Mulberry Helps Control Blood Sugar, and More
In case your Latin isn’t what it used to be, that quotation says, “A man will pass his summers in health, who will finish his luncheon with black mulberries.” And you thought mulberries were for the birds. Actually, birds are very fond of mulberries. Humans are less so, however, because, although mulberries are sweet and edible, they’re considered rather insipid, as berries go. With such an abundance of delicious blackberries (which mulberries resemble), raspberries, strawberries, blueberries, etc., most people just don’t care much for mulberries and are happy to let the birds feast on them.
But let’s get back to the quotation. The great Roman lyric poet Horace (his real name was Quintus Horatius Flaccus, and he lived from 65 to 8 B.C.) may have been onto something. The folk medicine of his time encompassed countless herbal remedies—in fact, botany and medicine were pretty much one and the same in those days, and remained so for about another 16 centuries—and a great variety of therapeutic benefits were ascribed to them. Some of the claims were specific, whereas others, such as Horace’s couplet about mulberries, were vague, leaving us to wonder just what it was that the ancients saw in these plants.
Mulberry leaves have long been
used in Chinese medicine for the
prevention and treatment of diabetes;
they contain compounds that
suppress high blood sugar levels.
There was probably at least a germ of truth in all their claims, though, and many of these claims have withstood the tests of time and scientific scrutiny to become accepted by modern medical practitioners as both genuine and significant. In many cases, we can now pinpoint the chemical compounds that gave these ancient herbal remedies their biological activity. Sometimes we extract the compounds from the plants so that they can be used in supplements or drugs, and sometimes we synthesize them in the laboratory for the sake of greater purity or lower cost.*
*A favorite practice of the pharmaceutical industry is to take a biologically active natural substance and synthesize novel chemical derivatives that have similar biological activities (often more pronounced, but usually with unwanted side effects that the original substance did not have). These derivatives, belonging exclusively to the drug company that made them, can be patented and sold at high prices as prescription drugs.
Mulberry Fights Arterial Plaque
Before I forget, a lot of people have asked about implementation strategies using Mulberry for blood sugar control. This page answers that and a whole lot more.
Scientists in Japan have pinpointed a number of biologically active compounds in extracts of the leaves of the white mulberry, Morus alba, a plant that silkworms are crazy about (see the sidebar).1 Not that the silkworms care, but the mulberry-leaf extract turns out to be effective in suppressing the progression of atherosclerosis, the buildup of cholesterol-rich plaque in our arteries.2 It does this, apparently, by inhibiting the oxidation of LDL-cholesterol (low-density lipoprotein, the “bad cholesterol”), which is a major factor in the development of atherosclerotic plaque.
Chances are, the only thing you knew about mulberries before today was the nursery rhyme from Mother Goose. But why dance around a mulberry bush? Wouldn’t a myrtle be as good, or perhaps a honeysuckle? Not according to the ancient Celts, who believed that dancing around a mulberry bush at the time of the summer solstice would help protect them from fairies. (Not all fairies are nice, you know—some are malicious, and they reach the height of their magic powers at the solstice.) History does not record how successful this strategy was for the Celts, but at least it led to a cute little song.
Some versions of the song call the mulberry a tree, which is botanically correct. Depending on the species—of which there are about a dozen in the genus Morus,family Moraceae—mulberry trees can grow to anywhere from 15 to 70 feet tall (some bush!). Two species are native to the United States, and two more have been naturalized here. Most of the rest are native to the Orient but are widely distributed throughout the warmer temperate regions of Eurasia, Africa, and North America. The plants have a milky sap and bear the fruit for which they are named.
One species, the white mulberry (Morus alba), is renowned as the primary food source for silkworms. Widely cultivated in its native China, this tree provides succulent leaves that the worms eat with relish (well, OK, they eat ’em straight—no relish). The beginning of silk production using mulberry leaves is generally attributed to the Chinese Empress Si-Ling, who lived five millennia ago, c. 2960 B.C. The fruit of the white mulberry (which is also found in the eastern United States) is white to pinkish, unlike the red or black berries of most other Morus species.
According to one source, white mulberry is the species that has been used exclusively in Chinese medicine since A.D. 659.1 The Chinese Pharmacopoeia (1985) lists the leaves, root bark, branches, and fruit as ingredients in medicinal preparations, but other parts, including the sap and wood ash, are also widely used. (It’s hard to imagine how wood ash could have medicinal value, except perhaps for its mineral content. The heat of the fire would have destroyed virtually all biologically active molecules. What little organic matter remained, if any, would consist of combustion-generated compounds, including some that might be carcinogenic.)
Whatever the plant parts, the Chinese prepare them in a great variety of ways. The leaves and root bark are traditionally processed with honey. Fresh leaves and fruit are sometimes juiced for internal consumption, but otherwise, all parts are dried for use in decoctions (internal use) or poultices (external use), to which many health benefits are attributed. The leaves alone contain a wide variety of nutrients, including proteins, sugars, polyphenols, flavonoids, steroids, triterpenes, vitamins, and minerals.2 No wonder the silkworms love them.
A group of nutritional scientists in India has suggested that the leaves of white mulberry might make a good food, because they’re so rich in nutrients, especially protein.3 They propose that a 1:4 mixture of mulberry-leaf powder and wheat flour would be suitable for making paratha, the most common food item of breakfast and dinner in the Indian diet. Since this predominantly vegetarian (mostly grain-based) diet is low in protein and too low in vegetables and fruits for good health, the highly nutritious, nontoxic, and inexpensive mulberry leaves are seen as a potential remedy. Paratha made according to the nutritionists’ proposal has even passed the taste test in studies with volunteers (who did not, however, start producing silk).
The Japanese researchers reached this conclusion based on their observations of the antioxidant effects of the mulberry extract on LDL-cholesterol taken from both rabbits and humans. They believe that the agents primarily (but not exclusively) responsible for this effect are two closely related compounds, isoquercitrin and astragalin. The former contains, as part of its molecular structure, the well-known antioxidant flavonoid quercetin, which is found in many foods and in a variety of nutritional supplements.
In studying the antioxidant effects of the whole mulberry-leaf extract and, separately, of the compound isoquercitrin, as well as of the compound quercetin (which is not found as such in mulberry), the researchers observed that all were effective but that isoquercitrin was somewhat less effective than the same amount of quercetin. They also reported, however, that when isoquercitrin is ingested (by mice), it is largely metabolized to quercetin. Thus, although quercetin is not found in mulberry, mulberry is still a good source for it (and the silkworms still couldn’t care less).
The antioxidant, antiatherosclerotic effects of mulberry are gratifying, of course (and here we’re making the assumption that the effects seen in laboratory and animal experiments would be seen in actual human beings as well), but there’s more to the story than that. Mulberry leaves have long been used in Chinese medicine for the prevention and treatment of diabetes, because, as we now know, they contain chemical compounds that suppress high blood sugar levels (hyperglycemia) following a carbohydrate-rich meal.
Controlling blood sugar (glucose) levels is vitally important. When these levels rise sharply, as they do after ingesting foods with a high glycemic index, such as potatoes or sweets, the body responds by producing more insulin to deal with the overload. But if this demand for more insulin occurs too strongly too often, the ability of the pancreas to produce enough insulin may become impaired, and our cells may become resistant to insulin as it tries to do its job of facilitating glucose transport through the cell walls. The result is insulin resistance, a dangerous condition that, if unchecked, leads to type 2 diabetes. Its primary cause is obesity. Generally speaking, if you are obese, your risk for diabetes is high; if not, it’s low (unless you happen to have a genetic predisposition for diabetes).
There Are Different Ways to Attack Diabetes
Diabetes is a complicated disease with many ramifications, among which are increased risks for atherosclerosis and cataracts, both of which are strongly linked to oxidative stress caused by insufficient blood levels of antioxidants. The fact that people with diabetes have significantly lower antioxidant levels than normal suggests that this disease is affected by oxidative stress—a view that is supported by the well-known clinical efficacy of lipoic acid (“the antioxidant’s antioxidant”) in preventing and treating diabetes. It is reasonable to suppose that many other antioxidants are also beneficial against diabetes, and some have indeed been proven to be effective. One of these is the compound EGCG (epigallocatechin gallate), a green-tea polyphenol that also happens to be a potent anticarcinogen.
But there are other therapeutic approaches to diabetes as well. One is through compounds that mimic the effects of insulin, such as MHCP (methylhydroxychalcone polymer), a constituent of cinnamon. Another approach is through compounds that inhibit the action of intestinal enzymes called alpha-glucosidases, whose function is to break disaccharides (double sugars, such as sucrose, maltose, and lactose) down to monosaccharides (single sugars, such as glucose, fructose, and galactose) so that they can pass through the intestinal walls into the bloodstream.
Mulberry Controls Blood Sugar
Another research group in Japan has found that white mulberry leaves contain compounds that inhibit these intestinal enzymes.3 In experiments with normal rats, they found that certain nitrogen-containing sugars in mulberry-leaf extract, notably one called 1-deoxynojirimycin, strongly inhibited the intestinal metabolism of disaccharides (especially sucrose), thereby restricting the amounts of monosaccharides that entered the circulation. They also found that pretreating the rats with mulberry extract before feeding them carbohydrates significantly suppressed the normal postprandial (after-meal) rise in blood glucose levels.
This beneficial effect occurred in a dose-dependent manner. The doses were, however, very large: 0.1–0.5 g/kg of body weight, which, for a 70-kg (154-lb) human, would be 7–35 g. (A lower dose, 0.02 g/kg, corresponding to 1.4 g for a human, was ineffective.) Nonetheless, the researchers suggested that mulberry extract might be beneficial in preventing human diabetes by suppressing intestinal alpha-glucosidase activities.
Mulberry Does Better than Prescription Drug
Some would say that there’s not much difference between rats and humans—a statement that can be interpreted on different levels. On the level of pharmacology, it is generally (but not always) true that there’s not much difference between the two species. Ultimately, however, there is no good substitute for clinical trials done on actual humans. Fortunately, a research group in India has done that for mulberry, using leaves from Morus indica (Indian mulberry), a species closely related to Morus alba.4*
*Some botanists have suggested that these two species are actually one and the same, but this remains a controversial question that can be answered only by more refined studies.5
Mulberry significantly reduced fasting
blood glucose levels in the diabetic
men, indicating that it could be
useful for controlling diabetes. It also
lowered the men’s cholesterol levels.
The Indian researchers studied the effects of mulberry on blood glucose levels, on blood lipid levels (cholesterol and triglycerides), and on lipid peroxidation in the cell membranes of erythrocytes (red blood cells). Their test subjects were 24 men, aged 40 to 60, with mild type 2 diabetes. The men were randomized to two groups: one group received two 500-mg capsules of powdered mulberry leaves three times daily, for a total of 3000 mg (3 g) daily, while the other group received a standard treatment with glibenclamide (more commonly called glyburide), an antidiabetic drug of the sulfonylurea type. The trial lasted for 4 weeks.
The results showed that, compared with glibenclamide, mulberry significantly reduced fasting blood glucose levels in the diabetic men, indicating that it could be useful for controlling diabetes. Mulberry also significantly lowered the patients’ total cholesterol, LDL-cholesterol, and triglycerides, while significantly increasing their HDL-cholesterol (high-density lipoprotein, the “good cholesterol”). By contrast, glibenclamide’s only significant effect was to lower triglycerides.
Mulberry Protects Blood-Cell Membranes
The researchers were interested in the patients’ erythrocyte membranes because these delicate structures, consisting primarily of lipids (fatty substances, including cholesterol), are subject to peroxidation, a destructive process brought about by the highly reactive molecular species known as free radicals. Such oxidative stress is normally offset by the presence of antioxidants, but the levels of these vital protective compounds are typically below normal in diabetic patients, as mentioned above. The resulting damage to the patients’ erythrocyte membranes can compromise their health in various ways—all part of the scourge of diabetes, in which excessive lipid peroxidation and its destructive effects are characteristic features.
It turned out that mulberry significantly reduced lipid peroxidation in the patients’ erythrocyte membranes, whereas glibenclamide did not. Mulberry also brought about significant reductions in the levels of lipid peroxides in the patients blood plasma and urine. The authors stated:
In conclusion, the present study provides preliminary data that suggest that mulberry therapy is capable of enhancing glycemic control in patients with type 2 diabetes. Our work suggests that serum and erythrocyte membrane lipids of diabetic patients were favorably affected by mulberry therapy.
Dance for Your Life!
Diabetes is one of the worst, yet one of the most easily preventable, of the chronic degenerative diseases that afflict us as we get older—and it’s becoming pandemic. Because of our self-indulgent lifestyle—too much rich food, too little exercise—we tend to be overweight, out of shape, and prone to high cholesterol and high blood pressure. That’s a recipe for insulin resistance and then full-blown diabetes, which opens a Pandora’s box of awful consequences.
The solution is obvious. Not so obvious, however, is the fact that there are nutritional supplements, such as mulberry, that can help us fend off diabetes while we strive to follow a healthier lifestyle. Among the many forms that such striving can take is dancing, which is probably the most enjoyable way to exercise ever invented (“the vertical expression of a horizontal desire,” as George Bernard Shaw put it). So get out there and dance! And if you should happen upon a mulberry tree … well, you’ll know what to do.
- Doi K, Kojima T, Makino M, Kimura Y, Fujimoto Y. Studies on the constituents of the leaves of Morus alba L. Chem Pharm Bull 2001;49(2):151-3.
- Doi K, Kojima T, Fujimoto Y. Mulberry leaf extract inhibits the oxidative modification of rabbit and human low-density lipoprotein. Biol Pharm Bull2000;23(9):1066-71.
- Miyahara C, Miyazawa M, Satoh S, Sakai A, Mizusaki S. Inhibitory effects of mulberry leaf extract on postprandial hyperglycemia in normal rats. J Nutr Sci Vitaminol 2004;50;161-4.
- Andallu B, Suryakantham V, Srikanthi BL, Reddy GK. Effect of mulberry (Morus indica L.) therapy on plasma and erythrocyte membrane lipids in patients with type 2 diabetes. Clin Chim Acta 2001;314:47-53.
- Vijayan K, Srivastava PP, Awasthi AK. Analysis of phylogenetic relationship among five mulberry (Morus) species using molecular markers. Genome2004;47:439-48.
Caution: If you have diabetes, do not take any supplement that may affect your blood sugar levels without first consulting your physician. Diabetes is a serious disease requiring careful professional management.