Horses and Humans: Eating For Two
- Nov 1, 1999
The athletic partnership between horse and rider is a truly remarkable one. Nowhere else in the long history of civilization do you see two individuals from two entirely different species working so closely or so equally. Ancient myths of centaurs seem to come true when horse and rider work as one--and when it happens, it feels as if we aren't so very far apart after all.
SHAWN HAMILTON PHOTO
Of course, there are vast differences between humans and horses. True, we're both mammals, but there the similarities might be said to end. Quite apart from the obvious (biped vs. quadruped, predator vs. prey), we have internal differences that make us very dissimilar types of athletes. Although our muscles both use ATP (adenosine triphosphate) as their main energy source for performance, how we accumulate and store it varies because our diets and our digestive systems vary.
If you're like most riders, you probably understand the workings of your horse's innards better than you do your own, and that can be a mistake, because as 50% of an athletic partnership, it's important for you to know how to fuel your own body. Let's have a comparative look at the human and equine digestive systems, and come to a better understanding of how to keep both running at optimal levels.
At first glance, we seem to share quite a lot with horses when it comes to our guts. Like equines, we're monogastric, meaning we have one stomach--unlike ruminants like cows, which have several. Like equines, we're equipped mainly with (proportionately) large, blunt teeth, designed for grinding, although we both have some sharper incisors at the front of our mouths to perform some tearing of fibers. We each have an esophagus, a small intestine, and a large intestine, and the basic order in which food flows through each of these organs is the same.
However, there are several important differences in the arrangement of our gastrointestinal tracts. First, equines are obligate herbivores, meaning they are designed to eat plants and only plants; they're not equipped to eat or to digest animal flesh. Humans, on the other hand, are true omnivores, meaning we'll eat practically anything. Our digestive systems are far more versatile and less specialized than the horse's. As a result of our varied diets, we're equipped to derive energy from a multitude of sources.
In horses, fiber digestion is the focus, and it happens in the cecum, or "fermentation vat," of the large colon, aided by millions of beneficial gut bacteria that are particularly skilled in breaking the complex bonds that hold cellulose and hemicellulose plant fibers together and in converting them into less complex carbohydrate chains that can be absorbed across the gut wall. Humans, in contrast, have a limited ability to digest fiber, as is indicated by the structure of our large colons. The fermentation vat has shrunk over the eons to become a vestigial organ called the appendix, which has no function other than occasional grief, necessitating its removal. However, we do have a population of beneficial gut bacteria (as do almost all mammals) that help break down other nutrients from our diets.
Humans and horses are alike in that their stomachs are relatively small affairs, which are only partially responsible for the process of digestion. In the stomach, the breakdown of foods is begun, in both species, by churning and mixing with stomach acid. In humans, the mixture is passed on to the small intestine before the bulk of real digestion occurs. In the duodenum, the first section of the human small intestine, carbohydrates and starches are broken down into simple sugars, proteins into amino acids, and fats into fatty acids and glycerol, with the help of enzymes secreted not only by the walls of the duodenum itself, but also by the liver and the pancreas. In the other two sections of the small intestine (the jejunum and the ileum), these nutrients are absorbed across the intestinal wall and sent to the parts of the body where they can do the most good, either for immediate use or to be stored for the future. Very little actual nutrient absorption goes on in the human large intestine. Its main function is to reclaim as much water as possible from the leftover indigestible material, and to eliminate the resulting semi-solids as feces.
For horses, the picture is slightly different. As herbivores, their digestive tracts are designed only for small amounts of food, delivered constantly over hours of grazing time. (In the wild, horses might wander and graze for up to 16 hours a day, taking in small mouthfuls at a time). As a result, the equine stomach has a relatively small capacity, and food passes through it quickly to make room for the next few mouthfuls. In the rush, feed only gets partially processed in the stomach. With the help of stomach acid, chewed grains are broken down into smaller particles, and the carbohydrates they contain are converted into simpler sugars. Fiber, the bulk of the diet, remains relatively untouched. The liquid slurry from the stomach is passed to the small intestine, where carbohydrates and fats are processed in much the same way as they are in the human gastrointestinal (GI) tract, with the help of liver and pancreatic enzymes. (One significant difference between humans and horses is that humans have a gall bladder, which acts as a reservoir for bile, the main digestive juice from the liver. Horses have no such organ and have to make do with their bile supply coming directly from the liver. Despite this, they seem to have no trouble processing diets that are up to 20% fat.) Proteins, too, are dealt with in the small intestine, dissolving into their composite amino acids and being absorbed across the gut wall.
The large intestine in horses, however, is the area where the bulk of the real work of digestion goes on. In contrast to the human approach, most of this digestion is microbial rather than enzymatic. Coarse plant fibers, essentially untouched by the small intestine's digestive efforts, land in the first part of the large intestine, called the cecum, ready to undergo fermentation by the gut bacteria. Later in the large colon most of the nutrients they extract from the forage (hay, pasture, or other fiber sources like hay pellets or beet pulp) are absorbed across the gut wall and distributed as needed.
If a horse is fed grain only in small meals at frequent intervals, his digestive system will function normally, processing the grain in the small intestine and the fiber in his diet in the large intestine. If he's fed an unusually large grain meal, he might run the risk of serious digestive upset. That's because the small intestine has a certain rhythm, like a conveyor belt, and it can only process so much feed before sweeping its contents along to the next stop in the digestive tract. Any carbohydrates that aren't thoroughly digested in the small intestine might be pushed on through to the fermentation vat of the cecum. When the horse's gut microflora try to digest them, the resulting toxic byproducts include lactic acid. An increase in lactic acid lowers the overall pH level of the hindgut, and that in turn makes the environment hostile for the gut bacteria. They begin to die off, and in the process they release endotoxins. So between the endotoxins and the lactic acid, the stage can be set for colic or laminitis. That's a good enough reason to adhere to the "small meals, often" rule.
Humans, on the other hand, are better equipped to digest whatever comes their way whenever it arrives. Being predators, we're designed to take full advantage of meals that present themselves, however sporadically. Many an overweight North American has lamented our genetic tendency to brace for a famine by stubbornly retaining as much body fat as possible, especially when the daily caloric intake is limited. Despite our lifestyle changes in recent centuries, our bodies still are programmed for the feast-or-famine diet of a nomadic hunter, gorging on buffalo meat one day and then subsisting on berries for several more until the next successful kill. It will take several more millennia before the veneer of civilization has any impact on this design.
There's one other difference between the human and equine digestive systems that's worth a mention. Unlike humans, horses have no mechanism for reverse peristalsis--vomiting. So when a horse ingests a toxic substance, he has no way to expel it backwards through his esophagus. It must work its way through his system in the usual direction. This makes horses considerably more vulnerable to poisoning than humans, although admittedly, horses seem to demonstrate a good deal more common sense than we do when it comes to sampling toxic substances in the first place!
Fueling Performance For Both Partners
When you and your horse perform together, you both operate as athletes, burning ATP energy to fuel the work of muscles, joints, and the cardiovascular system. If you've been reading my nutrition column regularly, you know we have a pretty good idea of how to fuel equine systems: with a dietary base of fiber, making up at least 50% of the daily intake by weight, and the addition of carbohydrates (from grains) and possibly fats to provide concentrated energy for high-impact performance. But what about you, the human athlete? You'll want your own body to have enough energy so that you can ride effectively, move naturally with your horse, make smart decisions, and still have enough juice left over at the end of the day for mucking stalls, lugging hay bales, slogging water buckets, and all those other glamorous jobs connected with caring for your equines.
Turns out, fueling you isn't so very different than fueling your horse. There's less emphasis on fiber, to be sure, but when it comes down to it, carbohydrates and fats are still our best energy sources, protein is a poor one (just as it is for horses), and adequate water intake makes all the rest of it possible.
Riders perform best when fueled by a diet that is high in carbohydrates. In fact, carbohydrates are the most ergogenic nutrient known--meaning that they support or stimulate athletic performance.
Carbohydrates come in two basic varieties: simple (sugars, such as glucose, sucrose, and fructose) and complex (sometimes called starches). Both are converted by the body into glycogen, a molecule that is stored in the muscles and the liver, and is available to be converted back into glucose whenever there's a need for energy. Carbohydrates can fuel both aerobic activities (those requiring slow, steady effort over a long period of time) and anaerobic (high-intensity, short-duration bursts of energy). They also help maintain your body's blood sugar levels; a healthy blood-sugar level is linked to your brain function and your ability to focus on a task, among other things.
Complex carbohydrates are the most valuable kind to include in your diet because they are stored more efficiently. Simple carbohydrates, or sugars, are easier for the body to break down, so they tend to supply a quick, but not lasting, energy burst. Good sources of complex carbohydrates include pasta, cereals, breads, whole grains (such as rice), and legumes (beans). Simple carbohydrates are found in fruits and vegetables as well as sugary foods like cookies and candy bars. Fruits and veggies are the better choice, because they are also excellent sources of vitamins and minerals, including the trace minerals called electrolytes that are so important for athletes to replenish after they perspire.
All athletes, riders included, should aim to make carbohydrates (both simple and complex) a full 55% to 65% of their daily diet. That's six to 11 servings per day of pasta, beans, bread, or grain; two to four servings of fruit; and three to five of vegetables. A diet too low in carbohydrates will tend to leave you feeling wrung-out and exhausted prematurely because your energy stores are depleted.
Just as it is with horses, the primary role of protein in the human diet is to help the body grow new tissue and to repair tissues that have been damaged by day-to-day wear and tear. A young, growing human has quite a high protein requirement, but adult athletes need to make protein only about 15% to 18% of their daily diet (two to three servings). That's because they are no longer building new bones and muscles; they're just maintaining the ones they have.
Protein requirements don't increase that much even when a mature athlete is exerting himself or herself to the max. Most humans eat far more protein than their bodies could ever need or use, so adding more protein to the diet, over and above what you normally consume, is almost never necessary. Instead, it's best to concentrate on finding good sources of protein that are also low in fat. Turkey, fish, chicken, beans, nuts, tofu, and low-fat dairy products are all quality protein choices. Also good, but higher in fat, are many cheeses, red meats like beef or pork, and spreads like peanut butter. Although everyone needs some protein, the best rule of thumb is this: When you put together a meal, consider high-protein foods an accompaniment, not the main focus on your plate.
Fats: Oh The Guilt!
We've all read the statistics on fat, and we all know that (at least in North America), we eat far too much of it. But fat isn't all bad. It's a dense energy source that can be used to fuel performance; it supplies the body with essential fatty acids, which are crucial for healthy skin and many other organic functions; and it carries the fat-soluble vitamins A, D, E, and K, without which our immune functions, our eyesight, and our blood-clotting ability (to name only a few functions) would be compromised.
The main reason fat tends to do so much damage to our waistlines is that it is more than twice as energy-dense as other nutrients. One gram of fat contributes nine Kilocalories of energy, while a gram or protein or carbohydrates contains only four Kcal. So a little fat goes a long way. The body tends to digest and absorb it slowly. A high-fat meal, eaten before an athletic event, can mean that your system is focused on fat digestion rather than muscle fiber firing, so your blood will be concentrated in your gut, rather than pumping nutrients to your muscle cells and your brain. Needless to say, that can be counter-productive to performance.
Our aim should be not to eliminate fat from the diet, but to regulate it. At most, fat should make up 20% to 25% of our daily diets. A lower fat intake has a number of benefits, including a lower risk of heart disease and some forms of cancer.
Water--The Forgotten Nutrient
Of all of the nutrients I've talked about, none is more crucial to you and your horse's health and athletic performance than ordinary water. Water accomplishes a wide array of functions in our bodies--including helping us regulate our internal temperatures, carrying nutrients through the body, and acting as a coolant for working muscles. We get rid of wastes by mixing them with water and expelling them from our system as urine and sweat; sweat, evaporating on the skin, also helps cool us. Without sufficient water, we become dehydrated, a state which affects almost every body system. Most importantly, a dehydrated rider doesn't think straight--and that can be a dangerous scenario.
All too often, we forget to keep our bodies hydrated, especially in adverse, high-stress situations such as horse shows. By the time you register that you are thirsty, chances are you're already dehydrated. A headache is another sign. To ward off dehydration, get in the habit of carrying bottled water with you wherever you go, especially to the barn and to horse shows. (Other beverages, such as milk, fruit juices, and sports drinks might be good choices, but water is the best way to go--it's 100% re-hydration and zero calories in one package!) Keep those fluids coming throughout the day, even when you're not feeling thirsty; this advice goes double in hot, humid conditions. Avoid coffee and tea, both of which contain caffeine and thus act as diuretics (substances that encourage the body to lose fluids). Alcoholic beverages are also diuretic in nature and a no-no for successful athletic performance. You should avoid sugary, carbonated beverages--especially caffeinated colas, which might be the worst of all worlds!
You're well-hydrated if you urinate every two to four hours, and the color of your urine is light to clear; darker urine means you need to increase your fluid intake.
Although a well-balanced diet should supply you with all the vitamins and minerals you need, even the best of us sometimes fall off the wagon and eat less well than we should. Riders should pay particular attention to three minerals that tend to be lost in sweat: sodium (usually found in sodium chloride form, which is salt), calcium, and potassium.
Getting enough sodium in your diet is rarely a problem, but most dietitians recommend that athletes not make any heroic efforts to cut down on salt; you need to replace the sodium you lose in order to help your body absorb water, maintain your fluid balance, and help stimulate the thirst reflex.
Calcium not only is needed for strong bones and teeth, but also might help protect against muscle cramps during athletic performance. Dairy products are the best calcium source, of course, but if you aren't a big milk drinker, consider adding more broccoli, kale, and collard greens to your diet. Supplementation in pill form might be a good idea for many people, especially those with a family history of osteoporosis or brittle bones.
Potassium is an electrolyte that sometimes gets depleted over a long period of exertion (such as an endurance rider on a 100-mile ride might experience). Bananas and orange juice are two excellent sources of this mineral.
Strategies For The Show Ring
On a day before a competition, where presumably you and your horse are both going to make extraordinary athletic efforts, it's a good idea to eat carbohydrate-rich meals and drink lots of extra fluids. On the day of your show, eat a light, easily digestible breakfast--and you might have to experiment to see what sits easily in your stomach when you've got the jitters. Avoid high protein or high fat foods, which not only tend to trigger unhappy digestive tracts, but can leave you with an energy deficit just when you need it most.
If you'll be riding early, eat light, but if your turn in the ring isn't until later in the day, eat a full-sized meal to fuel you through to the afternoon. Leave time for digestion; most high-carb snacks can be processed and absorbed in under an hour, but a full meal might take as much as four hours.
During the show, keep downing lots of water, and snack on carbohydrate-rich items every couple of hours. It's also a good idea to have a re-energizing snack within an hour after any strenuous exercise (such as the cross-country phase of a one-day event); that's when your muscles will be most receptive to replacing lost nutrients. Pack a cooler full of low-fat, high-carbohydrate foods so you'll be able to avoid the concession-truck jumbo curly fries (and the possibility of a queasy stomach from eating something unfamiliar). If you are forced to scavenge something at the show, eat smart as much as you can --even a slice of pizza can be healthy, provided you go for a thick crust, no extra cheese, and veggie toppings instead of high-fat meats like sausage or pepperoni. Try to refuel at least every four hours, and save something for that long drive home with the horse trailer, when you'll likely be nodding off at the wheel!
About the Author
Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.
POLL: Winter Horse Care Concerns