is compressed between two plates (yes, ouch) to flatten the tissue and to prevent movement while the X-ray is being taken. Both types of mammogram are used to identify early signs of breast cancer.

The 3D mammogram is different because, as the name suggests, it creates a multi-dimensional picture of the breast. This is achieved by capturing many images of the breast tissue from different angles, which generates thin cross sections of breast tissue. These combine to create a clearer and more detailed picture of the breast. The 3D mammogram, also known as breast tomosynthesis, takes a bit longer to complete than the standard mammogram. It emits a similar amount of low-dose radiation to the standard mammogram, but since it’s often used in addition to a standard mammogram, the total dose of radiation is higher.

For some women with dense breast tissue, even a 3D mammogram may not offer adequate diagnostic information. In these cases, the use of magnetic resonance imaging (MRI) or an ultrasound may be required. Other types of imaging tests are also being studied. These include an optical imaging test, which analyzes the movement of light through breast tissue, and molecular breast imaging, or MBI, which uses a radioactive tracer to identify the presence of cancer cells. Electrical impedance imaging distinguishes normal tissue from cancer cells through the use of a very small electrical current. None of these tests has yet been approved for breast cancer screening.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I’ve heard that the keto or paleo diets are good for weight loss and controlling blood sugar. Now I’m reading that a new study says they’re bad for your heart. What’s actually true?

Dear Reader: You’re referring to the ketogenic diet, also known as keto, and the Paleolithic diet, or paleo. Both are low-carb approaches to eating that are quite popular right now.

The paleo diet, also known as the caveman diet, draws from the foods that were presumably available to our Paleolithic ancestors. Since the Paleolithic era lasted 2.5 million years and ended about 12,000 years ago, the specifics of those diets are basically guesswork. But the core tenet of the paleo diet is that if a caveman didn’t eat it, neither should we. The result is a low-carb diet heavy on meat, with a limited amount of high-fiber fruit and vegetables. Since the Paleolithic era predates agriculture, things like grains, beans, cereals, legumes and dairy products, each of which require farming, don’t make it onto the plate.

The keto diet is even more restrictive. Its roots go back to the 1920s, when researchers found that a diet containing a very low proportion of carbohydrates and a very high proportion of fat appeared to reduce the number or severity of seizures in people with epilepsy. The goal of the diet is to put the body into a metabolic state known as ketosis. In ketosis, the body has depleted its stores of carbohydrates, its first go-to for energy, and instead begins to burn fat. This results in the creation of metabolic byproducts, including certain fatty acids, which are believed to ease the symptoms of epilepsy. Another side effect of ketosis is steady weight loss. The keto diet is heavy on protein and fat, including meat, fish, sausages, bacon, oils, butter, cheeses, nuts and seeds. The diet allows high-fiber carbohydrates, but in limited amounts.

It’s true that studies have associated both the paleo and keto diets with improved blood glucose control. They each also result in better appetite control and speedy weight loss. However, we don’t yet have enough reliable data about whether these diets promote long-term weight loss, or what health risks may be attached over time. The study you mentioned in your letter found a sharp increase in a certain blood biomarker linked to heart disease risk in participants who followed the paleo diet. At the same time, they had an increase in high-density lipoprotein, or HDL, the so-called “good cholesterol.”

Another study tied high-meat, low-carb diets to a drop in the diversity of the gut microbiome. An increase in the number of harmful bacteria was also observed. A separate analysis of a number of existing studies also found links between meat-heavy diets and an increase in cardiovascular risk. Bottom line -- we’re still sorting things out.

We understand the allure of the keto and paleo diets, but our advice continues to be a focus on whole rather than processed foods, lean proteins, a wide variety of fresh fruits and vegetables, whole grains, nuts and legumes, and healthful oils. Good for the heart, good for the gut and good for the planet.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I’m 53 years old, officially in menopause -- and officially miserable. I’ve got hot flashes, headaches, insomnia and crazy mood swings, and it’s making me depressed. My doctor means well, but he doesn’t really listen and keeps suggesting hormone therapy. Is this really my only option?

Dear Reader: Although we tend to talk about menopause in terms of the physical changes and symptoms that occur during this time of life, the experience affects us emotionally and psychologically as well. Like it or not, there’s long been a stigma attached to the ending of a women’s fertile years, which can make going through menopause an isolating time. The good news is that there are a number of approaches for managing menopausal symptoms.

Menopause is the stage of life when a woman has stopped having a monthly menstrual period. The ovaries have stopped releasing eggs, and the body is no longer producing the hormones estrogen and progesterone. Production of testosterone drops at this time, too. These hormonal changes often cause a range of physical symptoms.

From what we see in our practices, up to 80% of patients experience some degree of symptoms during menopause. These include hot flashes, flushing and night sweats, which are known as vasomotor symptoms, and they can cause great discomfort and distress. Additional symptoms can include the insomnia and mood swings that you have been experiencing, as well as urinary incontinence, vaginal dryness, changes to skin tone and elasticity, and a drop in sex drive. Anxiety, depression, headache and changes to the ability to concentrate can occur as well.

When it comes to hot flashes, hormone replacement therapy -- which can be oral, topical or vaginal -- is certainly effective. If this seems the best route for a particular patient, we always focus on using the lowest dosage for the shortest amount of time. Studies have shown that low doses of the antidepressants Paxil and Effexor can also offer relief. Their use in menopause treatment has been approved by the U.S. Food and Drug Administration. Other medications may provide some women with relief from hot flashes are gabapentin, an antiseizure medication, and clonidine, a high blood pressure medication. Although black cohosh, an herb sold as a dietary supplement, can be effective in relieving menopause symptoms, it can have adverse effects that range from mild -- stomach upset and headache -- to severe, including liver damage.

We help our patients explore nonpharmacological lifestyle interventions before moving to hormone replacement therapy. Acupuncture and yoga can improve sleep, concentration and mood. Mindfulness, relaxation, hypnosis and cognitive and behavior therapies can relieve stress, anxiety and fatigue. Foods like soybeans, chickpeas, lentils, flaxseed, grains and beans, which contain plant estrogens, may help. There is also evidence that sugar and sugary foods can worsen hot flashes.

Post-menopausal women are at higher risk of osteoporosis and heart disease, so a balanced and healthy diet becomes even more important. We are fans of MenoPro, a free app offered by the North American Menopause Society, which is designed to help you and your physician identify problems and make treatment decisions.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)