Nutrition & Physical Activity
Dear Worries about cancer and diet,
No doubt that losing your grandfather was difficult as we often have a special relationship with our grandparents. Now, while it can be tempting to make generalizations about which cultures have more or less healthy cuisines, it might be more useful to consider how specific ingredients and cooking methods can possibly impact our overall health. Research has shown that many cooking methods, including those you mentioned, can increase the likelihood of depositing carcinogens (cancer causing substances) into the food being prepared. However, there are things you can do to decrease your risk of developing cancer, while still enjoying Chinese food — or any cuisine you would like for that matter.
First, a few words about cancer: Cancer is not one disease, but actually a group of diseases caused by the unrestrained growth of cells in one of the body's organs or tissues. One factor that increases a person's risk of developing cancer is genetic makeup. Environmental triggers (e.g. food choices, sunlight, alcohol, viruses, tar in tobacco smoke, and pollutants in the air) also play a part in cancerous formations.
Research suggests that people with diets high in certain kinds of foods are more likely to develop cancer at some point in their lives. Diets high in fruits, vegetables and fiber have been shown to reduce cancer risk, while diets high in meats, animal products, and fats seem to increase risk. Even within the meat category itself there are distinctions. Red meats like beef, lamb, and pork are considered by experts to carry a greater risk of cancer (especially colorectal cancer) than white meats like chicken, turkey, and other poultry. By contrast, vegetarian diets seem to reduce the incidence of cancer. This appears to be due to the protective effect that fiber (which is found predominantly in fruits and vegetables) has against cancer in the body.
But even within those broad categories, the way your food is prepared can make a difference in the cancer rate associated with its consumption. This gets back to your question about hot cooking oil: Yes, cooking foods at a high temperature as in hot oil can generate carcinogens. Cooking meat at high temperatures is known to form carcinogenic substances inside the meat being cooked. Carcinogens such as heterocyclic amines (HCAs) are found in meats that have been grilled, fried, or broiled. Increased cooking time and temperature has been shown to increase the amount of HCAs in meat. Another family of carcinogens, polycyclic aromatic hydrocarbons (PAHs) are also found in cooked meats. Cooking methods such as direct flame gas grilling and smoking seem to generate the most PAHs in meats, while indirect flame gas grilling, pan-frying, microwave cooking, and steaming appear to produce progressively fewer PAHs. Increasing temperature and cooking time also tends to increase the number of PAHs in food. Another carcinogen, acrylamine is formed when plant based foods high in carbohydrates (such as potatoes, breads, and pastries) are cooked at high temperatures by frying, roasting, or baking. It is also probably not the safest idea to reuse cooking oil when preparing food.
While it appears that eating a vegetarian diet that includes limited frying and grilling in the cooking process is the gold standard in terms of cancer reducing diets, it is not the only way to reduce your risk of developing cancer. In addition to a healthy, varied diet, health experts recommend avoiding major causes of cancer by limiting alcohol consumption, avoiding smoking, maintaining safer sex practices, and avoiding overexposure to UV radiation (like from the sun!). Simply reducing the amount of fried and grilled foods you eat can also make a difference without eliminating them from you diet altogether. Additionally, avoiding unhealthy foods doesn’t mean you have to avoid an entire cuisine. Meals such as Chinese food or other types of cultural cuisines, contain a wide range of ingredients, with several possible ways to prepare or cook. If you want to maintain a healthier diet, you can be selective about the kinds of food you order from restaurants or try cooking them for yourself at home.
If you have questions or concerns about your diet, you may want to speak to your primary care provider or a nutritionist. If you are a Columbia student you might want to call 212-854-2284 or log in to Open Communicator to make an appointment on the Morningside campus or 212-305-3400 for the Medical Center campus. You may also want to consider visiting the Columbia Health website to see information about services and programs available on the Morningside campus or Student Health Services for options at CUMC. If your worries about cancer are negatively affecting you day-to-day life or you just want to talk with someone about your experience with your grandfather, you may want to make an appointment with a counselor or psychologist. Columbia students may want to consider scheduling a visit with Counseling & Psychological Services at Morningside by calling 212-854-2878 or Mental Health Services at CUMC by calling 212-305-3400. Balancing long-term health concerns like cancer with everyday dietary concerns can be challenging, but being informed about the risks and benefits associated with certain foods is a great first step to a long and healthy life.
To figure out your basic metabolic rate, it must be measured under very strict conditions such as after a night’s sleep, on a fast, and without any physical activity, etc. What is more common and often more useful is a person’s resting metabolic rate (RMR). RMR is the number of calories you burn to maintain vital functions such as breathing, pumping blood, and maintaining your muscle and nervous system at resting conditions. This is measured under less strict conditions and often does not require the person to fast or to sleep right before the measurement. An accurate RMR measurement requires the use of an apparatus called indirect calorimetry. This can be expensive, so estimating RMR using parameters such as body weight, height, and age can be used as well.
There are three common equations to estimate RMR: (1) the Harris-Benedict equation, (2) the Mifflin equation, and (3) the Cunningham equation. These equations are population specific, so it is important to be aware of their limitations.
Harris-Benedict Equation (widely used and relatively accurate for average body type):
Men: RMR (in calories per day) = 66.47 + 6.23 x Weight (lbs) + 12.67 x Height (in) - 6.76 x Age (yrs)
Women: RMR (cal/day) = 655.1 + 4.34 x Weight (lbs) + 4.69 x Height (in) - 4.68 x Age (yrs)
Men: RMR (cal/day) = 10 x Weight (kg) + 6.25 x Height (cm) - 5 x Age (yrs) + 5
Women: RMR (cal/day) = 10 x Weight (kg) + 6.25 x Height (cm) - 5 x Age (yrs) - 161
Cunningham Equation (uses fat-free mass, suggested for athletes):
For men and women: RMR (cal/day) = 500 + 22 x FFM (kg)
If you would still like to know more about measuring your metabolic rate, such as through an indirect calorimetry, it is recommended to see a health care provider. Columbia students can make an appointment at Medical Services (Morningside) or at the Student Health Service (CUMC). You can also visit the Columbia Health site to learn more about services and programs available on campus to help you stay in tip-top shape.
No need to pause that chip in midair, or order sushi sans avocado! Avocados are indeed high in fat, but they're high in monounsaturated fat, the good fat, the kind of fat that may actually help lower blood cholesterol levels. And as you rightly said, avocados contain no cholesterol — no plant foods do.
You may have heard the term low-density lipoproteins (LDL) in the discussion of different types of cholesterol. LDL cholesterol is often referred to as bad cholesterol because when the body has too much it can form plaque on the walls of arteries and veins which can cause heart attack or stroke. In contrast, high-density lipoproteins (HDL) clear the blood stream and artery walls of LDL and transport it to the liver where it can be broken down and eliminated. Lowering LDL and increasing HDL is considered desirable in terms of preventing heart disease and stroke. The good news in terms of those tasty avocados is that eating monounsaturated fats, especially while decreasing intake of carbohydrates and saturated fats, may decrease levels of LDL and raise HDL cholesterol.
The American Heart Association recommends that total fat intake be kept to 25 to 35 percent of your daily calories and that saturated fat comprise less than seven percent of total daily calories. That means the remaining fat should come from monounsaturated and polyunsaturated fat sources like nuts, seeds, fish and vegetable oils. Translated into layman's terms this would mean that a typical 2,000 calorie a day diet would include 50 to 70 grams of fat, with about 34 to 50 grams of that fat from poly- or monounsaturated sources and about 16 grams or less from saturated sources. Because it's hard to keep track of exactly how many grams of fat are coming from which sources, it's a good rule of thumb to choose unsaturated over saturated fats whenever presented the option. Saturated fats come from animal products like meat, seafood, milk, butter, cheese, and ice cream. Monounsaturated fats come from vegetarian sources like nuts, seeds, vegetable oils, olives, and, drum roll please… avocados.
In addition to containing healthful fat, avocados are also high in beta carotene, fiber, folate (a B vitamin), and potassium (ounce for ounce, avocados have 60 percent more potassium than bananas). To put the fat in perspective, avocados have less fat than lean beef per ounce, and a whole Haas avocado has less fat than 3 tablespoons of Italian salad dressing. While it's a good idea to take all fats in moderation, rather than shun the guacamole bowl at the party, help yourself to some of the green gooeyness, along with plenty of veggies, fruits, and whole grains. Enjoy!
Yes, it is true that there are recommendations for minimum and maximum heart rate during exercise. Two slightly different formulas are currently used to guide exercisers. Both formulas take your age into account, but one also factors in your resting heart rate and is particularly useful for individuals training with a specific performance goal in mind. Heart rate is measured in beats per minute (bpm). Before demonstrating each formula, it's useful to define a few terms:
- Maximum heart rate — an estimate of the heart rate that one potentially could (not should) achieve during maximum physical exertion.
- Resting heart rate — as simple as it sounds — your heart rate at rest with no physical exertion (best when measured in the morning before any stress, caffeine, or much movement).
- Target heart rate — a percentage of your maximum heart rate. Experts recommend keeping your heart rate in a certain range to achieve benefits during exercise, depending on your level of conditioning and exercise goals.
To demonstrate how each formula works, let's say that Devon is 24 years old, has a resting heart rate of 65 bpm, and wants to work out between 60 and 80 percent of maximum heart rate. Time for a little arithmetic!
Maximum workout heart rate =
(220 - age) X percent of maximum heart rate
(220 - 24) X .60 = 117
(220 - 24) X .80 = 157
According to this formula, Devon should maintain a target heart rate between 117 and 157 bpm to reach 60 to 80 percent of maximum heart rate while working out.
Maximum workout heart rate, adjusted for resting heart rate =
(220 - age - resting heart rate) X percent of maximum heart rate + resting heart rate
(220 - 24 - 65) X .60 + 65 = 144
(220 - 24 - 65) X .80 + 65 = 170
According to this formula, Devon should maintain a target heart rate between about 140 and 170 bpm to reach 60 to 80 percent of maximum heart rate while working out.
As you can see, these formulas give Devon different recommendations for target workout heart rates. This is because the second formula adjusts for resting heart rate, a number that normally gets lower for most people as they exercise and become more conditioned. Using the second formula can increase the accuracy of target heart rate recommendations for regular, consistent exercisers.
The easiest place to check your heart rate may be on your carotid artery in the neck (avoid pressing too hard or the reading may be less accurate). Check your heart rate before, during, and after exercise by taking your pulse for 10 seconds and multiplying by 6, or for 15 seconds and multiplying by 4. You can then adjust your workout accordingly. Remember, you are estimating your heart rate with these formulas, so always let safety come first. Stop exercising if you feel dizzy, faint, or shortness of breath.
Hope this heart to heart was helpful!
Dear Animal Lover,
Vitamin B12 is important in the formation of nerve cells and red blood cells. Natural food sources of the vitamin are found primarily in meat and other animal products, which mean those who stick with a plant-based diet have to find their source elsewhere. Though there are some foods that your friend may want to add to her/his diet, vitamin supplements may also be something to consider. However, because of the serious symptoms and long-term risks involved with B12 deficiency, consulting with a health care provider and/or a registered dietitian may help as well.
Contrary to popular belief that B12 deficiency takes many years to develop, it actually may only take a matter of two to four years to become symptomatic. A recent meta-analysis found that the prevalence rate of B12 deficiency among non-pregnant young adults who followed a vegetarian diet (lacto- or lacto-ovo) was at about 32 percent and among vegans, ( those who eschew all animal products: meat, eggs, dairy, honey, leather, silk, etc.) prevalence was at 43 percent. Symptoms of B12 deficiency include anemia, fatigue, weakness, constipation, loss of appetite, and weight loss. Long-term effects may be neurological changes such as numbness and tingling in the hands and feet. Additional signs of B12 deficiency include difficulty in maintaining balance, depression, confusion, dementia, poor memory, and soreness of the mouth or tongue. But be advised that these can also be symptoms of many different ailments, so having a blood test from a doctor like your friend did can help with diagnosis.
The recommended daily allowance (RDA) of B12 for adults is 2.4 micrograms (µg) and there are actually two forms of B12, active (which the body can actually use) and inactive (a.k.a.,pseudovitamin B12). Now, for the good news: Both vegetarians and vegans have various options for obtaining sufficient amounts of vitamin B12. Some varieties of mushrooms, green and purple nori (seaweed), and some fermented foods like sauerkraut and tempeh (fermented soy beans) are recognized as plant-based sources active B12. Fortified foods like some cereals, soy products, or meat substitutes are options for both vegans and vegetarians. Milk, yogurt, and eggs are rich in vitamin B12 and may also be added to a vegetarian diet. And while it is possible to get sufficient amounts of the vitamin from these sources, many vegans and vegetarians don’t seem to eat enough of these products. As such, it might be a good idea to look into vitamin supplements that contain B12. Due to the low absorption rate of the vitamin through supplements, taking a 250 microgram (µg) dose is recommended. Seeking out the guidance of a registered dietitian may prove helpful for your friend to identify where B12–rich sources can be added in her/his diet.
Happy healthy eating!
A high-impact yes to your question! In fact, there aren't many better pursuits than exercise for stress reduction. Before we delve deeper into why exercise is so great, however, let's first make sure we're on the same treadmill about our definition of "exercise." According to the Physical Activity Guidelines for Americans, it’s recommended that adults (ages 18 to 64) get 150 minutes of moderate physical activity or 75 minutes of vigorous activity each week. Physical activity is considered moderately intense if you are working hard enough to break a sweat, but you are still able to hold a conversation. If you're breathing hard and fast, your heart rate is up and you're not able to get many words in, that type of activity can be described as vigorous. Additionally, two or more days of muscle strengthening activity per week is also recommended.
Before you run in the other direction, consider some of the health-promoting and stress-controlling benefits of aerobic activity. Most notably, aerobic exercise strengthens your heart and lungs. These two vital organs — especially the heart — bear the brunt of the body's physiological stress response, as they are constantly being called upon to "fight or flee" from job, school, family, financial, relationship, and every other kind of stressor we confront daily.
You brought up another exercise plus: weight loss and maintenance. For many of us, looking good also means feeling good and vice versa. Exercise improves physical appearance, enhances self-esteem and self-confidence, and offers other mental health goodies. Regular exercisers report more energy and better ability to concentrate. Oh, and don't forget about improved quality of sleep, reduced stress reactivity (not getting as stressed out about things as you usually do), and, yes, maybe even a slowed aging process!
Exercise as stress-management strategy is easier said than done, so here are some tips that have helped many health-seekers to start and stick with exercise programs:
- Begin slowly. If you are not accustomed to exercising, start out with ten to fifteen minutes twice a week and build up from there.
- Snag a workout partner — there's nothing like the motivation of another sweaty, panting humanoid to keep you going.
- If the gym will be "workout central" for you, take a quick lesson from a trainer on proper equipment use. Simple direction from experienced health club personnel can reduce gymphobia (and possibly injuries) while improving the quality of your workout. Your gym should offer this one-time service free of charge to newcomers, but this doesn't mean that you can't ask for guidance down the line, too.
- Let friends and family know that you are exercising for your health — let them cheer you on.
- Finally, make your workout sessions regular and real. Schedule them in your calendar, just as you would record business appointments, classes, and social engagements.
If you are thirty-five or older or have any heart trouble, blood pressure problems, or other medical conditions, you will want to get a medical clearance from your health care provider before you choose your exercise plan.
By the way, you have a variety of exercise options, and you don't have to join a gym to partake. Walking briskly, running, biking (mountain if it sustains your heart rate), swimming, calisthenics, playing tennis or basketball, and cross-country skiing are just a few possibilities. Check out some of the archived questions in the Nutrition & Physical Activity category to learn more about your options for making physical fitness a priority in your life. Columbia University students, faculty, staff, and alumni can also participate in the CU Move initiative. CU Move encourages members of the Columbia community to engage in active lives that include regular physical activity. The program provides participants with motivation and incentives to be active throughout the year.
In addition to exercise, try to take breaks from your high-stress job. Walk around outside, take lunch, or sit in the bathroom for a few minutes if that's the only time you can get away. Just a few breathers during a hectic day can go a long way toward stress relief.
Good luck getting moving!
Before discussing their role in maintaining good health, let's first clarify what antioxidants are. "Antioxidant" is the collective name for the vitamins, minerals, carotenoids, and polyphenols that protect the body from harmful free radicals. The most well known antioxidants include the vitamins A (found in liver, dairy, and fish), C (found in bell peppers and citrus fruits), E (found in oils, fortified cereals, seeds, and nuts), and the mineral selenium (found in Brazil nuts, meats, tuna, and plant foods). The carotenoids beta-carotene, lutein, and lycopene also have high antioxidant activity and are responsible for adding color to many fruits and vegetables. Carrots and pumpkins wouldn't be orange without beta-carotene, for example. Lutein, also important in eyesight, is abundant in leafy green vegetables. Lycopene is present in red fruits and vegetables, most notably in tomatoes. No wonder why many experts stress the importance of eating a "colorful" diet!
So why are they called antioxidants? The name is indicative of the mechanism by which they help prevent disease. In humans, a small but significant percentage of oxygen molecules in the body will become electrically charged due to natural cellular activity and/or exposure to environmental factors such as tobacco smoke and radiation. The oxygen molecule becomes a "free radical" as it undergoes this process of oxidation. Free radicals are highly reactive as they try to steal electrons from other molecules, including DNA and cellular membranes. They will continue to react with other cellular molecules in a chain-reaction mechanism. This chain reaction of free radicals can damage cells, which may play a role in the development of certain conditions like heart disease and cancer. Antioxidants, however, stop the chain-reaction by giving up electrons and neutralizing free radicals so that they cannot induce any more oxidative damage. Unlike other molecules, antioxidants do not become reactive when they lose an electron.
Many studies have shown the link between free radicals and a number of degenerative diseases associated with aging. Thus, it is possible that antioxidants can be beneficial in reducing the incidence of cancer, cardiovascular disease, cognitive impairment, Alzheimer's disease, immune dysfunction, cataracts, stroke, and macular degeneration.
Read any fitness magazine, watch a few television ads, or simply pass by your local health food store, and notice the benefits of the latest supplement being touted. While new products emerge frequently, it is best to remember that vitamin and mineral supplements are not to be used as substitutes for a healthy, well-balanced diet. In fact, due to many conflicting studies on the effects of antioxidant supplements, the American Heart Association does not currently recommend using antioxidant vitamin supplements. It is also important to note that we can "over-supplement" our bodies, taking much more than the recommended daily value of certain vitamins and minerals. Vitamins A and E are fat soluble, meaning that excess amounts are stored in the liver and fatty tissues, instead of being quickly excreted, creating a risk of toxicity. Your best bet is to eat a diet rich in fruits, veggies, and whole grains.
For information on cancer, heart disease, and antioxidants (as well as on healthy diets, vitamins and minerals, etc.), you can visit the the National Cancer Institute website. Additional resources on supplements are provided by the National Institute of Health's Office of Dietary Supplements.
Remember, a balanced diet rich in colorful fruits and vegetables can provide you with immediate health and energy benefits and help fight the effects of aging for years to come. Happy antioxidizing!
Dear Banana Lover,
Nutritionally, bananas are packed with many good things. To get right to your question, according to the U.S. Department of Agriculture (USDA), one medium banana contains only 0.39 grams of fat. Compare that to a California avocado that has 21 grams of fat (with 3 grams of saturated fat). Like protein and carbohydrates, fat is an important macronutrient that plays a vital role in maintaining health. So while you don’t have to eschew avocados and olives, you can rest assured that eating a banana will provide some low-fat satisfaction in a balanced diet.
Bananas make a healthy and helpful snack choice for endurance athletes (and others) because they have higher carbohydrate content when compared to other fruits (by weight). They also provide a good source of potassium, which is vital for controlling the body's fluid balance, and regulating one's heartbeat and blood pressure, and preventing muscle cramping.
Think of it this way, if a contest called for designing an ideal food, you might just come up with a banana. They are neat (they come in their own wrapper!), they ripen best after harvest, they can be eaten at various stages of ripeness, there is a good supply all year, they tend to be inexpensive, and almost everyone can digest them. Chew on this, in an average year Americans consume about 25 pounds of bananas per person.
Perhaps you can help spread the word that people should just enjoy having their bananas and eating them, too!
Cholesterol is a necessary component for living cells. However, high levels of blood cholesterol are associated with an increased risk of heart disease. To complicate matters even more, blood cholesterol can be divided into two types, one of which actually lowers the risk of heart disease! To get the story on cholesterol straight, it's necessary to understand something about how cholesterol works in the body and how it can contribute to heart disease.
Most of the cholesterol in the body is produced by the liver. A significantly smaller amount comes from dietary sources, such as meat, eggs, and dairy products. Cholesterol travels throughout the body via the blood stream, being absorbed by cells along the way to be used for important processes, such as hormone production and cell membrane repair. Because it isn't water soluble, cholesterol is ferried along the bloodstream encased in protein. These cholesterol-filled protein orbs are called lipoproteins. Lipoproteins come in a variety of sizes that behave differently from one another. Broadly, health care providers and scientists talk about low-density lipoproteins (LDL) and high-density lipoproteins (HDL).
The role of both types of cholesterol in heart disease centers around the formation of arterial plaques — fatty, filmy deposits on arterial walls. Over time, plaques become hardened, leading to narrow, rigid arteries that impede blood flow and thereby increase the risk of heart attack. Also, smaller plaques sometimes develop blood clots on their surface, which can then detach and go on to block arteries downstream, potentially leading to heart attack. Although the biochemistry involved isn't simple, the take home message is that LDL contributes to the formation of plaques on the artery walls, while HDL helps prevent their formation. Accordingly, LDL is often called "bad" cholesterol while HDL is called "good" cholesterol. (These terms apply only to blood cholesterol; dietary cholesterol is neither good nor bad in this sense.)
For more information on cholesterol and heart disease, read the Related Q&As listed below.
The amount of radiation emitted from a microwave is set and monitored by the U.S. Food and Drug Administration (FDA) for a standard that is said to be safe for home use. The radiation itself is “non-ionizing,” which makes it less harmful than the radiation of X-rays. Radiation exposure from a home microwave does not pose any risks to your baby as long as your microwave’s safety mechanisms function properly. There is the potential of radiation leakage if the seal is cracked or caked with food, if the microwave has been dropped, or if a fire has occurred inside. In any of these cases, the microwave should be replaced. However, if your microwave is in good working order and you want to be extra safe, standing four feet away from the oven dramatically reduces radiation exposure — to just 1/100th of the maximum amount considered safe. As long as you keep your baby away from the radiation contained within the oven, you have nothing to worry about. Radiation cannot seep into the food or beverages you microwave.
However, there is a very real danger of serious burns from hot containers, overheated foods, and injury from exploding foods. The main precaution to take after heating milk in the microwave for babies is to be sure that there are no "hot spots." "Hot spots" are developed when microwaves heat foods unevenly, causing some sections to become much hotter than others. When the milk is checked for heat level, it may feel fine, although there may be some portions that are burning hot. It is recommended that you shake the bottle and let it stand for thirty seconds before checking the temperature. Other sources suggest not using the microwave to heat infant foods — neither bottles of formula nor baby food — because the uneven heat can severely burn a baby’s mouth.
According to the FDA, there is no additional damage to milk proteins or sugars when heated with a microwave rather than conventional oven or stove. In general, microwaves cook food faster and destroy fewer vitamins than conventional cooking methods. You may have read about research that shows a possible loss of human milk's immunologic qualities after microwaving, but further studies are necessary to support this. There is also the option of heating milk the old-fashioned way, on the stovetop.
If you do use the microwave, here are a few tips:
- Prick cooking pouches and foods that have tight skins (e.g., tomatoes, hot dogs) to release steam as they cook.
- Never cook eggs in the shell. If you crack an egg open to cook in the microwave, be sure to prick the yolk before cooking.
- Remove lids and caps from containers, and cover with microwaveable plastic wrap (don't let it touch food), waxed paper, or parchment paper for cooking.
- Arrange the food evenly and add liquid if necessary. Steam helps to destroy harmful bacteria and encourages uniform heating.
- Never use foam trays, empty plastic containers (such as yogurt cartons), or takeout containers in the microwave. These materials can overheat and become warped, which will allow harmful chemicals to penetrate your food. Only use cookware that is specifically labeled as “microwave safe.”
- Never turn on an empty microwave. Try keeping a glass of water or a box of baking soda in the oven just in case.
- Regularly clean the inside walls, the door, and the seal of your microwave with a mild detergent and water.
- Never operate the oven when something is caught in the door.
- Remove metal twist ties from bags. They act as antennae and can cause a fire.
- Never use brown paper bags for popping popcorn. They can catch fire, too.
(Adapted from Environmental Nutrition)
If you have further questions about microwave safety or child food preparation, you can contact your child’s pediatrician. Generally, however, you can rest assured that as long as your microwave works properly, your baby will not ingest harmful radiation.