Iron & Diabetes

A review

Abstract

Both anemia and iron overload are commonly encountered problems in clinical practice. In between is a huge gray area of iron levels, measured by various markers, that fall in the normal reference ranges and are viewed as not a cause for concern. However, to take as an example the risk of acute cardiovascular events in women, the prevalence is very small prior to menopause and then increases to approach the risk level where postmenopausal women have a prevalence similar to adult men. This has been attributed to the very low systemic iron burden in premenopausal women and has encouraged the questioning of the optimum levels in both men and postmenopausal women. This is not a frivolous suggestion since the iron levels, or more properly the iron stores, are easily adjustable by blood donation or phlebotomy and blood iron stores of premenopausal women are easily achieved by adult men, apparently with negligible risk of side effects including anemia. Rather like the argument of those who believe in statins that the lower the LDL the better, a valid concern can be raised as to the appropriate range of iron stores in both adult men and postmenopausal women. Elevated iron stores lead to elevated iron available for redox reactions which act as generators of reactive oxygen species and highly significant inflammation, both of which are associated with a number of chronic diseases having inflammation as a part of their etiology. In this review, the connection between iron overload and diabetes will be discussed.

Introduction

It is well established that humans need a certain level of iron for health, but higher levels are potentially toxic (Kell 2009). From the point of view of evolution, normal stores of iron during reproductive years provided reserves for hemorrhage or periods of severe dietary restrictions or starvation. However there is no homeostatic mechanism for excreting excess iron to maintain a certain level.

Hemochromatosis and thalassaemia involve very high pathological iron levels, but even mildly elevated iron stores over time which are implicated in excessive redox (oxidation-reduction) reactions have been associated with the pathogenesis of cancer, neurodegenerative disorders, atherosclerosis, cardiovascular disease, peripheral artery disease and diabetes (Kell 2009). Iron is mostly sequestered as ferritin, a ubiquitous intracellular protein that both stores iron and releases it in a controlled manner in a safe form. Transferrin also ties up iron but can be saturated. Its function is to transport iron through the blood to the liver, spleen and bone marrow, with the iron in part coming from diet and erythrocyte breakdown. Significant serum levels of non-transferrin bound iron can also be present. It is redox active, and appears to be present even when transferrin saturation is absent (Lee 2006). The blood level of ferritin is the most commonly used marker for the magnitude of iron stores and iron overload.

Elevated ferritin levels are not always a true indicator of iron stores since it is an acute phase reactant. In most studies involving diabetes, this does not appear to be an issue. Mean ferritin levels in the US population study NHANES III were for men about 150 ng/mL, for menstruating women ages 17-49, 25-35 ng/mL, and for menopausal women ages 50-59, 60 ng/mL and for ages > 60, about 90-100 ng/mL (Zacharski 2000). Low levels of stored iron in premenopausal women have been frequently evoked as an explanation for the well known low risk of cardiovascular disease. These numbers raise concerns that the normal male level or the level found in older postmenopausal women may be associated with elevated risk of morbidity or mortality.

Toxicity of Iron

The toxicity of iron is related to its role in producing oxidative damage and the ease with which it is reversibly oxidized and reduced. Ferrous iron catalyzes the production of the highly toxic and reactive hydroxyl radical from hydrogen peroxide, whereas superoxide dismutase serves to equilibrate superoxide and peroxide. Oxidized iron regenerates reduced iron by reacting with superoxide with redox cycling. This results in reactive oxygen species (ROS) responsible for oxidative stress. When these overwhelm the antioxidant capacity, damage occurs which has been related to diseases of aging and inflammation (Brewer 2007). One view is that the dangers of excess iron operate through inadequately liganded (tied up) iron ions. When the ions are tightly liganded they are unreactive but weak ligand formation leaves some reactive free iron. The pathophysiology of iron is thus related to the availability of so-called catalytic iron, or iron that is available to participate in free radical reactions. Due to their weak antioxidant defences the pancreatic β-cells are particularly susceptible to oxidative damage such as can be caused by iron-generated reactive oxygen species (Tiedge 1997). In fact, iron has been used to induce diabetes in animals. Correlations with ferritin levels are an indirect measure of risk from iron-induced oxidative stress, and high ferritin levels correlate with elevated inflammatory cytokine levels (Depalma 2010).

The Association between Iron Levels, Diabetes and the Metabolic Syndrome

The potential role of iron in the pathogenesis of diabetes is suggested by several observations (Rajpathak 2009): (1) Increased incidence of diabetes is seen in patients with diverse causes of iron overload. (2) The reduction in iron load by either chelation or phlebotomy can improve glycemic control or reverse diabetes. (3) Dietary intake of heme iron (e.g. red meat) and concomitant increases in iron stores is associated with the risk of developing diabetes. (4) Insulin sensitivity and insulin secretion are increased by frequent blood donation. The molecular mechanisms are numerous and incompletely understood but include oxidative stress, modulation of adipokines and intracellular singling transduction pathways (Simcox 2013, Swaminathan 2007).

It has been argued that the modest elevations of ferritin observed in diabetes may be a consequence of the disorder rather than a causal factor impacting insulin resistance and β-cell function and apoptosis (Jehn 2007). However, evidence suggests otherwise. Excessive amounts of nontransferrin- bound iron, the form most susceptible to redox activity, are found in diabetic patients with a strong gradient for disease severity (Lee 2006). Furthermore, as will be discussed below, phlebotomy in type 2 diabetes results in improvements in glycemic control and insulin sensitivity which also supports the hypothesis that iron plays a pathogenic role.

Two recently published systematic reviews plus metaanalyses have examined the association of diabetes incidence with ferritin levels. One study (Zhao 2012) reports a meta-analysis of 12 prospective or crosssectional studies which analyzed ferritin levels and involved 4366 type 2 diabetes patients and over 41,000 controls plus four studies that measured heme-iron intake involving 9246 type 2 diabetics and about 180,000 controls. It was found that for the highest vs. the lowest category of ferritin level, the risk of diabetes was increased 66% in prospective studies and 130% in cross-sectional studies. A similar comparison for heme-iron intake yielded a 31% risk increase.

A second study (Bao 2012) examined the association between the risk of diabetes and dietary iron intake in prospective studies. A meta-analysis of five studies gave a pooled relative risk increase of 33% in a comparison of the lowest vs. the highest heme-iron intake. For elevated ferritin levels, they found a 70% increase in relative risk in multivariableadjusted models (seven studies) and a 63% increase in multivariable-adjusted models which included inflammatory markers (five studies). There was no significant association with dietary intake and risk for non-heme or supplemental iron intake, a result consistent with the high bioavailability only of heme iron. Incidentally, another study found a correlation between ferritin levels and the risk of diabetic retinopathy (Canturk 2003).

For postmenopausal women (56-62 years of age) who typically have ferritin levels between 70 and 90 ng/dL (Zacharski 2000), data taken from one of the above studies (Bao 2012) for the risk of developing type 2 diabetes are given in the table below according to the highest vs. the lowest ferritin quartiles.

It would seem that for women in this age group, levels similar to the NHANES average already carry significant risk.

A recent review and meta-analysis relates to the above. At issue is the association between red meat intake and risk of developing type 2 diabetes. A 19% increase was found per 100 g/day of red meat and a 51% increase per 50 g/day of processed red meat (Micha 2012).

The metabolic syndrome (MetS) is recognized as a risk factor for diabetes. Population studies find an association between ferritin levels and the risk of MetS in the US (Jehn 2004), Korea (Lee 2011), and Germany (Wrede 2006). Ferritin levels are associated with the MetS in postmenopausal but not premenopausal Korean women (Cho 2011), High levels of ferritin in a Chilean population correlated not only with a three-fold increase in developing MetS but for high levels of oxidative stress indicated by serum markers, there was a 21 fold increase in the development of this syndrome when the highest vs. the lowest quartiles were compared (Leiva 2013).

Clinical use of Phlebotomy to reduce Body Iron Stores

Both blood donation and phlebotomy can dramatically reduce iron stores (Houschyar 2012, Zacharski 2011). Repeated blood letting very efficiently lowers ferritin levels even if the initial values are very high such as seen in hemochromatosis. Furthermore, no induced anemia has been reported. The following studies are of interest:

• In a randomized controlled trial with metabolic syndrome patients, reduction of mean ferritin levels from 183 to 105 ng/mL using phlebotomy resulted in significant reductions in blood glucose, HbA1c, and systolic blood pressure. Changes in blood pressure and the HOMA-IR insulin resistance index correlated with ferritin reduction (Houschyar 2012).

• In a study comparing lacto-ovo vegetarians and meat eaters, the former were found to have mean ferritin levels of 35 ng/mL compared to 72 ng/mL for meats eaters and to have higher insulin sensitivity. When body stores of iron were lowered by phlebotomy in the meat eating group there was a 40% increase in insulin mediated glucose disposal (Hua 2001).

• The effect of phlebotomy on insulin resistance in a group of patients with non-alcoholic fatty liver disease and strongly elevated ferritin levels found a significant reduction in the HOMA-IR from 4.81 to 3.12 when ferritin levels were reduced from 438 to 52 ng/mL (Valenti 2007).

• In a study designed to examine the pathogenesis of diabetes associated with mutations of the hemochromatosis gene, 17 carriers comprising eight patients with diabetes and nine with normal glucose tolerance (NGT) were subjected to phlebotomy and the impact on insulin sensitivity and secretion investigated. Baseline ferritin levels were 942 and 1148 in the NGT and diabetic subjects, respectively. Ferritin targets were ≤ 100 ng/mL or ≤ 50 ng/mL depending of negative or positive evidence for iron deposits in the liver. The target levels were maintained and at 24 months the endpoint parameters measured. In both the NGT and diabetic groups, insulin secretion and insulin sensitivity increased. In the diabetic patients, fasting glucose declined from 137 to 105 mg/dL (7.6 to 5.8 mmol/L), the latter being close to normal (Equitani 2008).

• Earlier studies also found that reduction of iron stores consistently produces an improvement in insulin sensitivity and β-cell function (Fernandez- Real 2002, Fernandez-Real 2005).

Chelation, the Alternative to Phlebotomy or Blood Donation

Advanced glycation end products are thought to play a role in the complications of diabetes and the basic biochemistry involves reactive oxygen species including those attributed to iron activity (Nagai 2012). Oral chelation has been the traditional mainstream approach to iron overload for patients having pathological levels, and several prescription drugs are available. However, iron overloads involved in most of the studies discussed above are nowhere near those encountered in pathological iron overload. Furthermore, while studies, both interventional and observational, suggest target ranges for both men and women, optimum levels are clearly debatable. Chronic low-dose oral chelation therapy may be an important tool for the prevention and treatment of diabetic complications.

If one wishes to use non-pharmaceutical interventions to lower ferritin levels to, for example, to the upper end of the normal range for premenopausal women even if one is male, there are a number of “natural” iron chelators. N-acetyl cysteine is in fact a standard therapy for treating pediatric pathological iron overload even in infants. Green tea extract, curcumin, silymarin, alpha-lipoic acid (or R-lipoic acid) and quercetin all have documented success in iron chelation (Anderson 2012). These chelators also act to eliminate other toxic metals although for mercury it may help to add selenium to N-acetyl cysteine and lipoic acid. Curcumin was recently found to be a very good iron chelator (Jiao 2006). A recent randomized controlled trial demonstrated the effectiveness of curcumin in significantly improving markers of glucose metabolism in diabetics (Chuengsamarn 2012).

The results of the Trial to Access Chelation Therapy (TACT), a randomized, placebo controlled intravenous EDTA chelation trial, recently reported. Included were the results that for diabetics, there was a 39% relative risk reduction and a number needed to treat of eight (median follow-up 55 months) found for the composite primary endpoint of total mortality, recurrent MI, stroke, coronary revascularization or hospitalization for angina (Lamas 2013). EDTA chelation generally results in large increases in urine iron immediately post infusion (Cranton 2001).

The TACT result is particular interesting since intensive glycemic control with multiple drugs and even the addition of insulin fails to impact cardiovascular or total mortality or almost all other complications associated with diabetics (Boussageon 2012, Hemmingsen 2011, Turnbull 2012, Turnbull 2009). The dramatically lowered fasting blood glucose or HbA1c produced by intensive drug therapy may be viewed as successful control and treatment, but engenders false optimism while the pathogenesis of complications relentlessly progresses to ultimately yield clinical manifestations.

Iron Stores Reductions and Diabetic Complications

Studies on humans are limited. A nine-month study among patients with diabetes using deferiprone oral iron chelation reduced ferritin levels from 144 to 59 ng/mL and decreased the mean albumin/creatinine ratio from 187 to 25 mg/L (Rajapurkar 2013). In addition, a study involving the progression of diabetic nephropathy used a polyphenol–enriched, low-iron carbohydrate-restricted diet over four years. There was no significant change in HbA1c, but there was an absolute decrease in the incidence of serum creatinine doubling of 18% and a decrease in mortality or end-stage kidney disease of 18% over four years (number needed to treat over four years for either was six) (Facchini 2003). Iron chelation due to the polyphenols (from red wine, tea and polyphenol enhanced olive oil) was probably partly responsible for reduced ferritin from 325 to 53 ng/mL and may have been a major contributor to these results.

Conclusions

Studies are clearly needed to establish optimum iron stores in both men and women in the context of not only diabetes incidence, progression and complications, but also for all inflammation-related chronic diseases, in particular those associated with aging. Furthermore, large clinical studies are needed to examine the impact of lowering iron stores on the incidence of clinical manifestations of the complications of diabetes, not just markers of glucose metabolism. Can aggressive iron stores reduction, perhaps with severe carbohydrate restriction, cure type 2 diabetes, i.e. eliminate need for any medication? This question should have high priority. There are health issues associated with iron where one of the potentially effective interventions, blood donation, is free with almost no side effects. Iron stores as measured by ferritin can be dramatically lowered in most individuals without inducing anemia.

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Vitamin E

Obstacles and opportunities in cancer prevention and treatment

Abstract

Vitamin E is one of the most researched compounds in the medical community because of what is believed to be its reduced risk association with a multitude of diseases, including cancer. There are eight forms of vitamin E, four tocopherols and four tocotrienols. Alpha tocopherol is by far the most studied form because it is the most biologically active (Aggarwal 2010). Gamma tocopherol and tocotrienols have shown the greatest promise with respect to recent cancer research. Gamma tocopherol has been found to prevent cancer cell growth both in vitro and in animal models by decreasing the formation of mutagens (Stone 2004). Cell-based studies have shown that tocotrienols exhibit even stronger anticancer activities than other forms of vitamin E, including gammatocopherol (Jiang 2000). For all forms of vitamin E, additional research is needed that involves human trials to understand the relationship between dietary supplementation, required dosages, and the long-term risks and benefits.

Introduction

Since Herbert M. Evans discovered vitamin E in his laboratory at the University of California, Berkley in 1922, vitamin E has become one of the most researched compounds within the medical community (Packer 2001). Gamma tocopherol and tocotrienols are often discussed within the medical literature as providing the greatest opportunities for disease prevention and treatment. The results of several studies have indicated that the tocotrienols may have stronger bioactivity than the tocopherols. Both types have shown anti-proliferative, pro-apoptotic and cyclooxygenase-2-inhibiting effects in in vitro studies (Wada 2012). These types of vitamin E have shown promise in treatment of a variety of cancers, including prostate cancer in men and breast cancer in women (Nesaretnam 2010, Sylvester 2005). The purpose of this paper is to examine some of the existing research regarding the potential benefits of gamma tocopherol and tocotrienols in relation to cancer prevention and treatment.

Vitamin E and Cancer

Before discussing the research that has shown the benefits of gamma tocopherol and tocotrienols with respect to cancer, it is important to briefly note the somewhat negative findings associated with supplemental alpha tocopherol intake and cancer. Alpha tocopherol is the most biologically active form of vitamin E in the human body and all other forms of vitamin E are measured in alpha tocopherol equivalents (National Academies Press 2000). A large randomized clinical trial, the SELECT trial, began in 2001 to determine whether daily supplementation with vitamin E (400 IU, as alpha tocopherol), with or without selenium (200 mcg), reduced the number of new prostate cancers in 35,533 healthy men over 50 years old. The trial was discontinued in 2008 when an analysis found that the supplements, taken alone or together for about five years, did not prevent prostate cancer. Results from an additional 1.5 years of follow-up from this trial showed that the men who had taken the alpha tocopherol had a 17 percent increased risk of prostate cancer compared placebo (Klein 2011). Other research has suggested that taking too much vitamin E can have pro-oxidant instead of anti-oxidant effects on cells (Brown 1997). Due to this effect, alpha tocopherol taken in high dosages may create a set of conditions in the body resulting in cancer cell formation that would not have otherwise occured. The warning that seems appropriate is that supplemental alpha tocopherol should not be viewed as a way of reducing cancer risk or cancer cell growth.

Gamma Tocopherol in Cancer Treatment

Research on human epithelial cells has indicated that gamma tocopherol, one of the forms of vitamin E and the most prevalent in the North American diet, has antiinflammatory properties as a COX-2 inhibitor that may be important in preventing a variety of diseases including cancer and cardiovascular disease (Jiang 2000). Research has shown that increased intake of gamma tocopherol was associated with a reduced risk of prostate cancer (Moyad 1999). Gamma tocopherol is superior to alpha tocopherol in the trapping of reactive nitrogen species, inhibition of COX-2 activity, activation of PPAR-γ and suppression of inflammation. Jihyeung et al. (2010) propose that a mixture of tocopherols, at ratios similar to those in our diet, could be a better cancer chemopreventive agent, based on their lab results demonstrating that gamma tocopherol inhibited colon, mammary, prostate and lung carcinogenesis in animal models. Human cell line study findings indicate that gamma tocopherol has potent anti-inflammatory activity and that at physiological concentrations, it may play an important role in human disease prevention (Jiang 2000). Well-designed human intervention trials with gamma tocopherol are needed to yield more definitive information on its cancer-preventive activities, and the most effective route of administration (ie. oral vs. injectable).

Tocotrienols in Cancer Treatment

As compared to tocopherols, tocotrienols have been found to be much more effective in prevention and inhibition of cancer cell growth in the body (Sylvester 2005). Part of the reason for this is that tocotrienols are more likely than tocopherols to achieve high cellular concentrations. The potential for higher cellular concentration of tocotrienols results in mitochondrial toxicity and apoptosis, a reduction of cancer cell reproduction, and the prevention of new cancer cell formation (Viola 2012). It has been noted that tocotrienols target different molecular structures than tocopherols. Specifically, the anti-inflammatory properties of tocotrienols have been found to suppress the transcription factor NF-kB, which has been linked to tumorigenesis and inhibition of HMG-CoA reductase, mammalian DNA polymerases, and some protein tyrosine kinases (Aggarwal 2010). Because of the unique anti-inflammatory properties and cell line targeting that occurs with tocotrienols, patients suffering from various types of cancers, specifically breast and prostate cancer, may be able to take a lower dosage of tocotrienols as compared to tocopherols, and achieve better results. This is important considering that research has indicated that high levels of vitamin E supplementation, in the form of alpha tocopherol, has been associated with increased levels of hemorrhagic stroke (Schurks 2010).

Research suggests that for women, taking tocotrienols as a dietary supplement may reduce the risk of developing breast cancer (Sylvester 2010). Part of the benefit of tocotrienols is indeed related to the lower dosages that are required in order to achieve the anti-inflammatory and anti-cancer properties. Other research has indicated that tocotrienols may increase immune function and response in the body (Nesaretnam 2012). The rationale is that tocotrienols bind to estrogen receptor beta ER-beta) leading to alteration of cell morphology and apoptosis of breast cancer cells (Nesaretnam 2012). Tamoxifen is currently one of the standard treatment in patients with estrogen receptor positive tumors. New research indicates that a combination of tamoxifen with tocotrienols may prolong the life of women with breast cancer (Nesaretnam 2012). A common problem with tamoxifen therapy is that patients develop resistance to the drug. Using a combination of tocotrienols and tamoxifen may reduce the problems that occur once patients develop tamoxifen resistance while also acting synergistically to extend breast cancer-specific survival (Nesaretnam 2012).

Therapeutic Dosing

The eight forms of vitamin E are not interconvertible within the human body. Instead, serum and intracellular concentrations of tocopherols and tocotrienols each rely upon the affinity of the hepatic alpha-tocopherol transfer protein (alpha-TTP) for their selective retention in plasma (National Academies Press 2000). As well, in vivo concentrations of vitamin E rely on the body’s ability to absorb each form. Typically, this absorption is below 80% and for some forms of vitamin E can be as low as 10% absorption from the gastrointestinal tract.

Although it is common for supplemental vitamin E products to measure doses in International Units (IU), this format is outdated. Most commonly, milligrams of alpha-tocopherol equivalents (alpha-TE) are used to show dosage and this more clearly represents the ability of the body to absorb and utilize different forms of vitamin E (National Academies Press 2000). The conversion factor is based on 0.67mg (alpha-TE)/IU. 1000mg/day (1500IU) is considered the Upper Limit (UL) for vitamin E supplementation based on statistical analysis of adverse effects in high dose studies as well as other factors (National Academies Press 2000). However, research by Johns Hopkins University showed that vitamin E supplementationin excess of 400IU daily for one year in the alpha tocopherol form resulted in increased all-cause mortality and should be avoided (Miller 2005). In terms of therapeutic dosing for maximal cancer prevention and apoptotic potential, there are no standardized protocols. Since many of the studies showing benefit for cancer treatment have been in vitro or in animal models, adult human dosing is difficult to determine. Nesaretnam et al. (2010) found that during a five year randomized controlled trial on women undergoing tamoxifen therapy, risk of mortality due to breast cancer was 60% lower in the intervention group supplemented with 400mg tocotrienols in the form of a tocotrienol rich fraction (TRF) daily versus the controls. This dosing provides a guideline for further investigation. Generally, dietary sources are considered safe due to the bodies inefficient absorption mechanisms for all forms of vitamin E. At higher levels, vitamin E may inhibit absorption of other fat soluble vitamins (A, D, and K). In particular, vitamin K may be decreased in some individuals supplementing with vitamin E and so caution should be taken at higher doses to monitor blood coagulation.

During cancer chemotherapy and radiotherapy, a research review (Lawenda 2008) suggests that supplementing any antioxidant (including vitamin E) should be avoided due to the potential for anti-oxidants to protect any cell regardless of whether it is a cancer cell or not. Most definitely, dosing protocols specific to cancer treatment should be researched further once clinical trials elucidating effectiveness have been undertaken. Common dosages on supplements range from a daily dose of 60mg mixed tocopherols in professional brand multivitamins to 200-400mg daily of tocotrienols in the form of a tocotrienol rich fraction (TRF) from palm oil.

Conclusion

The research that has been reviewed suggests that both gamma tocopherol and tocotrienols have antiinflammatory properties that can reduce cancer cell growth in the body. Tocotrienols may have a greater ability to reduce the risk of cancer development and spread, especially with estrogen receptor positive breast cancer in women. Much more research regarding the specific supplemental dosages of the sup-types of vitamin E is required. Clinical trials are necessary to establish safe and effective dosing protocols. What does seem clear is that gamma tocopherol, tocotrienols, and mixed tocopherols are safer forms of supplementation and provide a higher level of benefit than alpha tocopherol.

References:

Aggarwal, B. B., Sundaram, C., Prasad, S. & Kannappan, R. Tocotrienols, the vitamin E of the 21st century: its potential against cancer and other chronic diseases. Biochemical Pharmacology. 2010. 80(11), 1613-1631.

Dietrich, M., Traber, M. G., Jacques, P. F., Cross, C. E., Hu, Y. & Block, G.Does γ-Tocopherol play a role in the primary prevention of heart disease and cancer? A review. Journal of the American College of Nutrition. 2006. 25(4), 292-299.

Jiang, Q., Elson-Schwab, I., Courtemanche, C. & Ames, B. N. Gamma-tocopherol and its major metabolite, in contrast to alpha-tocopherol, inhibit cyclooxygenase activity in macrophages and epithelial cells. Proceedings of the National Academy of Sciences. 2000. 97(21), 11494-11499.

Jihyeung, Ju, Picinich S, Yang Z, et al. Cancer-preventive activities of tocopherols and tocotrienols. J Carcinogenesis. 2010 April; 31(4): 533–542.

Klein EA, Thompson Jr. IM, Tangen CM, Crowley JJ, Lucia MS, Goodman PJ, et al. Vitamin E and the risk of prostate cancer: the Selenium and Vitamin E Cancer Prevention Trial (SELECT). JAMA 2011;306:1549-1556.

Lawenda, B.D., Kelly, K.M., Ladas, E.J., Sagar, S.M., Vickers, A., Blumberg, J.B. Should Supplemental Antioxidant Administration Be Avoided During Chemotherapy and Radiation Therapy? J Natl Cancer Inst. 2008. 100(11), 773-83.

Miller, E.R.3rd, Pastor-Barriuso, R., Dalal, D., Riemersma, R.A., Appel, L.J., Guallar, E. Meta-analysis: High Dosage Vitamin E Supplementation May Increase All-cause Mortality. Ann Int Med. 2005. 142:37-46.

Moyad, M. A., Brumfield, S. K. & Pienta, K. J. Vitamin E, alpha- and gamma-tocopherol, and prostate cancer. Seminars in Urologic Oncology. 1999. 17(2), 85-90.

National Institutes of Health. Dietary Supplement Fact Sheet: Vitamin E. 2011. Retrievedfrom: http://ods.od.nih.gov/ factsheets/vitamine/.

National Academies Press. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC, 2000.

Nesaretnam, K., Meganthan, P., Veerasenan, S. D. & Selvadurary, K. R. Tocotrienols and breast cancer: the evidence to date. Genes Nutr. 2012. 7, 3-9.

Nesaretnam, K., Selvaduray, K.R., Razak, G.A., Veerasenan, S.D., Gomez, P.A. Effectiveness of Tocotrienol Rich Fraction Combined with Tamoxifen in the Management of Women with Early Breast Cancer: A Pilot Clinical Trial. Breast Cancer Research. 2010. 12; R81.

Packer, L. Weber, S. U. & Rimbach, G. Molecular aspects of alpha-tocotrienol antioxidant action and cell signaling. Journal of Nutrition.2001. 131(2), 369S-373S.

Schurks, M., Glynn, R.J., Rist, P.M., Tzourio, C., Kurth, T. Effects of Vitamin E on Stroke Subtypes: Meta-analysis of Randomized Controlled Trials. BMJ. 2010. 341.

Stone W, Krishnan K, Campbell S, Qui M, Whaley S, Yang H. Tocopherols and the Treatment of Colon Cancer. Annals of the New York Academy of Sciences Volume 1031, Vitamin E and Health pages 223–233, December 2004

Sylvester, P. W. & Shah, S. J. Mechanisms mediating the antiproliferative and apoptotic effects of vitamin E in mammary cancer cells. Frontiers in Bioscience.2005. 10, 699-709.

Sylvester, P. W., Kaddoumi, A., Nazzal, S. & El Sayed, K. A. The value of tocotrienols in the prevention and treatment of cancer. Journal of the American College of Nutrition. 2010. 29(3), 3245-3335.

Viola, V., Pilolli, F., Piroddi, M., Pierpaoli, E., Orlando, F., Provinciali, M., Betti, M., Mazzini, F. &Galli, F. Why tocotrienols work better: insights into the in vitro anti-cancer mechanism of vitamin E. Genes Nutr. 2012. 7, 29-41.

Wada, S. Cancer preventive effects of vitamin E. Curr Pharm Biotechnol. 2012 Jan;13(1):156-64.

Nigella Sativa

A Panacea for Human Disease

Abstract

Nigella sativa, also known as black cumin, is a highly-regarded and prominent herb that has been used in traditional Middle Eastern and Indian systems of medicine. The Prophet Muhammad was recorded as stating that the herb can cure any disease, other than death. Many therapeutic activities have been ascribed to Nigella, including astringent, bitter, stimulant, anthelminthic, carminative, anodyne, expectorant and other effects. In modern research, Nigella has been shown to possess potent anti-inflammatory activity, lipid, glucose, and blood pressure lowering effects, anti-allergic effects, as well as neuroprotective, antimicrobial, and smooth muscle relaxing effects. Preclinical research has indicated potentially important anticancer effects, though this has yet to be investigated in human studies. These effects have been attributed in large part to the constituent thymoquinone. This long list of therapeutic effects demonstrated by scientific research reinforces the traditional view of this impressive herb.

Introduction

Nigella sativa, also known as black cumin, is part of the Ranunculaceae family and an herb with a long history of traditional use in southeast Asia, Egypt, Greece, and the Middle East (Khan 2011). Nigella was regarded as a panacea by the ancients, and played a central role in the medical practice of Middle Eastern and South Asian societies for over 2000 years, where it was used for the treatment of a range of conditions including asthma, headache, dysentery, infection, back pain, dermatological and gastrointestinal conditions (Isik 2010). In traditional Indian medicine, Nigella seeds are astringent, bitter, stimulant, diuretic, emmenagogue, anthelmintic, galactogogue, carminative, anodyne, sudorific, febrifuge, expectorant, purgative, and abortifacient (Parrakh 2010). The medieval Islamic philosopher Avicenna wrote of Nigella in his Canon of Medicine, that it stimulates the body’s energy and helps recovery from fatigue and dispiritedness (Parrakh 2010). Mohammed is reported to have said that the seed has the power to cure every disease except death (Parrakh 2010).

Medicinally, Nigella has been used in the form of crushed seed, oil, and water extract. The activity of Nigella has been attributed in to its thymoquinone content, which is present in both the fixed and essential oils of Nigella; thymoquinone has been extracted and used therapeutically in isolation (Akhondian 2011, Paarakh 2010).

Nigella oil also contains plant sterols, as well as 25% oleic acid/ 55% linoleic acid, nigellone, and volatile oils including thymol, limonene, and carvacrol (Isik 2010, Paarakh 2010). It is also possible that fibre content may mediate part of the metabolic effects of Nigella.

Mechanism of Action: Preclinical Evidence

There is a wealth of information on Nigella and thymoquinione derived from preclinical research. Thymoquinone appears to be capable of protecting tissues and organs from various types of damage due to antiinflammatory and antioxidant activity, and has also been investigated for its anticancer effects (Woo 2012). In animal models of diabetes, thymoquinone was shown to inhibit cellular expression of the COX-2 enzyme and increased levels of the antioxidant enzyme superoxide dismutase (Al Wafai 2013). In models of hyperlipidemia, Nigella sativa volatile oil and methanol extract have both been shown to reduce triglyceride and increase HDL, as well as decrease hepatic HMG-CoA reductase activity (Ahmad 2013). In smooth muscle tissue, including intestinal and bronchial tissue, thymoquinone has been shown to inhibit spontaneous contraction via inhibition of voltage-gated calcium channels (Ghayur 2012). Thymoquinone has also been shown to inhibit liver fibrosis (Bai 2013); attenuate lung injury and fibrosis (El-Khouly 2012); attenuate diabetic nephropathy (Sayed 2012); prevent E. coli induced tissue damage in bacterial prostatitis (Inci 2013); and prevent dextran sulfate sodium-induced colitis (Lei 2012).

In an animal model of epilepsy, thymoquinone was shown to have antioxidant effects in attenuating malondialdehyde (a marker of lipid peroxidation), reduced neurodegenerative changes and neuron loss, and decreased the number of reactive astrocytes (astrogliosis) (Dariani 2013). Thymoquinone has also been shown to have protective effects against amyloid β-induced neurotoxicity, leading to the suggestion that Nigella may have therapeutic potential in Alzheimer’s disease (Alhebshi 2013).

Nigella and its constituent thymoquinone have also been extensively studied in lab models for its anticancer effects. Thymoquinone has been shown to have pro-apoptotic effects in breast cancer, including synergistically with tamoxifen (Rajput 2013); and has been shown to inhibit cancer cell growth and invasiveness in lung, liver, colon, melanoma, and breast cancer cells (Attoub 2012). This is an area where further research is needed to investigate these promising activities.

Clinical Trials

There is a well-developed body of evidence investigating Nigella in humans. Nigella has been shown to have anti-diabetic, blood pressure and cholesterol lowering effects. It also has activity against specific types of infection, possesses anti-allergic effects, and improves rheumatoid arthritis as well as pediatric seizures. Table 1 summarizes all available evidence from human intervention trials concerning the herb as identified through Pubmed and Google Scholar.

In metabolic syndrome, Nigella seed has been shown to significantly decrease total cholesterol, LDL, and triglyceride (Dehkordi 2008, Sabzghabaee 2012), improve fasting and post-prandial glucose and HbA1C (Bamosa 2010), decrease systolic blood pressure (Datau 2010, Dehkordi 2008) by almost 10 points in one study (Datau 2010), as well as promote reduction of body weight and waist circumference (Datau 2010). In the area of allergy and asthma, Nigella oil or extract has been shown to significantly reduce symptoms of allergic rhinitis (Kalus 2003,Nikakhlagh 2011), as well as reduce the severity and frequency of asthma symptoms, improve lung function tests, and reduce the need for asthma medications (Boskabady 2007). Also related to respiratory function are two studies showing that Nigella can act as an antimicrobial agent in acute pharyngitis (Dirjomuljono 2008), and improve lung function, respiratory symptoms, as well as medication requirements in patients who were victims of chemical warfare (Boskabady 2008). One study found that Nigella seed in combination with omeprazole was equal to triple therapy in the eradication of H. pylori (Salem 2010). Finally, one study each showed that Nigella was effective in reducing disease activity of rheumatoid arthritis (Gheita 2012), and reduce the frequency of seizures in patients with refractory epilepsy (Akhondian 2011).

Dosage

The effective dosage forms and quantities of Nigella used include 2g of ground seeds in metabolic syndrome or syndrome components (Sabzghabaee 2012); 1-4g seed oil for inflammatory conditions such as allergy and arthritis (Gheita 2012, Kalus 2003); 1mg/kg thymoquinone in pediatric seizure (Akhondian 2011); and varying doses of a boiled aqueous extract (Boskabady 2007, Boskabady 2008).

Safety

Based on the studies in Table 1 as well as the impressive range of activities demonstrated in preclinical research, Nigella appears to possess powerful disease modifying potential in a range of conditions. The only adverse events reported with any consistency among the trials were mild gastrointestinal upset (Akhondion 2011, Bamosa 2010, Salem 2010). Overall, Nigella and/ or thymoquinone appears to have a good safety profile (Al-Ali 2008). In animals, toxicity was demonstrated only at dosages of 250 mg/kg thymoquinone by oral route (maximum tolerated dose) (Abukhader 2012). When given by intraperitoneal injection, toxicity occurred at a dose of between 15-20mg/kg thymoquinone, more than 10-fold the dose used in human trials (Abukhader 2012). Signs of toxicity were acute pancreatitis and peritonitis (Abukhader 2012). In another study, the LD50 of thymoquinone by oral administration was 870.9 mg/kg, more than 100 to 150-fold higher than the therapeutic dose (Al-Ali 2008).

Conclusion

Nigella sativa is a highly regarded herb with a long tradition of use for infection, conditions of inflammation, respiratory and gastrointestinal conditions, and more. Human trials have demonstrated benefits from Nigella seed in metabolic conditions such as dyslipidemia, type 2 diabetes, and hypertension; and Nigella oil or extract in allergy and asthma, inflammatory conditions, infections including pharyngitis and H. pylori, as well as refractory epilepsy. Further research is needed to elucidate the potential anticancer effects of Nigella suggested by preclinical findings.

References

Abukhader MM. The effect of route of administration in thymoquinone toxicity in male and female rats. Indian J Pharm Sci. 2012 May;74(3):195-200.

Ahmad S, Beg ZH. Elucidation of mechanisms of actions of thymoquinone-enriched methanolic and volatile oil extracts from Nigella sativa against cardiovascular risk parameters in experimental hyperlipidemia. Lipids Health Dis. 2013 Jun 13;12(1):86. [Epub ahead of print]

Akhondian J, Kianifar H, Raoofziaee M, Moayedpour A, Toosi MB, Khajedaluee M. The effect of thymoquinone on intractable pediatric seizures (pilot study). Epilepsy Res. 2011 Jan;93(1):39-43.

Al-Ali A, Alkhawajah AA, Randhawa MA, Shaikh NA. Oral and intraperitoneal LD50 of thymoquinone, an active principle of Nigella sativa, in mice and rats. J Ayub Med Coll Abbottabad. 2008 Apr-Jun;20(2):25-7.

Alhebshi AH, Gotoh M, Suzuki I. Thymoquinone protects cultured rat primary neurons against amyloid β-induced neurotoxicity. Biochem Biophys Res Commun. 2013 Apr 19;433(4):362-7.

Al Wafai RJ. Nigella sativa and thymoquinone suppress cyclooxygenase-2 and oxidative stress in pancreatic tissue of streptozotocin-induced diabetic rats. Pancreas. 2013 Jul;42(5):841-9.

Attoub S, Sperandio O, Raza H, Arafat K, Al-Salam S, Al Sultan MA, Al Safi M, Takahashi T, Adem A. Thymoquinone as an anticancer agent: evidence from inhibition of cancer cells viability and invasion in vitro and tumor growth in vivo. Fundam Clin Pharmacol. 2012 Jun 11.

Bai T, Lian LH, Wu YL, Wan Y, Nan JX. Thymoquinone attenuates liver fibrosis via PI3K and TLR4 signaling pathways in activated hepatic stellate cells. Int Immunopharmacol. 2013 Feb;15(2):275-81.

Bamosa AO, Kaatabi H, Lebdaa FM, Elq AM, Al-Sultanb A. Effect of Nigella sativa seeds on the glycemic control of patients with type 2 diabetes mellitus. Indian J Physiol Pharmacol. 2010 Oct-Dec;54(4):344-54.

Boskabady MH, Farhadi J. The possible prophylactic effect of Nigella sativa seed aqueous extract on respiratory symptoms and pulmonary function tests on chemical war victims: a randomized, double-blind, placebo-controlled trial. J Altern Complement Med. 2008 Nov;14(9):1137-44.

Boskabady MH, Javan H, Sajady M, Rakhshandeh H. The possible prophylactic effect of Nigella sativa seed extract in asthmatic patients. Fundam ClinP harmacol. 2007 Oct;21(5):559-66. Erratum in: Fundam Clin Pharmacol. 2008 Feb;22(1):105.

Dariani S, Baluchnejadmojarad T, Roghani M. Thymoquinone Attenuates Astrogliosis, Neurodegeneration, Mossy Fiber Sprouting, and Oxidative Stress in a Model of Temporal Lobe Epilepsy. J Mol Neurosci. 2013 Jun 23. [Epub ahead of print]

Datau EA, Wardhana, Surachmanto EE, Pandelaki K, Langi JA, Fias. Efficacy of Nigella sativa on serum free testosterone and metabolic disturbances in central obese male. Acta Med Indones. 2010 Jul;42(3):130-4.

Dehkordi FR, Kamkhah AF. Antihypertensive effect of Nigella sativa seed extract in patients with mild hypertension. Fundam Clin Pharmacol. 2008 Aug;22(4):447-52.

Dirjomuljono M, Kristyono I, Tjandrawinata RR, Nofiarny D. Symptomatic treatment of acute tonsillopharyngitis patients with a combination of Nigella sativa and Phyllanthus niruri extract. Int J Clin Pharmacol Ther. 2008 Jun;46(6):295-306.

El-Khouly D, El-Bakly WM, Awad AS, El-Mesallamy HO, El-Demerdash E. Thymoquinone blocks lung injury and fibrosis by attenuating bleomycin-induced oxidative stress and activation of nuclear factor Kappa-B in rats. Toxicology. 2012 Dec 16;302(2-3):106-13.

Ghayur MN, Gilani AH, Janssen LJ. Intestinal, airway, and cardiovascular relaxant activities of thymoquinone. Evid Based Complement Alternat Med. 2012;2012:305319.

Gheita TA, Kenawy SA. Effectiveness of Nigella sativa oil in the management of rheumatoid arthritis patients: a placebo controlled study. Phytother Res. 2012 Aug;26(8):1246-8.

Inci M, Davarci M, Inci M, Motor S, Yalcinkaya FR, Nacar E, Aydin M, Sefil NK, Zararsiz I. Anti-inflammatory and antioxidant activity of thymoquinone in a rat model of acute bacterial prostatitis. Hum Exp Toxicol. 2013 Apr;32(4):354-61.

Işik H, Cevikbaş A, Gürer US, Kiran B, Uresin Y, Rayaman P, Rayaman E, Gürbüz B, Büyüköztürk S. Potential adjuvant effects of Nigella sativa seeds to improve specific immunotherapy in allergic rhinitis patients. Med Princ Pract. 2010;19(3):206-11.

Kalus U, Pruss A, Bystron J, Jurecka M, Smekalova A, Lichius JJ, Kiesewetter H. Effect of Nigella sativa (black seed) on subjective feeling in patients with allergic diseases. Phytother Res. 2003 Dec;17(10):1209-14.

Khan MA, Chen HC, Tania M, Zhang DZ. Anticancer activities of Nigella sativa (black cumin). Afr J Tradit Complement Altern Med. 2011;8(5 Suppl):226-32.

Lei X, Liu M, Yang Z, Ji M, Guo X, Dong W. Thymoquinone prevents and ameliorates dextran sulfate sodium-induced colitis in mice. Dig Dis Sci. 2012 Sep;57(9):2296-303.

Nikakhlagh S, Rahim F, Aryani FH, Syahpoush A, Brougerdnya MG, Saki N. Herbal treatment of allergic rhinitis: the use of Nigella sativa. Am J Otolaryngol. 2011 Sep-Oct;32(5):402-7.

Paarakh PM. Nigella sativa Linn. – a comprehensive review. Indian Journal of Natural Products and Resources. 2010 Dec;1(4):409-29.

Qidwai W, Hamza HB, Qureshi R, Gilani A. Effectiveness, safety, and tolerability of powdered Nigella sativa (kalonji) seed in capsules on serum lipid levels, blood sugar, blood pressure, and body weight in adults: results of a randomized, doubleblind controlled trial. J Altern Complement Med. 2009 Jun;15(6):639-44.

Rajput S, Kumar BN, Sarkar S, Das S, Azab B, Santhekadur PK, Das SK, Emdad L, Sarkar D, Fisher PB, Mandal M. Targeted apoptotic effects of thymoquinone and tamoxifen on XIAP mediated Akt regulation in breast cancer. PLoS One. 2013 Apr 17;8(4):e61342.

Sabzghabaee AM, Dianatkhah M, Sarrafzadegan N, Asgary S, Ghannadi A. Clinical evaluation of Nigella sativa seeds for the treatment of hyperlipidemia: a randomized, placebo controlled clinical trial. Med Arh. 2012;66(3):198-200.

Salem EM, Yar T, Bamosa AO, Al-Quorain A, Yasawy MI, Alsulaiman RM, Randhawa MA. Comparative study of Nigella Sativa and triple therapy in eradication of Helicobacter Pylori in patients with non-ulcer dyspepsia. Saudi J Gastroenterol. 2010 Jul-Sep;16(3):207-14.

Sayed AA. Thymoquinone and proanthocyanidin attenuation of diabetic nephropathy in rats. Eur Rev Med Pharmacol Sci. 2012 Jun;16(6):808-15.

Woo CC, Kumar AP, Sethi G, Tan KH. Thymoquinone: potential cure for inflammatory disorders and cancer. Biochem Pharmacol. 2012 Feb 15;83(4):443-51.