Nutrition Note: November - December 2006

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The Latest Information Coming from the Friedman School of Nutrition Science and Policy at Tufts University

Trans Fat Ban: Watch Saturated Fats and Calories Too

Boston — In December, New York City passed a law to phase out the use of trans fat in restaurants. Other cities, including Boston and Chicago, might follow suit. According to Alice H. Lichtenstein, DSc, Gershoff professor of nutrition science and policy at the Friedman School of Nutrition Science and Policy at Tufts University, the ban is a step in the right direction, but restaurateurs need to replace partially hydrogenated fat with unsaturated fat. If they choose saturated fat it would diminish the health benefits of this new initiative. Another new regulation that requires some restaurants to provide calorie information as prominently as price might be even more important, notes Lichtenstein.

"There is no biological need for trans fat and intake is associated with adverse health outcomes. However, the media attention on the trans fat announcement to the exclusion of the calorie labeling is unfortunate. Two-thirds of Americans are overweight or obese. The New York City Department of Health and Mental Hygiene has proposed that the calorie content of food items be displayed as prominently as the price, at the point of purchase," says Lichtenstein, also director of the Cardiovascular Nutrition Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts.

"That means," Lichtenstein continues, "that if you are wavering between placing an order for a small versus a medium order of French fries, both the price and the number of calories per serving will be displayed. People will become more aware of the caloric cost of the foods they order, and the next step on a public health level would be to educate the consumer on the amount of calories their body needs per day. This way, they will be able to put the numbers they see on the board or menu into perspective. Because the amount of food and beverages we eat that is prepared outside the home is so large, even if this regulation just covers a fraction of food service establishments, it can have a tremendous impact on caloric intake."

"Trans fat," says Lichtenstein, "is a double whammy, because like saturated fat, it raises levels of LDL or 'bad cholesterol,' but it also lowers levels of HDL or 'good' cholesterol." Most of the trans fats we eat are formed during the partial hydrogenation of oils used in fried foods and commercial baked goods. Partially hydrogenated oils provide processed foods with longer shelf lives and therefore greater economic profitability.

"But, trans fat is just one part of the diet. In general, people are still eating far more saturated fat than trans fat, and both need to be reduced in order to maintain optimal cholesterol levels and promote heart health," says Lichtenstein. "And the big giant total calories is always looming in the background."

In one study to assess the effects of consuming different types of oils on cholesterol levels, led by Lichtenstein and published earlier this year, fifteen adult volunteers with moderately high LDL cholesterol were fed each of four diets with a different source of primary fat, including partially hydrogenated soybean oil (trans fat), palm oil (50 percent saturated fat), non-hydrogenated soybean oil (only 16 percent saturated fat), and canola oil (only 7 percent saturated fat).

The results, published in the American Journal of Clinical Nutrition (AJCN), reported that after a trial of 35 days on each diet, participants consuming the partially hydrogenated soybean oil and palm oil diets had levels of LDL cholesterol that were 12 and 14 percent higher, respectively, than when consuming the non-hydrogenated soybean oil diet. An even greater difference was observed when the partially hydrogenated soybean oil and palm oil diets were compared to the canola oil diet. While participants were on the partially hydrogenated soybean oil and palm oil diets their LDL levels were 16 and 18 percent higher, respectively, than when on the canola oil diet.

"On the basis of this and other work, it's clear that phasing out partially hydrogenated oils (trans fats) will improve diet in some ways," says Lichtenstein, corresponding author on the AJCN study. "However, just decreasing trans fat intake without changing other dietary habits, such as minimizing saturated fat intake and controlling total calorie intake, will result in some real disappointments with respect to both heart health and obesity."

Lichtenstein recommends that other cities monitor the successes and challenges of the trans fat ban in New York City before implementing their own regulations, and also advises that the focus on the new regulations shift to the mandate to display calorie labeling in food service establishments, and educating people about their total daily caloric requirements.

Vega-Lopez S, Ausman LM, Jalbert SM, Erkkila AT, Lichtenstein AH. "Palm and partially hydrogenated soybean oils adversely alter lipoprotein profiles compared with soybean and canola oils in moderately hyperlipidemic subjects." American Journal of Clinical Nutrition. 2006 (July);84(1):54-62.

HIV Treatments Improve Health, but Nutritional Issues Remain

Despite the success of highly active antiretroviral treatment (HAART), people with HIV may still be at higher risk for nutritional deficiencies and abnormalities. In two different studies, researchers at the Nutrition/Infection Unit in the Department of Public Health and Family Medicine at Tufts University School of Medicine, and colleagues examined the incidence of metabolic syndrome and existing micronutrient deficiencies among participants in the Nutrition for Healthy Living (NFHL) study, a cohort with HIV. Both studies were published in the December 1st issue of the Journal of Acquired Immune Deficiency Syndromes, reporting that a high percentage of people with HIV have the same two defining characteristics of metabolic syndrome, and that people with HIV may be at risk for zinc deficiency.

Metabolic syndrome is defined as having three or more of the following medical conditions; low levels of high-density lipoprotein (HDL or 'good') cholesterol, hypertension, abdominal obesity, high levels of serum glucose (blood sugar), and/or hypertriglyceridemia, which is an elevation of triglycerides (fatty compounds) in the blood. Metabolic syndrome is often associated with obesity and related diseases like diabetes, but characteristics of metabolic syndrome have been observed among patients with HIV both before and after the introduction of HAART.

To investigate the prevalence of metabolic syndrome in populations with HIV, corresponding author Denise Jacobson, PhD, MPH, assistant professor at Tufts University School of Medicine, along with Christine Wanke, MD, and Sherwood Gorbach, MD, both of the Nutrition/Infection Unit and senior authors on the study, worked with colleagues to compare the incidence of metabolic syndrome among nearly 500 participants in the NFHL study to the population as a whole, using data from 1,900 participants in the National Health and Nutrition Examination Survey (NHANES).

"We determined that almost one fourth of the NFHL participants had metabolic syndrome, although this is lower than the incidence of metabolic syndrome in the population as a whole," says Jacobson. "Strikingly, 77 percent of people with metabolic syndrome in the NFHL study had the same two defining characteristics, low HDL cholesterol and hypertriglyceridemia."

"It appears that HIV viral load and metabolic syndrome are associated, as people with both HIV and metabolic syndrome were likely to have a clinically relevant increase in viral load within six months of developing components of metabolic syndrome," says Gorbach, who is a professor at Tufts University School of Medicine and at the Friedman School of Nutrition Science and Policy at Tufts. "An increased viral load is also linked to a decrease in HDL cholesterol levels, so this may be what drives metabolic syndrome in people with HIV."

Both HAART and non-HAART users in the NFHL study had a higher incidence of low HDL than the NHANES population. However, only HAART users demonstrated high triglyceride levels, leading the researchers to conclude that certain anti-retroviral therapies may also increase the risk for components of metabolic syndrome.

"We have seen that people with HIV have an increased prevalence of two of the characteristics of metabolic syndrome, components that are also associated with cardiovascular disease (CVD) and diabetes," says Wanke, a professor at Tufts University School of Medicine. "People with HIV are also living longer due to advances in treatment, and their risk of CVD and diabetes increases with age as it does in the general population. Since people with HIV are already at higher risk for low HDL cholesterol and hypertriglyceridemia, it might be important for health care providers to monitor risk for metabolic syndrome, as these risk factors may increase the likelihood of additional medical complications."

Using the same NHFL population, Clara Jones, MD, MPH, an assistant professor at Tufts University School of Medicine, and colleagues analyzed micronutrient levels of nearly 300 people infected with HIV on HAART, since little is known about the nutrient status of people taking anti-retroviral drugs. Jones determined that HAART users were unlikely to have low levels of selenium or vitamins A and E. However, despite these improvements in micronutrient levels (as compared to previous studies conducted before the widespread use of HAART), Jones found that HAART users still have an increased risk for zinc deficiency. Zinc, commonly found in seafood, meat, and dairy products, is crucial to many aspects of cellular metabolism, including immune and neurological function, as well as cell reproduction.

"We found that 40 percent of men and 36 percent of women in the study had low zinc levels," says Jones. "It has been thought for some time that low levels of micronutrients are associated with an increased viral load. This was demonstrated in the study, as people with lower levels of zinc had higher viral load levels, particularly women. However, we were also surprised to find that women with the highest levels of vitamin A in their blood had higher viral loads than those with the lowest levels of vitamin A. More studies are needed to confirm this observation. One could speculate that there is an optimal range of serum vitamin A needed for people with HIV that could contribute to maintaining lower viral loads."

The Nutrition/Infection Unit of the Department of Public Health and Family Medicine at Tufts University School of Medicine was established in 1986 to research the relationship between nutrition and various diseases. Since 1994, this group, originally led by Gorbach and now by Wanke, has specialized in the relationship between nutrition and HIV.

Jacobson DL, Tang AM, Spiegelman D, Thomas AM, Skinner S, Gorbach SL, Wanke C. Journal of Acquired Immune Deficiency Syndromes. (December 1, 2006); 43(4):458-466. "Incidence of metabolic syndrome in a cohort of HIV-Infected Adults and Prevalence Relative to the US Population (National Health and Nutrition Examination Survey)."

Jones CY, Tang AM, Forrester JE, Huang J, Hendricks KM, Knox TA, Spiegelman D, Semba RD, Woods MN. Journal of Acquired Immune Deficiency Syndromes. (December 1, 2006); 43(4): 475-482. "Micronutrient Levels and HIV Disease Status in HIV-Infected Patients on Highly Active Antiretroviral Therapy in the Nutrition for Healthy Living Cohort."

If you are interested in learning more about these topics, or speaking with a faculty member at the Friedman School of Nutrition Science and Policy at Tufts University, or another Tufts health sciences researcher, please contact Siobhan Gallagher at 617-636-6586 or via email to Siobhan.Gallagher@tufts.edu.

The Gerald J. and Dorothy R. Friedman School of Nutrition Science and Policy at Tufts University is the only independent school of nutrition in the United States. The school's eight centers, which focus on questions relating to famine, hunger, poverty, and communications, are renowned for the application of scientific research to national and international policy. For two decades, the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University has studied the relationship between good nutrition and good health in aging populations. Tufts research scientists work with federal agencies to establish the USDA Dietary Guidelines, the Dietary Reference Intakes, and other significant public policies.