American Society for Nutrition

Author: *ASN Member Contributor

  • Highlights from the Micronutrient Forum in Africa

    Highlights from the Micronutrient Forum in Africa

    By Sheela S. Sinharoy, MPH

    The 3rd Micronutrient Forum Global Conference took place from June 2-6, 2014 in Addis Ababa, Ethiopia, with approximately 1,000 attendees and more than 80 sessions. Some of my personal highlights were:

    • Lindsay Allen’s talk on biomarkers for vitamin B12. Dr. Allen argued that depending on the biomarker used, vitamin B12 deficiency may be more prevalent than iron deficiency.
    • Michael Fenech’s presentations on the exposome, especially the impact of nutrient deficiencies on the integrity of DNA. He has found that the DNA damage from folate deficiency is equivalent to the damage from 10 times the allowable annual exposure to ionizing radiation.
    • Daniel Raiten and Bas Kremer’s talks on the importance of a systems biology perspective. It’s good to be reminded of the need for research on nutrient-nutrient interactions and the role of nutrient “clusters” within biological systems.

    The most interesting session, however, was the plenary session on the risks and benefits of iron interventions. Many of us know that iron deficiency is the most common nutritional disorder in the world. It is a major cause of anemia but not always the dominant cause. We also know that the main anemia control strategy worldwide is iron supplementation. However, in cases of anemia that are caused by factors other than iron deficiency, iron supplementation can actually be harmful, exacerbating malaria and increasing pathogenic bacteria in the gut. How, then, to determine whether or not iron supplementation is appropriate?

    One possible solution came from Sant-Rayn Pasricha, one of the speakers in the plenary, who presented research on the use of the hormone hepcidin to assess iron status. He and his co-authors found that measurement of plasma hepcidin concentrations is useful for detecting iron deficiency and is more sensitive than ferritin. It is also more practical than the current approach, which involves measurements of ferritin, soluble transferrin receptor, and C-reactive protein to assess iron status.

    This is of major importance, especially for those of us who work in developing countries where anemia levels are high. In Dr. Pasricha’s sample of children in The Gambia and Tanzania, 61% had anemia, but only 13% had iron deficiency anemia. Under current recommendations, all of the anemic children would be given iron supplementation, even though most of them were not iron deficient. This is not only a poor use of resources but, more importantly, potentially hazardous.

    Iron supplementation is normally guided by hemoglobin levels, which measure anemia but not iron deficiency. Is it time to replace hemoglobin testing with hepcidin testing? There is no low-cost assay for hepcidin, so this is not a practical solution in the field just yet. In the meanwhile, it is important to consider the risks of infection and iron overload that can follow from inappropriate supplementation.

    The knowledge I obtained at Micronutrient Forum will undoubtedly enrich my work moving forward. As I continue to make my way through articles referenced in various presentations, I am already looking forward to the 4th Micronutrient Forum Global Conference, scheduled for 2016 in Mexico.

  • International Congress of Nutrition Featured in Advances in Nutrition

    International Congress of Nutrition Featured in Advances in Nutrition

    The May and September issues of Advances in Nutrition (AN) will feature selected proceedings from the 20th International Congress of Nutrition, held in Granada, Spain in September 2013. The proceedings are being published in supplements to AN; supplement coordinators were Angel Gil, Ibrahim Elmadfa, and Alfredo Martinez.

    According to Dr. Gil, “For 2014 we planned a comprehensive Congress under the theme Joining Cultures through Nutrition to promote nutrition and healthy lifestyles to people on a sustainable planet. Hence, the 20th ICN offered a modern and attractive Congress, joining different cultures, traditions, and knowledge with respect to new aspects of nutrition research, development, and innovation around the world.”

    The scientific program included 6 plenary lectures, 32 special lectures, 4 debates, 90 parallel symposia, 38 sponsored symposia, and 16 satellite symposia. A special effort was made to ensure the involvement of speakers and participants from all continents and countries, including nutrition and food specialists in research, academia, and industry, as well as policy makers, with a gender balance and applicability for all societies. During the 6-day meeting of the ICN, more than 4,000 delegates and 650 internationally renowned nutrition scientists, researchers, and clinicians from 120 countries were actively engaged in discussions, attended sessions and joined networking events. This year the planning committee was especially pleased with the participation of young investigators and nutrition professionals from developing countries.

    The IUNS and the 20th ICN wish to thank the California Walnut Commission and Mead Johnson Nutrition for generously providing educational grants to support the publication and distribution of proceedings from the 20th ICN. The contents of this supplement are solely the responsibility of the authors and do not necessarily represent official views of the IUNS.

  • Is Self-Reported Diet Data Good Enough for Nutrition Science?

    Is Self-Reported Diet Data Good Enough for Nutrition Science?

    By Colby Vorland

    Southwest Airlines is consistently rated as serving good food on their flights, yet they don’t serve food at all. Can we trust diet data if people don’t know if they even ate? This amusing anecdote was offered by Dr. David Allison at the following session during ASN’s Scientific Sessions in San Diego in April: “Not Everything That Counts Can be Counted and Not Everything That Can Be Counted Counts: How Should We Collect Dietary Data for Research?” chaired by Drs. Regan Bailey and Claire Zizza. The session was organized by ASN’s Nutritional Epidemiology, Aging/Chronic Disease, and Community/Public Health RISs. The panel took a critical perspective but also emphasized the value in using self-reported diet intake data.

    Dr. Allison was the first presenter, taking a hard position on self-reported energy intake in nutritional research: it just isn’t good enough. Not only that, it often flat-out misleads obesity research. Allison highlighted a recent paper by Archer and colleagues that looked at energy intake of respondents in NHANES from 1971-2012, finding that 67.3% of women and 58.7% of men were not physiologically plausible – i.e. the number of calories is “incompatible with life.” Correlations with the IOM’s gold standard equation for estimating total energy expenditure were 0.163 for women and 0.225 for men, effectively yielding no meaningful relationship. This “doesn’t seem like science anymore,” Allison stated. This problem has been known for a long time: in 1991, Goldberg and others looked at 37 studies across 10 countries and found that over 65% of the mean ratio between reported energy intake and basal metabolic rate measures were implausible. Forrestal also published a review in 2010 of 28 papers looking specifically at children and adolescents, finding that about half misreport energy intake.

    It is time to abandon self-reported energy intakes in favor of less misleading paths in obesity research, Allison said. It is not worthy of scientific use because the measurement errors are not random and modest, estimates are often not in the correct direction, and errors will not lead to the detection of false effects under plausible circumstances. He told a story of how originally, self-report intake data suggested that the overweight consumed less energy than they expended, but using more rigorous methods proved exactly the opposite to be true (here is a 1990 review by Schoeller). Allison said that we currently have no economic and social incentive to make a complete transition to incorporating doubly labeled water, as the cost has been flat since the 1980s. It will be painful initially, but clearly we need to make the transition.

    Dr. Amy Subar argued that energy intake is not the only important aspect of diet data, and improvements are being made to collection methods, and therefore we shouldn’t throw the baby out with the bathwater. Even if total energy intake isn’t accurate, we still can track food patterns, diet quality, nutrient intakes, and social and physical environments. Subar emphasized the utility of self-reported data- it can yield more comprehensive data with much less of an investigator burden compared to biomarkers or observation, but there is the issue with error. Within-person variation and memory are 2 potential errors, but adjustments are possible. New technologies, such as keeping food records with mobile phones or wearable sensors to reduce reactivity to monitoring and burden, are being developed to improve self-report data. In addition, Subar has been involved in the development of self-administered 24-hour recalls – ASA24 – to be able to gather a lot more data from participants without investigator burden. They have validated the accuracy of this method against interviewer-administered recalls. Dr. Subar noted that food frequency questionnaires have more bias than short-term methods but combining multiple recalls with food frequency questionnaires could reduce this.

    Dr. Elizabeth Yetley expanded on how self-reported diet data is currently relied on in national policy. For example, fortification strategies would not be possible without such data. Many considerations go into fortification, and modeling specific foods and evaluating the outcomes of such programs are important. The IOM uses diet data to track added sugars and salt disappearance. Nutrient safety can also be tracked. For example, data from the Total Diet Study in 1981 was able to quickly identify unexpected iodine sources in the food supply that were resulting in extremely high intakes. Diet data is also used for food additive/GRAS reviewing, to examine what has been added vs naturally occurring. Yetley states that there would be a significant adverse effect on policy if intake data wasn’t available. However, intake data can fail to accurately predict nutrient status, as Pfeiffer et al. (2012) have demonstrated. In 1988, Lewis and colleagues showed that cola intake could be underestimated by about 50%, though Yetley notes that surveys have been improved since then. Iron fortified cereals also virtually always underestimate the actual intake when using the amount listed on the label. Self-reported intake using label data is therefore not accurate. Infrequently consumed foods such as alcohol beverages also cause problems in nutritional epidemiology. However, Dr. Yetley reiterated that it is still crucial for many uses and we can work to improve precision while using caution when interpreting.

    Finally, Dr. Laurence Freedman discussed some studies that are being done to improve self-reported intake measurement. Freedman began by emphasizing that we can do validation for some nutrients by comparing to recovery of biological products; for example, using doubly-labeled water for energy expenditure, nitrogen for protein, potassium and sodium for themselves. The error is indicative of true intake. However, for many we don’t have accurate recovery products. Freedman described a project he is involved in – the Validation Studies Pooling Project – that aims to better understand measurement errors of food frequency questionnaires and 24-hour recalls using recovery biomarkers. For example, in the AMPM study, energy intake is underreported on 24-hour recalls by about 10%, but underreporting of intake differs by nutrient. Measurement error effects diet-health outcomes by attenuating relative risks and statistical power. This attenuation is expressed as an “attenuation factor” – the ratio of attenuation to the actual value. Preliminary data shows that attenuation factors are more extreme for energy intake compared to protein, and protein density is less so than both. Adjusting datasets from energy intake alleviates attenuation factors somewhat but does not solve it, and increasing samples size does not itself solve it because of unknown confounding. Freedman went into more detail about the ASA24 (multiple 24-hour recalls) – emphasizing that they have a high response and low attrition. With 3 or more recalls, the attenuation factor for protein improves. Relative risks increase with additional recalls compared to 1 food frequency questionnaire, and combining both methods yields even better data according to Carroll and colleagues (2012). Combining biomarkers with self-report data improves statistical power because measurement error is reduced, as Freedman and others (2011) have shown. Dr. Freedman reiterated that self-report data is extremely useful for surveillance, education, dietary guidance apart from the difficulties of using it to measure energy intake.

    It is clear that self-reported diet data has many important uses, but caution must be accepted when interpreting it. Hopefully improvements that are currently being validated will be adopted quickly, and for some measures such as energy intake, it seems necessary that current methods be abandoned because we know they are unacceptable.

  • EB 2014: The Underappreciated Role of Intestinal Fat Storage

    EB 2014: The Underappreciated Role of Intestinal Fat Storage

    By Colby Vorland, Student Blogger

    Could a “fatty intestine” be related to insulin resistance and energy balance? These and other provocative questions were addressed by Dr. Elizabeth Parks during ASN’s Scientific Sessions in San Diego. Organized by the Energy and Macronutrient Metabolism Research Interest Section, Dr. Parks gave a seminar titled, “Going with your gut: Individual responses in dietary fat absorption.”

    Dr. Parks’ research often focuses on the cephalic phase of digestion – or the early physiological response before food is even ingested. She presented a story that led her to her current path: Teff and Engelman demonstrated in 1996 with a sham feeding model that taste has an important effect on glucose metabolism and, in 2002, Robertson and colleagues published data showing that, compared to a high fat meal, consuming a high carbohydrate meal at night resulted in better glucose tolerance in the morning. Concurrently, they demonstrated a high fat meal at night yields a better fat tolerance the following day. These data suggest that there is some adaptive priming occurring and that, as Dr. Parks put it, “you best metabolize what you’ve just eaten.” She noted that we need to better match the challenge test with the eating pattern of interest.

    In 2003, Robertson and colleagues published the results of an experiment in 10 healthy participants scheduled for an endoscopy who were fed a high fat meal, then 5 hours later were fed 50 grams of fat with either 38 grams of glucose or water. The participants who consumed the glucose along with the fat in the second meal showed less lipid in the jejunum. In other words, some dietary fat was stored in the intestine from a meal and its release was accelerated when glucose in combination with fat was consumed. Since then, Dr. Parks and others have shown that simply tasting fat without ingesting it, or just consuming carbohydrate, can cause an early rise in chylomicron secretion and blood triglyceride levels. This means that the intestine stores some of the fat from previous meals; in fact, Parks estimates that ⅕ to ¼ of the fat in your meal is stored in the intestine for at least 16 hours, and it is released in response to taste. Their data also suggests that body fat is negatively correlated with the amount of fat coming from the intestine and entering the blood at a subsequent meal. If intestinal fat stores serve a regulatory function to control energy balance (by releasing in response to taste), this raises the possibility that the mechanism that controls how much is release is perturbed.

    Parks then discussed research supporting that we can taste fat. As further evidence, they have scoured literature for kinetic data and devised a mathematical model to show that rate of release of fat from the gut is consistent with the idea that this physiological response is due to our ability to taste fat. She also noted that chylomicrons may be supported in the absence of dietary fat by fatty acids in circulation entering the enterocyte, being packaged into chylomicrons, and secreted. Some data suggest that high free fatty acids increase the contribution from plasma to chylomicrons.

    Dr. Parks has also been asking: does the rate of fat absorption impact health? Dr. Jennifer Lambert and Parks have unpublished data showing that the time-course of triglyceride absorption between people can vary substantially – about 1 to 4 hours. She showed graphs of the fat absorption curves of individual participants, and the patterns were often variable, emphasizing that much remains to be understood about why this occurs. Finally, she showed that stratifying by an early or late absorption peak revealed differences in participants in each group. For example, participants with an early peak tended to be more insulin resistant than those with a later peak.

    Dr. Parks has been innovative in her use of stable isotopes for exploring lipid metabolism in health and disease. Clearly the intestine is an underappreciated tissue in fat storage and we are just on the cusp of understanding the role in which it mediates health and energy balance.

  • YPIG Asks: What’s the Winning Formula to Careers?

    YPIG Asks: What’s the Winning Formula to Careers?

    By Debbie Fetter, Guest Blogger

    It was an early start to the “Successful Scientist: What’s the Winning Formula” session hosted by ASN’s Young Professional Interest Group (YPIG) on April 29, but it was well worth it. The five panel members were pleased with the great turnout of young professionals at the early hour. Regan Bailey, PhD, RD, a Nutritional Epidemiologist from the National Institutes of Health, set the relaxed tone for the session by exclaiming, “If you are able to make it to an 8:00 a.m. session as a student, then you’re already more successful than I was!” The attendees laughed and knew they were about to get the rare opportunity to interact with and receive priceless advice about varying career paths with the well-established panel.

    Dr. Bailey proceeded to give the audience instrumental information; such as apparently there really isn’t a set way to land a government job. She reiterated the importance of networking, especially with those who could teach you. The best-kept secrets to finding a career path are serendipity and an open-mind. Also, bars in Copenhagen are a great place to hang out. That’s where Dr. Bailey ran into a prior contact and he ended up helping her get a job. You never know who may become a vital connection and help you discover your calling. This is why people are the best resource in the entire world and you should “be yourself; unless you are mean, then be nice.” It’s also important to get involved and to stay involved (i.e., professional organizations: hint, hint, ASN). Finding your balance is key, and Dr. Bailey reassured us with, “If ‘Plan A’ didn’t work. The alphabet has 25 more letters! Stay cool.”

    Marion B. Sewer, PhD from the University of California, San Diego was the next panel member to speak. Dr. Sewer told the attendees to embrace failure, since many will criticize–if the bottle of scotch hidden in your drawer is not sufficient, this may not be the career for you. Surround yourself with personal cheerleaders that understand how difficult this field is. Be a team player, but learn to say “no” to protect your time to be successful. To all the perfectionists in the crowd, Dr. Sewer said, “Sometimes, 70% is good enough.”

    After, Michael L. McBurney, PhD, FACN from DSM Nutritional Products, put in his two cents. Trust and reputation are earned, not given. Accumulate knowledge and expertise–know your science. It also probably takes about 10,000 hours to become an expert, so might as well start now. Work well with others and do what you do with intent. Most importantly, when you go on sabbatical, go somewhere warm.

    Connie M. Weaver, PhD from Purdue University, followed with an eye-opening thought, “Aiming for success is the wrong aim point, it’s not your goal. Your goal is to be of value and to like what you’re doing.” She also emphasized the significance of interdisciplinary interfaces and to explore unfamiliar areas. This is the pathway to discovery.

    The last panel member, Brian Wansink, PhD from Cornell University, told us to think of your career as chapters and each chapter could offer something different. He shared his observation that the single best predictor of success is “the number of papers you co-author and submit with a productive professor while you are in residence.” Dr. Wansink let us all in on the secret that the fourth times actually the charm. He ended with, “If my Dean knew how much I loved this job, he wouldn’t pay me.” We can all hope to find a career we are passionate and excited about; that’s definitely something to strive for.

    An open panel followed and more advice was given. Finding a way to turn negative energy into something positive was a common theme. Dr. Bailey suggests exercise for stress release. “There’s nothing a good run can’t cure,” she offers. Moving forward is important for success, Dr. McBurney told attendees. If the study didn’t work, find out why and try again. It’s also critical to set some “me” time. Dr. Weavers suggests budgeting it in, like an appointment. Dr. Sewer spends her “me” time doing home improvement. “Stress equals a new bathroom,” she shares and the audience laughed.

    In terms of figuring out your passion, Dr. Sewer said to pay attention to how you feel when you’re doing different activities to discover what you value in a career. Dr. Wansink recommends getting involved in as many projects as possible while in graduate school to explore different areas and to build your skill set. Dr. Sewer feels the winning formula to success is what works for you and keeps you motivated and excited. Never be afraid to change if you’re unsatisfied. Dr. Weaver told the attendees to find a way to be of value, and with that you will be happy. Dr. McBurney shared that life is a series of choices, some good, some bad, and no job is perfect. It’s far better to work for a great boss at a mediocre company than a mediocre boss at a great company. Dr. Wansink identified people in academics, who had a huge impact and attempted to find a commonality. He found they all not only dedicated a lot of time to their work and worked hard, but they took a seemingly strange risk that magnified their impact. Don’t be afraid of what others may think of you, if you want to take on a project that interests and entices you, do it. The real secret is there are many paths to success, you just have to find your own.

  • Added Fiber: The Answer to Our Weight Problems?

    Added Fiber: The Answer to Our Weight Problems?

    By Sarah Gold

    Determining how to stave off hunger while on a reduced calorie diet is the million-dollar question in the world of weight management. While there are many theories on how to increase satiety, slowing gastric emptying rate, or the rate at which food leaves the stomach, is a common tactic among many weight loss plans. Fiber, a carbohydrate found mostly in plant foods, is known to slow digestion and is often touted as the not-so-secret ingredient to weight loss.

    Diets that contain fiber-rich foods such as fruits, vegetables, whole foods, and legumes have been associated with a decreased risk of obesity among other health benefits. In addition, a significant amount of research over the last 30 years has linked fiber-rich foods to improved glycemic control, increased production of hunger-suppressing hormones in the hours after a meal, reduced production of hunger hormones, and overall increased satiety. In theory, reduced hunger should lead a person to eat less, and ultimately lose weight.

    For this reason, fiber has received a lot of attention from dietitians and weight management counselors to food companies and health journalists. And it has begun to show up in unlikely places. A 90-calorie brownie with 20% of your daily fiber needs – who would have thought it possible? Food scientists, that’s who! Food companies are adding synthetic, or functional, fiber to anything from white bread to sugary breakfast cereals and even baked goods. You can now get 100% of the recommended 25-30g of dietary fiber per day without ever eating a fruit, vegetable, or whole grain. However, the question that remains is, does this added fiber actually aid weight-loss?

    There are two types of naturally occurring fiber: soluble and insoluble. Both are found in plant foods, insoluble in the skins of fruits and vegetables, and soluble found in oats, legumes, and whole grains. Researchers have tested the effect of synthetic soluble and insoluble fibers on satiety with mixed results. For example, beta-glucan (the kind of fiber found in oats) has been shown to have some effect on satiety, while inulin (found in plant roots) has been ineffective. There are a number of different synthetic fibers that food companies use to boost the fiber content of food, so it’s difficult to know if the product your buying will actually offer any benefit.  In addition, studies that have tested the effect of supplemental fiber on weight management have been less than promising.

    When it comes to weight management, fiber-rich foods certainly play a role. But is fiber the magic ingredient we’ve all been looking for? Probably not.  Much of the research that links fiber-rich diets to lower weight are population studies, which are not able to completely control for other lifestyle factors that play a role in weight management such as physical activity and presence of other foods in the diet. In addition, many foods that naturally contain fiber also have a high percentage of water, which can also play a role in satiety. If you’re looking to reduce calories and control hunger, stick with whole foods that contain fiber such as whole-grains, fruits, vegetables, and legumes.

    References
    Bolton, R., Heaton, K., Burroughs, L. (1981). The role of dietary fiber in satiety, glucose, and insulin: studies with fruit and fruit juice. American Journal of Clinical Nutrition; 34(2): 211-217.

    Kristensen, M., Georg Jensen, M. (2011). Dietary fibers in the regulation of appetite and food intake. Importance of viscosity. Appetite; 56(1): 65-70.

    Lyon, M. & Kacnik, V. (2012). Is there a place for dietary fiber supplements in weight loss? Current Obesity Reports; 1(2): 59-67.

  • The Milk Debate

    The Milk Debate

    By: Jovana K.

    Over the past decade the use of low fat milk has become more prominent than the use of whole milk because there is substantial scientific evidence that consumption of foods high in fat causes weight gain and increases the risk of heart disease and cancer. However, there is some controversy over whether processed low-fat pasteurized milk can meet the needs of developing offspring and whether it should be consumed during pregnancy and development.

    Milk Consumption During Pregnancy

    Human brain development involves increased incorporation of long-chain polyunsaturated fatty acids (LCPUFA) in brain phospholipids. From the third trimester through to second year of postnatal life LCPUFA (i.e. docosahexaenoic acid (DHA) and arachidonic acid (AA)) are actively incorporated into the developing brain. The proportion of DHA and AA that the infant has reflects the presence of these fatty acids in the maternal diet. Dietary sources of LCPUFA include fish, fish oil and DHA fortified dairy including milk.

    Naturally, cow’s milk does not provide a rich source of DHA however in North America whole milk and partially skimmed milk (2%) are fortified with DHA by adding DHA rich feed additive to cattle’s diet. Skim milk or low fat milk (1%) cannot be fortified with DHA because DHA is contained in the milk fat. The DHA-fortified milk products may allow mothers who do not eat large quantities of fish to obtain the levels of DHA that their baby needs for brain and central nervous system development.

    Milk Consumption During Postnatal Development

    The American Academy of Paediatrics recommends that toddlers drink whole milk because fatty acids are helpful for brain and bone development. However, some doctors recommend low fat or skim milk to overweight or obese children. Whether low fat or skim milk protects children from weight gain is under debate.

    According to a cohort study of 12,829 US children aged 9 to 14 years, weight gain is associated with excess calorie intake and consumption of low fat or skim milk, but is not associated with drinking whole milk products. This finding although surprising is consistent with some animal findings. Pigs fed reduced-fat milk gain weight easily while pigs fed whole milk stay lean. Male rats fed whole milk had significantly lower concentrations of plasma triglycerides, very low-density lipoproteins and apolipoprotein B than rats fed low fat milk. The effects of whole milk on lipid profile and body composition are not well understood, but the process of removing fat from milk may in part be responsible for some of the observed effects.

    Milk is an emulsion of butterfat globules and water-based fluid. Butterfat contains unique nutrients that support thyroid function and help the body develop muscle rather than fat. The butterfat properties of whole milk are different from that of low fat or skim milk, which may help to explain the effects of whole milk on body composition. Future studies should explore the mechanism by which whole milk may protect infants from gaining weight.