Home > Facts > Mediterranean Diet  

More About:

mediterranean and diet

Corn- or Maize-Based Diets
(99% Match)

...diets in the Americas and Africa. While niacin
Dietary Supplements
(99% Match)

...dietary supplements are defined by the 1994 Die
Dietary Reference Intakes
(99% Match)

...diets. DRIs are specific to age group, gender,
Diet
(99% Match)

...diet refers to a person's pattern of eat
Dietary Supplements
(99% Match)

...dietary supplements in the United States catapu
Dietary Reference Intakes
(99% Match)

...diets, set national nutrition policy, and estab
Dietary Guidelines
(99% Match)

...diet with few resources, and the USDA produced


Highlight any text in the article to look up more information!

Mediterranean Diet

Definition

The Mediterranean diet is better described as a nutritional model or pattern of food consumption rather than a diet in the usual sense of the word. To begin with, there is more than one Mediterranean diet, if the phrase is understood to refer to the traditional foods and eating patterns found in the countries bordering the Mediterranean Sea. Francesco Visioli, a researcher who has edited two books on the subject, prefers the term ‘‘Mediterranean diets’’ in the plural to reflect the fact that ‘‘the populations in the Mediterranean area have different cultures, religions, economic prosperity, and [levels of] education, and all these factors have some influence on dietary habits and health.’’ For example, Visioli notes that alcohol intake is very low in the Maghreb (coastal northwestern Africa) because most inhabitants of the region are Muslim, and consequently cereal grains figure more prominently in their diet than in most other Mediterranean countries. In addition, the differences among the various forms of the Mediterranean diet are important in understanding some of the research studies that have been done on it, as will be described more fully below.

Origins

The origins of the pattern of food consumption found in Mediterranean countries go back several millennia into history; descriptions of meals in ancient Greek and Roman literature would not be out of place in contemporary Mediterranean diet cookbooks. The first description of the traditional Mediterranean diet as it was followed in the mid-twentieth century, however, was not in a cookbook; it was in a research study funded by the Rockefeller Foundation and published in 1953. The author was Leland Allbaugh, who carried out a study of the island of Crete as an underdeveloped area. Allbaugh noted the heavy use of olive oil, whole-grain foods, fruits, fish, and vegetables in cooking as well as the geography and other features of the island.

The Cretan version of the Mediterranean diet became the focus of medical research on the Mediterranean diet following the publication of Ancel Keys’s Seven Country Study in 1980. Keys (1904–2004) was a professor of physiology at the University of Minnesota who had a varied background in biology and biochemistry before turning to nutrition almost by accident. Hired by the Army in 1941 to develop portable rations for troops in combat, Keys was responsible for creating what the Army then called K rations. His next wartime project was a starvation experiment, which he conducted in order to determine the food needs of starving civilians in war-torn Europe. American soldiers who were trying to re-feed refugees in the newly liberated countries found that there was no reliable medical information about treating starvation victims. Keys recruited 36 healthy male volunteers in 1944 who were conscientious objectors, most of them from the historic peace churches. For five months the subjects were given half the normal calorie requirement of an adult male and asked to exercise regularly on a treadmill. The average weight loss was 25% of body

Mediterranean diet

FrequencyFoodTips
MonthlyRed meatsNo more than a few times month
WeeklySweetsOpt instead for naturally sweet fresh fruit
 EggsLess than 4 per week, including those in processed foods
 PoultryA few times a week. Take the skin off and choose white meat to lower fat intake
 FishA few times a week
DailyCheese and yogurtCheese and yogurt are good sources of calcium. Choose low-fat varieties
 Olive oilThe beneficial health effects of olive oil are due to its high content of monounsaturated fats and antioxidants. Olive oil is high in calories, consume in moderation to reduce calorie intake
 FruitsAt least a serving at every meal. A serving of fruit is a healthy option for snacks
 VegetablesAt least a serving at every meal. Choose a variety of colors
 Beans, legumes, nutsBeans are a healthy source of protein, and are loaded with soluble fiber, which has been shown to lower blood cholesterol levels by five percent or more. Most nuts contain monounsaturated (heart-healthy) fat. A handful of nuts is a healthy option for snacks
 Whole grains, including
breads, pasta, rice,
couscous, and polenta
A grain is considered whole when all three parts—bran, germ and endosperm—are present. Substitute whole wheat for
white bread, brown rice for white rice and whole-wheat flour when baking. Mix pasta, rice, couscous, polenta and
potatoes with vegetables and legumes
 WaterAt least 6 glasses daily
 Wine (in moderation)The U.S. Department of Agriculture defines moderation as no more than a five-ounce glass of wine daily for women and up to 2 glasses (10 ounces) daily for men
 Physical activityThirty minutes of cardiovascular activity a day is recommended to get in shape, burn calories and boost the metabolism

Based on the Mediterranean diet pyramid. (Illustration by GGS Information Services/Thomson Gale.)

weight. Three months after the experiment ended, Keys found that none of the subjects had regained their weight or physical capacity. He learned that renutrition following starvation requires several months of above-average calorie intake, that vitamin supplements are needed, and that the proportion of protein in the diet must be increased. He wrote a booklet with this information for use by relief agencies after the war ended.

In the process of studying the effects of starvation in European men who survived the war, however, Keys noticed that the rate of heart attacks among them dropped markedly as food supplies decreased. He wondered whether dietary factors might be involved in heart disease. A study of Minnesota businessmen and professors in the mid-1950s showed him that the fat content of food—particularly the saturated fats found in the meat and dairy products consumed in large amounts by Midwesterners—was indeed a factor. After that experiment, Keys began to think in terms of diet as preventive medicine. He first encountered Mediterranean diets during visits to Italy and Spain to conduct research for the World Health Organization. His studies of food consumption patterns in those countries eventually led to the Seven Countries Study, which was a systematic comparison of diet, risk factors for heart disease, and disease experience in men between the ages of 40 and 59 in eighteen rural areas of Japan, Finland, Greece, Italy, the former Yugoslavia, the Netherlands, and the United States from 1958 to 1970. (Women were not included as subjects because of the rarity of heart attacks among them at that time and because the physical examinations were fairly invasive). In addition to asking the subjects to keep records of their food intake, the researchers performed chemical analyses of the foods the subjects ate. It was found that the men living on the island of Crete—the location of Leland All-baugh’s 1953 study—had the lowest rate of heart attacks of any group of subjects in the study.

Subsequent studies of Mediterranean diets have been conducted in subjects who have already suffered heart attacks and in women subjects. One consistent finding of recent research, however, is that subjects are less healthy in the early twenty-first century than the participants of the late 1950s because the traditional diets of the Mediterranean region have been increasingly abandoned in favor of fast foods and higher consumption of fatty meat products and sweets, as well as other staples of American and Northern European diets that are high in trans-fatty acids. In addition, changing agricultural practices around the Mediterranean have resulted in poultry and meat with higher fat content than was the case in the 1960s. As a result of concern about these trends, an association for the advancement of the Mediterranean diet was formed in Spain in 1995 and later funded the Foundation for the Advancement of the Mediterranean Diet, which is presently headquartered in Barcelona. The

KEY TERMS

Alpha-linolenic acid (ALA)—A polyunsaturated omega-3 fatty acid found primarily in seed oils (can-ola oil, flaxseed oil, and walnut oil), purslane and other broad-leaved plants, and soybeans. ALA is thought to lower the risk of cardiovascular disease.

Glycemic index (GI)—A system devised at the University of Toronto in 1981 that ranks carbohydrates in individual foods on a gram-for-gram basis in regard to their effect on blood glucose levels in the first two hours after a meal. There are two commonly used GIs, one based on pure glucose as the reference standard and the other based on white bread.

Metabolic syndrome—A group of risk factors related to insulin resistance and associated with an increased risk of heart disease. Patients with any three of the following five factors are defined as having metabolic syndrome: waist circumference over 102 cm (41 in) for men and 88 cm (34.6 in) for women; high triglyceride levels in the blood; low levels of HDL cholesterol; high blood pressure or the use of blood pressure medications; and impaired levels of fasting blood glucose (higher than 110 mg/dL).

Monoamine oxidase inhibitors (MAOIs)—A group of antidepressant medications that may interact with foods used in Mediterranean diets, particularly red wines and aged cheeses.

Monounsaturated fat—A fat or fatty acid with only one double-bonded carbon atom in its molecule. The most common monounsaturated fats are palmi-toleic acid and oleic acid. They are found naturally

in such foods as nuts and avocados; oleic acid is the main component of olive oil.

Purslane—A broad-leafed plant native to India, commonly considered a weed in the United States. Purslane has the highest level of omega-3 fatty acids of any leafy vegetable, however, and is eaten fresh in salads or cooked like spinach as part of the Cretan diet.

Trans-fatty acid—A type of unsaturated fatty acid that takes its name from the fact that its alkyl chains are arranged in the so-called trans configuration (in which the carbon atoms that have double bonds form a long chain rather than a kinked shape). Trans-fatty acids occur naturally in small quantities in meat and dairy products; however, the largest single source of trans-fatty acids in the modern diet is partially hydrogenated plant oils, used in the processing of fast foods and many snack foods. Trans-fatty acids are not necessary for human health and increase the risk of coronary artery disease.

Unsaturated fat—A fat or fatty acid in which there are one or more double bonds between carbon atoms in the fatty acid chain, which means that the compound could absorb more hydrogen atoms. A saturated fat is one that has no room for more hydrogen atoms.

Whole-diet approach—The notion that the beneficial effects of any dietary regimen are produced by the diet as a whole rather than by one specific food or other factor.

Foundation’s objectives include publication and dissemination of scientific findings about the diet and the promotion of its healthful use among different population groups.

Typical Mediterranean diet

In general, Mediterranean diets have five major characteristics:

  • High levels of fruits and vegetables, breads and other cereals, potatoes, beans, nuts, and seeds.
  • Olive oil as the principal or only source of fat in the diet.
  • Moderate amounts of dairy products, fish, and poultry; little use of red meat.
  • Eggs used no more than 4 times weekly.
  • Wine consumed in moderate amounts—two glasses per day for men, one glass for women.

Since wine and olive oil are obtained from their respective plant sources by physical (crushing or pressing) rather than chemical processes, their nutrients retain all the properties of their sources. Wine contains polyphenols, which are powerful antioxidants and also have a relaxing effect on blood vessels, thus lowering blood pressure.

The Cretan diet

The Cretan version of the Mediterranean diet as it was used on the island in the 1960s was distinctive in several respects because it contained:

  • A higher proportion of total calories from fat (40% ), almost all of it from olive oil. It was low in animal fats (butter was rarely eaten) and saturated fats.
  • A relatively low level of carbohydrate intake (45% of daily calories), with most of the carbohydrates coming from fruits (2 to 3 per day) and vegetables (2 to 3 cups per day)—many of them foods with a low glycemic index. Vegetables are an integral part of meals in the Cretan diet—they are not considered side dishes.
  • Generous portions of whole-grain bread (8 slices per day). The bread was made from slowly fermented dough, however, and had a lower glycemic index than most contemporary breads.
  • Moderate intake of fish (about 40 grams per day), which, however, is rich in omega-3 fatty acids.
  • A higher intake of meat than in most versions of the Mediterranean diet, mostly as lamb, chicken, or pork.
  • High intake of alpha-linolenic acid (ALA; an omega-3 fatty acid thought to lower the risk of heart disease) from nuts (particularly walnuts), seeds, wild greens (particularly purslane [Portulaca oleracea]), and legumes. Lamb is also a good source of ALA.

Online versions of the Mediterranean diet

Two of the diets available through eDiets.com as of early 2007 are Mediterranean-type diets, the New Mediterranean Diet and the Sonoma Diet. Both plans are recipe-based, are customized to incorporate foods that the dieter enjoys, and provide personalized weekly meal plans. The New Mediterranean Diet costs $4.49 per week, with a minimum enrollment of 12 weeks, or $53.88 for the three-month trial period. The Sonoma Diet, which is an adaptation of the traditional Mediterranean diet to foods more commonly available in the United States, costs $5 per week for a minimum enrollment period of five weeks. The Sonoma Diet comes with a portion guide and wine guide as well as a customized weekly meal plan.

Function

The function of Mediterranean diets as used in the United States and Western Europe is primarily preventive health care and only secondarily as a means to weight loss. There are several books available with weight-loss regimens based on Mediterranean diets, as well as cookbooks with recipes from a variety of Mediterranean countries.

Preventive health care

Most of the scientific research that has been done on Mediterranean diets concerns their role in preventing or lowering the risk of various diseases.

HEART DISEASE. Mediterranean diets became popular in the 1980s largely because of their association with lowered risk of heart attacks and stroke, particularly in men, following the publication of the Seven Countries study. Mediterranean diets are thought to protect against heart disease because of their high levels of omega-3 fatty acids even though blood cholesterol levels are not lowered.

ALZHEIMER’S DISEASE. A study published in Annals of Neurology in 2006 reported that subjects in a group of 2000 participants averaging 76 years of age who followed a Mediterranean-type diet closely were less likely to develop Alzheimer’s than those who did not. Further study is needed, however, to discover whether factors other than diet may have affected the outcome.

ASTHMA ANDALLERGIES. A group of researchers in Crete reported in 2007 that the low rate of wheezing and allergic rhinitis (runny nose) on the island may be related to the traditional Cretan diet. Children who had a high consumption of nuts, grapes, oranges, apples, and tomatoes (the main local products) were less likely to suffer from asthma or nasal allergies. Children who ate large amounts of margarine, however, were more likely to develop these conditions.

METABOLIC SYNDROME. Research conducted at a clinic in Naples, Italy, suggests that Mediterranean diets lower the risk of developing or reversing the effects of metabolic syndrome, a condition associated with insulin resistance and an increased risk of heart disease and type 2 diabetes. The results from this clinic were corroborated by a study done at Tufts University in Massachusetts, which found that the symptoms of metabolic syndrome were reduced even in patients who did not lose weight on the diet.

Weight loss

Precautions

People who are making any major change in their dietary pattern in general should always consult their physician first. In addition, people who are taking monoamine oxidase inhibitors (MAOIs) for the treatment of depression should check with their doctor, as these drugs interact with a chemical called tyramine to cause sudden increases in blood pressure. Tyramine is found in red wines, particularly aged wines like Chianti, and in aged cheeses.

People using a Mediterranean diet for weight reduction should watch portion size and monitor their consumption of olive oil, cheese, and yogurt, which are high in calories. Dieters may wish to consider switching to low-fat cheeses and yogurts.

Because olive oil is a staple of Mediterranean diets, consumers should purchase it from reliable sources. The safety of olive oil is not ordinarily a concern in North America; however, samples of olive oils sold in Europe and North Africa are sometimes found to be contaminated by mycotoxins (toxins produced by molds and fungi that grow on olives and other fruits). Some mycotoxins do not have any known effects on humans, but aflatoxin, which has been found in olive oil, is a powerful carcinogen and has been implicated in liver cancer.

Risks

There are no major risks associated with following a traditional Mediterranean diet for people who have consulted a physician beforehand if they intend to use the diet as a weight-loss regimen. Health crises caused by food interactions with MAOIs are uncommon but can be fatal (about 90 deaths over a 40-year period).

The risk of cancer or any other disease from aflatoxin-contaminated olive oil is minimal in the United States and Canada.

Research and general acceptance

Mediterranean diets have been the subject of more medical research since the 1960s than any other

QUESTIONS TO ASK YOUR DOCTOR

  • Would you recommend a Mediterranean type of diet for general wellness as well as weight control?
  • Have any of your other patients tried a Mediterranean diet? Did they enjoy it?
  • Would you recommend the modified version of the Cretan diet used in the Lyon Diet Heart Study?

regional or ethnic diet. Interest in Mediterranean diets has been high because nutritional research in general has moved away from curing deficiency diseases in the direction of preventive health care.

The Seven Countries Study

The results from the Seven Countries study were published in book form in 1980. The research teams found that Japanese and Greek men had far lower rates of cardiovascular disease than men from the other five other countries, with the Greek subjects from the island of Crete having the lowest rate of all. Although the study and thirty years of follow-up reports showed that the relationship among heart disease, body mass, weight, and obesity is complex, the Seven Countries research also showed that the type of fat in the diet is more important than the amount, and that the use of monounsaturated fats—particularly olive oil—is correlated with a lower risk of heart attack and stroke. The twenty-year follow-up report indicated that 81% of the difference in coronary deaths among the seven countries could be explained by differences in the average intake of saturated fatty acids.

A detailed description of the Seven Countries study, the research that preceded it, and an overview of its findings can be found online on the website of the University of Minnesota School of Public Health, Division of Epidemiology and Community Health, at <http://www.epi.umn.edu/about/7countries/index.shtm>.

The Lyon Diet Heart Study

Ongoing research

Mediterranean diets continue to be fruitful subjects for medical investigators, partly because the countries where they originated are changing so rapidly, and partly because discussion continues as to which of the components of these diets is the most important in disease prevention. Although olive oil has been the focus of many studies, recent research done in Greece seems to indicate that the combination of the various foods and food groups in Mediterranean diets is what makes them so healthful, rather than any one specific component. This position is sometimes called the whole-diet approach.

In addition, other researchers are studying lifestyle factors other than food that may well contribute to the beneficial effects of Mediterranean cooking. These include a generally more relaxed attitude toward life; higher levels of physical activity (made possible in part by the warm sunny climate of the region); and the fasting practices of Greek Orthodox Christians, which lower fat intake and restrict the believer to a vegetarian diet for about 110 days out of every year.

BOOKS

Keys, Ancel B., with Christ Aravanis. Seven Countries: A Multivariate Analysis of Death and Coronary Heart Disease. Cambridge, MA: Harvard University Press, 1980.

Keys, Ancel B., and Margaret Keys. How to Eat Well and Stay Well the Mediterranean Way. Garden City, NY: Doubleday, 1975.

Keys, Margaret, and Ancel B. Keys.The Benevolent Bean. New York: Noonday Press, 1972.

Parker, Steven Paul, MD. The Advanced Mediterranean Diet: Lose Weight, Feel Better, Live Longer. Mesa, AZ: Vanguard Press, 2007.

Simopoulos, Artemis P., and Francesco Visioli, eds. Mediterranean Diets. New York: Karger, 2000.

Simopoulos, Artemis P., and Francesco Visioli. More on Mediterranean Diets. New York: Karger, 2007.

COOKBOOKS

Gutterson, Connie. The Sonoma Diet Cookbook. Des Moines, IA: Meredith Books, 2006.

Jenkins, Nancy Harmon. The Mediterranean Diet Cookbook: A Delicious Alternative for Lifelong Health. New York: Bantam Books, 1994.

Seaver, Jeannette. My New Mediterranean Cookbook: Eat Better, Live Longer by Following the Mediterranean Diet. New York: Arcade Publishing, 2004.

PERIODICALS

Carollo, C., R. L. Presti, and G. Caimi. ‘‘Wine, Diet, and Arterial Hypertension.’’ Angiology 58 (February-March 2007): 92–96.

Chatzi, L., G. Apostolaki, I. Bibakis, et al. ‘‘Protective Effect of Fruits, Vegetables, and the Mediterranean Diet on Asthma and Allergies among Children in Crete.’’ Thorax, April 5, 2007.

Dalziel, K., L. Segal, and M. de Lorgeril. ‘‘A Mediterranean Diet Is Cost-Effective in Patients with Previous Myo-cardial Infarction.’’ Journal of Nutrition 136 (July 2006): 1879–1885.

Ferracane, R., A. Tafuri, A. Logieco, et al. ‘‘Simultaneous Determination of Aflatoxin B1 and Ochratoxin A and Their Natural Occurrence in Mediterranean Virgin Olive Oil.’’ Food Additives and Contaminants 24 (February 2007): 173–180.

Hoffman, William. ‘‘Meet Monsieur Cholesterol.’’ University of Minnesota Update, Winter 1979. Available online at http://mbbnet.umn.edu/hoff/hoff_ak.html (accessed April 8, 2007). Interesting and readable biographical profile of Ancel Keys and his interest in Mediterranean diets.

Keys, Ancel, PhD, Henry L. Taylor, PhD, Henry Blackburn, MD, et al. ‘‘Coronary Heart Disease among Minnesota Business and Professional Men Followed Fifteen Years.’’ Circulation 28 (September 1963): 381–395.

de Lorgeril, M., and P. Salen. ‘‘The Mediterranean Diet in Secondary Prevention of Coronary Heart Disease.’’ Clinical and Investigative Medicine 29 (June 2006): 154– 158. /bibcit.composed>

de Lorgeril, M., P. Salen, J. L. Martin, et al. ‘‘Mediterranean Diet, Traditional Risk Factors, and the Rate of Cardiovascular Complications after Myocardial Infarction: Final Report of the Lyon Diet Heart Study.’’ Circulation 99 (February 16, 1999): 779–785.

Malik, V. S., and F. B. Hu. ‘‘Popular Weight-Loss Diets: From Evidence to Practice.’’ Nature Clinical Practice; Cardiovascular Medicine 4 (January 2007): 34–41.

Meydani, M. ‘‘A Mediterranean-Style Diet and Metabolic Syndrome.’’ Nutrition Reviews 63 (September 2005): 312–314.

Panagiotakis, D.B., C. Pitsavos, F. Arvaniti, and C. Stefa-nidis. ‘‘Adherence to the Mediterranean Food Pattern Predicts the Prevalence of Hypertension, Hypercholes-terolemia, Diabetes and Obesity among Healthy Adults; the Accuracy of the MedDiet Score.’’ Preventive Medicine, December 30, 2006.

Sarri, K. O., M. K. Linardakis, F. N. Bervanaki, et al. ‘‘Greek Orthodox Fasting Rituals: A Hidden Characteristic of the Mediterranean Diet of Crete.’’ British Journal of Nutrition 92 (August 2004): 277–284.

Scarmeas, N., Y. Stern, M.X. Tang, et al. ‘‘Mediterranean Diet and Risk for Alzheimer’s Disease.’’ Annals of Neurology 59 (June 2006): 912–921.

Schroder, H., J. Marrugat, J. Vila, et al. ‘‘Adherence to the Traditional Mediterranean Diet Is Inversely Associated with Body Mass Index and Obesity in a Spanish Population.’’ Journal of Nutrition 134 (December 2004): 3355–3361.

Trichopoulou, A., and E. Critselis. ‘‘Mediterranean Diet and Longevity.’’ European Journal of Cancer Prevention 13 (October 2004): 453–456.

OTHER

American Heart Association (AHA). Lyon Diet Heart Study. Available online at http://www.americanheart.org/presenter.jhtml?identifier=4655 (accessed April 10, 2007).

American Heart Association (AHA). Mediterranean Diet. Available online at http://www.americanheart.org/presenter.jhtml?identifier=4644 (accessed April 10, 2007).

European Food Information Council (EUFIC). ‘‘Secrets of . . . the Mediterranean Diet.’’ Food Today 43 (May 2004). Available online at http://www.eufic.org/article/en/page/FTARCHIVE/artid/mediterranean-diet/?low-res=1ndash (accessed April 9, 2007).

Mayo Clinic staff. Mediterranean Diet: Can It Prevent Alzheimer’s? Available online at http://www.mayoclinic.com/health/mediterranean-diet/AN01475 (posted November 21, 2006; accessed April 9, 2007).

Mayo Clinic staff. Mediterranean Diet for Heart Health. Available online at http://www.mayoclinic.com/health/mediterranean-diet/CL00011 (posted June 21, 2006; accessed April 7, 2007).

Mediterranean Diet Info. Mediterranean Diet Food Pyramid. Available online at http://www.mediterraneandietin-fo.com/Mediterranean-Food-Pyramid.htm (accessed April 9, 2007).

Visioli, Francesco, PhD. ‘‘Mediterranean Diets.’’ Linus Pauling Institute Newsletter, Fall/Winter 2000. Available online at http://lpi.oregonstate.edu/f-w00/medi-terr.html (accessed April 9, 2007).

ORGANIZATIONS

American Heart Association (AHA). National Center, 7272 Greenville Avenue, Dallas, TX 75231. Telephone: (800) 242-8721. Website: http://www.americanheart.org.

Fundacin Dieta Mediterrnea. Website (Spanish only): http://www.dietamediterranea.com.

Linus Pauling Institute (LPI). Oregon State University, 571 Weniger Hall, Corvallis, OR 97331-6512. Telephone: (541) 737-5075. Website: http://lpi.oregonstate.edu/index.html.

University of Minnesota School of Public Health, Division of Epidemiology and Community Health (EpiCH). West Bank Office Building, 1300 South Second Street, Suite 300, Minneapolis, MN 55454-1015. Telephone: (612) 624-1818. Website of Seven Countries Study: http://www.epi.umn.edu/about/7countries/index.shtm.

Rebecca J. Frey, Ph.D.


ADVERTISEMENT


Popular Web Searches:


McAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams