A moderate increase in daily protein intake causing an enhanced endogenous insulin secretion does not alter circulating levels or urinary excretion of dehydroepiandrosterone sulfate

A Whole Food Plant-Based Diet Is Effective for Weight Loss: The Evidence

What does the best available balance of scientific evidence show is the optimum way to lose weight? Calorie density, water content, protein source, and other components significantly influence the effectiveness of different dietary regimes for weight loss. By "walling off your calories," preferentially deriving your macronutrients from structurally intact plant foods, some calories remain trapped within indigestible cell walls, which then blunts the glycemic impact, activates the ileal brake, and delivers prebiotics to the gut microbiome. This may help explain why the current evidence indicates that a whole food, plant-based diet achieves greater weight loss compared with other dietary interventions that do not restrict calories or mandate exercise. So, the most effective diet for weight loss appears to be the only diet shown to reverse heart disease in the majority of patients. Plant-based diets have also been found to help treat, arrest, and reverse other leading chronic diseases such as type 2 diabetes and hypertension, whereas low-carbohydrate diets have been found to impair artery function and worsen heart disease, the leading killer of men and women in the United States. A diet centered on whole plant foods appears to be a safe, simple, sustainable solution to the obesity epidemic.

A meat, processed meat, and French fries dietary pattern is associated with high allostatic load in Puerto Rican older adults

BACKGROUND

Consumption of certain dietary patterns, such as a Western diet, has been associated with unfavorable physiologic outcomes. Diet has been proposed as a contributor to allostatic load, a composite measure of physiological dysregulation.

OBJECTIVE

To determine the association of dietary patterns, defined by "meat and french fries," "traditional Puerto Rican foods" (rice, beans, and oils), or "sweets," with allostatic load, and with the 10 individual physiologic parameters that comprise it.

PARTICIPANTS

Baseline data collected from participants of the Boston Puerto Rican Health Study (n=1,117; aged 45 to 75 years) was used to run linear and logistic regression models, adjusting for age, sex, alcohol intake, smoking, medications, energy intake, and body mass index or physical activity.

RESULTS

Significant trends across increasing quintiles of the meat and french fries pattern were observed for higher allostatic load score (P=0.002), waist circumference (P=0.032), systolic blood pressure (P=0.008), and diastolic blood pressure (P<0.0001). Participants in the highest quintile of the meat and french fries pattern had significantly higher allostatic load score than those in the lowest quintile (mean 4.3±0.11 vs 3.9±0.12, P=0.030), and had higher odds of having high allostatic load (odds ratio [95% confidence interval]: 1.8 [1.2 to 2.9]), low dehydroepiandrosterone sulfate (odds ratio 1.9 [95% confidence interval: 1.2 to 3.1]), and high glycosylated hemoglobin (odds ratio 1.7 (95% confidence interval: 1.0 to 2.9]). The traditional pattern was not associated with allostatic load, whereas a significant association between the sweets pattern and allostatic load disappeared after restricting analysis to participants without diabetes.

CONCLUSIONS

A meat, processed meat, and french fries dietary pattern may contribute to the deregulation of multiple physiologic parameters in Puerto Rican adults. Efforts to limit consumption of this pattern may help prevent further cumulative physiological dysregulation in this high risk population.

Effect of oxidative damage due to excessive protein ingestion on pancreas function in mice

The present study was undertaken to evaluate the effect of oxidative damage due to excessive protein diet on pancreas function in mice. For this purpose, thirty male (C57BL/6J) mice were randomly divided into three groups and fed on different diets as follows: group 1 was fed on a normal diet, group 2 was fed on an excessive protein diet and group 3 was fed on an excessive protein diet supplemented with 0.06 g/kg cysteamine. Each group was fed for 2 weeks, and then pancreas samples were collected to examine oxidative and antioxidant parameters and pancreas function. The results showed that ingestion of an excessive protein diet markedly increased contents of malondialdehyde (MDA) and decreased T-AOC and activities of antioxidants SOD and GSH-Px, compared with a normal diet (P < 0.05). Pancreas weight and concentration of protein, DNA and RNA were significantly higher (P < 0.05), digestive enzyme activities were significantly lower and levels of somatostatin and insulin were higher in mice fed with an excessive protein diet than those fed with a normal protein diet. In the group fed with excessive protein diet supplemented with cysteamine, oxidative stress was mitigated and pancreas function was improved. These data demonstrate that excessive protein ingestion could increase oxidative damage of free radicals on pancreas function through destroying the balance of oxidants and antioxidants.

Role of Dietary Proteins and Amino Acids in the Pathogenesis of Insulin Resistance

Dietary proteins and amino acids are important modulators of glucose metabolism and insulin sensitivity. Although high intake of dietary proteins has positive effects on energy homeostasis by inducing satiety and possibly increasing energy expenditure, it has detrimental effects on glucose homeostasis by promoting insulin resistance and increasing gluconeogenesis. Varying the quality rather than the quantity of proteins has been shown to modulate insulin resistance induced by Western diets and has revealed that proteins derived from fish might have the most desirable effects on insulin sensitivity. In vitro and in vivo data also support an important role of amino acids in glucose homeostasis through modulation of insulin action on muscle glucose transport and hepatic glucose production, secretion of insulin and glucagon, as well as gene and protein expression in various tissues. Moreover, amino acid signaling is integrated by mammalian target of rapamycin, a nutrient sensor that operates a negative feedback loop toward insulin receptor substrate 1 signaling, promoting insulin resistance for glucose metabolism. This integration suggests that modulating dietary proteins and the flux of circulating amino acids generated by their consumption and digestion might underlie powerful new approaches to treat various metabolic diseases such as obesity and diabetes.

Consumption of Lactobacillus acidophilus and Bifidobacterium longum does not alter phytoestrogen metabolism and plasma hormones in men: a pilot study

OBJECTIVE

The aim of this study was to determine whether equol excretion status and plasma hormone and leptin concentrations can be influenced by consumption of a probiotic supplement. A secondary focus was to investigate whether male equol excretors have a hormone profile consistent with reduced prostate cancer risk.

DESIGN

The design was a randomized, single-blinded, placebo-controlled, parallel-arm trial.

SUBJECTS

Thirty-one (31) of the initially enrolled 39 subjects, 18 to 37 years old, completed all study requirements.

INTERVENTION

Subjects consumed either probiotic capsules (containing Lactobacillus acidophilus and Bifidobacterium longum) or placebo capsules for 2 months. Fasting plasma concentrations of testosterone (T), dihydrotestosterone (DHT), androstanediol glucuronide (AAG), androstenedione (A), dehydroepiandrosterone sulfate (DHEAS), sex hormone-binding globulin (SHBG), and leptin were measured on days 1 and 57. Urinary excretion of genistein, glycitein, daidzein, O-desmethylangolensin (O-Dma), and equol was measured on days 4 and 61 following a 4-day soy challenge.

RESULTS

Probiotic consumption did not significantly alter equol excretor status, plasma hormone, or leptin concentrations in these subjects. At baseline, there were no differences in plasma hormone concentrations between equol excretors and nonexcretors; however, the low number of equol excretors included in this study limits the strength of this finding.

CONCLUSIONS

The 2-month intervention with probiotic capsules did not significantly alter equol excretion, plasma hormone, or leptin concentrations in these subjects. A secondary finding was that male equol excretors in this study did not exhibit a hormone profile consistent with reduced prostate cancer risk, although this result should be interpreted with caution.

Urinary C-peptide excretion in free-living healthy children is related to dietary carbohydrate intake but not to the dietary glycemic index

This study first examined whether urinary C-peptide (UCP), stored at -20 degrees C, remains stable over the long term, and second, whether the dietary glycemic index (GI) and the glycemic load (GL: GI x g carbohydrates) are related to the 24-h UCP excretion of healthy children. Participants in the Dortmund Nutrition and Anthropometric Longitudinally Designed Study with 24-h urine collections and a simultaneously completed weighed dietary record were included. From these, 3 comparable groups of 7- to 8-y-old children (n = 40 each) from 1990, 1996, and 2002 were randomly selected (total n = 120). C-peptide was measured with a 1-site ELISA. A GI value was assigned to all recorded foods containing carbohydrates (CHO). Statistical equivalence tests corroborated that UCP excretion in the 3 sampling periods was equivalent when corrected for body weight and protein intake (P < 0.05). UCP excretion was associated with the GL after adjustment for body weight, protein, and fiber intake [mean UCP (95% CI) in GL tertiles 1-3: 6.19 (5.37, 7.14) vs. 7.82 (6.77, 9.02) vs. 7.76 (6.71, 8.97) nmol/d, P for difference 0.04]. GI was not significantly related to UCP excretion [adjusted means (95% CI): 7.27 (6.28, 8.41) vs. 6.51 (5.64, 7.51) vs. 7.94 (6.86, 9.18), P for difference 0.2]. In conclusion, UCP retrospectively measured with a 1-site ELISA remained stable for up to 12 y (from 1990 until 2002). The observed positive relation of UCP with GL appears to result largely from its association with the amount of CHO, whereas dietary GI may be relevant only at higher intake levels.

Modulation of insulin action by dietary proteins and amino acids: role of the mammalian target of rapamycin nutrient sensing pathway

PURPOSE OF REVIEW

An increasing number of studies point towards an important role of dietary proteins and amino acids in the modulation of insulin action in peripheral tissues. The purpose of this review is to discuss how these nutrients affect insulin sensitivity and the potential mechanism by which they exert their action.

RECENT FINDINGS

Increased plasma amino acid availability in both animals and humans has been shown to cause enhanced translation initiation and protein synthesis and the inhibition of insulin-stimulated glucose transport in skeletal muscle. Moreover, dietary interventions in animals fed proteins from various sources resulted in drastically different outcomes in terms of glucose metabolism and insulin signaling in skeletal muscles. Finally, amino acids, particularly leucine, were shown to modulate insulin action by specifically activating the mammalian target of rapamycin nutrient sensing pathway.

SUMMARY

Dietary proteins and amino acids are important modulators of glucose metabolism and insulin signaling via their ability, at least partly, to modulate the mammalian target of rapamycin pathway.

Diabetes: insulin resistance and derangements in lipid metabolism. Cure through intervention in fat transport and storage

We present multiple findings on derangements in lipid metabolism in type 2 diabetes. The increase in the intracellular deposition of triglycerides (TG) in muscles, liver and pancreas in subjects prone to diabetes is well documented and demonstrated to attenuate glucose metabolism by interfering with insulin signaling and insulin secretion. The obesity often associated with type 2 diabetes is mainly central, resulting in the overload of abdominal adipocytes with TG and reducing fat depot capacity to protect other tissues from utilizing a large proportion of dietary fat. In contrast to subcutaneous adipocytes, the central adipocytes exhibit a high rate of basal lipolysis and are highly sensitive to fat mobilizing hormones, but respond poorly to lipolysis restraining insulin. The enlarged visceral adipocytes are flooding the portal circulation with free fatty acids (FFA) at metabolically inappropriate time, when FFA should be oxidized, thus exposing nonadipose tissues to fat excess. This leads to ectopic TG accumulation in muscles, liver and pancreatic beta-cells, resulting in insulin resistance and beta-cell dysfunction. This situation, based on a large number of observations in humans and experimental animals, confirms that peripheral adipose tissue is closely regulated, performing a vital role of buffering fluxes of FFA in the circulation. The central adipose tissues tend to upset this balance by releasing large amounts of FFA. To reduce the excessive fat outflow from the abdominal depots and prevent the ectopic fat deposition it is important to decrease the volume of central fat stores or increase the peripheral fat stores. One possibility is to downregulate the activity of lipoprotein lipase, which is overexpressed in abdominal relatively to subcutaneous fat stores. This can be achieved by gastrointestinal bypass or gastroplasty, which decrease dietary fat absorption, or by direct means that include surgical removal of mesenteric fat. Indirect treatment consists of the compliant application of drastic lifestyle change comprising both diet and exercise and pharmacotherapy that reduces mesenteric fat mass and activity. The first step should be an attempt to effectively induce a lifestyle change. Next comes pharmacotherapy including acarbose, metformin, PPARgamma, or PPARgammaalpha agonists, statins and orlistat, estrogens in postmenopausal women or testosterone in men. Among surgical procedures, gastric bypass has been proven to produce beneficial results in advance of other surgical techniques, the evidence basis of which still needs strengthening.

A shift in myocardial substrate, improved endothelial function, and diminished sympathetic activity may contribute to the anti-anginal impact of very-low-fat diets

A new category of anti-anginal drug - exemplified by ranolazine - is believed to work by partially inhibiting cardiac oxidation of fatty acids; oxidation of glucose requires less oxygen per mol of ATP generated, and thus is preferable to fat oxidation when oxygen availability is limiting in underperfused cardiac tissue. Unfortunately, there is no reason to believe that these drugs inhibit fat oxidation selectively in the heart; thus, chronic use of these drugs can be expected to increase body fat stores until the original rate of fat oxidation is restored by mass action - presumably negating the therapeutic benefit in angina, while exacerbating the manifold adverse effects of insulin resistance syndrome. The rational way to decrease cardiac metabolic reliance on fatty acids is to consume a very-low-fat quasi-vegan diet (i.e., 10% fat calories). Indeed, such diets are known to have a rapid and substantial therapeutic impact on anginal symptoms, while concurrently benefiting insulin sensitivity, markedly improving serum lipid profile, promoting leanness, and lessening coronary risk. A reduction in diurnal insulin secretion might also be achieved, which would be expected to decrease sympathetic activity. While reduced myocardial demand for oxygen doubtless contributes to the beneficial impact of such diets on angina, it is likely that improved cardiac perfusion consequent to improved endothelium-dependent vasodilation also plays a role in this regard. Supplemental carnitine, also beneficial in angina, appears to improve utilization of glucose in the ischemic myocardium by lowering elevated acetyl-coA levels and thereby disinhibiting pyruvate dehydrogenase. Certain other nutraceuticals may aid control of angina by improving endothelial function. In the longer term, these measures have the potential to slow or reverse the progression of stenotic lesions that underlie most cases of angina. These safe and relatively inexpensive nutritional strategies for coping with angina deserve far more attention than orthodox medical practice has thus far accorded them.

A wholly nutritional 'multifocal angiostatic therapy' for control of disseminated cancer

A great deal of effort is now being devoted to the development of new drugs that hopefully will control the spread of inoperable cancer by safely inhibiting tumor-evoked angiogenesis. However, there is growing evidence that certain practical nutritional measures have the potential to slow tumor angiogenesis, and it is reasonable to anticipate that, by combining several measures that work in distinct but complementary ways to impede the angiogenic process, a clinically useful 'multifocal angiostatic therapy' (MAT) might be devised. Several measures which might reasonably be included in such a protocol are discussed below, and include: a low-fat, low-glycemic index vegan diet, which may down-regulate the systemic IGF-I activity that supports angiogenesis; supplemental omega-3-rich fish oil, which has been shown to inhibit endothelial expression of Flk-1, a functionally crucial receptor for VEGF, and also can suppress tumor production of pro-angiogenic eicosanoids; high-dose selenium, which has recently been shown to inhibit tumor production of VEGF; green tea polyphenols, which can suppress endothelial responsiveness to both VEGF and fibroblast growth factor; and high-dose glycine, whose recently reported angiostatic activity may reflect inhibition of endothelial cell mitosis, possibly mediated by activation of glycine-gated chloride channels. In light of evidence that tumor-evoked angiogenesis has a high requirement for copper, copper depletion may have exceptional potential as an angiostatic measure, and is most efficiently achieved with the copper-chelating drug tetrathiomolybdate. If logistical difficulties make it difficult to acquire this experimental drug, high-dose zinc supplementation can achieve a slower depletion of the body's copper pool, and in any case can be used as maintenance therapy to maintain an adequate level of copper depletion. A provisional protocol is offered for a nutritionally based MAT entailing a vegan diet and supplemental intakes of fish oil, selenium, green tea polyphenols, glycine, and zinc. Inasmuch as cox-2 is overexpressed in many cancers, and cAMP can boost tumor production of various angiogenic factors as well as autogenous growth factors, adjunctive use of cox-2-specific NSAIDS may be warranted in some cases.

A preliminary fast may potentiate response to a subsequent low-salt, low-fat vegan diet in the management of hypertension - fasting as a strategy for breaking metabolic vicious cycles

Although a salted diet appears to be a sine qua non for the development of essential hypertension, low-salt diets often have a modest or even negligible impact on the blood pressure of hypertensives; this suggests that salt, perhaps often acting in concert with other aspects of a modern, rich diet, may set in place certain metabolic vicious cycles that sustain blood pressure elevation even when dietary salt is eliminated. Therapeutic fasting is known to lower elevated blood pressure - presumably in large part because it minimizes insulin secretion - and may have the potential to break some of these vicious cycles. Goldhamer has recently reported that a regimen comprised of a water-only fast of moderate duration, followed by a transition to a low-fat, low-salt, whole-food vegan diet, achieves dramatic reductions in the blood pressure of hypertensives, such that the large majority of patients can be restored to normotensive status, in the absence of any drug therapy. Although long-term follow-up of these subjects has been sporadic, the available data suggest that these large reductions is blood pressure can be conserved in patients who remain compliant with the follow-up diet - in other words, a 'cure' for hypertension may be feasible. If a protein-sparing modified fast can be shown to be virtually as effective as a total fast for achieving these benefits, it may be possible to implement this regimen safely on an outpatient basis. The ability of therapeutic fasts to break metabolic vicious cycles may also contribute to the efficacy of fasting in the treatment of type 2 diabetes and autoimmune disorders. As a general principle, if a metabolic disorder is susceptible to prevention - but not reversal - by a specific diet, and therapeutic fasting has a temporary favorable impact on this disorder, then a more definitive therapy may consist of a therapeutic fast, followed up by the protective diet as a maintenance regimen.

Modulation of adipocyte lipoprotein lipase expression as a strategy for preventing or treating visceral obesity

As compared to subcutaneous adipocytes, visceral adipocytes have high basal lipolysis, are highly sensitive to catecholamines, and are poorly sensitive to insulin; these traits are amplified when visceral adipocytes hypertrophy. As a result, enlarged visceral fat stores tend to flood the portal circulation with free fatty acids at metabolically inappropriate times when fatty acids are unlikely to be oxidized, thus exposing tissues to excessive free fatty acid levels and giving rise to the insulin resistance syndrome. A logical approach to preventing or correcting visceral obesity is to down-regulate the lipoprotein lipase (LPL) activity of visceral adipocytes relative to that expressed in subcutaneous adipocytes and skeletal muscle. IGF-I activity appears to be a primary determinant of visceral LPL activity in humans; systemic IGF-I activity is decreased when diurnal insulin secretion is low, when hepatocytes detect a relative paucity of certain essential amino acids, and when estrogens are administered orally. The ability of alpha-glucosidase inhibitor therapy to selectively reduce visceral adiposity suggests that down-regulation of diurnal insulin secretion and/or IGF-I activity may indeed have a greater impact on LPL activity in visceral fat than in subcutaneous fat. Thus, low-glycemic-index, vegan, high-protein, or hypocaloric diets can be expected to decrease visceral LPL activity, as can postmenopausal estrogen therapy. Furthermore, estrogen enhances the LPL activity of non-pathogenic gluteofemoral fat cells, whereas testosterone decreases visceral LPL activity in men; this may explain why sex hormone replacement in middle-aged people of both sexes has a favorable impact on visceral fat and insulin sensitivity. Beta-adrenergic activity suppresses transcription of LPL in adipocytes; this phenomenon may contribute to the favorable impact of exercise training on visceral obesity; conceivably, preadministration of safe drugs that boost catecholamine activity (caffeine, yohimbine) could potentiate this beneficial effect of exercise. Glucocorticoids selectively increase the LPL activity of visceral adipocytes; while there is currently no convincing evidence that psychological stress is a major determinant of visceral adiposity, or that stress management techniques can help to correct visceral obesity, reports that anxiolytic therapy can improve glycemic control in type 2 diabetes should encourage further research along these lines.

Insulin secretion as a determinant of pancreatic cancer risk

New epidemiology confirms that glucose intolerance is a risk factor for pancreatic cancer, and that this association cannot be accounted for by an adverse impact of early pancreatic cancer on beta cell function. Previous reports indicate that risk for pancreatic cancer is increased in adult-onset diabetics. Since streptozotocin diabetes inhibits carcinogen-mediated induction of pancreatic cancer in hamsters, the most reasonable interpretation of these findings is that insulin (or some other beta cell product) acts as a promoter for pancreatic carcinogenesis. This view is consistent with a report that human pancreatic adenocarcinomas express insulin receptors that can stimulate mitosis; an additional possibility is that high insulin levels indirectly promote pancreatic carcinogenesis by boosting effective IGF-I activity via hepatic actions. In international ecologic epidemiology, pancreatic cancer rates correlate tightly with dietary intake of animal products; this may reflect the fact that vegan diets are associated with low diurnal insulin secretion. There is also suggestive evidence that macrobiotic vegan diets, which are low in glycemic index, may increase mean survival time in pancreatic cancer. However, other types of diets associated with decreased postprandial insulin response, such as high-protein diets or 'Mediterranean' diets high in oleic acid, may also have the potential for pancreatic cancer prevention. The huge increases of age-adjusted pancreatic cancer mortality in Japan and among African-Americans during the last century imply that pancreatic cancer is substantially preventable; a low-insulin-response diet coupled with exercise training, weight control, and smoking avoidance, commendable for a great many other reasons, may slash pancreatic cancer mortality dramatically.

Does dietary protein in early life affect the development of adiposity in mammals?

This article examines the proposition that dietary protein in pre- and early postnatal life influences the development of adiposity in later life. In rodents, low protein intake during gestation can result in low birth weight and subsequently leads to various metabolic disturbances in adulthood, such as high blood pressure, impaired glucose tolerance and insulin resistance. The few controlled studies conducted in animals suggest that high protein or energy intake during gestation leads to low birth weights. Observational studies in humans have been inconclusive in establishing a relationship between dietary protein intake in pregnancy and effects on birth weight and adiposity of the offspring later in life. There is only weak epidemiological evidence linking high protein intake during early childhood and the development of obesity. By contrast, studies in domestic animals have found that higher levels of protein intake are often associated with lower rates of fat accretion. Additional studies are proposed to explore claims linking protein nutrition in early life to the postnatal development of obesity and disease in humans.

Current prospects for controlling cancer growth with non-cytotoxic agents--nutrients, phytochemicals, herbal extracts, and available drugs

In animal or cell culture studies, the growth and spread of cancer can be slowed by many nutrients, food factors, herbal extracts, and well-tolerated, available drugs that are still rarely used in the clinical management of cancer, in part because they seem unlikely to constitute definitive therapies in themselves. However, it is reasonable to expect that mechanistically complementary combinations of these measures could have a worthwhile impact on survival times and, when used as adjuvants, could improve the cure rates achievable with standard therapies. The therapeutic options available in this regard include measures that: down-regulate serum free IGF-I; suppress the synthesis of mevalonic acid and/or certain derivatives thereof; modulate arachidonate metabolism by inhibiting 5-lipoxygenase, 12-lipoxygenase, or COX-2; antagonize the activation of AP-1 transcription factors; promote the activation of PPAR-gamma transcription factors; and that suppress angiogenesis by additional mechanisms. Many of these measures appear suitable for use in cancer prevention.

Up-regulation of hepatic IGFBP-1 production as a strategy for preventing benign prostatic hyperplasia

Many lines of evidence point to a prominent role for excess production and activity of stroma-derived, androgen-induced IGF-II in the stromal and epithelial hyperplasia characteristic of benign prostatic hyperplasia (BPH). Increased stromal expression of the type I IGF receptor, as well as altered local production of IGF binding proteins, appear to contribute to this increase in IGF activity. Systemic IGFBP-1, primarily of hepatic origin, is a functional antagonist of IGF-II; thus, boosting IGFBP-1 production might be expected to lessen risk for BPH. Minimizing diurnal insulin secretion, and possibly avoiding intake of animal proteins over-rich in essential amino acids, are practical strategies for increasing hepatic IGFBP-1 synthesis. This hypothesis may rationalize recent evidence that exercise and moderate alcohol consumption decrease risk for BPH, whereas heavy smoking increases this risk. A clinical impression that BPH is becoming more common in Japan, and evidence that Japanese making frequent use of meat and dairy products are at increased risk for this disorder, also appear consistent with this view.

The origins of western obesity: a role for animal protein?

A reduced propensity to oxidize fat, as indicated by a relatively high fasting respiratory quotient, is a major risk factor for weight gain. Increased insulin secretion works in various ways to impede fat oxidation and promote fat storage. The substantial 'spontaneous' weight loss often seen with very-low-fat dietary regimens may reflect not only a reduced rate of fat ingestion, but also an improved insulin sensitivity of skeletal muscle that down-regulates insulin secretion. Reduction of diurnal insulin secretion may also play a role in the fat loss often achieved with exercise training, low-glycemic-index diets, supplementation with soluble fiber or chromium, low-carbohydrate regimens, and biguanide therapy. The exceptional leanness of vegan cultures may reflect an additional factor - the absence of animal protein. Although dietary protein by itself provokes relatively little insulin release, it can markedly potentiate the insulin response to co-ingested carbohydrate; Western meals typically unite starchy foods with an animal protein-based main course. Thus, postprandial insulin secretion may be reduced by either avoiding animal protein, or segregating it in low-carbohydrate meals; the latter practice is a feature of fad diets stressing 'food combining'. Vegan diets tend to be relatively low in protein, legume protein may be slowly absorbed, and, as compared to animal protein, isolated soy protein provokes a greater release of glucagon, an enhancer of fat oxidation. The low insulin response to rice may mirror its low protein content. Minimizing diurnal insulin secretion in the context of a low fat intake may represent an effective strategy for achieving and maintaining leanness.

Increased risk of iodine deficiency with vegetarian nutrition

Observational studies primarily based on diet questionnaires or food records have reported that vegetarians can have a very low I intake. However, analytically ascertained data on the possible degree of I deficiency with this form of diet is lacking. Six healthy adult volunteers participated in the present controlled experimental diet study carried out in four separate 5 d diet periods. The study diets, normal, protein-rich, lactovegetarian, and repeat of the initial normal diet, were almost isoenergetic and contained no fish, sea food, iodized salt or processed foods fortified with I. During the last 48 h of each diet period two 24 h urine samples were obtained from each subject. I analyses were performed in the urine samples and in representative samples taken from all ingested diets. Urinary I excretion was significantly lower with the lactovegetarian diet (36.6 (SD 8.8) micrograms/d) than with the normal and the protein-rich diets (50.2 (SD 14.0) and 61.0 (SD 8.0) micrograms/d respectively). Accordingly, a markedly reduced I intake was confirmed analytically for the lactovegetarian diet (15.6 micrograms/d v. 35.2 and 44.5 micrograms/d respectively). Our results provide experimental confirmation of literature findings indicating that I supply is higher with non-vegetarian than with vegetarian diets. Specifically, the extremely low intake and urinary output of I as analytically determined for one exemplary vegetarian diet, demonstrate that dietary I may be limiting when strict forms of vegetarian dietary practices (no iodized salt, no I supplements) are followed. The present study is, therefore, the first diet-experiment-based pointer to the potential danger of I deficiency disorders due to strict forms of vegetarian nutrition, especially when fruits and vegetables grown in soils with low I levels are ingested.