Nutrition and Prevention of CVD: An Interview With Gary Fraser, MBChB, FACC
March 30, 2017 | Tushar Tuliani, MD
In an interview with Tushar Tuliani, MD, a Fellow in Training (FIT) at the Loma Linda University, California, Gary Fraser, MBChB, FACC, professor of preventive medicine at Loma Linda University School of Medicine, and cardiologist at Loma Linda University Medical Center and Veterans Affairs Loma Linda Healthcare System, discusses the importance of lifestyle modification in the prevention of heart disease and the challenges faced by researchers in nutrition health. Fraser has been a pioneer in developing a large cohort study called Adventist Health Study-2. His research interests include studying the effects of nutrition on heart disease and cancer.
With the incidence of metabolic syndrome on the rise, how do you emphasize the importance of diet and physical exercise to your patients to prevent cardiovascular events?
GF: The rising prevalence of metabolic syndrome reflects changes in our environment and the way people are living their lives. Many aspects of lifestyle have changed over the last few decades. Causal factors probably center on diet and exercise, acting through effects on gene expression, the metabolome. Other factors like the gut microbiome must be taken into account as it is partly determined by diet and complicates the picture. How one conveys the importance of lifestyle modification to patients depends on their educational level and socioeconomic status. A lot of our patients face social and economic challenges which determine their choices in diet and may limit opportunity for physical activity. Recommendations must be tailored to these circumstances. A diet that is plant based will be beneficial, and will prevent premature manifestations of cardiovascular disease, diabetes mellitus and hypertension in most (but not all) persons. There is an “epidemic” of vegetarianism going on in Germany with 30 vegan restaurants in Berlin right now. Changes are possible, but changing ingrained behaviors like diet at the societal level generally takes decades. Reducing the consumption of meat and dairy products and an emphasis on consumption of whole grains, fruits, vegetables and nuts is the essence of the necessary changes. Moderation in portion sizes will also be necessary particularly for many in the U.S.
It is unfortunate that in the U.S., and elsewhere, family restaurants sell calorie dense, often fatty and sweet, foods for a very small dollar amount and people have become used to that. Timing of meals during the day is also important. There is increasing evidence to support consumption of calories earlier in the day rather than later, as this appears to have a beneficial effect on body weight. Another challenge is to incorporate exercise into the daily routine. This requires motivation to initiate and subsequently sustain physical activity. Thirty (30) minutes of moderate aerobic physical activity four – five times a week is a common recommendation. Long periods of sitting or lying down (physical inactivity) may be a risk factor independent of even moderate physical activity at other times. Making changes in one’s regular working life like avoiding elevators and using stairs, parking your car at the farthest parking lot can help contribute to staying active.
What are some of the challenges faced by researchers in the field of nutrition research?
GF: Challenges fall in to two – three main categories. Nutrition studies benefit from prospective study designs where we can measure potential cause-effect relationships in a way that at least establishes that there is the correct time order, avoiding the well-known “chicken-egg conundrum”. In order to accomplish this we need to establish the dietary habits of a very large number of people. Diet, like most forms of human behavior, is very varied and has many facets making it hard to measure accurately. With the availability of thousands of foods people can choose from, the synthesis of data in nutrition research is very challenging. The second and related issue is gathering large amounts of data with acceptable accuracy in an economical fashion. Small, even random, errors in data accuracy can adversely affect relative risks that are calculated subsequently. Ongoing research on measuring dietary consumption using hand-held devices may help solve some of these challenges. Online questionnaires have already shown promise of improving the accuracy and efficiency of nutrition data gathering. Then there remains the challenge of providing support for claims that associations are indeed causal. A major focus at present is providing evidence about mechanisms whereby diet may affect disease at the molecular level. This is requiring interesting work with so-called “-omic”-level data (metabolome, DNA methylome, gut microbiome, etc.). Thus nutrition research continues to be a very challenging field to make sense of, but the potential rewards are great. If effective, nutritional interventions are inexpensive and mostly risk-free.
Over the last few years, big databases have emerged as an important tool in cardiovascular research. What are some of the advantages and shortcomings of big data research?
GF: The big data that I am familiar with and currently starting to work with are: the genome, various forms of gene expression such as the DNA methylome and RNA transcriptome, etc; then there is the metabolome which includes thousands of chemicals that one can measure in blood and urine, some of which presumably can characterize an individual’s health/risk status; third, the gut microbiome is another category of “big data” dealing with different families of bacteria as measured by the bacterial genome. Characteristics of all these “big data” is that one person may have tens of thousands of variables, a situation that we are not used to in traditional statistical analyses. We are more used to having a thousand people and five to 20 variables in a statistical model. The challenge of “big data” is to make sense of the data in ways that are statistically meaningful and so be able to draw conclusions that will be repeatable in other datasets.
With constantly changing diet fads what are some of the fundamental diet choices that have withstood the test of time and have a positive effect on cardiovascular health?
GF: My response to this question will probably reflect on some of my biases. It is true that despite thousands of publications over the last few decades in nutritional research, we know surprisingly little about the effects of particular foods with much conviction. Having said that we know a lot that is probably true. You can make the argument that if we wait long enough to know something is definitely true, you will also be long dead. So, it is reasonable to make some assumptions and make some lifestyle changes based off the large themes. It is very clear that plant based foods are better from a cardiovascular standpoint and that red meat should be avoided. We have good evidence that trans-fatty acids are to be avoided. There is very little controversy about that. There is good evidence that small quantities of nuts four to five times a week significantly protect against risk of heart attack, and that they decrease blood LDL cholesterol. We were the first to report that.
Good evidence also suggests saturated fats are associated with high levels of LDL-cholesterol and poly-unsaturated fats are associated with lower level of LDL-cholesterol. These results come from carefully constructed “feeding trials” performed decades ago. Thus it makes sense to be careful about the consumption of saturated fats particularly trans-fatty acids although all fats are calorie dense. Interestingly in epidemiologic research when associating different fatty acids to risk of cardiovascular disease, the most consistent finding has been the protective effect of poly-unsaturated fats. Dietary fiber has received its share of positive press. Yet, it is hard to dissect the beneficial effects of dietary fiber from other components of plants, fruits and nut-based diets. Animal products do not contain dietary fiber. Over the last few decades there has been controversy about the effect of simple sugars on coronary artery disease. In the 1960s-70s there was adverse press about the adverse influence of sugars on cardiovascular disease which was not based on good evidence and was appropriately discounted at that time. More recently we have better evidence to suggest that sugar may have an adverse effect on cardiovascular health and that this is probably driven in substantial part by increased body weight. Small doses of omega 3 fatty acids are probably mildly protective against sudden cardiac death. Animal research has demonstrated that omega 3 fatty acids increase fibrillation thresholds under ischemic challenge.
What advice would you give to FITs to pursue a healthy work-life balance?
GF: (Laughs) Very difficult question! The immediate threat of cardiovascular mortality and morbidity is very small, given the young age of FITs. So motivation is not high. However, our lifestyle choices in earlier decades of life do influence choices later in life. The intensity of work during fellowship may make it difficult to eat timely meals and have dedicated time for physical activity. Frankly, this is not the best time to develop an optimal and healthy lifestyle—an unfortunate fact. Try to survive it! If you are married, your spouse may be able to help. Food choices you make when you are busy should not differ from those when you are not. If appropriate, try to identify fast-food choices that are more healthy. They do exist. Get physical activity when you can. Interspersed with study it can be a welcome relief and refreshing. Overall the advice I would give to fellows would not be different from what I would give to my patients. One must tailor advice to the subject’s circumstances for best compliance.
This article was authored by Tushar Tuliani, MD, a Fellow in Training (FIT) at Loma Linda University.