Is the U.S. Ready for Sustainable Dietary Guidelines? New Research Makes a Compelling Case
By Sarah Reinhardt
Back in February 2015, a committee of leading health and nutrition experts published a scientific report intended to inform the development of the 2015-2020 Dietary Guidelines for Americans (Dietary Guidelines), the national nutrition recommendations that guide the food choices of millions of kids, adults, seniors, and veterans every day. For the first time, the report contained a significant and rigorous review of research on sustainable eating, including the ways that our food choices can impact our climate, natural resources, and ability to produce food in the future.
But within months, sustainable diets were a nonstarter — at least as far as federal nutrition policy was concerned.
By October that year, the Obama administration's secretaries of agriculture and health and human services announced their decision to reject sustainable diets on principle. In doing so, they sided with meat industry groups who claimed it was outside the scope of the Dietary Guidelines, and who had lobbied Congress to help make sure it didn't happen.
Fast forward to today, as a new committee prepares the scientific report underpinning the 2020-2025 Dietary Guidelines—under an administration that has been decidedly less interested in science-based policymaking and protecting public health and the environment. It might seem all but impossible that sustainability should make a triumphant return now. Indeed, the 2020 committee wasn't asked to review current literature on the topic in the first place.
But a lot can change in five years.
From Congress to Corporate America, Climate Change is Catching Up
These last five years, in particular, were the hottest ever recorded, producing some of the worst wildfires in history in places like California and Australia. Family farm bankruptcies hit an eight-year high as farmers across the U.S. faced extreme weather events, rising debt, and the fallout from a trade war. And new Congressional resolutions, corporate alliances, and youth-led movements helped catapult issues like conservation and climate change to the center of national conversation.
Meanwhile, the evidence connecting dietary patterns, sustainability, and food insecurity has become a lot harder to ignore. Between July 2015 and September 2019, nearly 100 new scholarly articles were published on this topic, including 22 focused specifically on U.S. diets. That's more than four times the number of articles published on the same topic between 2000 and 2015 — in about a quarter of the time.
How do I know?
Rethinking Dietary Guidance: A New Review of Sustainable Diets Research
These are the findings of a new peer-reviewed paper I authored with colleagues at the Union of Concerned Scientists (UCS) and the Tufts University Friedman School of Nutrition Science and Policy which updated the systematic review of evidence on sustainable diets, replicating the methodology used by the scientific committee and USDA. In other words, it's the systematic review that could (and should) have been the charge of the 2020 committee.
In addition to revealing a rapidly expanding body of research, our results pointed to several key conclusions: New US research continues to support prior findings that diets higher in plant-based foods and lower in animal-based foods can provide greater benefits for human health and the environment, and that such diets can be achieved without excluding any food groups. However, recent U.S. research challenges prior findings that diets aligning with national dietary guidelines are consistently more sustainable than what we're already eating. Our results show that the healthy diet recommended by the Dietary Guidelines may actually result in similar or increased heat-trapping emissions, energy use, and water use compared with the current average U.S. diet.
What that means is this: if the Dietary Guidelines continue to sideline sustainability research, the diet the U.S. government recommends today could put a healthy diet further out of reach tomorrow.
What's more, by sidelining conversations about sustainability, this committee of experts will miss out on a critical opportunity to identify research gaps that can help inform directions for future studies. Though we now know much more about the environmental impacts of our eating patterns, we still have a lot to learn about the social and economic dimensions of sustainable diets. For example, what are the costs associated with more environmentally sustainable diets? What would dietary shifts mean for farmers, food producers, and families — particularly those who face food insecurity and the consequences of climate change firsthand?
The better we understand the practical implications of our diets, the better we can leverage that knowledge to protect our food systems and the health of our children, and their children, and so on, for generations to come.
What Do We Have to Lose?
Although the 2020 committee wasn't charged with reviewing current research on dietary patterns and sustainability, it has an obligation to review current scientific and medical knowledge, as well as public comments, to ensure its findings address the most pressing diet-related threats to public health. What's more, the committee has an opportunity to include additional recommendations in a discussion section within its scientific report, due to federal agencies in May 2020.
A lot can change in five years. We're not waiting until 2025 to find out what's at risk if we don't start supporting sustainable food policies.
If you're an advocate, scientist, or other member of the general public, you can submit a public comment to the scientific committee through the UCS website until May 2020. (Check out our comment guide for tips and talking points.)
If your organization or institution can lend its support to sustainable dietary guidance, join more than 50 organizations and leading public health experts nationwide in signing our letter to the U.S. Department of Agriculture and the Department of Health and Human Services asking them to include sustainability research in the 2020-2025 Dietary Guidelines.
For more information, take a look at our policy brief, In Support of Sustainable Eating, and see the public comment I delivered to the Committee at a recent public meeting in Houston, below.
Dietary Guidelines Public Meeting 4: Oral Comment
January 24, 2020
My name is Sarah Reinhardt. I am a public health dietitian and the Lead Analyst of Food Systems and Health at the Union of Concerned Scientists in Washington, DC.
I want to thank the members of the Committee for lending your time and expertise to this process. Thank you to the staff at the USDA and HHS for the hard work that you do to make this process transparent and accessible to the public.
The stated goal of the Dietary Guidelines for Americans is "to make recommendations about the components of a healthy and nutritionally adequate diet to help promote health and prevent chronic disease for current and future generations." I'm here today to ask the Committee to fulfill its obligation to protect the health of future generations by evaluating the scientific basis for sustainable diets and incorporating its findings into the scientific report.
The 2015 Dietary Guidelines Advisory Committee, in its rigorous review of the evidence on the relationship between dietary patterns, sustainability, and food security, found that "a diet higher in plant-based foods, such as vegetables, fruits, whole grains, legumes, nuts, and seeds, and lower in calories and animal-based foods is more health promoting and is associated with less environmental impact than is the current U.S. diet." Though dismissed amid political controversy, these findings remain relevant and provide a foundation from which the current committee may draw conclusions.
However, the last five years have also seen rapid growth in research on healthy and sustainable diets. Because the present Committee was precluded from updating the systematic review on this topic, my colleagues at the Union of Concerned Scientists and the Friedman School of Nutrition Science and Policy undertook this task. Closely replicating the methodology described in the Scientific Report of the 2015 Dietary Guidelines Advisory Committee, we evaluated the body of scientific literature on dietary patterns, food sustainability, and food security to identify relevant studies published between July 2015 and September 2019. Our results, now under scientific peer review, include twenty-two relevant studies on U.S. dietary patterns alone.
Our results broadly support the key findings of the 2015 Committee, but also point to another important conclusion: Of eight studies explicitly comparing the current average U.S. diet to the Healthy U.S.-style diet recommended by the Dietary Guidelines, a majority found that the Healthy U.S.-style diet is not inherently more sustainable. What that means is this: If the federal government publishes and promotes Dietary Guidelines that disregard sustainability research, the diet it recommends today will put a healthy diet further out of reach tomorrow.
In its forthcoming report, I urge the Committee to review and report findings based on the current body of scientific research on sustainable diets, including the systematic review by the 2015 Committee and the recent update we have completed, which will be submitted to the public record for the committee's consideration.
By Melissa Gaskill
Two decades ago scientists and volunteers along the Virginia coast started tossing seagrass seeds into barren seaside lagoons. Disease and an intense hurricane had wiped out the plants in the 1930s, and no nearby meadows could serve as a naturally dispersing source of seeds to bring them back.
Restored seagrass beds in Virginia now provide habitat for hundreds of thousands of scallops. Bob Orth, Virginia Institute of Marine Science / CC BY 2.0<p>The paper is part of a growing trend of evidence suggesting seagrass meadows can be easier to restore than other coastal habitats.</p><p>Successful seagrass-restoration methods include <a href="https://www.sciencedirect.com/science/article/abs/pii/S0304377099000078?via%3Dihub" target="_blank">transplanting shoots</a>, <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1061-2971.2004.00314.x" target="_blank" rel="noopener noreferrer">mechanized planting</a> and, more recently, <a href="https://www.nature.com/articles/s41467-020-17438-4" target="_blank" rel="noopener noreferrer">biodegradable mats</a>. Removing threats, proximity to donor seagrass beds, planting techniques, project size and site selection all play roles in a restoration effort's success.</p><p>Human assistance isn't always necessary, though. In areas where some beds remain, seagrass can even recover on its own when stressors are reduced or removed. For example, seagrass began to recover when Tampa Bay improved its water quality by reducing nitrogen loads from runoff by roughly 90%.</p><p>But more and more, seagrass meadows struggle to hang on.</p><p>The marine flowering plants have declined globally since the 1930s and currently disappear at a rate equivalent to a football field every 30 minutes, according to the <a href="https://www.unep.org/resources/report/out-blue-value-seagrasses-environment-and-people" target="_blank" rel="noopener noreferrer">United Nations Environment Programme</a>. And research published in 2018 found the rate of decline is <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GB005941" target="_blank" rel="noopener noreferrer">accelerating</a> in many regions.</p><p>The causes of decline vary and overlap, depending on the region. They include thermal stress from climate change; human activities such as dredging, anchoring and coastal infrastructure; and intentional removal in tourist areas. In addition, increased runoff from land carries sediment that clouds the water, blocking sunlight the plants need for photosynthesis. Runoff can also carry contaminants and nutrients from fertilizer that disrupt habitats and cause algal blooms.</p><p>All that damage comes with a cost.</p>
The Value of Seagrass<p>As with ecosystems like rainforests and <a href="https://therevelator.org/mangroves-climate-change/" target="_blank">mangroves</a>, loss of seagrass increases carbon dioxide emissions. And that spells trouble not just for certain habitats but for the whole planet.</p><p>Although seagrass covers at most 0.2% of the seabed, it <a href="https://www.unenvironment.org/news-and-stories/story/seagrass-secret-weapon-fight-against-global-heating" target="_blank">accounts for 10%</a> of the ocean's capacity to store carbon and soils, and these meadows store carbon dioxide an estimated 30 times faster than most terrestrial forests. Slow decomposition rates in seagrass sediments contribute to their <a href="https://www.researchgate.net/publication/238506081_Assessing_the_capacity_of_seagrass_meadows_for_carbon_burial_Current_limitations_and_future_strategies" target="_blank" rel="noopener noreferrer">high carbon burial rates</a>. In Australia, according to <a href="https://onlinelibrary.wiley.com/doi/10.1111/gcb.15204" target="_blank" rel="noopener noreferrer">research</a> by scientists at Edith Cowan University, loss of seagrass meadows since the 1950s has increased carbon dioxide emissions by an amount equivalent to 5 million cars a year. The United Nations Environment Programme reports that a 29% decline in seagrass in Chesapeake Bay between 1991 and 2006 resulted in an estimated loss of up to 1.8 million tons of carbon.</p>
Eelgrass in the river delta at Prince William Sound, Alaska. Alaska ShoreZone Program NOAA / NMFS / AKFSC; Courtesy of Mandy Lindeberg / NOAA / NMFS / AKFSC<p>Seagrasses also protect costal habitats. A healthy meadow slows wave energy, reduces erosion and lowers the risk of flooding. In Morro Bay, California, a 90% decline in the seagrass species known as eelgrass caused extensive erosion, according to a <a href="https://www.sciencedirect.com/science/article/abs/pii/S0272771420303528?via%3Dihub" target="_blank" rel="noopener noreferrer">paper</a> from researchers at California Polytechnic State University.</p><p>"Right away, we noticed big patterns in sediment loss or erosion," said lead author Ryan Walter. "Many studies have shown this on individual eelgrass beds, but very few studies looked at it on a systemwide scale."</p><p>In the tropics, seagrass's natural protection can reduce the need for expensive and often-environmentally unfriendly <a href="https://www.nioz.nl/en/news/zeegras-spaart-stranden-en-geld" target="_blank" rel="noopener noreferrer">beach nourishments</a> regularly conducted in tourism areas.</p><p>Seagrass ecosystems improve water quality and clarity, filtering particles out of the water column and preventing resuspension of sediment. This role could be even more important in the future. By producing oxygen through photosynthesis, meadows could help offset decreased oxygen levels caused by warmer water temperatures (oxygen is less soluble in warm than in cold water).</p><p>The meadows also provide vital habitat for a wide variety of marine life, including fish, sea turtles, birds, marine mammals such as manatees, invertebrates and algae. They provide nursery habitat for <a href="https://wedocs.unep.org/bitstream/handle/20.500.11822/32636/seagrass.pdf?sequence=1&isAllowed=y" target="_blank" rel="noopener noreferrer">roughly 20%</a> of the world's largest fisheries — an <a href="https://www.floridamuseum.ufl.edu/science/seagrass-meadows-harbor-wildlife-for-centuries/" target="_blank" rel="noopener noreferrer">estimated 70%</a> of fish habitats in Florida alone.</p><p>Conversely, their disappearance can contribute to die-offs of marine life. The loss of more than 20 square miles of seagrass in Florida's Biscayne Bay may have helped set the stage for a widespread <a href="https://www.wlrn.org/2020-08-14/the-seagrass-died-that-may-have-triggered-a-widespread-fish-kill-in-biscayne-bay" target="_blank">fish kill</a> in summer 2020. Lack of grasses to produce oxygen left the basin more vulnerable when temperatures rose and oxygen levels dropped as a result, says Florida International University professor Piero Gardinali.</p>
Damaged Systems, a Changing Climate<p>Governments and conservationists around the world have already put a lot of effort into coastal restoration efforts. And that's helped some seagrass populations.</p><p>Where stressors remain, though, restoration grows more complicated. <a href="https://www.rug.nl/research/portal/en/publications/the-future-of-seagrass-ecosystem-services-in-a-changing-world(3a8c56db-7bed-4c9e-ac7f-c72453e2a102).html" target="_blank">Research</a> published this September found that only 37% of seagrass restorations have survived. Newly restored meadows remain vulnerable to the original stressors that depleted them, as well as to storms — and <a href="https://www.ecowatch.com/tag/climate-crisis">climate change</a>.</p>
Seagrass in Dry Tortugas National Park, Florida. Alicia Wellman / Florida Fish and Wildlife / CC BY-NC-ND 2.0<p>In Chesapeake Bay a cold-water species of seagrass is currently hitting its heat limit, especially in summer, according to Alexander Challen Hyman of University of Florida's School of Natural Resources and Environment. As waters continue to warm due to climate change, the species likely will disappear there.</p><p>Climate-driven sea-level rise complicates the problem as well. Seagrasses thrive at specific depths — too shallow and they dry out or are eaten, too deep and there isn't enough light for photosynthesis.</p>
But There’s Good News, Too<p>Luckily, left to its own devices, a seagrass meadow can flourish for hundreds of years, according to a <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2019.1861" target="_blank" rel="noopener noreferrer">paper</a> published last year by Hyman and other researchers from the University of Florida. The researchers arrived at their conclusion by looking at shells of living mollusks and fossil shells to estimate the ages of meadows in Florida's Big Bend region on the Gulf Coast.</p><p>That area has extensive, relatively pristine seagrass meadows. "Our motivation was to understand the past history of these systems, and shells store a lot of history," said co-author Michal Kowalewski.</p><p>A high degree of similarity between living and dead shells indicates a stable area, while a mismatch suggests an area shifted from seagrass to barren sand. The researchers found that long-term accumulations of shells resembled living ones, suggesting that the seagrass habitats have been stable over time.</p><p>That stability allows biodiversity to thrive, creating conditions where specialist species can survive and flourish, according to Hyman.</p><p>Discovering the long-term stability of seagrass meadows has implications for choosing restoration sites, Kowalewski notes.</p><p>"There must be reasons they thrive in one place, while a mile away they don't and fossil data says they probably never did," he said. "If we remove a seagrass patch, we cannot hope to plant it somewhere else. It's not just the seagrass that is special. The location at which it's found is special, too."</p><p>A better approach is conserving these habitats in the first place, but we're not doing enough of that right now. The UN reports that marine protected areas safeguard just 26% of recorded seagrass meadows, compared with 40% of coral reefs and 43% of mangroves.</p>
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