The following blog is excerpted from a Center for Disease Prevention and Control (CDC)  blog and raises important issues regarding genomic (genetic) testing.

Campaigns against public spitting in the 19th century were largely driven by concerns about the spread of tuberculosis. However, at the beginning of the 21st century, spitting seems to be making a comeback since it is a common source of DNA for testing.  Over the past few years, several companies have begun offering personal genomic tests online to the public. There have been famous images of “spit parties”, where celebrities are seen filling tubes with saliva to ship for DNA testing. Getting information on one’s genes has been promoted as fun, as part of social networking, and as a basis for improving health and preventing disease.

When it comes to spitting to improve one’s health, we say: think before you spit.  Our knowledge of the potential benefits and harms of these tests is incomplete at best.  Despite exciting research advances in genomics of common diseases, there is still much to learn about what this information means and how to use it to prevent disease. A little bit of incomplete or inaccurate information may even be harmful.

There are at least 2 key questions to consider when deciding whether personal genomic tests are worth your spit. First, how well can these tests detect or predict particular health conditions?  Most common diseases, such as diabetes, cancers, and heart disease, are caused by multiple genes and interactions with environment and behavior. Therefore, a risk estimate based only on genes is bound to be uncertain and can rapidly change based on new information. Different companies may even arrive at different interpretations of the same information. In 2010, a special undercover investigation by the Government Accountability Office found that tests by different companies of the same samples gave contradictory results. Second, can the test provide additional information that leads to better health? If the test indicates increased or decreased risk for a disease, what can be done about it? Will the test tell us more than what we know to do already?

Many interventions for reducing one’s risk for common diseases–such as smoking cessation, weight loss, increased physical activity, and blood pressure control–are beneficial regardless of a person’s genetic background. In the words of one consumer who responded to the CDC podcast on personal genomics in 2010:  “…seems one should just assume you have many health risks, then take really good care of yourself to lessen risks. Pretend you did the tests. Get ‘pretend-scared’ straight! You can then motivate yourself to keep healthy weight, exercise, reduce stress, get enough rest, consume healthy foods, avoid unhealthy habits,  enjoy hobbies & keep mind active, build friendships & family bonds…” In fact, new data from CDC  show that people who engaged in four healthy behaviors — not smoking, eating a healthy diet, getting regular physical activity, and limiting alcohol consumption- had much lower likelihoods of dying (over an 18 year period) from cancer, cardiovascular disease and other causes than those who did not engage in all four healthy behaviors.  Not smoking provides the most protection from dying early from all causes.

Several scientific studies designed to evaluate the potential impact of personal genomic information on health behavior and outcomes have been published and more are under way. Recommendations for setting scientific standards and a research agenda for personal genomics were published in 2009 by a panel convened by the Centers for Disease Control and Prevention and the National Institutes of Health.  Those recommendations for scientific evaluation still hold today.

In 2008, Dr Kari Stefansson, a leading scientist in the genetics community and founder of one of the companies that offer personal genomic tests said: “I am convinced that within five years every college-educated person in America is going to have a [genomic] profile like this. You cannot afford not having this.”  While this prediction may or may not be fulfilled based on the evolving scientific evidence, when a valid and useful test becomes available, the public health imperative is to have such tests widely available,  regardless of educational levels or other socioeconomic factors. For example, a recent national survey found that BRCA1/2 testing for breast and ovarian cancer—which is clearly beneficial for some women at high risk—is underutilized, especially among black and Hispanic women.

A very informative and inexpensive “genomic test” is available right now: family health history. An accurate, updated family health history can help healthcare providers assess the presence of many genetic conditions and whether patients and their relatives may have an increased risk for specific diseases. Family history also captures shared genetic, environmental and cultural disease risk factors.

No bones about it:  eating prunes helps prevent fractures and osteoporosis.   When it comes to improving bone health in postmenopausal women — and people of all ages, actually — a Florida State University researcher has found a simple, proactive solution to help prevent fractures and osteoporosis: eating dried plums.

“Over my career, I have tested numerous fruits, including figs, dates, strawberries and raisins, and none of them come anywhere close to having the effect on bone density that dried plums, or prunes, have,” said Bahram H. Arjmandi, of  Florida’s chairman of the Department of Nutrition, Food and Exercise Sciences in the College of Human Sciences. “All fruits and vegetables have a positive effect on nutrition, but in terms of bone health, this particular food is exceptional.”

Arjmandi and a group of researchers from Florida State and Oklahoma State University tested two groups of postmenopausal women. Over a 12-month period, the first group, consisting of 55 women, was instructed to consume 100 grams of dried plums (about 10 prunes) each day, while the second — a comparative control group of 45 women — was told to consume 100 grams of dried apples. All of the study’s participants also received daily doses of calcium (500 milligrams) and vitamin D (400 international units).

The group that consumed dried plums had significantly higher bone mineral density in the ulna (one of two long bones in the forearm) and spine, in comparison with the group that ate dried apples. This, according to Arjmandi, was due in part to the ability of dried plums to suppress the rate of bone resorption, or the breakdown of bone, which tends to exceed the rate of new bone growth as people age.

The group’s research, “Comparative Effects of Dried Plum and Dried Apple on Bone in Post Menopausal Women,” was published in the British Journal of Nutrition.  In the United States, about 8 million women have osteoporosis because of the sudden cessation of ovarian hormone production at the onset of menopause. What’s more, about 2 million men also have osteoporosis.

“In the first five to seven postmenopausal years, women are at risk of losing bone at a rate of 3 to 5 percent per year,” Arjmandi said. “However, osteoporosis is not exclusive to women and, indeed, around the age of 65, men start losing bone with the same rapidity as women.”

Arjmandi encourages people who are interested in maintaining or improving their bone health to take note of the extraordinarily positive effect that dried plums have on bone density.

“Don’t wait until you get a fracture or you are diagnosed with osteoporosis and have to have prescribed medicine,” Arjmandi said. “Do something meaningful and practical beforehand. People could start eating two to three dried plums per day and increase gradually to perhaps six to 10 per day. Prunes can be eaten in all forms and can be included in a variety of recipes.”

Source: Florida State University

A new simulation model predicts weight changes with varying diets and exercise plans.  Researchers at the National Institutes of Health (NIH) have created a mathematical model — and an accompanying online weight simulation tool — of what happens when people of varying weights, diets and exercise habits try to change their weight. The findings challenge the commonly held belief that eating 3,500 fewer calories — or burning them off exercising — will always result in a pound of weight loss.

Instead, the researchers’ computer simulations indicate that this assumption overestimates weight loss because it fails to account for how metabolism changes. The computer simulations show how these metabolic changes can significantly differ among people. Findings are published Aug. 26 in a Lancet issue devoted to obesity.

However, the computer simulation of metabolism is meant as a research tool and not as a weight-loss guide for the public. The computer program can run simulations for changes in calories or exercise that would never be recommended for healthy weight loss. The researchers hope to use the knowledge gained from developing the model and from clinical trials in people to refine the tool for everyone.

“This research helps us understand why one person may lose weight faster or slower than another, even when they eat the same diet and do the same exercise,” said Kevin Hall, Ph.D., an obesity researcher and physicist at the NIH, National Institute of Diabetes and Digestive and Kidney Disorders (NIDDK)  and the paper’s first author. “Our computer simulations can then be used to help design personalized weight management programs to address individual needs and goals.”

The online simulation tool based on the model enables researchers to accurately predict how body weight will change and how long it will likely take to reach weight goals based on a starting weight and estimated physical activity. The tool simulates how factors such as diet and exercise can alter metabolism over time and thereby lead to changes of weight and body fat.

To test the model, the researchers compared predicted weight changes to actual changes in people. For example, the team found that people’s bodies adapt slowly to changes in dietary intake. They also found heavier people can expect greater weight change with the same change in diet, though reaching a stable body weight will take them longer than people with less fat.

The model also points to a potential simplified method to approximate weight loss in an average overweight person. An adult who has a body mass index (a measure of a person’s weight in relation to his or her height) between 25 and 29.9 is considered overweight. One example: For every pound you want to lose, permanently cut 10 calories from your current intake per day. At that rate, it will take about one year to achieve half of the total weight loss, and almost all of the weight loss will have occurred by three years. This calculation shows how long it takes to achieve a weight-loss goal for a single permanent change of diet or exercise. Researchers can use the web simulation tool to plan for a phase of more-rapid weight loss followed by a weight maintenance phase. People should consult with their physician prior to embarking on a diet plan.

“This research illustrates how the interdisciplinary skills of NIH scientists, like a physicist doing obesity research, can help lead to innovative ways to test, understand and treat a major public health epidemic,” said NIDDK Director Griffin P. Rodgers, M.D. “Advancing research from the laboratory to the bedside enables us to make the discoveries that can better people’s lives.”

Over the years, we hear about "cancer clusters" or a growing rise in behavioral conditions like autism and advocates and families want answers.  Is it our genes or something in the environment?   This concern often leads to an epidemiological study that tracks these diseases over time.   But sometimes, despite the time, effort and expense, no definitive causation is established.  This  can be frustrating to families facing these conditions and the scientists who are looking for answers.  This is the conundrum of  nature vs. nurture.

The problem is that the causes of  particular diseases may be part of both.  For example, it is not uncommon to have the explanation of a disease presented as 25% genetic (nature) and 75% environmental (nurture), adding up to 100% (like slices of a whole pie).

However, what we have learned from gene-disease association studies is that in reality, human disease is rarely a product of such simple and clearly defined relationship.  Causation of human disease is not about nature OR nurture but more about nature AND nurture.   Gene-environmental  interactions underlie almost all human diseases. The Center for Disease control (CDC), explains this on a recent blog.

Most common diseases such as coronary heart disease, cancer, and diabetes are caused by modifiable environmental risk factors such as smoking, diet and lack of exercise.   However, if you have a family history of one of these conditions, your risk will likely be higher than someone without a family history.    Even though the human genome has been uncovered, we do not yet have the tools to quantify or even guess at the vast number of variations that can exist.

Rather than think about slices of pie, the CDC suggests we look at a different metaphor:   vegetable stew!   The genes are represented by the different combinations of vegetables used, and the environment can be the amount of time the stew is cooked, the temperature, what kind of pot was used (aluminum vs. cast iron).   Taking this further, there are different varieties of corn, tomatoes, herbs and beans and the spices used can change the taste immensely.  Once assembled, the ingredients blend and cook to produce a combined but unique flavor.    Biologic processes function in a similar way, as genes respond to constantly changing environment.

As scientists continue to work with the human genome, there may come a day when we can learn more about our personal vegetable stew recipe.