November 2008:
Whole foods vs. Supplements by Edward Siguel, MD, PhD
Edward Siguel, MD, PhD, is a medical doctor and pioneering biochemical researcher who studies the role of essential fats and trans-fatty acids in health and disease.
How can pregnant or nursing mothers ensure that they are getting sufficient quantities of omega-3 fatty acids, such as those found in fish?
Eating a variety of seafood is important because omega-3s are a family of fatty acids that are critical for cell development, particularly the brain. If pregnant or nursing women don’t have enough omega-3s in their bodies, the cells in the children will not optimally develop. By eating fish, they will also consume a mixture of nutrients, such as anti-oxidants, vitamins, proteins, etc., which help protect the omega-3s’chemical structure and enhance their biological effects.
What are the benefits of eating whole fish vs. supplements?
Eating whole foods, like fish, makes it easier for women to eat a balanced diet. By eating fish, women consume mixtures of fats, protein, vitamins, minerals and other key nutrients in a form that the body can easily digest, absorb and use. It is hard to eat too much of a particular vitamin or mineral when eating whole natural foods. On the other hand, supplements may contain too much of some nutrients and too few of others, which may overwhelm the body and cause it to erroneously discard useful nutrients. It’s like cleaning out your e-mail inbox. If you receive huge amounts of junk mail, you might eventually delete an important e-mail during the process.
Additionally, nutrients are better preserved in whole foods than in supplements or highly-processed foods. When food is processed (heat, pressure, etc.), nutrients usually take on different structures. Although fish oils contain omega-3s, they do not necessarily have the same chemical structure as the omega-3s found in whole fish. Researchers do not know all the complexities and changes in chemical structure associated with eating nutrients extracted and modified from foods. The safer approach would be to avoid eating foods too different from their original state. Animals have survived for millions of years eating plants and animals in their natural habitat, without the need for supplements. Like most species, humans have evolved to eat natural foods.
In particular, fish has the additional advantage that it is nutrient dense, meaning that few calories provide a breadth of nutrients and curbs hunger. Although it is difficult to eat too much fish, it is very easy to eat too much cake, bread or pastries. A diet high in fish provides essential nutrients in mixtures useful to the body, makes one feel full, and helps prevent undesirable weight gain.
Specifically, how are the long-chain omega-3 fatty acids in fish distinct from those in fish oil supplements?
Omega-3s retain their maximum biological benefits in their natural state, like in minimally-processed fish making them easier to digest, absorb and use. Fish contain omega-3s in their optimal molecular structure; therefore, omega-3s are protected against deterioration, or change in molecular shape.
In fish oil supplements, omega-3s are separated from their natural state and may deteriorate more rapidly, changing their shape or chemical structure. In fish, the omega-3s are in optimal shape because they fulfill their biological and structural function in food. Once extracted, the omega-3s may change shape and form other similar molecules. They may still be known as “omega-3s,” but may not have the same functional effect.
There are many different shapes of the omega-3s docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Although these molecules are omega-3s and resemble the original molecules, they are less likely to have the same biological function. The body may think these altered molecules are good enough, and use them to build defective structures like suboptimal brain cells and membranes.
For example, it could be possible that there is a link between consumption of modified omega-3s and omega-6s (through processing or other means) and developmental disorders in children. Until we develop better technology to measure changes in the shapes of omega-3s and omega-6s, we will not fully know the impact of supplements.
Can you get omega-3 fatty acids from other foods than fish?
Omega-3s are a family of fatty acids, and alpha linolenic acid (ALA) is a precursor to other omega-3s, such as DHA and EPA. Humans cannot make ALA, which is why it is called an essential fatty acid. Plants make ALA from scratch and the human body has the enzymes to make longer-chain omega-3s. However, the process is inefficient (only a fraction of the linolenic converts to long-chain forms) and this takes time.
Fish is a desirable source of omega-3s because it provides more EPA and DHA faster than vegetable sources. However, pregnant women that prefer a vegetarian diet may obtain the omega-3s their bodies need from selected natural vegetables. The human body can make the needed EPA and DHA from vegetables or vegetable oils, rich in ALA, but people may need to eat large quantities to get a sufficient amount of EPA and DHA. For a vegetarian diet to provide enough omega-3s, it must be followed consistently for long periods of time and must contain plenty of traditional vegetables in their natural state.
Animals, algae and a few other species have long-chain fatty acids. The omega-3 fatty acids found in flax seed and some other vegetables only partially converts to longer-chain derivatives like DHA. Most eggs (the yolk) and some lean meats such as chicken contain small amounts of EPA and DHA. Other foods, such as olives or olive oil, have practically zero omega-3s.
Note: Sources with very low omega-3s such as many vegetables may be enough if eaten repeatedly. Olives have almost zero, I do not think they are an appropriate source even though some authors disagree.
So, women can get omega-3s from other sources, but fish is the best source.
References
Siguel E, Maclure, M. Relative Activity of Unsaturated Fatty Acid Metabolic Pathways in Humans. Metabolism, 1987; 36: 664-69.
Warren SE, Siguel E, et al. Effects of Cod Liver Oil on Plasma Lipids, Eicosanoids, Platelet Aggregation, and Exercise in Stable Angina Pectoris. J. Applied Cardiology, 1988; 3(4):227-36.
Chee KM, Gong JX, Rees DMG, Meydani M., Ausman L, Johnson J, Siguel E, Schaefer EJ. Fatty Acid Content of Marine Oil Capsules. Lipids 1990; 25:523-27.
Siguel E. Dietary Sources of Long-Chain n-3 Polyunsaturated Fatty Acids. JAMA, 1996; 275:836-37 (let).
Siguel, E. Issues and Problems in the Design of Foods Rich in Essential Fatty Acids. Lipid Technology, 1996; 8(4):81-86 (July).
Siguel, E. Deficiencies and Abnormalities of Essential Fats in Gastrointestinal and Coronary Artery Disease. Journal of Clinical Ligand Assay 2000; 23:104–11.
Siguel, E. Clinical Impact of Methodological Issues in the Diagnosis of Deficiencies and Abnormalities of Essential Fats. Journal of Clinical Ligand Assay 2000; 23:112–21.
Siguel, E. n-3 Fatty Acids and the Risk of Sudden Death. N.Engl.J.Med. 2002; 347(7):531-33 (let).
September 2008:
Food Safety During Pregnancy by Patricia Kendall, PhD, RD
Are there foods women should avoid during pregnancy and why?
Yes. The list of foods to avoid during pregnancy can seem quite long. Drinks containing alcohol are the first to come to mind. Larger and rarely consumed fish like swordfish, shark, tilefish and king mackerel are often mentioned, as well, because of an FDA advisory for pregnant women. While I plan to touch briefly on the safety concerns associated with raw fish and mercury, this column will focus on a different set of foods – those that pose an increased risk of foodborne illness to the mom and potentially her unborn child. A foodborne illness is an illness caused by pathogenic micro-organisms (bacteria, viruses, parasites, etc.) in the foods you eat. Symptoms can be mild or severe and may include stomach cramps, nausea, diarrhea, vomiting, muscle aches, headaches, fever and/or chills. If the pathogen causes a food intoxication, you will probably experience symptoms within 4 to 8 hours; however, if it sets up an infection, it may take 12 hours to several weeks for symptoms to occur.
The top five types of foods of special concern for causing foodborne illness during pregnancy include:
- raw milk;
- soft cheeses like Brie, Camembert and queso fresco, if made with raw or unpasteurized milk;
- raw or undercooked fish, meat and poultry products;
- cold smoked fish that has not been reheated; and
- deli or luncheon meats, spreads, pâtés and hot dogs that have not been reheated before eating.
However, it’s important to note that almost any food can be a source of foodborne illness through cross-contamination with raw animal food products, unwashed hands or contaminated kitchen surfaces.
What are the risks of consuming these foods and will I do irreparable harm to my baby if I do?
The risks both to you and your baby depend upon the offending micro-organism, your immune status and whether the pathogen crosses the placent The five food types listed above all have been implicated as sources of the bacteria, Listeria monocytogenes. Raw and undercooked meats are common sources of the parasite, Toxoplasma gondii (Toxo). Both pathogens rarely cause illness in healthy immune competent non-pregnant persons. And, even among pregnant women the symptoms produced may be mild and flu-like. However, because both pathogens prefer to exist in the intracellular environment of the host cells they invade, they are uniquely favored by the down-regulation of cell-mediated immune function that occurs during pregnancy. This down-regulation (promoted by increased levels of progesterone) is absolutely necessary to prevent rejection of the fetus. But, it also allows intracellular pathogens like Listera and Toxo to cross the placental barrier, passing the infection to the fetus, and potentially resulting in abortion, stillbirth or a baby born prematurely or with serious complications.
Listeria monocytogenes is a hardy pathogen found nearly everywhere in the environment, in soils, plant vegetation and animals. What makes it unique is its ability to survive and grow slowly at refrigerator temperatures. Because of this, it has come to be associated with raw and refrigerated ready-to-eat foods that have been held a long time and are served without reheating. Pregnant women account for about a third of the estimated 2,500 cases of listeriosis that occur each year in the United States. Newborns, the elderly and persons with compromised immune systems due to diseases like AIDS or organ transplants account for most of the rest of the cases.
If you become infected with Listeria during pregnancy you will likely experience mild gastrointestinal flu-like symptoms within 2 days of exposure. Because these symptoms are hard to distinguish from morning sickness, you may not even recognize the symptoms, yet could still pass the infection to your unborn baby. If your body does not clear itself of the pathogen, symptoms such as fever, chills, headache, muscle aches, loss of balance and back aches may develop within two to six weeks of the initial infection. You may also develop bacteremia (blood poisoning). If you experience any of these symptoms, call your doctor right away.
You are less susceptible to infection with Listeria early in pregnancy, but if you do contract the disease, you may abort the fetus. You’re much more susceptible to infection later in pregnancy, especially in the third trimester when immune suppression is greatest. Infection with Listeria later in pregnancy tends to be associated with premature delivery, still birth or a baby born with septicemia (severe blood poisoning), respiratory distress, pneumonia or meningitis. Prompt diagnosis of the disease and treatment of the mother and/or infant with antibiotics will help improve the outcome for mother and baby.
Toxoplasma gondii is typically associated with cats and cat litter. If you have a cat, you can reduce your risk of Toxo by feeding the cat only dry, canned or cooked food, keeping indoor cats in and outdoor cats out, and making sure the cat litter box is cleaned every day, preferably by someone else. Cats, however, are only one risk factor. The parasite can also infect other animals such as pigs and sheep and thus be acquired by eating raw or undercooked meat. It can also find its way into the soil and be acquired by eating unwashed vegetables or from unclean hands used to dig in the garden.
When people are exposed to Toxo, they will experience no symptoms or develop a low grade fever with rash, headache, muscle aches, and possibly swelling of the lymph nodes around 10 days after exposure, then develop protective immunity against the parasite. The concern is if your first exposure to the parasite occurs shortly before or during pregnancy. If this happens, you have a 30 to 40% chance of passing the infection to your unborn child. Transmission to the fetus is less likely in the first trimester, but if it happens there is a good chance of miscarriage. The chances of passing the infection to the fetus increase as pregnancy progresses, but fetuses infected later in pregnancy often develop a milder form of the disease, with 85% appearing normal at birth. If you are diagnosed with Toxo during pregnancy, treatment with an antibiotic such as spiromycin may help reduce the risk of passing the infection to the fetus. If the fetus does become infected, then a more complex treatment program may be recommended.
Toxoplasmosis can cause a wide range of problems in children born with the disease, including mental retardation, cognitive and motor dysfunction, ocular problems, blindness and problems with major organs such as the kidneys and liver. While only 15% of infants infected with Toxoplasma gondii show signs of the disease at birth, most will develop some symptoms in the months or years to come. Treatment in utero and during the first year of life has been shown to lessen the severity of the disease.
Your list of foods to avoid includes raw fish and cold smoked fish. I’ve also heard that I should limit my consumption of fish during pregnancy to minimize mercury exposure to the developing baby. Should I just avoid fish altogether?
Definitely not. As mentioned in the June 2008 column by Dr. Mary Harris, seafoods are a pregnant woman’s best source of an essential omega-3 fatty acid called docosahexaenoic acid (DHA), which is critical for optimum brain and eye development in the baby. Our bodies do not make omega-3 fatty acids and the best whole food source for pregnant women is fish. Because of this, fish is a very important food to include in one’s diet during pregnancy. It just needs to be cooked to minimize the risk of unwanted parasites or bacteria like Listeria, or reheated, as in the case of cold smoked fish (often labeled as nova-style, lox, kippered, smoked or jerky).
As noted by Dr. Harris, “Pregnant women can get all the omega-3 DHA they need by consuming two 4-6 ounce servings of fish each week.” This level of fish consumption which fits well within the FDA advisory of limiting fish to 12 ounces per week to minimize mercury exposure during pregnancy. The ten most commonly eaten fish in the U.S., shrimp, canned tuna, salmon, pollock, catfish, tilapia, crab, cod, clams and flatfish, are all considered naturally low in mercury. These fish represent 90% of the fish Americans eat annually. Other high omega-3 fish include herring, mackerel, sardines and anchovies. The only species that the FDA warns against eating because of possible higher mercury levels are the less commonly eaten swordfish, shark, king mackerel and tilefish. White albacore tuna, if consumed at high levels, may also increase mercury exposure. For this reason, FDA recommends that tuna lovers who prefer white albacore can eat six ounces or half their weekly total as white albacore tuna during pregnancy.
What are the most common mistakes pregnant women make when it comes to food safety during pregnancy?
Probably the most common mistake people, including pregnant women, make is to assume that their hands are clean and not sources of germ transfer. It’s important to wash hands often with soap and warm running water, and especially before and after handling foods, after using the toilet, after changing a baby’s diaper, and after touching animals.
Another common mistake is to assume that if a food looks cooked, it’s been cooked to a safe internal temperature. Ground beef, in particular, can turn brown before it reaches a safe internal temperature. The best way to ensure that foods are adequately cooked is to use a food thermometer. Fish, eggs and whole muscle meats are adequately cooked if they reach an internal temperature of 145 degrees Fahrenheit, ground meats and eggs dishes are safe to eat at an internal temperature of 160ºF, and everything else (including chicken, turkey, leftovers and hot dogs) should be cooked or reheated to 165ºF. If you can only remember one temperature, all foods are safe to eat if cooked or reheated to 165ºF.
The third most common mistake, and one of great concern to pregnant women, is the assumption that any food in your refrigerator that looks or tastes good enough to eat is safe for you to eat. That half eaten package of deli meat or leftover turkey salad could look and taste perfectly good, but be harboring Listeria monocytogenes. The best way to keep refrigerated foods safe to eat is to use a refrigerator thermometer to make sure the refrigerator’s temperature is between 35 and 40ºF, to not keep unopened packages of luncheon meats and other refrigerated ready-to-eat foods past their “use by” date, to discard any leftovers within 3-4 days of opening regardless of the date on the package, and to clean and clean out the refrigerator every month.
What should a pregnant woman do to avoid contracting a foodborne illness during pregnancy?
A good place to start is with the Fight BAC!® campaign steps of Clean, Separate, Cook and Chill. The Fight BAC!® campaign was created by the Partnership for Food Safety Education, a not-for-profit multi-agency organization, to educate the public about safe food handling. For more information on the campaign, go to: http://www.fightbac.org/.
- The Clean step is all about keeping hands and working surfaces clean, including the kitchen sink. Given the possible exposure of unwashed vegetables to Toxoplasma gondii and other pathogens, it’s also an important strategy for keeping raw vegetables safe to eat.
- Separate means keeping raw foods separate from ready-to-eat foods and washing all knives, cutting boards and food prep surfaces with hot soapy water after contact with raw poultry, meat or seafood. This strategy is very important in preventing the spread of all pathogens, including Listeria, E. coli and Salmonella.
- Cooking is the one sure way to destroy any pathogen that may be present in or on foods. Reheating leftovers and refrigerated ready-to-eat meat products to 165ºF is also very important during pregnancy and the only way to ensure a food is free of Listeria. And, as mentioned above, the only way to be sure you have cooked to a safe internal temperature is to use a food thermometer.
- Chill, the last prevention step, is especially important for keeping Listeria in check. Listeria grows slowly in the refrigerator, but more slowly at 40ºF than at 45ºF, and hardly at all at 35ºF. The only way to know if your refrigerator is between 35 and 40ºF is to use a refrigerator thermometer. Chill also means putting foods, including leftovers, in the refrigerator as soon as possible after eating or bringing them home.
If you follow these steps, choose pasteurized milk and cheese products, and cook your meat, poultry and fish products you should enjoy a safe pregnancy.
What are the most common myths about food safety during pregnancy and why are they myths?
Probably the most common myth among pregnant women is that they should avoid all fish during pregnancy. When you hear from your doctor to avoid certain fishes because of high levels of mercury, it’s easy to translate this into, “to be on the safe side, I’ll just avoid all fish during pregnancy.” According to a Harvard Medical School survey of 2235 pregnant women reported in 2003, this was in fact what many pregnant women were doing. However, these women were also giving up a highly nutritious food and an important source of the omega-3 DHA their developing baby needed for optimum development of his brain and eyes. DHA is also important in helping prevent preterm labor and may help protect against postpartum depression.
Cold-water/oily fish, such as salmon, herring, mackerel, sardines, anchovies and whitefish, are our best dietary sources of DHConsuming two 4-6 ounce servings of these and other cooked fish each week during pregnancy and while breastfeeding will help ensure a full-term pregnancy and the development of healthy baby. The only fish that need to be avoided are four larger predatory species that are not commonly eaten but are known to have more mercury because of their size: swordfish, shark, king mackerel and tilefish. If you eat fish from local ponds and lakes, you should check local fishing advisories. And, as mentioned earlier, it’s important that the fish be cooked to adequately destroy any unwanted micro-organisms.
About this Month’s Expert
Patricia Kendall is a professor and extension specialist in the Department of Food Science and Human Nutrition at Colorado State University in Fort Collins, Colorado. Kendall received her Bachelor of Science in Home Economics Education and Master of Science in Food and Nutrition at Kansas State University in Manhattan, Kansas.
Pat went on to receive her Doctor of Philosophy in Nutrition from Colorado State University in Fort Collins, Colorado. Dr. Kendall has received many awards and honors, including Distinguished Alumni Research Awards from Kansas State and Colorado State Universities in 2006, the Distinguished Alumni Award for Service to Cooperative Extension from Colorado State University in 2003, and Outstanding Dietitian of the Year from the Colorado Dietetic Association in 1996.
Pat is active in several professional organizations, including the Society for Nutrition Education, the Institute for Food Technologists, the International Association for Food Protection and the Colorado Dietetic Association. She is former president of the Society for Nutrition Education and the Colorado Dietetic Association and is a Science Communicator for the Institute of Food Technologists.
Pat’s current research projects include the development and evaluation of food safety education training programs for health professionals and dietary managers focusing on prevention of Listeria monocytogenes. She also is involved in a large study with The Ohio State University to determine if food safety education during pregnancy improves pregnancy outcome factors in low income English- and Spanish-speaking women.
