Vitamin D and Gestational Diabetes

Maternal Plasma 25-Hydroxyvitamin D Concentrations and the Risk for Gestational Diabetes Mellitus
Original source: PLoS ONE 3(11): e3753
Authors: Cuilin Zhang (corresponding author), Chunfang Qiu, Frank B. Hu, Robert M. David, Rob M. van Dam, Alexander Bralley, Michelle A. Williams
Publication date: November 18, 2008
DOI (digital document ID): 10.1371/journal.pone.0003753
Requires subscription? No
Publicly-available abstract: Yes

Synopsis:
There is increasing evidence that Vitamin D plays a role in maintaining stable blood glucose levels, but the studies directly examining circulating levels of 25-hydroxyvitamin D (25-[OH] D) are limited and inconsistent. This study aims to determine the association between levels of (25-[OH] D) earlier in pregnancy than previously examined, and the risk of the mother's developing gestational diabetes later on in the pregnancy.

A nested case-control study was conducted among 953 pregnant women. 57 had diabetes at the start of the study, and 114 women who were not diagnosed with GDM were selected as controls.

Blood samples were taken at 16 weeks gestation, with known time since last meal, and frozen at -80C until analysis. Per American Diabetes Association guidelines, participants were screened for gestational diabetes at 24-28 weeks gestation, using fasting blood glucose and an oral glucose tolerance test. The process used to measure 25-[OH] D levels produces a maximum 12% probability of error.

The results were categorized as sufficient, insufficient, or deficient.

The odds ratios were adjusted based on mother's age at conception, season of conception, diet, vitamin supplementation, mother's pre-conception body mass index, family history of Type 2 diabetes, physical activity, and whether or not the mother smoked.

The women who developed gestational diabetes tended to follow the known risk patterns: overweight, older, being non-white or Latino, and having a family history of diabetes. The heavier these women were, the lower their circulating levels of 25-[OH] D.

At 16 weeks' gestation, 25-[OH] D levels of the women who went on to develop gestational diabetes were, on average, 20% lower than those of the controls. This difference remained even when filtering out the known and suspected risk factors for diabetes. About one third of the women who developed diabetes, versus one seventh of the women who did not, had 25-[OH] D levels considered to be deficient.

Further analysis showed an inverse relationship between vitamin D levels and risk of developing gestational diabetes was observed and remained even after considering all the factors mentioned above.

Reliability:
The number of women studied was moderately large and restricted to women who sought prenatal care prior to the halfway mark in the pregnancy. The study was also limited to women who read and wrote English, and who planned to deliver at one of two study hospitals. This may or may not filter out less-affluent women in higher-risk populations.

A 12% error in the assay method may skew the results, despite statistical attempts to minimize them.

The authors submit that a single blood test for 25-[OH] D levels may not provide an accurate picture of the mother's levels of Vitamin D throughout the pregnancy; also, that some of the 25-[OH] D deficient women may have developed impaired glucose tolerance or gestational diabetes earlier in the pregnancy (but had not been screened for it). The authors would like to see a much larger study conducted to confirm (or refute) their findings.

Practical Applications:
If a firm relationship between 25-[OH] D and gestational diabetes (or diabetes in general) is confirmed, then lifestyle changes and dietary supplementation can be advised earlier in the pregnancy (or pre-pregnancy) to minimize the risks of developing gestational diabetes.

This study also contributes to the general body of research regarding Vitamin D metabolism and diabetes in general. There may be good reasons for people with diabetes, or at risk for developing diabetes, to screen for Vitamin D levels and to increase Vitamin D intake. [Please note that Vitamin D is a fat-soluble vitamin and that excess intake is not easily excreted from the body, so please consult your physician before adding additional vitamin D supplements to your diet.]


This synopsis was based on the entire article.

Diet planning as conversation, not monologue

Implementing shared decision making in nutrition clinical practice: A theory-based approach and feasibility study
Original source: Implementation Science 2008, 3:48
Authors: Sophie Desroches (corresponding author), Sylvie Tapp, Marie-Pierre Gagnon, and France Legare
Publication date: 5 November 2008
DOI (digital document ID): 10.1186/1748-5908-3-48
Requires subscription? No
Publicly-available abstract: Yes

Synopsis:
Shared decision making is one of several methods that a health professional can use to help us change our eating habits to better control diabetes and other chronic illnesses. The investigators are looking primarily at dietary approaches to lower cholesterol levels.

The traditional low-fat/low-saturated fat strategy to lower cholesterol is perceived as restrictive, leading to a tendency for people to either "cheat" or to not follow the diet at all. Recently, a number of different dietary approaches have been shown effective in lowering cholesterol -- but the variety, added to the many diet systems discussed in the popular media, can leave the general public confused. Shared decision is a method in which the dietician works collaboratively with the patient, taking into account his cultural and financial perferences, to create a healthy diet that the patient is willing to follow. The process includes explaining the best evidence of the risks and benefits of different dietary models, and explicitly states that the method does include some uncertainties.

The authors of this investigation found no formal studies supporting the use and training of a shared decision making approach using evidence-based practice, and note that some dieticians have reported difficulty in suggesting and implementing this approach.

In this paper they propose a study to learn how shared decision-making is currently used in the field of nutritional consultation, to assess dieticians' intention to adopt two specific behaviors related to shared decision making using the Theory of Planned Behavior, and to learn what the obstacles are to dieticians adopting this approach. Their proposed protocol includes the education of dieticians, the introduction of the Theory of Planned Behavior, focus group discussions in which the dieticians' views and issues are discussed, and audiotaped observation of the dieticians' interactions with patients.

The proposed research project is expected to provide preliminary data about the adoption of shared decision making by dieticians and their patients, look at dieticians' beliefs regarding their intention to adopt shared decision making behaviors and comparing their actions to their intentions, and develop questionnaires to measure this information. The researchers hope that the results generated by the proposed research project will help improve the rate at which dieticians adopt a shared decision-making approach.

Reliability:
The initial study is intended to cover only 40 dieticians, but this is considered mostly as a focus group from which the parameters of a larger study can be planned.

Practical Applications:
The end goal of this research is to increase the adoption of shared decision making in the field of nutritional consulation. Having our dieticians engage us actively, and pay attention to our input, will help us find diets we can -- and will -- live with.

This synopsis was based on the entire article.

Can fish oil counteract sleep deprivation?

Dietary fish oil did not prevent sleep deprived rats from a reduction in adipose tissue adiponectin gene expression
Original source: Lipids in Health and Disease 2008, 7:43
Authors: Ana BM Mattos, Monica JS Pinto, Cristiane Oliveira, Carolina Biz, Eliane B Ribeiro, Claudia M Oller do Nascimento, Monica L Andersen, Sergio Tufik, and Lila M Oyama (corresponding author)
Publication date: 5 November 2008
DOI (digital document ID): 10.1186/1476-511X-7-43
Requires subscription? No
Publicly-available abstract: Yes

Synopsis:
Sleep deprivation has been one of the hallmarks of modern society. Where it was once limited to the elderly, now even youth are chronically sleep deprived. Sleep deprivation is linked to adverse metabolic effects, including insulin resistance. Omega-3 fatty acids found in fish oil have been seen to improve insulin sensitivity -- decrease insulin resistance. We don't yet know how this works, but researchers believe that adiponectin has a role.

The aim of this study is to assess the effects of diets high in fish oil on sleep-deprived subjects. The authors note that while in humans, sleep deprivation is associated with weight gain, sleep-deprived rats tend to lose weight. This suggests to them a method of measuring insulin resistance in such a way that it is not related to weight gain. Glucose tolerance, serum insulin, and adiponectin levels are examined in both sleep-deprived and non-sleep-deprived rats.

The rats were kept awake for 96 hours, which is when the most dramatic alterations in lipid and hormone concentrations occur. At that time, the rats were subjected to a glucose tolerance test, starting with blood drawn after a 12-hour fast, and then after the glucose was given, at time intervals of 4, 12, 20, 24, 28 and 32 minutes. The blood sampled was tested for glucose concentration, insulin, and adiponectin levels. The animals were then killed, weighed, and the fat and protein contents of their bodies separated and measured. Adiponectin and transfer-RNA were measured from the animals' adipose tissues.

Sleep deprivation caused the rats to lose weight whether or not they were on fish-oil-rich diets (this is normal for rats). Non-sleep-deprived rats did not lose weight. Sleep-deprived rats fed a normal diet lost fat; those fed a fish-oil-rich diet did not. No change was observed in protein content of any of the groups.

Following the glucose tolerance tests, glucose concentration was significantly higher in the rats allowed to sleep than those who were sleep-deprived -- and in the last measurement, the glucose level in the rats who were both sleep-deprived and fed a fish-oil-rich diet dropped even further relative to the other groups.

Serum insulin and adiponectin was similar across all groups; however, the gene expression of adiponectin in abdominal tissue was lower in the sleep-deprived rats than the non-sleep-deprived rats. Insulin levels were lower in sleep-deprived male rats, so there may have been unaccounted-for factors in the test.

The authors examine the findings of previous studies on lipid consumption, fish oil, sleep deprivation, and adiponectin expression in rats to put their study into context. They conclude that sleep deprivation does cause a stress-related drop in adiponectin gene expression, which negatively effects insulin sensitivity.


Reliability:
There were only 5-9 rats per group studied. This is a very small sample, in which results can be skewed. Rats may not be a good model for humans in this environment, as humans tend to gain weight when sleep-deprived and there are perceived correlations between weight gain and insulin sensitivity. The readings for the rats were taken at the point of peak change of a single episode of sleep deprivation, rather than after a long period of chronic sleep deprivation (e.g., 1 month at 2 hrs less sleep than normal mice get). This is the difference between students spending a couple of all-nighters cramming for an exam versus a young professional working sixteen-hour days for several years to establish himself in a competitive field.

Practical Applications:
If it could be proven that fish oil supplements (or a diet rich in fish) could protect humans against some of the adverse metabolic effects of sleep deprivation, then this could be an effective and inexpensive treatment against those medical risks.

This synopsis was based on the entire article.

Food in the home and obesity

The validation of a home food inventory
Original source: International Journal of Behavioral Nutrition and Physical Activity 2008, 5:55
Authors: Jayne A Fulkerson (corresponding author), Melissa C Nelson, Leslie Lytle, Stacey Moe, Carrie Heitzler, and Keryn E Pasch
Publication date: 4 November 2008
DOI (digital document ID): 10.1186/1479-5868-5-55
Requires subscription? No
Publicly-available abstract: Yes

Synopsis:
A validated home food inventory can be a useful tool to assess what foods are readily available to a person or family, and by consequence, what foods are frequently eaten. This differs from a self-reported food inventory, as it allows a trained professional to independently inventory both the items in general and their relative quantities, and for the results to be compared with the self-reported inventory. The authors of this study are looking to see if there is a relationship between the types of food available in the home and the likelihood that members of that household are obese.

The authors find that in many previous studies on home food inventories, the list of foods leaves out a lot of categories and specific foods, and there have been few attempts to see if the person doing the reporting is accurately including all the food and food types in the household. They note four previous studies that have had validation, each of which has focused only on a small group of food items, with a particular health goal in mind.

Their goal is to create a comprehensive food inventory, which can be completed by an average adult, and which takes into account both healthy and unhealthy foods, as well as "reduced fat" versions of foods often associated with obesity.

Using both trained volunteers and volunteers from the community, they developed a home food inventory form. They validated the inventories for 51 families and analyzed the results for accuracy of self-reporting. They then distributed the inventory survey to 349 families with adolescent children, measured the adults and the children and recorded their demographic characteristics, and then asked them what foods they ate over the previous 24 hours. They were given information on how to estimate portion sizes, and told to expect three phone calls over the next month asking them to recall their food intake for the past 24 hours. In addition, dietary health questionnaires were distributed; these are shown to be relatively accurate in assessing the usual food and nutrients that the participant consumes.

The final home food inventory included 190 items which were community-specific. Participants were instructed on key package words that might indicate a reduced-fat version of a dessert or snack food, since these were categorized separately from the original (full-fat/full-sugar) versions.

Foods were ranked according to their association with obesity, or the likelihood that eating a lot of those foods would cause a person to become obese over time.

The home food inventories filled out by the initial 51 families in the pilot project were compared with the identical inventory filled out by the trained volunteers to determine whether or not the consumers understood brands as being part of larger categories, and how well they understood the questionnaire overall. The results showed a high degree of correlation, which the researchers take to mean that an unvalidated inventory should be reasonably accurate.

The researchers note several limitations of the study, including some issues with correctly categorizing a number of prepared foods and frozen desserts, the limitation of specific food items and types, and the limitation of food items and categories to "yes-no" answers rather than measuring quantity and variety. The initial set of families had a greater number of educated Caucasian adults than was representative of the community at large, and may not accurately represent the responses of less-educated and/or non-white populations.

Reliability:
The authors are affiliated with the University of Minnesota, in the professional realms of nursing and community health. The study was published in a peer-reviewed journal.
The researchers note that there are several food categories that were not as well-correlated as others -- primarily, prepared and frozen desserts, and breads. Some of this is due to the large variety of products available in these categories.
There is some limitation in correlating food inventories with dietary intake, as about half of the the foods listed in the 24-hour recalls were not on the home food inventories. (This would suggest a fair amount of eating outside the home.)

Practical Applications:
A useful, friendly home food inventory is a basic tool that anybody can use in menu planning, grocery shopping, and disaster planning. It is also a tool that can provide your nutritionist, social worker, or Certified Diabetes Educator a better idea of what foods you have, and what you regularly eat. This information is helpful in showing you ways to improve your diet to lose weight, maintain healthy blood glucose levels, and reduce your risks of cardiovascular disease.

A validated home food inventory is also a useful basis from which to gather information for community health and public health studies regarding nutrition and health.

This synopsis was based on the entire article.

Are moderate-protein diets better than low-protein diets for people with metabolic syndrome?

Moderate carbohydrate, moderate protein weight loss diet reduces cardiovascular disease risk compared to high carbohydrate, low protein diet in obese adults: A randomized clinical trial

Original source: Nutrition & Metabolism 2008, 5:30
Authors: Denise A Walker Lasker (corresponding author), Ellen M Evans, and Donald K Layman
Publication date: 7 November 2008
DOI (digital document ID): 10.1186/1743-7075-5-30
Requires subscription? No
Publicly-available abstract: Yes

Synopsis:
This study compares the effectiveness of the standard USDA Food Pyramid diet with a higher-protein, lower-carbohydrate diet for weight loss in general, for fat loss in particular, and for lowering the blood-based indicators of cardiovascular risk and insulin resistance. A total of 50 people completed the testing, split between the two dietary approaches.

Both diets under test had the same amount of calories, with about 30% of total calories coming from fats. Carbohydrates supplied about 55% of the Food Pyramid diet group's caloric intake, and protein, the remaining 15%. The people assigned to this group were instructed to eat whole grains for their bread products. About 30% of the high-protein group's calories came from protein, with the remaining 40% coming from carbohydrates. (This is the same protein-carbohydrate-fat distribution advocated by the Zone Diet.) This group was instructed to eat primarily "high quality protein", including lean meats, dairy, and eggs. Both groups had similar amounts of fruits and vegetables in their daily diets. All subjects were instructed on portion sizes, dietary substitutions, how to weigh foods, and how to keep a food diary. There was no difference in exercise between the two groups.

Baseline measurements (weight, body fat percentage, cholesterol, and postprandial insulin) were taken at the start of the experiment. The subjects followed their assigned diet plans for four months, at which time the same measurements were repeated.

• The moderate-protein group lost about 5 pounds more per person than the USDA group, and more of their weight loss was from fatty tissues.
• Fasting glucose levels were unchanged, but fasting insulin levels decreased in the moderate protein group, while it increased in the USDA group. In addition, postprandial insulin levels dropped 85% for the protein group, but only 50% for the Food Pyramid group. (High plasma insulin levels are indicative of insulin resistance, which is often a predecessor to Type 2 diabetes.)
  
• There was a greater drop in total cholesterol in the USDA group than in the protein group. LDL ("bad") cholesterol dropped in the USDA group but rose in the protein group; on the other hand, HDL ("good") cholesterol dropped in the USDA group but rose in the protein group. The protein group also showed greater improvement in triglyceride levels than the USDA group. (High triglyceride levels are associated with increased risk of heart attack.)
  

Reliability:
The study was small scale, with only 50 people completing the four-month study. While the two groups of subjects were selected to be closely-matched, there is still opportunity for the results to be skewed. An initial run-in period put all subjects on as close to an even footing as possible before the trial started.
The authors are associated with an accredited university; the paper was published in a peer-reviewed journal.
Longer-term studies of larger groups may be needed to determine the long-term safety and effectiveness of high-protein diets.

The principal investigator (Denise A Walker Lasker) received funding from the National Cattleman’s Beef Association, The Beef Board and Kraft Foods. Both Beef associations have a vested interest in increasing protein consumption (in the form of beef).
The investigators have made no comparison between a higher-fat restricted-carbohydrate diet and a higher-protein restricted-carbohydrate diet.

Practical Applications:
The 30/40/30 protein/carb/fat (PCF) ratio is the basis of the Zone Diet. While this diet is higher in protein than traditionally advised for people with diabetes, recent publications suggest that this is not as high a risk as formerly perceived.

For further reading:
WebMD evaluates the Zone Diet
Wikipedia entry on the Zone Diet

This synopsis was based on the entire article.

Could antioxidants fight diabetes?

The role of antioxidant supplement in immune system, neoplastic, and neurodegenerative disorders: a point of view for an assessment of the risk/benefit profile
Original source: Nutrition Journal 2008, 7:29
Authors: Daria Brambilla, Cesare Mancuso, Mariagrazia Rita Scuderi, Paolo Bosco, Giuseppina Cantarella, Laurence Lempereur, Giulia Di Benedetto, Salvatore Pezzino, and Renato Bernardini (corresponding author)
Publication date: 30 September 2008
DOI (digital document ID): 10.1186/1475-2891-7-29
Requires subscription? No
Publicly-available abstract: Yes

Synopsis:
The authors discuss the use of antioxidant foods and supplements in the treatment of chronic disease. They are particularly interested in the effect of dietary antioxidants on the management of cancer and neurological and immune disorders. They are particularly interested in antioxidant enzyme systems, such as the heme oxygenase/biliverdin reductase system, which may be directly affected by the presence of antioxidants in the diet. They believe these enzyme systems may efficiently reduce oxidative damage and minimize the progression of disease-related oxidative stress. The clinical effects of dietary antioxidants is still under debate. Along the same lines, the excess consumption or bioavailability of fat-soluble vitamins has been associated with increased incidence of cancer.

The concepts of "free radicals" and "oxidative stress" are defined, and are said to damage the body's proteins, DNA, and lipids (fats). The authors mention some of the pathways in which oxidative stress occurs and can be measured, how oxidation can affect the digestive and immune systems, and how micronutrient deficiencies can cause the immune system to be depressed. This includes the discussion of methods for determining how the human body uses vitamins, minerals, and antioxidants, how chronic and autoimmune diseases may be affected by oxidative stress, and how antioxidants -- both alone and along with other chemicals -- may affect the disease process.The authors caution that the potential benefit of using antioxidants to reduce this damage must be weighed against the possible damage they might cause if overused, and that a thorough understanding of how these nutrients act chemically, in the cellular environment, and on a person as a whole.

Reliability:
The authors are associated with the pharmacology departments of their universities. The issues discussed are related to the pharmacological properties of nutrients and nutrient supplements (nutriceuticals). This is a general article; while specific diseases, oxidants, and disease pathways are mentioned, no quantitative analysis is given. The authors are optimistic about the use of antioxidants in the management of chronic illnesses, but are concerned about people blindly adding antioxidant supplements before their effects are thoroughly tested.

Practical Applications:
While neurological disorders are given particular emphasis, that the authors touch on "chronic diseases" and "autoimmune disorders" suggests that their findings may be useful in the use of dietary supplements for both Type 1 and Type 2 diabetes. Better understanding of how oxidative stress affects diabetes, and controlled experiments using particular antioxidants, are both needed both to verify whether or not this will work for most people, and to determine what specific antioxidants and combinations should be taken.

For further reading:
Check the authors' bibliography for studies relating to specific diseases.

This synopsis was based on the entire article.

Mediterranean Diets: low-carb versus low glycemic load

Spanish Ketogenic Mediterranean diet: a healthy cardiovascular diet for weight loss
Original source: Nutrition Journal 2008, 7:30
Authors: Joaquin Perez-Guisado (corresponding author), Andres Munoz-Serrano, and Angeles Alonso-Moraga
Publication date: 26 October 2008
DOI (digital document ID): 10.1186/1475-2891-7-30
Requires subscription? No
Publicly-available abstract: Yes

Enhancement of a modified Mediterranean-style, low glycemic load diet with specific phytochemicals improves cardiometabolic risk factors in subjects with metabolic syndrome and hypercholesterolemia in a randomized trial
Original source: Nutrition & Metabolism 2008, 5:29
Authors: Robert H Lerman (corresponding author), Deanna M Minich, Gary Darland, Joseph J Lamb, Barbara Schiltz, John G Babish, Jeffrey S Bland, and Matthew L Tripp
Publication date: 4 November 2008
DOI (digital document ID): 10.1186/1743-7075-5-29
Requires subscription? No
Publicly-available abstract: Yes

Synopsis:
Both of these studies looked at variants of the Mediterranean Diet, followed over a period of 12 weeks (three months). The Spanish study emphasized the use of virgin olive oil as the primary source of dietary fat, green vegetables and salads as the primary source of carbohydrates, and fish as a primary source of protein. The US study is a follow-on to a previous study comparing a low-glycemic-load Mediterranean diet with added soy protein and phytosterols (plant-based fats) to the American Heart Association's diet plan. In this study, the diet is supplemented with plant-derived substances (phytochemicals) that they believe will improve insulin sensitivity and reduce cardiovascular and metabolic risk factors.

In the Spanish study, 31 obese people (BMI approximately 36) in their mid- to late-thirties were studied. They were not given caloric limits, but their diets included approximately 2 tablespoons of virgin olive oil (2 teaspoons per meal), 1-2 glasses wine daily (half at lunch and half at dinner),
green vegetables and salads to a maximum of 30 g carbohydrate per day, and unlimited protein. Non-nutritive sweeteners were allowed on this diet. Protein was divided into "fish" and "non-fish" (meat, fowl, eggs, shellfish and cheese), with "fish" and "non-fish" being consumed on separate days, and at least four "fish days" per week. In addition, subjects were allowed up to two cups of coffee or tea per day, and required to drink at least three liters of water per day. The subjects were given a standard multivitamin-and-mineral supplement and a calcium supplement; they were also asked to check their urine for ketones using ketostrips.

• Results: After 12 weeks, the subjects lost about 14 kg (30-35 lb), lowered their blood pressure (by about 15 points (millimeters mercury) systolic and 9 points diastolic), lowered their total cholesterol about 10%, significantly dropped their triglyceride levels (from about 218 down to 114 mg/dl), and reduced their fasting blood glucose level about 16 mg/dl. In addition, LDL ("bad") cholesterol levels dropped about 8%, and raised their HDL ("good") cholesterol about 9%. While the subjects were not heavy enough to have moved from "obese" to "overweight" in this time frame, the measured changes moved the patients' statuses from "prehypertension" to "normal blood pressure", from "prediabetic" to "normal", and from "high cholesterol" to "normal cholesterol". Based on the factors used to diagnose it, these subjects would be considered to no longer have metabolic syndrome. The researchers did not measure the beginning and ending percentages of body fat versus muscle mass, but their visual observation suggests that the weight lost was primarily fatty tissue.
• Limitations: The study had a number of limitations, including small size, short duration, highly-selected population, no measurement of total caloric intake, and the possibility that weight loss alone, as well as any of the factors of the program -- either by itself or in combination with others -- may have accounted for these changes. The authors suggest further study with a larger group of people, for a longer period of time, and also comparison with other low-carb diets.

The US researchers' initial viewpoint is that modern diets induce tissue inflammation, resulting in metabolic syndrome. They state that a number of active ingredients in medicinal plants target the pathways of this inflammation, and believe that the addition of these active agents to a low-glycemic-load adaptation of the Mediterranean diet can assist the body in repairing this damage. The US study included 49 patients with metabolic syndrome, average age 53 years, average BMI approximately 34. All subjects had high LDL cholesterol and triglycerides, and had at least two of the other signs used to diagnose metabolic syndrome (low HDL cholesterol, stage I hypertension or drug-treated hypertension, large waist size, and impaired fasting glucose. Half were put on a modified Mediterranean diet alone; the other half were put on the modified diet with the inclusion of phytochemical supplements. The two groups were split out in a way to minimize the initial differences between them.
In this version of the Mediterranean diet, wine was limited to 1 glass per day. Whole grains were allowed, but only one serving per day. Vegetables were mostly limited to very low glycemic load vegetables, with a maximum of one "occasional" serving of a small category of
phytochemical-rich vegetables with a moderate glycemic index (55-70). The only sweeteners allowed were stevia and low-glycemic agave nectar syrup.
The group receiving phytochemical supplementation received a nutritional supplement beverage (powdered) and supplement tablets. All subjects were required to engage in moderate aerobic exercise (at 70-75% target heart rate) for at least 2.5 hours per week. Food cravings, as well as food intake and satiety levels, were monitored (patient-generated logs and surveys). The results were analyzed, accounting for the effects of weight loss, consuming fewer calories, and consuming lower levels of carbohydrate.

• Results: At the end of 12 weeks, the diet-alone subjects lost about 5.7 kg (about 12.5 lb), and the supplemented group about an extra half-pound. While both groups showed lowered total cholesterol, LDL, and triglycerides, the group receiving the supplements saw greater reductions in these readings. Only the group with the supplements had increased HDL cholesterol. The group receiving the supplements were able to lower both systolic and diastolic blood pressure by about 6 points, while those receiving diet alone were only able to lower their systolic blood pressure, by about 4 points. Hemoglobin A1c (HbA1c), a measure of long-term blood glucose levels, went down in both groups, but fasting blood glucose did not drop in the group receiving supplements. Twice the number of subjects in the group receiving supplements were able to move from "having metabolic syndrome" to "normal".

Reliability:
The authors in the Spanish study are associated with the Genetics department of the University of Cordoba and do not report any conflicts of interest. Their bibliographic references are from peer-reviewed journals, mostly in the realm of nutrition.

The authors in the US study all work for the MetaProteomics, a research subsidiary of Metagenics, a company which produces and sells dietary plans, including a number of dietary supplements and meal replacement formulas, which it states will improve the health, weight,
and longevity of people with metabolic syndrome and cardiovascular disease. The MetaProteomics subsidiary is aimed at research into human proteins and how specific chemicals in foods are used by the human body. The bibliographic references are from peer-reviewed journals, and their source research is aimed more at finding the causes of cardiometabolic disease as well as specific chemicals that might lessen the probability of developing these diseases. As employees of a subsidiary of Metagenics, the authors' research is aimed at developing new products (both diets and supplements) for Metagenics to sell.

Both studies are limited in small sample size over short amounts of time; additionally, the Spanish study considers fewer variables.

There are significant differences in the two low-glycemic/low-carb "Mediterranean diets" studied: the Spanish study centers on healthy proteins and fats, while the US study aims more at trying to determine the effect of an anti-inflammatory diet and of the phytochemical
supplements the company sells.

Practical Applications:
Both versions of "Mediterranean diet", unsupplemented, showed favorable changes in cholesterol levels and blood glucose levels. The Spanish study showed greater changes in weight loss, blood pressure, triglycerides, and HDL cholesterol than the US study including supplements; however, the limitations of both studies does not indicate how effective either diet is at maintaining long-term health, or how safe they are over long periods of time.

Any highly-restrictive diet has its limitations, and even some less-restrictive diets may not be suitable for your personal medical conditions. Please consult your doctor and nutritionist before making any large-scale changes to your diet.

This synopsis and comparison was based on the full articles.

Prenatal diet may affect insulin resistance for multiple generations

Insulin sensitivity is normalized in the third generation (F3) offspring of developmentally programmed insulin resistant
(F2) rats fed an energy-restricted diet
Original source: Nutrition and Metabolism 2008, 5:26
Authors: Daniel C Benyshek (corresponding author), Carol S Johnston, John F Martin and William D Ross
Publication date: 17 October 2008
DOI (digital document ID): 10.1186/1743-7075-5-26
Requires subscription? No
Publicly-available abstract: Yes

Synopsis:
A number of studies have shown that the way animals develop before birth can affect the birth weights, blood pressure, and glucose metabolisms of their children, grandchildren, and so on. Most research to date has only gone two generations beyond the original parents. This study takes observation to the third generation (great-grandchildren) and focuses on impairments to the animals' glucose metabolisms. A parent generation of female rats were fed protein-deficient diets while pregnant and nursing, and both they and three generations of their offspring were fed low-calorie diets, to see how this affected the insulin sensitivity of multiple generations of their offspring. A group of control rats was fed normal-calorie diets over the same number of generations.

The first generation of offspring (children) tended to be of low birth weight, while the second and third generations (grandchildren and great-grandchildren) were of normal birth weight. All generations were of lower than normal weight as adults, due to the caloric restriction. The first=generation offspring had normal insulin metabolism, While the second generation, as adults, had reduced insulin sensitivity and reduced insulin production -- a set of symptoms consistent with impaired glucose tolerance. The third generation did not show insulin resistance -- indeed, the males were even more insulin-sensitive than the control animals, whether they were fed calorie-restricted diets or allowed to eat at will.

Previous studies of this type showed insulin resistance in the first-generation offspring, which was not found in this particular study; however, the second-generation female offspring in this study were insulin-resistant.

The investigators are unsure why the third-generation offspring did not show impaired glucose tolerance or insulin resistance, even though both of those traits are considered to be adaptive traits that show up in "nutrient poor environments" (reduced protein, reduced calories). They suggest that one reason for this may be that the second-generation mother's insulin resistance left more energy in the bloodstream to be used by the fetus. On the other hand, the relative insulin sensitivity of previous-generation mothers (who had not been fed sufficient calories after weaning) made fewer nutrients available for the developing fetus, resulting in insulin resistance in the offspring.

The investigators suggest that more research is required to determine how pregnancy and nursing diets, and maternal insulin sensitivity, affects the insulin sensitivity of her offspring.

Reliability:
The authors are from accredited institutions, across a number of medical and social disciplines. The research was published in a peer-reviewed online journal. References are all from peer-reviewed journals. Therefore the experiment design is reliable. Since only four female rats from each child generation were bred, the study was small in size and therefore subject to skew. The authors did note that further research was warranted to find out why they got the results they did.

Practical Applications:
The normal birth weight and increased insulin sensitivity of child generations born to insulin-resistant mothers suggests a parallel mechanism for the large baby size common for human mothers with diabetes. While this study was conducted on rats, the rats are intended to be a shorter-lived and expendable model for human childbirth and development. A closer understanding of which maternal nutrients affect insulin resistance may lead to improved recommendations for pregnancy and nursing diets and supplements, and will ideally prevent insulin resistance in future generations of human adults.

This synopsis was based on the entire article.