Vitamin A is an essential, fat-soluble vitamin that has many diverse benefits for humans. Vitamin A promotes eyesight and helps us see in the dark; aids in the differentiation of cells of the skin (lining the outside of the body) and mucous membranes (linings inside of the body); helps the body fight off infection and sustain the immune system; and, supports growth and remodeling of bone. In addition, dietary vitamin A, in the form of beta carotene (an antioxidant), may help reduce your risk for certain cancers.
Adequate vitamin A intake is essential to human health. Vitamin A deficiency can lead to night blindness (inability to see in the dark or to recover sight quickly after being exposed to a flash of bright light in the dark) and xerophthalmia (progressive blindness that becomes irreversible if not treated in time with vitamin A).
Vitamin A deficiency can also reduce the health and integrity of skin and other epithelial tissues. The effect on skin can result in dry skin and hyperkeratosis (the development of clumps of skin around hair follicles). The effect on epithelial tissues can negatively affect the digestion and absorption of nutrients and cause infections of major systems and their organs (i.e., gastrointestinal, nervous/muscular, respiratory, and urogenital). In addition, bone growth can stop and normal bone remodeling can become impaired, resulting in anemia and weakened immunity.
The Recommended Dietary Allowance (RDA) for vitamin A is measured in retinol equivalents (RE), retinol being the active form of vitamin A. For adult men, the RDA is 900 micrograms of RE per day and for adult women it is 700 micrograms of RE per day.
Despite its benefits, too much Vitamin A can cause toxicity, the effects of which can vary depending on its source. Excessive intake of vitamin A in dietary form is not harmful, but will cause one's skin to turn yellow in color. In contrast, large dose supplements (10 - 15 times the RDA) of vitamin A (as retinol) is harmful, and could result in the development of a fatty liver (hepatomegaly), dry skin, nausea, vomiting, fatigue, weakness, headaches, anorexia, and/or possibly increase the risk of birth defects among pregnant women. Symptoms depend upon whether or not vitamin A intake was taken over a long period of time (chronic) or a single excessive dose at one point in time (acute). In general, fat-soluble vitamins should not be consumed in excess of the recommendations because, unlike water-soluble vitamins in which the excess is excreted out of the body, an excess of fat-soluble vitamins will be stored and accumulated in the body.
It is highly recommended that vitamin A be consumed in the diet rather than from supplements. The richest sources of dietary vitamin A are liver, fish liver oils, milk, milk products, butter, and eggs. Liver is an especially rich source because vitamin A is primarily stored in the liver of animals and humans. Vitamin A is also found in a variety of dark green and deep orange fruits and vegetables, such as carrots, sweet potatoes, pumpkin, spinach, butternut squash, turnip greens, bok choy, mustard greens, and romaine lettuce. Beta carotene is the most active carotenoid (the red, orange, and yellow pigments) form of vitamin A. In addition, cooking (but not overcooking) increases the bioavailability of carotenoids in plant foods and absorption of dietary vitamin A is improved when consumed along with some fat in the same meal.
Hope this helps,
Dear Joyful Juicer,
Juicers can be a great low calorie, high nutrient, tasty treat. However, they don’t generally carry all the benefits of eating the original fruit or veggie from whence it came.
If you've made juice, you know that it takes a lot of fruit to make a container of juice. Usually, juicers extract the juice and some pulp from fruits and/or vegetables. You’ll get all of the vitamins, minerals, beneficial plant chemicals (phytochemicals), and carbohydrates in juice that's extracted from a whole fruit. However, you won’t get much of the fiber, and depending on the fruit, you may not get any of it.
Fiber aids in the digestive process. It acts sort of like a scrub brush for your intestines and speeds up the movement of waste through your system. It also can fill you up, and may help protect against certain cancers. Fiber in fruit is found in the membranes between sections, the white part around the outside (as in oranges and grapefruits), the seeds, the skin, and the peels. For example, orange juice contains no fiber (even if it has pulp) because the fiber is found in the membrane, which is lost during the process of juicing.
It is also important to remember that juice is not a low calorie drink. An eight ounce glass of orange juice contains 110 calories — the equivalent of two oranges (each contains about 60 calories). But you won't feel as filled up from juice since it doesn't contain any fiber. For many people, drinking a caloric beverage, such as juice, isn't as satisfying as eating the same amount of calories in food. For those who need to increase caloric intake — such as athletes, children, or teens — juice is a great choice.
Fresh juice is certainly tasty and an excellent source of many nutrients. Less stable vitamins, such as vitamin C, are not compromised in fresh juice as they may be in some processed varieties. Also, watch for added sugar in many processed juices that can increase caloric content.
In general, juice is just fine. But if fiber’s what you’re after, go for the whole fruit or veggie over the liquefied form. Happy juicing!
As a general rule, fasting all day on a regular basis is not a good idea, even if you "make up" the skipped calories at night. Although our bodies are remarkable in their ability to adapt to over and under eating at times, they need energy throughout the day to perform at an optimal level.
Paying attention to hunger signals (they are there for a reason!) and being aware of how much food you need to maintain physical and mental energy is healthy. By fasting all day you deny your body nutrients and energy which may lead to headaches, mood swings, feeling tired and dizzy, and even fainting. Your metabolism may also slow down and you could lose muscle mass. Fasting also may make you more likely to binge in the evenings, and you may be more likely to choose unhealthy foods.
You may want to ask yourself why you are skipping meals during the day. Observing religious holidays or special occasions is one reason many people fast from time to time. For most people, our bodies can adapt and function through the occasional fast, whether it is a sun-up to sun-down fast, or extends for a full day (children and people with certain medical conditions may need to forgo even occasional fasting; consult your health care provider if you are uncertain).
If you fast frequently you may want to consider some of your motivations. Are you trying to lose weight? Do you not feel hungry during the day? Are you too busy to eat? If you are trying to lose weight, eating several small meals throughout the day might be a better option. This will provide you with a more constant and consistent source of energy in a form that makes it easier for your body to metabolize and burn calories. Skipping meals is not a healthy approach to weight loss since fasting slows down metabolism and makes people more likely to overeat later. See Will skipping breakfast and lunch lead to weight loss? and Importance of eating breakfast for more information on skipping meals.
You mention eating "whatever you want" at night. Could this be because you feel guilty about eating certain kinds of foods, or about the amount of food you eat? These concerns are issues to think about before you can adopt a more healthful eating plan and positive attitudes toward eating. They may also be a sign of disordered eating, or other issues such as depression. If you're experiencing guilt or are anxious about food, contact a mental health professional who can help you get to the bottom of these feelings and behaviors.
If your question is motivated by the desire to lose or manage your weight, consider making an appointment with a nutritionist or registered dietician who can help you figure out a meal plan that works for you and fits your lifestyle.
Although it's not always easy to change your eating habits, taking care of your health is worth it in the long run.
Dear Breakfast Boycotter,
Your brain (and central nervous system) run on glucose — that's the fuel you need to think, walk, talk, and carry on any and all activities. Let's say that the last time you eat something at night is at 10 or 11 PM (not optimal, just an example). The following day, you don't eat breakfast but wait until about noon or so to eat — you've gone thirteen or fourteen hours with nothing in your system. Your poor brain is surely deprived — and your body has to work extra hard to break down any stored carbohydrate or turn fat or protein into a usable form for your brain to function. That's a lot to ask for when you're sitting in a classroom, trying to concentrate on reading, or doing any other work. Eating breakfast has been proven (many times) to improve concentration, problem solving ability, mental performance, memory, and mood. You will certainly be at a disadvantage if your classmates have eaten breakfast and you've gone without. On average, they will think faster and clearer, and will have better recall than you. School or work can be tough enough without this extra added pressure.
Breakfast skippers also have a harder time fitting important nutrients into their diet. Many foods eaten at breakfast contain significant amounts of vitamins C and D, calcium, iron, and fiber.
Some people believe that skipping breakfast may help them lose weight. Not so! Skipping meals often leads to overeating later in the day. Becoming overhungry often leads to a lack of control and distorted satiety signals (meaning it's hard to determine when you're full). This can result in taking in more calories than if one had an appropriate breakfast. As a matter of fact, it's easier to control one's weight by eating smaller meals and snacks more frequently.
What if there's just no time in the morning to eat breakfast? There are plenty of items you can bring along with you to school or work. Carry a resealable bag of easy-to-eat whole grain cereal, or bring a yogurt or small box of skim milk, juice, or fruit. If you just can't stomach food in the morning, try to have a little something — such as some juice — and bring along a mid-morning snack. Other good portable items include: whole grain crackers, a hard boiled egg, cottage cheese, low-fat granola bars, or even a peanut butter sandwich. Single serving hot cereals, such as oatmeal, are handy — all you have to do is add hot water, available at most cafeterias or delis.
Whatever your choice, eat something. If you think you're doing fine with no breakfast, just try changing your tune for a week —you're likely to notice a difference. You will undoubtedly perform better with some fuel in your system, and, hopefully, become a breakfast believer.
You are quite right that some questions have been raised about whether microwaving food using plastic wrap and plastic containers is harmful to our health. Much of the focus has been on plasticizers (chemicals used to make plastic more flexible), polyvinyl chloride, and polycarbonate. More recently, bisphenol-A (BPA), primarily used in hard plastics like polycarbonate, has also been called into question.
Research suggests that plasticizers, BPA, and other chemicals may leach into food while being heated in a microwave. Plastics tend to break down and release chemicals when exposed to high temperatures, and the fear is that some plasticizers could mimic or compete with our hormones, producing a hormonal imbalance. This imbalance has been associated with the development of cancer, birth defects, and fertility difficulties. The United States Food and Drug Administration (FDA) does consider BPA to be an endocrine disruptor, meaning it can alter hormonal levels if present in high enough quantities. What is in dispute, however, is whether BPA and other chemicals leach into food in amounts high enough to cause serious health issues. Recently the FDA updated its stance on BPA to indicate moderate concern about its harmful effects during fetal development and for infants and young children. However, the FDA has not taken the same position regarding adults, who are generally less susceptible to chemicals.
While time and more testing will show whether or not heated plastics pose a health threat, limiting exposure to plastic containers with BPA, and all plastics when heated in a microwave, is a precaution some people have decided to take recently. Infants and developing embryos are especially vulnerable to potential chemical leaching, so pregnant and breastfeeding women and parents with young children might want to be particularly careful not to heat plastics in the microwave.
Here are some hints for safe microwaving:
- Choose microwave-safe plastic wrap and never let it directly contact food.
- Try using waxed or parchment paper instead of plastic wrap.
- Only use containers that have been designated as microwave-safe. Best to use microwaveable glass and ceramic cookware. Otherwise, choose those made of polyethylene plastic which is plasticizer-free.
- Never use microwave convenience food trays and containers more than once.
- Do not microwave plastic containers used for cold food storage. They often melt and warp because they are not designed to withstand the high heat of microwaving.
- Avoid microwaving food in freezer cartons and on Styrofoam trays.
Since microwaves are so common this is information everyone can use. Thanks again for the heads up!
Dear Calcium and Iron Maiden,
It seems like you're approaching a supplement regimen with a healthy consideration of various factors like absorption and affects on your system — a great idea! You're right that there are certain foods that can inhibit iron absorption, like the oxalic acid in spinach, phosphates primarily in milk, other dairy products, and egg whites, phytates in beans, and tannins in tea and coffee. While it would take a lot of these foods to seriously impair your ability to absorb iron, you might want to consider going easy on them while trying to boost iron levels.
On the opposite side of the spectrum, there are many foods that are rich in iron, and it's usually preferable to get your essential nutrients from food rather than supplements. The body has an easier time digesting and absorbing nutrients like iron and calcium in the amounts and forms in which they occur naturally. You can check out Sources of Iron in Alice's Fitness & Nutrition archives for a list of these iron-boosting foods (sneak preview: meat, fish, dark leafy greens, dried beans, and nuts are all healthy iron-rich foods). Another dietary tactic to boost iron absorption is to eat a vitamin C rich food with your iron-rich food or supplement, as vitamin C aids in iron absorption. For example, eating citrus (oranges, grapefruits, lemons) along with your spinach salad will help unlock the iron in spinach. You can also cook your food in cast iron pots and pans to enrich your food with iron.
In terms of your sensitive GI system, the least constipating iron formula is hydrolyzed protein chelate, but again, diet can come into play here. In addition to looking for gentle and non-constipating types of iron supplements, you can also alleviate constipation by drinking plenty of water and by eating fibrous foods like whole grains, fresh fruits, fresh vegetables, and other foods as unprocessed as you can find them (whole grain bread instead of white, whole grain pasta instead of white, brown rice instead of white). It's a good idea to increase fiber intake slowly — too much too soon can cause gas and bloating. And to underscore again, when increasing fiber it's important to drink even more water than you think you need to make sure all that bulk moves through your system smoothly.
As for calcium, the two most common forms in supplements are calcium citrate and calcium carbonate. Studies show that calcium citrate is the most absorbable supplement form, and may be taken between or with meals. Vitamin D helps to assimilate calcium into bones. When exposed to sufficient sunlight, the human body synthesizes its own vitamin D. Fatty fish like salmon, tuna, and sardines are great food sources of vitamin D. If you want a D supplement, which might be a good idea for folks who live in northern climates and don't get adequate sun exposure during the winter, or for people who don't eat a lot of fish, look for supplements that contain vitamin D3 (cholecalciferol), rather than vitamin D2 (ergocalciferol) — vitamin D3 is more potent. You might also want to consider taking a magnesium supplement with your calcium at a ration of two-parts calcium to one part magnesium, as magnesium is needed to fully absorb and utilize calcium.
Finally, see if you can avoid taking your calcium and iron supplements together, as they compete for absorption. It may seem like a lot of juggling of different foods, supplements, and timing of the two, but hopefully this kind of careful consideration and knowledge will boost your iron and calcium levels to new heights.
Farewell, fair Iron (and calcium) Maiden,
Dear Confused and College Bound,
You are not alone with your concerns. Going to college is a big step in a person's life involving major changes. You and those around you may be living on your own for the first time, making decisions on a buffet of issues, including what to eat.
Eating healthy at college is possible. Many college dining services are offering more healthy choices and are often quite receptive to students' concerns and dietary preferences. But, this is only part of the challenge. In an environment where time, friends, and finances may combine in new ways, having options available only solves some of the puzzle. It's important to experiment with what works best for you. For example, that traditional idea of three square meals a day has been updated with a more contemporary concept of eating five smaller meals spread throughout the day. Steer clear of diets or fads, especially those that drastically limit a particular nutrient. Remember, balance, moderation, and variety win out over trendy and extreme. For some practical tips, navigate through the many options on Choosemyplate.gov. Columbia students can also take advantage of the resources from the get balanced! initiative. Plan ahead when possible so you don't have to rely on vending machines when you're hungry; think of ways to incorporate fruits, vegetables, and whole grains on a daily basis. Eating more of these will fill you up and possibly even enhance your already stellar brain power.
Making time for physical activity is important, too. Most college fitness centers have a variety of movement classes and options. When the weather is right, grab a friend and walk, run, bike, or blade outdoors. If you are Columbia affiliated, you can connect with 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, incentives to be active throughout the year, and event calendars with access to plenty of free and low-cost physical activity options on campus and around NYC.
Now, to address the second part of your question: an eating disorder, such as anorexia nervosa, is less about food, eating, and body weight. It has more to do with mental health, emotional, physical, socio-cultural, and family issues. If this is a particular concern of yours, you might want to take a look at Eating disorders vs. normal eating. Additionally, if you are a Columbia student, you can make an appointment with a health care provider or a registered dietitian to discuss your concerns by contacting Medical Services (Morningside) or the Student Health Service (CUMC).
Give yourself some time to adjust to a new environment and ask for help when you need it. Everything in moderation, even moderation.
Enjoy your time at college,
It's a great idea to plan consciously when switching over to a vegetarian diet. Not eating meat can offer many health benefits, as well as addressing environmental and ethical concerns you may have regarding eating animals. However, before making the switch to a meat-free lifestyle, it is important to get a sense of the pros and cons.
Here’s the best news of all: with a well-planned diet, vegetarians can live a totally healthy lifestyle and help contribute to a better planet. The following list describes various benefits of vegetarianism:
- Plant foods are abundant in nutrients, including vitamins, minerals, and protein. They also contain phytochemicals — plant chemicals that are not essential to life, but may help protect against disease — such as beta-carotene. Eating a variety of colors of fruits and vegetables can help ensure that the benefits nature provides are reaped.
- Reduce your risk of type 2 diabetes. Vegetarians benefit from eating less saturated fat and cholesterol, and higher amounts of complex carbohydrates, dietary fiber, certain minerals, and phytochemicals. Cholesterol is only found in animal foods, so vegan diets are completely cholesterol-free.
- Contribute to the vegetarian cause! Whether you have aim to respect animals, lessen your carbon footprint on the environment, or just want to make a lifestyle change, as a vegetarian you are making your own positive impact on the world. You can be proud that you are living according to the beliefs that you stand for.
Whenever you cut a food group out of your diet, it is important to understand how to replace the vital nutrients that go along with it. While the positives are all fine and dandy, it is important to be aware of the challenges of being a vegetarian:
- It can be harder to get the protein you need. Protein is important formaintaining and repairing muscle tissue, and manufacturing blood cells, antibodies, hormones, and enzymes. Fortunately, there are plenty of non-meat proteins to supplement your diet.
- Possible vitamin and mineral deficiencies can develop without a balanced eating plan. Cutting out dairy, meat, fish, and poultry reduces your intake of vitamin B12 (important for nerve transmission and necessary for life), calcium (for strong bones, among other functions), iron (for blood), and zinc (for immunity and healing), just to name a few.
- Depending on where you live, it may be challenging to adhere to a meat-free lifestyle. For example, living in a big city may provide you with endless veggie options, while a small-town lifestyle may make it more difficult to find healthy substitutions for meat.
- You may have difficulty explaining your eating habits to family and friends.While it may seem that being a vegetarian is relatively mainstream, certain cultures leave little room for herbivores. You may encounter some sticky situations where people have prepared for you a meaty meal, or perhaps, your friends and family may challenge your decision to remain meat-free.
Remember, what is included in your diet (rather than what is excluded) is what counts. It is extremely important to incorporate a balanced eating plan full of nutrient-rich foods. For help in selecting a healthy eating plan appropriate for your state of health, age, size, activity level, preferences, and moral and ethical values, consult with a registered dietitian. Columbia students can make an appointment with a registered dietician at Medical Services through Open Communicator or by calling (212) 854-7426. Informed choices are the best choices!
February 23, 2012507783
As they say, everything in moderation — including fiber! Eating enough fiber can have many health benefits, while too much may have consequences. By learning how much fiber you need, how much is in your food, and adjusting your diet accordingly, you’ll be able to strike a balance that’s ideal for your body (and your bowels).
Fiber is basically composed of plant-based food matter (fruits, veggies, whole grains, and legumes) that can’t be broken down by your digestive system. Whole foods contain both soluble (dissolves in water) and insoluble (does not dissolve in water) fiber. Although the recommendations below don’t distinguish between these two types of fiber, they are different and have distinct functions — soluble fiber helps to reduce cholesterol and glucose levels, and insoluble fiber helps with constipation by increasing fecal bulk.
Overall, fiber may lead to many health benefits, such as:
- Keeping you regular. Fiber decreases the risk of constipation by bulking up and softening your stool.
- Maintaining your bowel health. Fiber may prevent the development of diverticulitis and hemorrhoids. It has also been shown to reduce the symptoms of irritable bowel syndrome (IBS) in some cases.
- Lowering cholesterol and blood glucose levels. By reducing bad (LDL) cholesterol and blood glucose levels, soluble fiber also leads to a decreased risk for cardiovascular disease, coronary heart disease, and type II diabetes.
- Controlling your appetite/weight. Foods that contain fiber are typically low in fat, energy-dense, take more time to chew, keep you full for longer, and block some of the digestion of fats and proteins.
- Preventing cancer. Fiber consumption may lower the risk for colorectal cancer, but the evidence is not yet conclusive.
Curious if you are getting enough fiber in your diet? You can use either the USDA Food List or WebMD’s Fiber-o-Meter to figure out the fiber content of the foods you eat and get suggestions for high-fiber foods. Making a habit out of reading the nutrition facts on food labels will also help. Generally, women need less fiber than men, and those aged 51 years or older need less than younger individuals. The following table can give you an idea of how much fiber you need on a daily basis:
Age 50 or younger
Age 51 or older
Source: Institute of Medicine
However, having too much fiber in one's diet can cause problems. When the intake of fiber is too high, it can replace other energy and nutrients that you need in your diet. Some insoluble fibers bind certain minerals, including calcium, magnesium, phosphorous, and iron. Too much fiber can also cause abdominal discomfort, gas, and diarrhea, and block the gastrointestinal (GI) tract if you add too much fiber too fast. For some, fiber supplements may potentially cause additional, more severe side effects such as allergic reactions and asthma, gastrointestinal distress, and drug and nutrient interactions. If you feel that you might benefit from taking fiber supplements, it's best to speak with a health care provider first to make sure it’s right for you.
So, before you load up on fiber, try adding it to your diet gradually, so that your GI tract has time to adapt. You'll also want to drink lots of fluids to keep the fiber soft. Choosing a variety of soluble and insoluble fiber-rich food sources, such as fruits, vegetables, whole grain breads and cereals, and legumes (beans and peas) will ensure that not only will you get a good mix of fiber, but beneficial nutrients, too. Remember that brown rice and 100 percent whole wheat bread have more fiber than white rice or white bread. Also, eating the skins of your fruits and vegetables whenever possible can also help increase fiber intake. If you need advice or more information about incorporating fiber-rich foods into a balanced diet, consider making an appointment with a health care provider or registered dietitian.
Hope this was helpful!
RDAs (Recommended Dietary Allowances), prepared by the Food and Nutrition Board of the National Academy of Sciences, have been around for over 50 years, with periodic updates. The RDA is the average daily dietary intake level that would adequately meet the nutritional needs of nearly all (98 percent) healthy persons. RDAs include nutrients for which there is sufficient scientific evidence that they are required for good health. Their intention has always been to establish "standards to serve as a goal for good nutrition." RDAs provide the basis for evaluating the adequacy of diets of population groups. They are set at a level that includes a safety factor appropriate to each nutrient; so, this level actually exceeds the requirement for most individuals.
The Food and Nutrition Board has established Dietary Reference Intakes (DRIs). In addition to RDAs, DRIs include recommendations for food components for which RDAs cannot be established. Some of these include fat, carbohydrate, fiber, and plant estrogens, among others. DRIs also include maximum intake levels. Three dietary intake reference values for DRIs are:
- Adequate Intake — the dietary intake level that would adequately sustain health when an RDA cannot be determined because of insufficient scientific evidence.
- Estimated Average Requirement — the estimated dietary intake level that would maintain the health of half of a specified age and sex group.
- Tolerable Upper Intake Level — the maximum level of daily nutrient intake that's apparently safe and unlikely to cause negative health effects in most healthy individuals.
DRIs and RDAs are not developed for specific individuals, but are for the making of policies for feeding programs, food labeling, and food fortification. The numbers signify levels of each compound that are appropriate for most healthy people in each category. To access information on RDAs and DRIs, check out the United States Department of Agriculture's (USDA) Food and Nutrition Information Center website.
Vitamin supplements may contain an amount equivalent to the RDA for DRI, but you'll probably not find a supplement with every imaginable nutrient, vitamin, and mineral. There are innumerable substances that keep us healthy, many of which cannot be packaged in a pill. In addition, many nutrients are difficult for the body to absorb when they come in pill form. Obtaining nutrients directly from a balanced diet of fruits, vegetables, whole grains, and lean proteins is still the recommended manner of giving your body all it needs to be healthy.
To assess whether your current diet is filled with nutrients, check out ChooseMyPlate.gov. You can also speak with your health care provider about whether you need a multivitamin or if the food you eat is sufficient. Students at Columbia can also make an appointment to speak with a registered dietician or a health care provider either through Medical Services (Morningside) or the Student Health Service (CUMC). Take care,