Ask the Doctors: Studies shed light on diet soda consumption

Dear Doctors: There is some folklore that diet pop is bad for you. I gave up sugar and most carbohydrates to help with weight and A1C control, but I continued to drink diet cola. What do the actual studies — ones that are not from biased sources and are peer-reviewed — say about diet cola?

Dear Reader: You are correct that a number of observational studies have linked the regular consumption of artificially sweetened beverages, including diet soda, to adverse health effects. These include weight gain, disruptions to gut health, cardiovascular problems and an increased craving for sweets. More recently, studies have linked the diet soda habit to an increased risk of stroke. News stories have tended to focus on the health problems that were identified in the research. We think it's important to note that these ill effects are linked to the regular and long-term consumption of at least one, and often more than one, serving of diet soda per day.

The findings come from what are known as "observational studies." This is a type of study in which researchers gather and analyze information about the effects of a certain behavior, treatment, diagnostic test, environment or risk factor. They do not intervene in any way. The goal of an observational study is to uncover statistical patterns or trends. However, because human behavior is complex, it's not always possible to say for sure why certain patterns occur.

The data for observational studies is typically drawn from a variety of public health records and from large population studies. A famous example of the latter is the Nurses' Health Study series, which is still ongoing. Established in 1976, these studies have analyzed detailed health, environmental and behavioral data gathered from more than 100,000 female registered nurses between the ages of 30 and 55. This research uncovered early links between tobacco use and heart disease, the role of diet in cancer risk and that being obese or sedentary can raise the risk of developing Type 2 diabetes. The credible studies that you asked about in regard to artificially sweetened beverages follow that model.

Specific research linking frequent diet soda consumption to adverse cardiovascular effects includes an analysis of seven large studies, with a total of 308,420 participants, conducted by scientists in Great Britain. A link to an increased risk of longterm weight gain was found when analyzing data from the San Antonio Heart Study, a 10-year study with 5,000 participants. A study that found evidence tying diet beverage consumption to an increased risk of stroke was conducted by researchers at Albert Einstein College of Medicine in New York. They used the health data of 81,714 women who had participated in the Women's Health Initiative Observational Study.

When it comes to drinking diet soda, we think it's wise to err on the side of caution. Rather than consume it daily, save it for an occasional treat. Many people find that it's the bubbles as much as the sweet taste that they crave. That makes the many varieties of fizzy water that are now available a viable option.

Dear Doctors: How long does the smallpox vaccine stay effective? I ask because I received it as a child in the 1950s. Is it known if the vaccine would be effective against monkeypox some 60 years later, or is a booster needed? Does a booster even exist?

Dear Reader: With cases of monkeypox spreading throughout the world, concern about this rare virus is growing. The disease, which is endemic to central and west Africa, began to appear in Europe and the United States in May. Since that time, the U.S. has recorded more than 350 cases. Yet health officials warn that, due to unfamiliarity with the disease and limited testing, the actual number of cases in this country is likely higher. We've discussed this outbreak before, but with cases on the rise, we think a recap is wise.

Monkeypox is related to smallpox, but the disease that it causes is not as severe. For the majority of people who become infected, symptoms are similar to those of the flu. That includes fever, chills, headache, body aches, swollen lymph nodes and fatigue. In more severe cases, patients develop a distinctive rash and lesions, most often on the hands, the face and the soles of the feet.

Monkeypox is not known to linger in the air, and it is not transmitted during brief periods of shared airspace. Instead, the disease most often spreads through direct physical contact with an infected individual, or with their bodily fluids. Because sores may be inside the body, including the mouth, vagina or anus, sexual transmission is possible. The virus can also be spread by contact with items that have touched either the infectious rash or bodily fluids, such as linens or clothing.

An infected individual is contagious from the moment symptoms begin. Those who develop a rash or lesions can continue to spread the disease until the rash has healed completely and is covered by a fresh layer of skin.

Adults like yourself who received the smallpox vaccine during the nationwide program that was in effect from the late 1940s until 1972 are believed to have continuing immunity. This includes members of the U.S. military, who continued to receive smallpox vaccinations until 1991.

The Centers for Disease Control and Prevention says that, based on past data collected in Africa, the smallpox vaccine is at least 85 percent effective in preventing monkeypox. However, since this situation is so new, the precise degree of protection is not known. Researchers say that while older adults who have been vaccinated against smallpox may be susceptible to monkeypox infection, they are likely to experience only mild symptoms. The data show that the majority of healthy adults who become infected do not become severely ill. And to your question about smallpox boosters, no, they are not available.

To combat this outbreak, the U.S. has just purchased 2.5 million doses of monkeypox vaccine, which bolsters the 500,000 doses already stockpiled. Distribution to high-risk individuals is expected to begin soon. You can find detailed information about smallpox and monkeypox at the CDC website. Visit cdc.gov/poxvirus and click the appropriate link.

Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health.