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 benefits and side effects of melatonin are still under review by researchers and medical professionals — so any discussion about those should be considered tentative, based on what is known thus far. Similar to a wide array of supplements available over the counter, manufacturers do not need Food and Drug Administration (FDA) approval before marketing dietary supplements like melatonin. So, exercising caution and asking questions of a trusted health expert can really help consumers make more informed choices.
Melatonin is a hormone produced by the pineal gland in the brain that has a quick acting, sleep-inducing effect (more like Mellow-tonin, am I right?). It is a light-sensitive hormone, meaning that the absence of light stimulates its secretion. Melatonin may play a role in controlling the circadian rhythm, the body's internal clock and sleep cycle. Before puberty, the pineal gland produces comparatively large amounts of melatonin. As we age, melatonin production continually decreases, perhaps explaining why older people either have difficulty sleeping, or sleep less.
The melatonin you may find in health food stores and pharmacies is actually a synthetic version of the hormone; you can also purchase a form that combines synthetic and natural (from sheep pineal glands) melatonin. Both types of melatonin mimic the real thing in chemical composition and behavior. However, some people favor the entirely synthetic form because it does not carry the risk of contamination that the partially organic form does. Research has also found melatonin in some food sources, including meats, eggs, many vegetables, fruits, seeds, oils, coffee, tea, wine, and beer. Consumption of melatonin from food sources may increase the circulation of melatonin and it’s benefits as an antioxidant, but more research is needed on these potential benefits.
Many claims have been made to melatonin's miraculous powers. So far, scientific evidence has revealed melatonin to be clearly beneficial for a few sleep issues — like insomnia, jet lag, and delayed sleep syndrome. However, recent studies also reveal potential benefits in the following areas:
- reducing pre-operative anxiety and post-operative pain
- improving symptoms of irritable bowel syndrome (IBS)
- reducing symptoms of depression and anxiety in patients undergoing breast cancer surgery
Melatonin taken in recommended doses between one and three months in duration may have very few negative side effects. That said, side effects are possible. Special caution is advised if you:
- are pregnant, breast-feeding, or trying to get pregnant
- are younger than 18 years old
- have high blood pressure
- have diabetes
- have depression
- have a seizure disorder
Depending on what your intended use is for melatonin, dosing can vary. And just like many medications, people can respond very differently to melatonin — some people are more sensitive than others to the supplement and dosage may factor into this as well. If you decide to supplement with melatonin, it's best to discuss dosage recommendations with a health care provider. Too high a dose could lead to anxiety. Large doses of melatonin to children under 15 could also cause seizures.
More research is still needed in all of these arenas — evidence regarding the long-term use of melatonin, in addition to its benefits and side-effects, may not be available for years to come. Talking with a health care provider about taking melatonin can help you decide if you're at high risk for negative side effects.
Hope this helps!
While jetting cross-country can be a fun adventure, coping with jet lag is often an unwelcome effect. Jet lag is a temporary disorder that occurs when air travelers rapidly travel across three or more time zones. Traversing time zones appears to interfere with a person's production of melatonin, a hormone that helps regulate our sleep-wake cycles (see Melatonin from the Go Ask Alice! archives for more information). This may explain why jet travel disrupts our sleeping patterns and why it takes a while for us to adjust to a new time zone. Travelers have the option of taking melatonin to help counteract the effects that flying has on getting a good night's sleep.
Taking melatonin to reduce jet lag is a well-tested and safe use of the hormone. When the goal is to be in bed and asleep during the normal nighttime hours of your destination, timing is everything. If you take melatonin at the wrong time while still at home in New York, you may land safely in London, but your inner clock may be wandering around the Los Angeles airport wondering how it got on the wrong flight! So, what's the trick?
The secret to shifting your internal clock lies in the direction of your flight and duration of your journey. Travelers who cross three or more time zones generally require more time to adjust. Depending on your travel direction, it is recommended to take melatonin as follows:
- Westward travel is associated with early evening sleepiness and predawn awakening. When traveling westward, melatonin can be taken in the morning.
- Traveling to the east is associated with struggling to fall asleep at the destination bedtime and difficulty arising in the morning. In this case, it is best to take melatonin in the evening at your local time.
- Melatonin can be taken 30 minutes before sleeping. You can also ask your health care provider about the right time to take it.
- Though side effects are uncommon, it is a good idea to avoid alcohol when using melatonin.
The severity of jet lag is also dependent on whether a person is able to sleep while traveling, their age, and the availability of local circadian time cues at the destination (such as natural sunlight). Other than taking melatonin, your health care provider may recommend that you:
- Avoid alcohol, large meals, and caffeinated beverages during travel
- Eat meals at the appropriate time of your destination
- Drink plenty of water
- Sleep, if possible, during long flights
- Consider timed bright light exposure prior to and during travel
- Take sleep-inducing medications, such as zolpidem (Ambien), eszopiclone (Lunesta) and zaleplon (Sonata), during travel and to help you sleep during the first couple of days after your arrival
While adjusting to a new time zone may seem like a drag, don't worry, for your body will adjust in due time. Jet lag may last for several days, but it is a temporary condition that is normally manageable. Whether or not you choose to take melatonin depends on the severity of your jet lag and your preference to induce sleep. In the meantime, don't forget to adjust your watch as well. Happy (and restful) travels!
Dear Not worried...just curious,
If your diet is leaving you drowsy, it may be related to not eating enough calories — especially since many vegetarian foods tend to be relatively low-calorie. Eating too few calories would leave your body without enough energy to "get up and go" in the morning. To increase your calorie intake, try buying a variety of nuts, seeds (sunflower, pumpkin, etc.), and dried fruits to make your own trail mix: each day, put about one cup into a bag and carry it with you to snack on. Besides added calories, you will also be getting a good source of vitamins, minerals, and some protein into your diet.
At meal times, include healthy size portions of grains (whole wheat, brown rice, oats, barley, buckwheat, etc.), vegetables, fruit, and legumes (dried beans and peas), and use a moderate amount of vegetable oil (canola and olive are good choices) for cooking. If you eat eggs and dairy, they can also serve as a great source of protein, calcium, and added calories.
In terms of exercise, aim for about 30 minutes of aerobic activity five or more times a week to get cardiovascular and energy-boosting benefits. Exercise in excess of about one hour of aerobic activity, five or more times a week, should be reserved for those training for a competitive sport (and who are eating higher-calorie diets!). High levels of exercise increase the risk of sports-related injury and may make it harder to take in a sufficient amount of calories.
Even if you think you sleep the right number of hours, keep in mind that some people, particularly college-aged people, require up to ten hours of sleep a night. Other sleep habits might also give you problems; for example, it's important to try to go to bed and wake up at close to the same time each day. Although this may seem nearly impossible on a student schedule, try to get on an even keel to start off the semester. If you wake up at 11:00 AM most days and get up for an 8:00 AM class two days a week, you most likely will feel like you never quite wake up on the two early days, even if your total amount of sleep is adequate. You may want to adjust your routine so that you go to bed early enough to wake up at the same time each day (weekends included), and see if your tiredness improves.
If you feel overly exhausted or your drowsiness is interfering with school and life activities, you may want to consider seeing your health care provider. Students at Columbia can make an appointment through Open Communicator (Morningside) or by contacting the Student Health Service (CUMC).
Good luck getting up and at 'em!
Beans, seafood, poultry, meat, and eggs. These are just a few sources for protein. Our bodies need protein for numerous functions. Hemoglobin, which carries oxygen, is an essential protein that gives blood its red color when oxygenated. Antibodies, which act as defenders against disease, are composed of proteins. Hormones, some of which are made from amino acids (the building blocks of protein), regulate many systems in our bodies. These include the regulation of metabolism, digestion, and nutrient absorption, and the concentration of blood glucose. Proteins are also used by our cells to regulate the distribution of water and the movement of nutrients in and out of cells, particularly since proteins are one of the components of cell membranes. Furthermore, proteins are involved in blood clotting, acid-base balance, and visual pigmentation.
Considering we need protein to help our bodies carry out and sustain essential physiological functions, a diet very low in protein is obviously not a good idea. The good news is that it is not difficult to obtain sufficient protein from our diet and most Americans have no trouble doing so. Dietary protein can be obtained from animal and vegetable sources. If your diet is insufficient in protein, you could also be deficient in many important vitamins and minerals found in protein-rich foods. Deficiencies could occur in niacin, thiamin, riboflavin, B-12, B-6, iron, zinc, and calcium, among others, depending on what foods are missing from your diet. The effects of prolonged low protein in the diet would eventually manifest themselves as impaired immune function, and irregularities in other bodily functions and systems described above.
The Recommended Dietary Allowances (RDA) for protein are as follows:
Recommended Dietary Allowance for Protein
|Grams of protein needed each day|
|Children ages 1 - 3||13|
|Children ages 4 - 8||19|
|Children ages 9 - 13||34|
|Girls ages 14 - 18||46|
|Boys ages 14 - 18||52|
|Women ages 19 - 70+||46|
|Men ages 19 - 70+||56|
Protein recommendations vary from individual to individual depending on her/his amount of lean body mass.
As you can see, proteins are an integral and necessary part of our functioning. Animal sources, such as meat, fish, poultry, eggs, and dairy products, contain complete proteins — all the amino acids our bodies require to form the proteins we need. Vegetable sources, such as nuts, seeds, legumes (beans, peas, lentils, and soy products), grains (breads and cereals), and green leafy vegetables, contain incomplete proteins. This means that not all of the amino acids are found in one food. Mother Nature is tricky — the amino acids absent in some foods are present in others. Rice and beans, which together have all the essential amino acids, form a complete protein. This is an example of a way vegetarians can make sure they get complete proteins from their diet; however, according to research, it's not necessary to get complete proteins for every meal. Having some amino acids during breakfast and the others during lunch will have the same effect as consuming them together, during the same meal. Your body has the ability to combine complementary proteins as long as their eaten on the same day.
The following is a broad overview of the protein content in different food groups:
|1 cup dairy or soy milk||6-8 g|
|3 oz. lean beef, fish, or poultry||21 g|
|1/2 cup beans||7 g|
|1 slice of bread||3 g|
|1/2 cup cooked vegetables||2 g|
Dietary protein adds up rather quickly, and, as mentioned earlier, without too much effort. In the US, it is rare to find protein deficiencies among the general population. Ours is more a problem of excess than deficiency.
If you have special dietary needs and/or would like some nutrition counseling to help you eat enough protein from your diet, talking with a nutritionist can be a big help. Columbia students on the Morningside campus can use Open Communicator or call 212-854-7426 to make an appointment. Students on the CUMC campus can contact Medical Services at 212-305-3400.
February 4, 2014550964
March 11, 2013525286
Dear Cow lover,
Why does a milking stool have only three legs? Because the cow has the udder! Get it? Unfortunately, there’s not such a definitive answer to YOUR question. Research on the health effects of drinking milk has produced mixed results. As with any other food group, it is important to consider the pros and cons of dairy consumption.
Before a discussion of pros and cons, here is a run-down on recent milk research as it relates to osteoporosis. Although it is thought that drinking milk every day helps ward off osteoporosis, a small group of renowned researchers recently found that drinking too much milk can actually contribute to calcium loss. This is because the high amount of protein in milk thins blood and tissue, causing it to become acidic. In order to neutralize the acidity, the body draws out calcium from bones. As a result, the more milk you consume, the more calcium you need to process the protein intake. With that being said, drinking moderate amounts of milk each day (500 to 700 milligrams daily) is still thought to be good for your bones. More information on osteoporosis can be found in Calcium, milk, and osteoporosis?.
Moooving on, here is a list of the various pros and cons of drinking milk:
- Milk is high in calcium, which is important for healthy bones. Additionally, the calcium in milk is well absorbed by the digestive tract because the vitamin D and lactose found in milk facilitate calcium absorption. Still, it's possible to get ample calcium without drinking dairy milk — by eating foods such as tofu, soy milk, or greens such as kale. See Calcium — how much is enough? for more information.
- Whole milk is brimming with protein, which is beneficial for muscle growth.
- Studies have shown that drinking milk can help regulate weight gain.
- Skim milk is very low in fat and cholesterol, and is a complete source of protein.
- Milk is also a good source of phosphorous, magnesium, vitamin A, vitamin D, and riboflavin (a B vitamin).
- Whole milk is high in saturated fat, which can increase cholesterol level.
- Milk is a common cause of food allergy (allergy to milk protein).
- Many people lack the enzyme to digest lactose (milk sugar). This is called lactose intolerance, which causes bloating, gas, and diarrhea.
- Milk may contain the antibiotics given to the cow while it is lactating. It has been argued that humans subsequently absorb these antibiotics upon drinking milk, potentially leading harmful bacteria to become more resistant to these antibiotics. As a result, when antibiotics are prescribed, they may not be as effective at killing the bacteria.
- Some research has found a correlation between drinking milk that is produced by cows injected with the bovine growth hormone (rBST) and cancer. However, research shows highly mixed results.
As a side note, if you are concerned about the possible effects of antibiotics and rBST on your body, it is possible to buy antibiotic-free (and typically hormone-free, as well) milk from specialty grocers that carry natural foods. Alternatively, you can purchase USDA-certified organic milk, which is available at most supermarkets.
Overall, when researching the pros and cons of milk, it is important to take into account that there are two opposing sides — one that believes that milk is great for the body, and another that believes that milk does not aid against osteoporosis and is even harmful for the body. Whatever camp you choose to join, it is important to be informed. Seize every opportunity (to obtain information), and milk it for all its worth!
Dinner's in a few hours. Lunch seems like it was ages ago. You still have to work on a paper, drive your little brother to soccer, and do the dishes. The deliciousness of chocolate and the sweet sugar/caffeine fix it offers may seem to be the only thing to get you through, so you reach for a bar… is that so bad? New research says no, and yes, depending largely on which type of chocolate you choose and how much of it you eat. Cacao, the bean from which chocolate is made, is not itself unhealthy. In fact, it offers many potential health benefits like lowering blood pressure, increasing sensitivity to insulin, improving coronary vasodilatation (widening of blood vessels) as well as other cardiovascular benefits, and acting as an anti-oxidizing agent. But not all chocolates are created equal.
The good guys in chocolate are flavonoids, health-promoting compounds found in plant-based foods (fruits, veggies, nuts, legumes) that belong to a larger class of compounds called polyphenols. In plants, flavonoids work to repair damage and protect from environmental toxins. When we consume plant-based foods rich in flavonoids, it appears that they can act the same ways in our bodies, offering antioxidant protection from free radicals, and protection from plaque formation on our arterial walls.
Dark chocolate is the most flavonoid-rich variety of chocolate, and therefore the most likely to offer health benefits. However, as chocolate is processed flavonoids are lost, and most commercial chocolates are highly processed. Flavonoids also tend to have a bitter flavor, so many commercial chocolates intentionally process them out. In addition, many chocolate products are made with milk, which can interfere with the antioxidant functioning of flavinols, negating most of the potential health benefits. Finally, many chocolate products are laden with caramel, nuts, marshmallow, and other high-fat, high-calorie add-ins that decrease the amount of flavinols in every bite and make a small chocolate snack a hefty caloric load. Even the best, most flavonoid-rich dark chocolate is replete with fat, sugar, and calories (one ounce of any kind of chocolate has about 140 to 150 calories and 9 to 10 grams of fat), so if you're upping the amount of chocolate you eat to gain health benefits, keep in mind that you may want to trim calories in other areas.
One final consideration: there is currently no research that definitively suggests the amount of chocolate that should be eaten to achieve health benefits. You could also get the polyphenol-related health benefits by eating other flavonoid-rich foods like apples, red wine, tea, cranberries, and onions. That said, for most people, enjoying a small piece of dark chocolate once in a while is probably not going to be harmful, and is more favorable than reaching for the common trick-or-treat variety candy bar.
Over time chocolate has gotten a mixed reputation. It used to be seen as a fattening, pimple-producing crutch for the premenstrual. But chocolate does not cause acne, raise blood cholesterol, cause addiction, nor is it fattening if eaten in moderation. More recently, the pendulum has swung in favor of chocolate, which has come to be regarded as a kind of superfood. While it can offer some wonderful benefits, it may not be the antioxidant source of choice for everyone. Chocolate, as well as red wines and certain cheeses, contains phenylethylamine (PEA), a substance that can dilate blood vessels in the brain. People sensitive to PEA might find that eating chocolate can trigger headaches, even migraines. And for those prone to heartburn, chocolate can cause an episode, as would any other high-fat food.
So is chocolate bad for you? Each person should answer this question for themselves taking into consideration which kind of chocolate is within reach and their own health needs. For most healthy and fit individuals, chocolate is a pleasurable and reasonably healthy way to get some flavonoids into the system. For those prone to migraines or who have to watch their fat intake, they might want to stick with the cranberries and onions.
As vegetarianism, veganism, and even just eating less meat become more popular dietary and lifestyle choices for a growing number of people, adequate protein sources are always a topic of discussion. There have been scores of arguments about protein in all its facets: how much you need, what kinds are most useful to the body, and how to prepare it. But what it comes down to is: every body is different, has different needs, and digests foods uniquely, so the best non-meat sources of protein for one person might be the worst for someone else.
The recommended daily protein intake for healthy adults is about 0.4 grams per pound of body weight. Vegans (those who avoid all animal products, including dairy and eggs) may require a bit more at 0.5 grams per pound of body weight. Protein facilitates growth, metabolism, immune system functioning, repair, muscle contraction, and the transmission of nerve impulses and hormones in the body. It can also be a source of energy when the body runs out of carbohydrates and fat for fuel. And protein's not that hard to find, even for vegetarians. Almost every food contains protein: nuts, seeds, beans, soy products (tofu, soy milk, tempeh), grains (wheat, oats, rice), eggs, and dairy products all being excellent vegetarian sources (many of which tend to be low in saturated fat, cholesterol, and sodium).
The list below gives the protein content of some of the highest protein and/or most popular vegetarian foods:
- Tempeh — 1 cup — 31 g
- Lentils — 1 cup — 18 g
- Chickpeas — 1 cup — 15 g
- Tofu (firm) — 4 oz — 11 g
- Peanut butter — 2 tbsp — 8 g
- Soymilk — 1 cup — 7 g
- Soy yogurt — 1 cup — 6 g
- Whole wheat bread — 2 slices — 7 g
- Broccoli, cooked — 1 cup — 4 g
Protein is a macronutrient made up of smaller parts, called amino acids. There are different amino acids, many of which the body can produce, but nine which the body cannot. These nine must be eaten, and are therefore called essential. Animal proteins contain all nine of these essential amino acids in appropriate proportions, while the proteins found in plants often do not. Plant-based sources of protein have various amounts of amino acids in them. As such, it was previously thought that certain ‘complimentary proteins’ or combinations of plant-based proteins were needed in order to get all essential amino acids. However, rather than planning specific food combos at each meal, eating a variety of plant-based proteins over the course of a day should ensure that you get the essential amino acids you need.
You might find it helpful to consult with a registered dietitian if you want a more specific evaluation of your diet and unique nutritional needs. Columbia students can contact Medical Services (Morningside) or the Student Health Service (CUMC) to schedule an appointment. There is also a wealth of information online about vegetarian recipes, philosophies, and nutritional facts about specific foods.
People decide to eat less meat or no meat for myriad reasons that include health, animal rights, environmental sustainability, and religion. You can rest assured that your decision will further any or all of these goals without depriving you of the protein you need. Enjoy!
There is a lot of conflicting information about the pros and cons of supplements, so thanks for asking an important question. A healthy and nutritious diet involves six classes of nutrients:
Carbohydrate, fat, and protein are considered macronutrients [because our bodies require them in large quantities (grams/day)] and they yield energy. Vitamins and minerals are considered micronutrients [because our bodies need them in smaller amounts (milligrams or micrograms/day)] and instead of yielding energy, they help our bodies carry out necessary and important physiological processes. About 40 of these nutrients are essential for life because our bodies cannot synthesize enough to meet physiological needs (so our diet provides us with the bulk of these essential nutrients).
Vitamins are either water-soluble (water is required for absorption and are excreted in urine) or fat-soluble (requires fat for absorption and are stored in fat tissue). There are 9 different water-soluble vitamins: vitamin C and the eight B vitamins (thiamin, riboflavin, niacin, vitamins B6 and B12, folate, biotin, and pantothenic acid); and, 4 different fat-soluble vitamins: vitamins A, D, E, and K. Each of these vitamins have unique roles and functions in our bodies. For example, vitamin A promotes eyesight and helps us see in the dark, and vitamin K helps blood to clot.
Minerals are categorized as major or macro- (calcium, phosphorus, potassium, sodium, chloride, magnesium, and sulfur), and trace or micro- (iron, iodine, zinc, chromium, selenium, fluoride, molybdenum, copper, and manganese) minerals, the former needed in quantities of 100mg/day or more, and the latter required in much smaller, or "trace," amounts. These 16 essential minerals also play vital roles in the body, such as calcium in osteoporosis prevention and iron in (iron-deficiency) anemia prevention; and, they can be found in the body dissolved in body fluids as ions and/or are part of important compounds, such as calcium and phosphorus in hydroxyapatite found in bones and teeth. Other minerals, such as lead, are contaminant minerals and not nutrients because they can cause harm by disrupting normal bodily functions and processes, i.e. lead poisoning.
Vitamins ("vita" = life and "amine" = containing nitrogen) are organic (containing carbon, which is an element found in all living things) compounds (containing atoms of one or more different elements). Minerals are pure inorganic elements (containing atoms of the same element), meaning they are much simpler in chemical form than vitamins. All vitamins are essential or required by our bodies, whereas only some minerals are essential nutrients. Vitamins are vulnerable to heat, light, and chemical agents, so cooking, food preparation, processing, and storage must be appropriate to preserve vitamins in food. Minerals, on the other hand, are more stable to food preparation, but mineral loss can occur when they are bound to other substances in foods (such as oxalates found in spinach and tea, and phytates found in legumes and grains), making them unavailable for the body to utilize.
There is not a lot of research to state unequivocally if taking extra vitamins or minerals is harmful or helpful for the body. Our bodies do have a natural maximum capacity for different types of vitamins and minerals, so taking a lot of supplements may result in nausea or other side effects as your system works to get rid of the excess. While some vitamins and minerals are water soluble and can be excreted through urine if they are in excess, others are absorbed in fat and can accumulate over time. Some supplements can also interact with prescribed medications, so you may want to include them when asked about any medications during medical exams. You may also want to speak to your health care provider before adding any new supplements to your diet.
Health care professionals do agree that the best source of both macro and micro nutrients is from a well-balanced diet. Try visiting ChooseMyPlate.gov for information on the health benefits, nutrients, and vitamins available in different foods. Depending on the person, current levels of vitamins and minerals may be higher or lower than necessary and may warrant a supplement or dietary changes. To understand what vitamins and minerals are most appropriate for you, you may want to consult with your health care provider or a registered dietician. If you’re a Columbia student, you can make an appointment by contacting Medical Services (Morningside) or the Student Health Service (CUMC) to speak with either a health care provider or dietitian. You might also want to check out the get balanced! Guide for Healthier Eating. The National Institutes of Health (NIH) or the U.S. Food and Drug Administration (FDA) websites have additional information about dietary supplements in general.
Here’s to finding the balance that’s right for you!
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!