Given the public health burden of lifestyle-related diseases, dietary interventions have been studied widely. Successful dietary approaches, such as the Mediterranean and DASH diets, are often limited by the regional food system and cultural adaptation.
The New Nordic Diet (NND) was developed as part of the Danish multidisciplinary OPUS project (1). The NND was designed by gastronomic, nutritional, and environmental specialists to be a culturally sensitive Nordic diet that is palatable, healthy and environmentally sustainable. The average Danish diet (ADD) tends to be low in fruits and veggies, high in animal foods, sugar products and processed foods. The NND is a predominantly plant-based cuisine comprised of locally grown fruits and veggies in season (more berries, cabbage, root vegetables but less tomato and cucumber), whole grains, rapeseed oil, fish and shellfish, high quality meat but less of it, and more organic produce.
The health effects of the NND were compared with the ADD in a cohort of centrally obese adults (2). A “shop model” was used by participants to collect food ad libitum and free of charge. Cooking courses and cookbooks were also provided as part of the study. Despite the ad libitum design, the NND group consumed significantly less energy (- 422 calories/d) than the ADD group and had higher self-evaluated diet satisfaction. Significant weight loss in the NND group was accompanied by greater reductions in anthropometric measures. Aside from weight loss, systolic and diastolic blood pressure, plasma triglyceride, total cholesterol, and VLDL cholesterol were reduced in the NND group. It is also worth noting that CRP (C-reactive protein; inflammatory biomarker) levels decreased in the NND group relative to the ADD group. This is in accordance with previous studies where a plant based diet has been associated with lower levels of inflammatory biomarkers.
Another study evaluated the environmentally sustainable elements of the NND (3). The effects of diet composition, food transportation (local vs imports), and production method (organic vs conventional) were evaluated based on 16 environmental impact categories, including global warming potential, respiratory inorganics, and nature occupation. The socioeconomic impact of choosing NND resulted in 5% reduction in the overall environmental cost of ADD. The reduction in the overall environmental cost increased from 5% to 32% when the effect of NND's high organic content was discounted (note: the overall environmental cost of ADD was equated to €835/person per year). In other words, the greater reductions in the overall environmental costs were mainly driven by reduced meat consumption but higher quality meat consumption (i.e. less beef and more grass-fed lamb) and few imported commodities. Organic produce unfavorably increased environmental cost associated with inefficient land use.
Similar multidisciplinary projects are needed in other parts of the world to develop evidence-based strategies that are specific to each region, where policy makers could make use of evidence-based strategies to improve environmental policies. Adapting a regional based diet has the potential to protect both health and the environment but future research should assess the long-term potential of food-environment studies.
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.
Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Dr. Meydani is a respected leader in the field. A long-time member, she has also served as ASN's Vice President and Vice-President Elect, as well as in a wide variety of other important roles. In the interview (click link), Dr. Meydani discusses her goals for her presidency and her views on the future of the field.
Dr. Simin Meydani (right) and immediate past president Dr. Gordon Jensen share a fun moment during the symbolic passing of the gavel during the annual meeting in San Diego.
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.
Read the guest blog here and tell us what you think about FDA's suggested changes!
The Journal of Nutrition, The American Journal of Clinical Nutrition, and Advances in Nutrition, remain the most trusted sources of rigorous, cutting-edge research in the field. To learn what keeps one of ASN's publications top-ranked, we spoke with JN Editor Teresa A. Davis, PhD, who became Editor on January 1, 2014. Dr. Davis is a Professor of Pediatrics at the Children's Nutrition Research Center at Baylor College of Medicine and a Past President of ASN. In this interview, she discusses JN's submission process, her goals for the publication, and some exciting changes readers can expect to see in future issues.
Nutrition Notes Daily is now available. This concluding version features a recap of the 100% fruit juice sponsored satellite, a summary of video coverage, and an interview with the Danone International Prize recipient Dr. Gokhan Hotamisligil. Attendees can share their thoughts on the meeting by completing the post-EB survey here.
Over the last century, food fortification has been one of the great public health successes in nutrition, dramatically reducing the risk for diseases like pellagra, rickets, and goiter. But as Dr. Christine Taylor discussed, there has been a gradual paradigm shift in how we think about fortification. These changes were discussed in the session: “Fortification and Health: Opportunities and Challenges” sponsored by ILSI North America on Saturday, April 26 at Experimental Biology in San Diego. The session was chaired by Dr. Johanna Dwyer and Kathryn Wiemer.
The session began with Dr. David Allison giving a touching tribute to the late Dr. John Milner, who was originally a chair of the session. It was noted that Milner was a promoter of public-private relationships, and “in the spirit of John Milner” was a frequent phrase. His impact on nutrition science and many of the speakers was clearly boundless. Read more about his prolific career here.
Read the entire post on Colby's blog, which features an in-depth summary of this event.
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.
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.