Insulin Potentiating Factor and Chromium Content

of Selected Foods and Spices

At_aM KHAN, NOELLA A. BRYDEN, MARILYN M, POLANSKY,

AND RICHARD A. ANDERSON*

US Department of Agriculture, Agricultural Research Service, Beltsville Human Nutribon Research Center, Vitamin and ,a'lineral Nutrition

Laboratory, Bldg. 307, Room 224, BARC-East, Beltsville, ,aiD 20705

Received June 5, 1989; Accepted August 10, 1989

ABSTRACT

An unidentified factor that potentiates the action of insulin in glucose metabolism was investigated in selected foods and spices. Chromium content of these foods and spices was also determined. Foods and spices were extracted with 0.1N NH4OH (1:20, w/v) and the supernatants assayed for insulin potentiation activity in the rat epididymal fat cell assay (see ref. 6). Among the selected foods, tuna fish, peanut butter, and vanilla ice cream had some insulin potentiat- ing activity. Among the spices, apple pie spice, cinnamon, cloves, bay leaves, and turmeric potentiated insulin activity more than three- fold. Chromium concentration of foods ranged from 1 to 145 ng/g, and spices ranged from 4 to 1818 ng/g. Insulin potentiating activity of foods and spices did not correlate with total chromium. Spices are generally used for flavor and taste in food preparations, but cinna- mon, cloves, bay leaves, and turmeric may have an additional role in glucose metabolism.

INTRODUCTION

Certain foods contain unidentified factors that potentiate the action of insulin in glucose metabolism. A factor that has been shown to ira-

*Author to whom all correspondence and reprint requests should be addressed.

Biological Trace Element Research, Editor-in-Chief: G.N. Schrauzer �9 1990 by the Humana Press Inc.

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184 Khan et al.

prove glucose tolerance in chromium-deficient rats (1) has not been fully characterized. Toepfer et al. (2) reported that a biologically-active extract from brewer's yeast contained chromium, nicotinic acid, glycine, cys- teine, and glutamic acid. They provided further evidence by synthesizing biologically-active complexes comprised of trivalent chromium, nicotinic acid, glycine, glutamic acid, and cysteine. Attempts to purify the com- plexes were only partially successful. Yamamoto et al. (3) isolated a biologically-active, Cr-binding substance from bovine colostrum and des- ignated it as an anionic organic Cr compound of mol wt 1500. The compound had aspartic acid, glutamic acid, glycine, and cysteine in the ratio of 5:4:2:1. They assumed that nicotinic acid was present in the compound since it has absorption at 260 nm. Cooper et al. (4) reported that, among the different synthetic complexes of chromium with nico- tinic acid and amino acids, glycine, cysteine, glutamic acid, and glu- tamine, only chromium diglutamine, chromium-nicotinic acid-glycine, and mixture of complexes of chromium-glycine were biologically active in the yeast bioassay. Therefore, nicotinic acid may not be necessary for biological activity under their assay conditions.

Various foods have been shown to have biological activity (5), and chemical complexes have been prepared that display biological activity in a particular bioassay system (2,4,6). However, natural and synthetic compounds that display biological activity may not have the same chemi- cal structure, and further studies are required to isolate and characterize naturally-occurring insulin potentiating complexes.

We analyzed different foods and spices to locate good sources of this dietary factor and to see whether this factor is correlated with total chromium concentration. In this preliminary study, we report the insulin potentiating activity and chromium content of selected foods and spices.

MATERIALS AND METHODS

Beef, chicken, peas, potatoes, rice, eggs, and spaghetti were pre- pared in the diet kitchen of the Human Nutrition Research Center, Beltsville, MD. Foods for bioactivity measurements were dried at 70~ for 24 h and ground in a mortar and pestle. Salad dressing, fruit punch, ice cream, mustard, peanut butter, sherbet, strawberry jam, and spices were extracted as purchased.

All food items were shaken with a 20-fold excess (w/v) of 0.1N NH4OH for 30 min and then centrifuged at 12,000 g for 20 rain (7). The supernatants were assayed for bioactivity in the rat epididymal fat cell assay (6). The chromium content of foods and spices was determined as reported (8,9). A composite human diet sample, Reference Material 8431, recommended value 0.102 _+ 0.006 Ixg/g, was run as a check on the accuracy of analysis. Under our conditions, the chromium concentration of the composite sample was 0.092 +__ 0.006 ~g/g.

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Insulin Potentiating Factor in Foods 185

RESULTS AND DISCUSSION

It has been reported that chromium is an essential part of a dietary factor that improves glucose tolerance in chromium-deficient rats (1). Chromium has been postulated as an essential part of an insulin poten- tiating factor, but is not yet proven. The beneficial effect of chromium is related to a usable form of chromium and not total chromium. This usable form of chromium may be present in foods, as such, or can be biosynthesized within the body by most people (10).

The insulin potentiating activity and chromium content of the se- lected foods are given in Table 1. Tuna fish, vanilla ice cream, and peanut butter potentiated insulin activity by more than twofold in rat epididymal fat cell assay (6). the chromium concentration of these foods was very low, i.e., 4, 5, and 6 ng/g of food eaten, respectively. The remaining foods tested did not display insulin potentiating activity. The chromium content of these foods ranged from 1-145 ng/g of food eaten.

The insulin potentiating activity of spices and their chromium con- tent are presented in Table 2. Among the spices, apple pie spice, cinna- mon, cloves, bay leaves, and turmeric have good insulin potentiating activity. However, their chromium content did not correlate with bioac- tivity. The insulin potentiating activity of cinnamon and cloves are simi- lar, but cloves has about seven times more chromium than cinnamon (411 vs 65 ng/g). Similarly, the bioactivity of turmeric and bay leaves are the same, but the chromium content of turmeric is fourfold that of bay leaves. The insulin potentiating effect of cinnamon is higher than tur- meric (4.3 vs 3.1 ng/g), but the chromium content is 24 times less than turmeric (65 vs 1564 ng/g). Other spices that do not yield biological activity, such as basil leaves, oregano, and sage, contain high levels of Cr (1818 _+ 66, 1431 + 10, and 1058 + 80 ng/g, respectively). It is possible that spices may be contaminated with exogenous chromium during pro- cessing and/or grinding. This contaminating chromium does not potenti- ate insulin activity (6,11).

Spices are generally used in food preparations for taste, palatability, and aroma purposes. However, spices that have insulin potentiating activity may play an important role in carbohydrate metabolism. Al- though some spices are rich sources of chromium, they are used in very small quantities and would not contribute substantial amounts of total chromium to foods. However, spices that have insulin potentiation activ- ity and, presumably, increased bioavailability would be interesting to those who have impaired glucose metabolism and/or maturity onset diabetes. Regular use of these spices may improve glucose tolerance by increasing insulin efficiency.

Chromium deficiencies interfere with carbohydrate and lipid metab- olism, and severe cases may lead to diabetes mellitus and cardiovascular abnormalities. Many foods are low in endogenous chromium, but may be contaminated with chromium from external sources. Some of this

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186 Khan et al.

Table 1 Insulin Potentiat ing Activity

of Prepared and Ready to Eat Foods

Food Item

Insulin Cr potentiat ing concentrat ion,

activity' ng/g ~'

Beef (roast) 0.9 19 _ 6 Chicken 1.7 8 • 2 Cookies (butter) 1.0 15 + 2 Cookies (sugar) 1.0 8 - 1 Cookies (van. sandwich) 0.8 12 + 1 Dinner roll 1.2 34 • 5 Dressing (Thousand Island) 0.7 11 -+ t Eggs (scrambled) 0.8 1 • 5 Frosted Flakes 1.4 30 • 3 Fruit punch 1.5 3 +- 1 H o n e y Smacks 1.0 22 • 3 Ice cream (vanilla) 2.1 5 +- 1 Jelly (Strawberry) 1.4 13 • 3 Lemon sherbert 1.7 4 + 1 Mustard 1.1 29 --+ 6 Noodles 0.8 29 • 10 Peanut butter 2.9 6 + 1 Peas (cooked) 1.5 13 + v Potato (baked) 0.8 20 -+ 2 Potato (boiled) 0.8 1 • 5 Oatmeal (old fashion) 1.1 4 • 1 Oatmeal (quick) 1.1 8 • 2 Raisin Bran 1.5 145 • 14 Rice (brown) 1.3 7 +_ 1 Rice (cooked) 1.0 21 • 1 Rice Krispies 1.3 54 • 3 Rye bread 1.0 20 + 2 Shredded Wheat 1.1 7 _+ 1 Spaghetti 1.1 18 • 1 Triscuit 1,4 5 --+ 1 Tuna fish 2.2 4 • 1

"Values are an averhge of duplicate analyses. Insulin potentiating activity is the increase in activity above a low level (2 p~U) of insulin alone. A value of one denotes no activity above insulin. Measurements were as described (6), except the assay was run at pH 7,0 instead of pH 7.4.

"Values are the mean -+SD of triplicate samples.

c o n t a m i n a t i n g c h r o m i u m a p p e a r s to be a b s o r b e d a n d ut i l ized (11). F o o d p r e p a r a t i o n m e t h o d s , c o o k w a r e , g e n e r a l h a n d l i n g , a n d p r o c e s s i n g m a y be a d d i n g subs t an t i a l a m o u n t s of c h r o m i u m to f o o d s (12).

Th is w o r k d e m o n s t r a t e s tha t s e l e c t e d f o o d s a n d spices are h i g h in in su l in p o t e n t i a t i n g ac t iv i ty a n d tha t this ac t iv i ty is n o t c o r r e l a t e d w i t h to ta l c h r o m i u m . T o e p f e r e t al. (5) also r e p o r t e d " n o s ign i f ican t re la t ion-

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Insulin Potentiating Factor in Foods

Table 2 Insulin Potentiating Activity of Spices"

187

Spice Name

Insulin Cr potentiating concentration,

activity ng/g

Apple pie spice 3.2 75 + 3 Basil leaves 0.9 1818 _+ 66 Bay leaves 4.5 406 _+ 6 Black pepper 0.9 509 - 3 Caraway 0.9 94 _+ 6 Chili powder 0.7 355 • 31 Chives 0.3 561 • 26 Cinnamon 4.3 65 + 13 Cloves 5.3 411 • 26 Coriander 0.8 108 -+ 2 Garlic powder 0.6 102 • 15 Mace 0.8 684 • 38 Mint flakes 1.2 258 • 43 Mustard 0.5 28 - 2 Nutmeg 1.2 69 • 8 Onion powder 0.6 92 _+ 1 Oregano 1.3 1431 + 10 Paprika 0.9 575 • 34 Red pepper 0.8 303 • 41 Sage 0.6 1058 • 80 Turmeric 3.1 1564 • 28 Vanilla 0.2 4 _+ 0.3

"Same condi t ions as Table 1.

ship . . . b e t w e e n total c h r o m i u m and biological act ivi ty." Nei ther this s tudy nor that of Toepfer et al. es tabl ishes that glucose tolerance factor (GTF), as def ined by Mertz (1), is or is not a chromium-conta in ing c o m p o u n d . Future s tudies involving pure forms of insulin potent ia t ing complexes are n e e d e d to establ ish a direct link with c h r o m i u m and isolated insulin potent ia t ing complexes . Only a small fraction of the total c h r o m i u m in foods is associa ted with bioactivity; therefore, conclusions regarding insulin potent ia t ing factors and ch romium cannot be der ived from prel iminary data.

In summary , insulin po ten t ia t ing activity of foods and spices does not correlate with total ch romium. Spices are general ly u sed as flavor enhancers , bu t specific spices, such as c innamon, cloves, bay leaves, and turmeric, may have an addi t ional role in glucose metabol ism.

REFERENCES

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J. Agric. Food Chem. 25, 162 (1977).

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188 Khan et al.

3. A. Yamamoto, O. Wada, and H. Suzuki, J. Nutr. 118, 39 (1988). 4. J. A. Cooper, L~ F. Blackwell, and P. D. Buckley, Inorg. Chimica Acta 92, 23

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