Archive for February 2015
By: Amanda Whiting, Ph.D.
Many Americans, at one point or another, have probably heard about the “food pyramid” and know that it has something to do with what the government says makes up a healthy diet. But have you ever wondered where those federal food and nutrition guidelines actually come from, or what information they’re based on, or just who gets to decide what is “healthy” for everyone?
The United States Department of Agriculture’s (USDA) Center for Nutrition Policy & Promotion (CNPP) is responsible for the general nutritional guidelines for Americans. The most recent nutritional icon, called “MyPlate,” was released on June 2, 2011 by First Lady Michelle Obama and USDA Secretary Tom Vilsack and replaced the previous “MyPyramid” model. The visual guide features a colourful plate divided into approximate portions for fruits, vegetables, grains, protein and dairy. The dinner table imagery is meant to help children, parents, and other adults prioritize their food choices at meal times to include all of the groups listed, as well as consume them in proportions relative to each other (e.g. half a plate of fruits and veggies) as a model diet to promote good health.
The nutritional recommendations behind the simpler MyPlate came from the 2010 Dietary Guidelines for Americans (DGA), a policy document jointly produced by the USDA’s CNPP and the United States Department of Health and Human Services (HHS) Office of Disease Prevention and Health Promotion. Since the publication of the first edition in 1980, the Guidelines have been updated every five years to reflect the most current knowledge on health and nutrition. A Dietary Guidelines Advisory Committee (DGAC), made up of 13 to 17 nationally recognized experts in the field of health and nutrition, meets in the year prior to each update to discuss what should be included, removed, or revised in the guidelines by conducting a thorough review of scientific and medical literature, as well as soliciting comments from the public. A scientific report is written and delivered to Secretaries of the USDA and HHS containing the DGAC’s recommendations for the next edition. The next revision to the guidelines is currently in process, with the final report due to the USDA and HHS by early 2015.
As with any guide that tries to cater to a population as large and diverse as the American public, MyPlate and the Dietary Guidelines are not without disagreements and multiple opinions. Everyone likes to think that how they eat is “healthy” – be it vegetarian, fruitarian, vegan, gluten-free, dairy-free, carnivore, paleo, primal, veggie-free, or what-have-you. In addition, MyPlate has been criticized for removing a reference to physical activity, another important contributor to good health, which was present on the MyPyramid icon as a person climbing stairs.
While some people might be of the opinion that what the federal government says is “good food” and “healthy” isn’t all that important (because they’re going to eat however they want anyway), the Dietary Guidelines for Americans does play an important role in public health. In addition to consisting of guidelines for the general public’s own consumption, the DGA is a policy document that is used to set policy related to nutrition within the government. In the USDA, the dietary guidelines are used to set standards for school lunch and other feeding programs such as Supplemental Nutrition Assistance Program (SNAP) and Women Infants and Children (WIC) program. Within HHS, the DGA is used by parts of the National Institutes of Health (NIH) to produce consumer information materials supporting healthy lifestyles for various diseases (such as hypertension), while the Food and Drug Administration (FDA) uses parts of the DGA as the basis for the Nutrition Facts information guides found on all packaged food. Thus, it is important that the final DGA and the recommendations made by the DGAC are firmly based on rational, scientific facts and arguments and are not unduly influenced by groups with their own interests at heart.
This influential effect on other governmental policies is what makes the content of the DGA itself very political. It seems that every step forward in terms of recommendations based solely on scientific evidence for advancing optimal human health, is met head on by opposition from groups with powerful incentives to make money and/or preserve a status quo. As one example, it is likely that the 2015 DGA will include a recommendation that sugar be limited to no more than 10% of a person’s daily calories. All previous editions of the DGA have not included a recommendation for an upper limit on daily sugar consumption, which is why there is no number for % daily value (%DV) for sugar on any food product nutrition label. Meanwhile, the World Health Organization (WHO) is currently in the process of updating their guidelines on sugar consumption. This guidance, expected to be published in early 2015, suggests that a reduction in sugar consumption from less than 10% of total energy intake per day (the current 2002 guideline) to below 5% would have additional health benefits on body mass and tooth decay. For an average adult, the 5% mark would be equivalent to approximately 25 g of sugar per day or less. The American public currently consumes an average of 126 g of sugar per day, with much of that coming from added sugars in processed foods, and specifically, from sweetened beverages. Success in this one single area – reducing American’s consumption of sugar-sweetened beverages – could have a significant impact on the overall health and body mass of Americans. Not surprising, the beverage industry has issued some pushback for the inclusion of any specific limits on added dietary sugar (among other concerns) in the newest DGA. The American Beverage Association has submitted public comments for the DGA, suggesting that the WHO-commissioned review lacked scientific evidence and that the setting of Dietary Reference Intakes (DRIs) is not the responsibility of the DGAC and therefore should be done by other organizations. Similar arguments have been made by the Grocery Manufacturers Association, the Juice Products Association, the National Council of Farmer Cooperatives and the Sugar Association among others.
Other groups have tried to take the politics out of what we should eat and focus just on what the science of nutrition says. “Unfortunately, like the earlier U.S. Department of Agriculture pyramids, MyPlate mixes science with the influence of powerful agricultural interests, which is not the recipe for healthy eating,” said Walter Willett, professor of epidemiology and nutrition and chair of the Department of Nutrition at the Harvard School of Public Health (HSPH)1. HSPH released its own version of MyPlate known as the “Healthy Eating Plate”. This plate featured even more vegetables compared to fruit, an even split between grains and healthy protein, an emphasis on drinking water over dairy, and indicated that healthy oils should also be consumed. It also included a direction to “Stay Active” as a part of a healthy lifestyle. The goal of the Healthy Eating Plate is to give more specific information for a healthy diet in a way that is as clear and intuitive to follow as the MyPlate icon, without influence from the food industry or agricultural policies.
What one eats (and what one does) on a daily basis has a profound impact on one’s overall health and quality of life. “One of the most important fields of medical science over the past 50 years is the research that shows just how powerfully our health is affected by what we eat. Knowing what foods to eat and in what proportions is crucial for health,” said Anthony Komaroff, a professor of medicine at Harvard Medical School and editor in chief of Harvard Health Publications1. It will be interesting to see what the recommendations for the 2015 update to the Dietary Guidelines are and what recommendations actually make it into the final document. At the end of the day, what you choose to eat is up to you. However, everyone is entitled to accurate information about the health consequences of their personal food choices. Regardless of how you eat or what diet you follow, we are all human and the basic principles for good health and longevity remain the same for everyone. Like it or not, you are what you eat.
By: Tamara Litwin, Ph.D
The British House of Commons recently voted to approve techniques that will enable couples to conceive children without inheriting deleterious mutations in their mitochondrial DNA1. In the United States, the FDA is considering the safety and efficacy of the same techniques, which raise a variety of medical and ethical issues because they involve manipulation of the human genome2. There are two closely related techniques, both known as mitochondrial replacement therapy, that aim to cure mitochondrial DNA disorders by combining mitochondrial DNA from a woman with healthy mitochondrial DNA, nuclear DNA from a woman with a mitochondrial DNA disorder, and nuclear DNA from a man.
Mitochondrial replacement therapy will create children who, in a sense, have three parents because the healthy mitochondrial DNA is donated by a woman who would not otherwise be related to the child3. What are the biological implications for this three parent model? Mitochondrial DNA contains less than 17,000 DNA base pairs out of the 3 billion base pairs that make up the total human genome. Therefore, mitochondrial DNA proportionally makes up a small percentage when compared to the total amount of DNA. Furthermore, mitochondrial DNA is found in mitochondria, a separate compartment of the cell from the nucleus of the cell where the nuclear DNA (all the rest) is located. While few in number, mitochondrial genes are essential to biological processes that focus on energy storage and consumption from oxygen and sugar4. When the mitochondria do not function properly, the result can be mitochondrial myopathy, a family of disorders with symptoms including muscle weakness, vision problems, heart problems, and others5. Mitochondrial disorders may also accelerate aging6.
Mitochondria are inherited solely from the mother because mitochondria from the sperm are actively degraded7. Therefore mitochondrial DNA disorders are passed down to every child (both boys and girls) conceived by an affected woman. The disorders can vary in severity among children in the same family. The potential benefits of the new mitochondrial replacement therapy to the children of mothers with mitochondrial disorders are enormous. One intervention at or before conception can prevent a lifetime of symptoms of mitochondrial dysfunction. Even better, any daughters will not have to face the same decision when they grow up and hope to start their own families, because they will pass on the healthy mitochondria to their children.
Mitochondrial replacement therapy has the potential to help specific families stop the chain of transmission of mitochondrial disorders. It is a medical technology that is not very different from traditional in vitro fertilization (IVF) techniques and does not lie on a slippery slope to ethically challenging eugenics techniques. If we have the technology to help these families, how can we withhold it on the grounds that someone may someday misuse the technology for other purposes? The technology already exists. However, it is worth proceeding cautiously because there could be health ramifications to manipulating eggs in this way. Animal studies have already shown the growth of healthy offspring for several generations with this technique8, which is very promising, but it would be wise to generate more data in animals before proceeding with human trials of this technique in the United States. The FDA can also watch the developments across the pond to help determine when and how to introduce mitochondrial replacement therapy to the United States.