As summer temperatures ramp up I thought it would be a good idea to discuss heat stress and how our body can be negatively affected by long hot days on the field or trail. With proper knowledge and some dietary modifications it’s possible to prevent heat stress from occurring. Here’s some background information to help put it in perspective.
Water, water everywhere
Our bodies are mostly water (50-70%, depending on fat vs. muscle composition). Water serves many important functions: nutrient digestion and transportation; removal of body waste (urine); amniotic (joint) fluid, saliva, and bile; maintenance of blood volume; and body temperature regulation. With regard to temperature regulation, dissipation of heat via sweat evaporation is the most effective way of keeping our bodies cool during prolonged exercise in hot or humid environments.
Sweating the details
When our core body temperature rises, our cardiovascular systems shunts hot blood from our core to our skin. Sweat then transfers this heat outside of our body where it is dissipated via evaporation. In addition to heat and water, sweat contains a number of important electrolytes, namely sodium, chloride, and small amount of potassium. If we exercise in hot environments and/or for more than 60 minutes, it very important to replace the water and minerals lost via sweat.
Failure to replace lost water and/or electrolytes may result in one of three forms of heat stress: 1) heat exhaustion, 2) heat stroke, and 3) hyponatremia. Heat exhaustion is defined as a 3% or greater loss of body weight in fluids. Less fluid volume = thicker blood = less oxygen transport to our muscles = premature fatigue (exhaustion). Heat exhaustion is characterized by excessive sweating (our body’s way of trying to keep us cool). A 1-3% loss of bodyweight negatively affects performance, and if heat exhaustion goes unchecked it may progress to a life-threatening case of heat stroke.
Heat stroke occurs after a significant amount of fluid (>3% body weight) volume is lost and represents an overload on our temperature regulation system. Our body simply does not have enough fluid (blood) to shunt to our skin, and therefore we stop sweating — a very, very bad sign. If physical activity is not stopped and/or body fluids are not replaced, core temperature may rise to deadly levels (>105 degrees Farenheit).
Hyponatremia refers to low sodium levels. Sodium is needed to maintain fluid balance in our body and also plays a critical role in muscle contraction. Hyponatremia occurs when we replace water lost via sweat, but forget about the electrolytes (mostly sodium and potassium) lost via sweat. Chugging gallons of water in the heat is better than developing heat exhaustion or heat stroke, but it presents its own problems. You lose water and sodium via sweat. If you replace just the water then you are further diluting the sodium concentration in your body. This can result in severe, debilitating muscle cramps and compromised athletic performance.
Typically we get plenty of salt (Na+Cl–) in our diet to maintain sodium and chloride stores during moderate intensity and duration exercise. However, as exercise duration increases past 1-2hrs in hot and/or humid climates, electrolyte replacement (particularly sodium and to a lesser extent potassium) can benefit performance. To avoid hyponatremia, drink a sports beverage that contains water AND electrolytes: 100-150mg sodium and 30-40mg potassium per 8oz of fluid is ideal. While you’re at it, you should also consume a simple form of carbohydrate to maintain energy levels. Suggested intake is 30-60 grams of carbohydrate per hour, ideally in a 6-8% solution — your body cannot absorb greater quantities of carbohydrate, especially during intense exercise. A 6-8% solution is very important because this matches the carbohydrate concentration (osmoality) of your blood.
Food for thought
Sports beverages like Gatorade have been specifically developed to help you prevent or cope with heat stress. It’s possible to make your own sports drink from diluted fruit juice (a source of potassium) and table salt. Avoid juices with intact fiber. How much water, juice, and salt would be needed to replicate the ideal electrolyte concentration and osmoality? In addition to sport beverages, what other modifications could you make to your diet to prevent heat stress?
Words. They’re pretty nice, wouldn’t you agree? They allow us to talk, read, and articulate our thoughts. Without them we wouldn’t be able to communicate very effectively (can you imagine a world of grunters?). Nor would we be able understand things to quite the same degree. And we certainly wouldn’t be able to debate the finer details of various topics near and dear to our hearts like, say, baseball, dark chocolate, or the environment.
Given the power and utility of words, they are the primary focus a new program called the Lexicon of Sustainability. “Lexicon” is a fancy word for “language”. And “sustainability” is, well, a fancy word that many people banter about, but don’t truly understand or embrace. The Lexicon of Sustainability is based on a simple premise: people can’t be expected to live more sustainable lives if they don’t even know the most basic terms and principles that define sustainability.
For instance, what are food miles? What is the difference between annual vs. perennial plants? Organic vs. conventional food? Grass-fed vs. grain-fed meat? What is food sovereignty? Or biodiversity? For most people, these topics aren’t even a consideration because they don’t even know the words for them exist. In the meantime, the health of our bodies and our planet hangs in the balance. The hope of the Lexicon of Sustainability project is that as more people become aware of these issues, the more progress we’ll make towards achieving a socially, economically, and ecologically sustainable future.
Food for thought
Take a moment to look at the following samples of educational art pieces produced by The Lexicon of Sustainability. There are many, many more posted on their website, as well as videos produced in cooperation with PBS.org. Have you ever thought about these words and concepts before? If yes, thank you (please pass them on). If not, perhaps it’s because you never had the opportunity to learn them before. Check out The Lexicon of Sustainability website for more words and information.
After a long, cold winter, spring has finally sprung in this neck of the woods. The sun is shining, the snow is melting, and tiny green leaves are beginning to poke through the brown earth. It’s a seasonal cycle that birds, bees, and bunnies look forward to every year, as do the 1% of folks who grow food for the remaining 99% of us. That’s right, I’m talking about farmers.
The industrial U.S. food system is a thing of absolute wonder. It’s a complex network of machines, synthetic chemicals, and economies of scale that produces a staggering amount of food – enough to provide each American with 3,800 kilocalories every day (U.S. Department of Agriculture), plus countless more that are fed to livestock and/or exported to exotic places across the globe.
And yet less than 1% (!) of Americans identify themselves as farmers. And of those who do, only 45% claim farming as their full-time occupation, meaning that the majority of farmer income is actually earned off-farm. In addition, the average age of U.S. farmers is approaching sixty years old. To put this matter into a historical context, at one point in the early 1900s the vast majority of Americans farmed. But the number of U.S. farms peaked at 6.8 million in 1937, then declined to the current two million. Keep in mind that there are more than 300 million citizens in the United States. (All data from the U.S. Environmental Protection Agency).
My point of this blog post is threefold: First, most of us are not actively involved in food production. Second, most of us don’t know a spade from a harrow (meaning that we haven’t got a clue about the time, effort, and energy required to produce food). Third, most of us keep clamoring for cheaper and cheaper food (from farmers who already struggle to make a living working multiple jobs), even as we eat more and more of it.
Food for thought
Please consider the plight of U.S. farmers. Not only for their health, but for your health as well. There is certainly nothing wrong with choosing career paths outside of farming (we need mechanics, doctors, teachers, and plumbers, too), but let’s not forget about the people that literally put food on our table. If you haven’t yet, I strongly suggest volunteering for a day (or more!) at a local farm or community garden. Get to know the people and places that produce your food. The rewards will extend far beyond your belly.
Welcome to the latest and greatest wrinkle in the world of nutrition science: a recent study has suggested that saturated fat – long considered a primary culprit in the development of heart disease – is perhaps no more than an innocent bystander. The meta-analysis, published March 18th in the Annals of Internal Medicine, found no association between saturated fat intake and increased risk of heart attacks or other cardiac events.
To be clear, the researchers did find a link between trans fat intake and heart disease. But they found no evidence that saturated fat increased the risk of heart disease, or that unsaturated fats decreased the risk of heart disease. Does this mean that you can now inhale steak, butter, and whole milk with abandon? Or stop taking those expensive flaxseed and/or fish oil supplements? Well, it depends.
On one hand, some folks believe that this study demonstrates a need to more specifically analyze individual types of saturated and unsaturated fats (e.g., some saturated dairy fats are associated with a lower risk of heart disease, whereas some unsaturated vegetable fats are associated with a higher risk of heart disease).
On the other hand, some folks believe that this study demonstrates a need to stop focusing on nutrients altogether and start focusing on whole foods. For instance, Dr. Frank Hu, a professor of nutrition and epidemiology at the Harvard School of Public Health who was not involved with the study at hand opined that “The single macronutrient approach is outdated. I think future dietary guidelines will put more and more emphasis on real food rather than giving an absolute upper limit or cutoff point for certain macronutrients.”
Food for thought
The whole food approach is nothing new. For instance, take a look back at Jamie’s October blog post about the Mediterranean Diet. Or, for a more lengthy review, read Michael Pollan’s essay, Unhappy Meals, that was originally published in the January 2007 edition of the New York Times Magazine. Pollan’s take-home message is definitely good food for thought: Eat food. Not too much. Mostly plants.
What do you think? Should saturated fat be avoided like the plague? Or is it more complicated than that?… Or perhaps more simple?
A recent proposal by the U.S. Food and Drug Administration (FDA) to revamp food labels on packaged food for the first time in twenty years is welcome news. The new design promises to be easier to read and potentially more effective at communicating important health information to consumers. However, could the FDA do even better? For instance, Great Britain encourages front-of-package “traffic light” labels on processed foods (see Figure 1). Despite strong resistance from food industry groups, the British National Health Service believes that such labels are quite useful for consumers.
Indeed, a recent study (Thorndike et al, 2014) conducted in the United States suggests that traffic light labels might be an effective intervention for obesity. Using the cafeteria at Massachusetts General Hospital as their study site, researchers reported that sales of “red” foods decreased from 24% of food sales at the start to 20% at two years; red beverages went from 26% of beverage sales to 17% at two years. Green foods sales grew from 41% to 46%, and green beverages from 52% to 60%. The researchers concluded that, “These results suggest that simple food environment interventions can play a major role in public health policies to reduce obesity”.
What information is important to you?
What information do you feel is important to consider when purchasing food? In addition to the typical energy and nutrient content present on current food labels, what other information would you like to see? Think beyond the typical quantities represented on food labels and consider more complex food qualities. Back in 2011 the University of California, Berkeley, School of Journalism, asked this very same question in an open label design contest. Take a look at some of the contest submissions below.
Food for thought
Which of the above label designs do you like most? What unique bits of information or methods of communication do you think are most important and effective? Is there any other information that you imagine would helpful for consumers to be aware of? If so, help the FDA out and come up with a better label design!
On February 27th the U.S. Food and Drug Administration announced a planned revision to its longstanding Nutrition Facts label design. Though it may seem like an inconsequential bit of food package real estate to some people, the Nutrition Facts panel actually provides a lot of key information for consumers – everything from serving size to calorie content to macro and micronutrient content. However, the current version (in effect since 1994) has been deemed out-of-date and a bit misleading. Or at least not as effective as it could be.
According to the FDA, the label revisions “would replace out-of-date serving sizes to better align with how much people really eat, and it would feature a fresh design to highlight key parts of the label such as calories and serving sizes” (FDA ). In a concerted effort to educate and empower consumers about nutrition-related health issues such as heart disease and obesity, some specific label changes proposed by the FDA would:
- Require information about the amount of “added sugars” in a food product. The 2010 Dietary Guidelines for Americans states that intake of added sugar is too high in the U.S. population and should be reduced. The FDA proposes to include “added sugars” on the label to help consumers know how much sugar has been added to the product.
- Update serving size requirements to reflect the amounts people currently eat. What and how much people eat and drink has changed since the serving sizes were first put in place in 1994. By law, serving sizes must be based on what people actually eat, not on what people “should” be eating.
- Present “dual column” labels to indicate both “per serving” and “per package” calorie and nutrition information for larger packages that could be consumed in one sitting or multiple sittings.
- Focus on potassium and vitamin D intakes, nutrients that some in the U.S. population are not getting enough of, which puts them at higher risk for chronic disease. Vitamin D is important for its role in bone health. Potassium is beneficial in lowering blood pressure. Vitamins A and C would no longer be required on the label, though manufacturers could declare them voluntarily.
- Revise the Daily Values for a variety of nutrients such as sodium, dietary fiber and Vitamin D. Daily Values are used to calculate the Percent Daily Value on the label, which helps consumers understand the nutrition information in the context of a total daily diet.
- While continuing to require “Total Fat,” “Saturated Fat,” and “Trans Fat” on the label, “Calories from Fat” would be removed because research shows the type of fat is more important than the amount.
- Refresh the format to emphasize certain elements, such as calories, serving sizes and Percent Daily Value, which are important in addressing current public health problems like obesity and heart disease. (FDA)
All in all the proposed label updates have received widespread support from folks in the nutrition and public health fields. On the other hand, Food industry groups like the Grocery Manufacturers Association, are a little less enthusiastic. The FDA will officially release their proposal on March 3rd, after which a public comment period will open for 90 days. It will be interesting to see how it turns out.
Food for thought
How much do you pay attention to the Nutrition Facts panel on packaged foods? What do you think of the proposed label revision? Do you think it is an improvement on the original design? Is there any additional information that you would like to see highlighted or changed? Next week we’ll take a look at food labeling in other countries.
FDA news release, February 24, 2014: http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm387418.htm
Of the approximately seven billion people inhabiting our planet today, 842 million live in (or die of) hunger every day (United Nations World Food Programme). This, despite the fact that there is more than enough food to go around. What gives?
It’s not about production
According to the United Nations Food and Agriculture Organization, there are 2700 calories available worldwide per person per day. To put that in perspective, the average American consumes approximately 2500 calories per day (Centers for Disease Control). Therefore, the problem of world hunger is not a shortage of food production. We already produce enough food. The problem of world hunger is inadequate food distribution… Or is it?
It’s not about distribution
Before we attempt to solve world hunger by producing even more food or shipping food long distances at great expense to the environment, it would be a good idea take a step back and a holistic look forward. Case in point: the United States. Here in a country with notable rates of obesity and a strong food distribution infrastructure, six percent of the population experiences “very low food security”. Meaning that roughly seven million households go hungry every day (Feeding America). This goes to show that hunger – nationwide or worldwide – is not simply about food production or distribution. It’s about a multitude of factors, including economics, education, compassion, empowerment, and, ultimately, food sovereignty.
It’s about food sovereignty
“Give a man a fish and you feed him for the day. Teach a man to fish and you feed him for a lifetime.” If you understand the basis of this quote then you understand, in part, the concept of food sovereignty. As defined by the 2007 Declaration of Nyéléni, food sovereignty is the right of all people to “healthy and culturally appropriate food produced through ecologically sound and sustainable methods, and their right to define their own food and agriculture systems.”
Though complex, food sovereignty has several basic premises. It focuses on food for people by putting the right to sufficient, healthy, and culturally appropriate food for all at the center of food and agriculture policies. It values food providers by respecting all those who grow, harvest, and process food. It localizes food systems by bringing food providers and consumers closer together so they can make joint decisions on that benefit and protect all. It respects the right of food providers to have control over their land, seeds, and water and rejects the privatization of natural resources. It builds knowledge and skills by sharing local knowledge and skills that have been passed down over generations. Lastly, food sovereignty works with nature by focusing on production and harvesting methods that add to environmental health rather than detract from it. For more information, visit the website of the U.S. Food Sovereignty Alliance.
Food for thought
World hunger is not due to a simple shortage of food production or inadequate distribution. It’s due to a lack of food sovereignty. Can you think of any additional factors not mentioned in the previous paragraph that contribute to food sovereignty? More importantly, what steps do you think need to be taken – at both a local and global level – to achieve a more food sovereign world?
Centers for Disease Control: http://www.cdc.gov/nchs/fastats/diet.htm
United Nations Food and Agriculture Organization, Agriculture and Food Security: http://www.fao.org/docrep/x0262e/x0262e05.htm
United Nations World Food Programme: http://www.wfp.org/hunger/stats
United States Food Sovereignty Alliance: http://usfoodsovereigntyalliance.org/
There are myriad factors that determine what we eat: taste, cost, convenience, culture, education, weight management goals, disease risk, etc. In addition, do you ever consider the impacts of your food choices on “planetary” health? After all, without our wonderful planet Earth, there would be no wonderful you or me! Before you slap your forehead and exclaim just how complicated food choices are, do you think it’s possible that one “diet” could satisfy your needs as well as those of Mother Earth? The answer is, unequivocally (and refreshingly), yes! It’s called the Mediterranean Diet.
A while back (October 2013) my colleague Jamie wrote about the human health benefits of the Mediterranean Diet (MD): “The modern MD is high in beans, whole grains, fruit and vegetables, fish and nuts, and low in red and processed meats, added sugars and saturated fats with moderate alcohol consumption. Studies have consistently shown that this dietary pattern is associated with a lower incidence of cardiovascular disease and may also decrease the risk of cancer and other chronic diseases.”
Research studies from the field of ecological sustainability indicate that that the Mediterranean Diet is good for the planet, too. In short, agricultural production of beans, whole grains, fruits, and vegetables utilizes significantly less energy and generates significantly fewer greenhouse gases than production of meat. For a detailed analysis of these data, check out this report from the Environmental Working Group.
The Double Pyramid
The personal and ecological health benefits of the Mediterranean Diet are nicely summarized in the graphic below. Created by the Barilla Center for Food and Nutrition, the Double Pyramid shows that what’s good for us is also good for the planet.
Food for Thought
Were you already aware how detrimental meat production can be for the planet? Take this quiz offered by the Environmental Working Group to shed further light on the issue. Then, after the quiz, consider what modifications you could make to your diet that would be “doubly” beneficial for both you and the planet.
Last week Jamie wrote a great piece about the relative cost of healthy vs. unhealthy food. It’s sad indeed that healthy food costs more – potentially thousands of dollars per year more – than less healthy processed food. Misguided government subsidies are certainly at the root of the issue in the United States. Designed to spur economic growth and provide cheap calories for the masses, current subsidies do perhaps more harm than good. Particularly when it comes to the absolute cost and relative value of food.
To put things in perspective, here’s an interesting question for you: how much money do Americans spend on food – a lot or a little? Responses will vary from person to person, but on average Americans spend just 10% of disposable income on food (USDA). Ten percent! That’s less than any other country in the world.
Which brings me to the next question: how much do Americans value food? Again, responses will vary, but the general consensus seems to be “not much”. Consider, for instance, that when finances get tight many folks resort to eating Top Ramen® or frozen pizza to make ends meet. We are too quick to sacrifice healthy foods. Some expenses, like rent and basic utilities, we can’t or shouldn’t cut, but what about “luxury” items like fancy clothes, cable television, smartphones, or cars? To be sure some people need a smartphone or car to survive in today’s society, but others not so much.
Do you think that the relatively small amount that Americans spend on food affects how much we value it?
Food for thought
Activist and author Michael Pollan once wrote that the only quality that Americans look for in food is quantity. Meaning that we place more emphasis on how much a food costs than on how it affects our health, our society, or the environment. Do you agree or disagree? Do you think food, particularly healthy food, is expensive? If a person opts to buy “cheap” processed food today, what do you think the long term health (and financial) consequences are? Do you think that government subsidies should be restructured to better address American health issues? Lastly, how much do you spend on and value food?
U.S. Department of Agriculture (USDA), Economic Research Service (ERS). Food CPI, Prices and Expenditures: Food Expenditures by Families and Individuals as a Share of Disposable Personal Income. Accessed January 26, 2014: http://www.ers.usda.gov/data-products/food-expenditures.aspx#.UuUrKbTTnIU
It’s time now to discuss yo-yo dieting or “weight cycling”. Many folks are unfortunately familiar with this phenomenon, which can lead not only to lasting physiological damage, but psychological damage as well. Yo-yo dieting refers to the “annoying” habit of losing five pounds, only to later gain back seven. A person in this situation will often then refocus their energies to lose another ten pounds, only to gain back twelve. You get the idea. Fluctuating body weight in this manner is associated with high blood pressure and triglyceride levels. It’s also understandably difficult from a mental and emotional perspective.
Resting metabolic rate
Resting metabolic rate (RMR) is the amount of energy your body expends to maintain physiological equilibrium at rest. In other words, RMR accounts for the number of calories (kcal) needed to maintain your heartbeat, brain activity, organ function, etc. while you sit in bed and stare at the ceiling all day. There are many elaborate formulas to estimate a person’s RMR, but for the sake of this article let’s approximate it at 10 kcal/pound/day. Eddie, for example, weighs 200 pounds and has an RMR of 2000kcal/day.
Here is how RMR relates to yo-yo dieting: the primary determinant of RMR is muscle mass. As a person loses weight they will likely lose both fat and muscle mass. Thus, as Eddie drops from 200lbs to 185lbs his muscle mass decreases, as does his RMR (from 2000kcal/day to 1850kcal/day). The good news is that Eddie managed to achieve his weight loss goal. The bad news is that he can never “go home again”, meaning that unless he increases his physical activity energy expenditure he can never eat what he used to eat at 200lbs and maintain his new, current weight. His body simply doesn’t need as many calories to maintain itself.
Although this makes perfect sense, many folks fall prey to yo-yo dieting. Eddie, for example, decides to enroll in a new fad diet. He loses a significant amount of weight in a short period of time, but then cracks, binges, and gains it all back. Or perhaps he decides to lose weight for a special occasion, succeeds, and then returns to his previous diet and lifestyle. In both scenarios Eddie’s weight loss results from a decrease in both fat and muscle mass; subsequent weight gain is associated primarily with an increase in fat mass. When Eddie returns to his original weight of 200lbs, his RMR is less than what it used to be (perhaps 1950kcal/day) because he does not have as much muscle mass. Unless Eddie increases his physical activity, it shouldn’t come as a surprise that over the next few months he will put on several additional pounds.
The take home message is two-fold. First, be realistic about weight loss goals – both the total amount you intend to lose as well as the rate. Two pounds per week may be the maximum sustainable rate of weight loss, but one pound per week (or less) is more manageable. Second, no diet will be successful long term unless it is also accompanied by a change in lifestyle; physical activity is key to maintaining muscle mass and/or increasing energy expenditure. However, lifestyle changes can be difficult to make. Next week we’ll explore some practical behavior modifications related to weigh loss and management.