Nutrients and Functional Foods in Diabetes
| Diabetes |
| By 2030 Asia is expected to have 190 million Diabetes cases, more than half of them in India & China. - Newsweek Magazine |
Sugar, Fructose, and High-Fructose Corn Syrup
White sugar, usually in the form of granulated sugar, is purified sucrose, the crystals of which are naturally white. Brown sugar is less refined and so still contains some molasses from sugar cane.
Alternatively, manufacturers may add back molasses to purified sucrose in order to control the ratio and the color. Nutritionally, the differences between white and brown sugar are fairly trivial. When matched on the basis of volume, brown sugar has more calories because it tends to pack more densely; one cup of brown sugar provides 829 calories, while a cup of white granulated sugar provides 774 calories. However, when matched by weight, brown sugar has slightly fewer calories due to the presence of water in the molasses; 100 g of brown sugar contains 373 calories, as opposed to 396 calories in white sugar. Sugar crystals provide no nutrients other than sucrose, but molasses adds enough calcium, iron, and potassium to distinguish brown sugar from white sugar, although not enough to make it an important source of any of these nutrients.
Fructose, referred to as fruit sugar, is a monosaccharide that does not require insulin for its metabolism. Fructose in the diet comes from honey and fruit; from sucrose, which is made up of fructose and glucose; and from the use of high-fructose corn syrup as a sweetener in soft drinks and processed foods. Fructose intake reduces postprandial glucose relative to other sugars and starches, but it has been associated with increased levels of LDL. Fructose restriction in diabetes is not indicated, but substitution of fructose for sucrose does not appear to confer benefit and is not recommended. Ingested fructose is largely cleared by the liver, where it is a substrate for triglyceride production; ingestion of fructose is associated with postprandial hypertriglyceridemia.
High-fructose corn syrup (HFCS), produced industrially through a series of enzymatic reactions on corn syrup, is widely used as a sweetener in the US food supply. There is unresolved debate about the relative contributions of HFCS, as compared to sucrose, to weight gain and diabetes risk. The inconclusive nature of this literature, reviewed recently in the New York Times, suggests that HFCS is, at present, best considered roughly comparable to other forms of added sugar in terms of adverse metabolic effect. However, corn subsidies in the United States make HFCS a particularly inexpensive sweetener, leading to its use in a startling variety of foods and often in surprisingly copious amounts. (The author has identified, for example, popular commercial brands of marinara sauce with more added sugar in the form of HFCS than chocolate fudge ice cream topping, matched for calories.) The ubiquity and abundance of HFCS likely makes it a particular and noteworthy dietary hazard, a contention supported by recent reviews linking soft drink consumption to obesity.
Other Sweeteners
Nutritive sweeteners, including corn syrup, honey, molasses, and fruit juice concentrates, appear to offer no advantage to sucrose in the management or prevention of diabetes. Nonnutritive sweeteners, such as aspartame, sucralose, and saccharin, confer sweetness without calories and do not raise serum glucose. Such sweeteners may be of some benefit in efforts to control serum glucose and facilitate or maintain weight loss, but evidence is lacking of sustainable benefit in either case. Although fructose does not induce an insulin release, this may actually be disadvantageous with regard to effects on satiety.
Aspartame, marketed as Equal and Nutrasweet, is made by linking two amino acids together. While it contains no sugar, it is roughly 200 times as sweet as sugar. Aspartame does contain some calories, but it is used in small amounts due to its intense sweetness, so the calories it adds to the diet are negligible. There is ongoing controversy about health effects of aspartame, but claims that it can cause brain tumors or neurological disease are not considered credible by the FDA. Because aspartame lacks bulk and is not heat stable, it cannot be used in baked goods.
Sucralose, marketed as Splenda, is made by modifying the structure of sugar molecules through the addition of chlorine atoms. It is marketed in the United States as a no-calorie sweetener, but it actually contains 96 calories per cup, about one-eighth the calories of sugar. Splenda contains roughly 2 calories per teaspoon, but FDA regulations allow a product to be labeled as free of calories if it contains fewer than 5 calories per standard serving. Sucralose is up to 1,000 times as sweet as sugar, so Splenda contains relatively small amounts of sucralose combined with fluffed dextrose or maltodextrin to give it bulk for use in baking.
Stevia is a sweetener made by purifying extracts from a group of herbs by the same name that grow in Central and South America. Due to some controversy about the safety of the extracts, called stevioside and rebaudioside, stevia is available as a dietary supplement but not a food additive in the United States. Stevia has been widely used in foods in Japan for the past several decades, without any apparent adverse effects. Stevia provides 30 to 300 times the sweetness of sugar, but it can produce a slightly bitter aftertaste.
While there is much made of the potential toxicity of artificial sweeteners in the blogosphere, the evidence that these compounds directly cause disease is not strong. However, the evidence that they serve to reduce calories or weight or offer other benefits is comparably slim. Research on artificial sweeteners does not show convincingly that they take calories out of the diet over time; they may simply cause calories to be displaced. Given that these sweeteners are as much as 1,000 times as sweet as sugar, they may raise the preference threshold for sweet and contribute to the consumption of processed foods with significant, and arguably superfluous, additions of sugar, typically in the form of HFCS.
Fiber
A daily intake of approximately 30 g of dietary fiber from a variety of food sources is recommended to the general public for health promotion and in the management of diabetes. There is evidence that soluble fiber in particular may be of benefit in controlling both glucose and lipid levels in diabetes. However, the levels of fiber intake required to achieve significant improvements in fasting and postprandial glucose levels have been considered too high for practical application. In a study of men with type 2 diabetes, Anderson et al. reported significant improvements in both serum lipids and glucose with twice daily psyllium totaling 10 g, for a period of eight weeks. Of note, our Paleolithic ancestors were thought to have consumed nearly 100 g of fiber daily, and this pattern persists among rural peoples in the developing world. Fruits, oats, barley, and legumes are particularly good sources of soluble fiber . Fiber intake of up to 40 g per day is advocated by the American Diabetes Association; average fiber intake by US adults ranges between 12 and 18 g per day.
Ethanol
Ethanol consumption independent of other food intake can result in hypoglycemia by transiently interfering with hepatic gluconeogenesis. Therefore, diabetics, particularly those treated with insulin or sulfonylureas, should be advised to consume alcohol only with food. Excessive alcohol intake may contribute to hypertriglyceridemia and deterioration of glucose control. Moderate alcohol intake in diabetes is generally without known adverse effects.
Chromium
Chromium is established as an essential nutrient, with roles in lipid and carbohydrate metabolism. Known to function as an insulin cofactor, chromium may bind to a carrier molecule and thereby activate the insulin receptor kinase . Chromium may stimulate expression of insulin receptors in skeletal muscle as well . Evidence of improved glycemic control with chromium supplementation has been reported , but there are conflicting reports in the literature. Discordant findings to date may relate to varied utility of chromium among the various populations studied; efforts to identify specific populations in which chromium may prove of certain therapeutic benefit are ongoing. Daily supplementation with as much as 8 µg/kg/day is apparently safe and potentially beneficial. A National Institutes of Health–funded trial of chromium picolinate in insulin resistance at doses of 500 µg and 1,000 µg per day is ongoing in the author's lab at this time.
Vanadium
Vanadium is an ultratrace element. Evidence of a potentially therapeutic role of vanadium in disorders of glucose metabolism has been reported. A review of vanadium suggests potential benefit as a cofactor in insulin metabolism in both type 1 and type 2 diabetes. The therapeutic window for inorganic vanadium is very narrow. Efforts to improve the safety of vanadium are proceeding concurrently with research into its mechanisms of action. Until further progress is made in each of these endeavors, therapeutic applications of vanadium cannot be encouraged.
n-3 Fatty Acids (Fish Oil)
Fish oil is used in the treatment of refractory hypertriglyceridemia, typically when treatment with fibric acid derivatives is incompletely effective. A meta-analysis by Friedberg et al. indicates that fish oil consistently lowers triglycerides by as much as 30%, with no untoward effects on glucose control in diabetes. The same analysis revealed a modest elevation of LDL in response to fish oil therapy. The authors concluded that fish oil may be an appropriate means of managing the dyslipidemia commonly seen in diabetes. There is some evidence to suggest that n-3 fatty acids stimulate hepatic gluconeogenesis and thereby can degrade glycemic control. Thus, their role in routine diabetes management remains uncertain. While reviews to date fail to define a clear role for n-3 fatty acids in diabetes management per se, a role for fish oil in the attenuation of certain cardiac risks is better substantiated. Thus, fish oil supplementation in diabetes as one among many strategies to mitigate cardiovascular risk may be considered. A standard dose is 1 g once to twice daily.
Mufas (Monounsaturated Fat)
Improvements in glycemic control and insulin metabolism have been seen in numerous trials that increased the proportion of calories from monounsaturated fats. A relatively generous intake of monounsaturated fat is now widely recognized among the salient features of a healthful dietary pattern.
Cocoa/Flavonoids
A quickly burgeoning literature suggests beneficial effects of dark chocolate on glycemic control and insulin sensitivity; the dense concentration of bioflavonoid antioxidants in cacao is the purported “active” ingredient. There are as yet no clear guidelines for the dosing of dark chocolate as a functional food, although efforts to generate such guidance are under way.
