In traditional Chinese medicine, which has been blended with Western knowledge and continues to be practiced widely throughout the East, ginseng is prescribed as a tonic for stress and fatigue. But despite the abundance of Chinese literature beginning in the first century AD describing the use and benefits of ginseng, they contain surprisingly few double-blind case-controlled studies. This deficiency began to be addressed only in the latter part of the twentieth century.

In scientific studies that meet modern Western standards, ginseng has been found effective for combatting feelings of fatigue [ref], reducing the frequency of winter colds [ref], improving cognitive function in Alzheimer’s patients [ref], reducing cancer risk [ref, ref], and treating erectile dysfunction [ref]. Ginseng has also been used by cancer patients to mitigate DNA damage from radiation therapy [ref]. But life extension? There is one small study in humans suggesting that ginseng lowers overall mortality in men and cancer risk in women. (It is difficult to interpret the study’s finding that ginseng failed to lower cancer mortality in men, or overall mortality in women. This is a reminder that long-term human epidemiology is a difficult discipline, full of subtleties about correlated behaviors, and ambiguities about causality. In the present case, the smoking rates differed between men and women.) I have found only two studies that asked whether ginseng might increase life span in mice, and both were negative [1979, 2014]. (Perhaps the take-home message is that if the gods had intended ginseng for mice, the root would be shaped like a mouse.)

Related to longevity, there is good support for cancer prevention, but the best-established benefit of ginseng is for insulin sensitivity. This is nothing to sneeze at. As we get older, we all develop insulin tolerance, and the body pours out more and more insulin to compensate. What would be considered diabetes in a young person is considered “normal aging” in a 60-year-old. This proto-diabetes contributes to cancer, heart disease, and all the other maladies of old age. Can ginseng help?

A 2005 study found that rats fed a high-fructose diet developed insulin resistance more slowly when ginseng was added to their diets. Last week, it was reported that ginseng improves insulin sensitivity and decreases weight gain in mice on a high-fat diet. A Canadian study (2000) found that ginseng could dampen the blood sugar spike following a meal of pure sugar…and there are many studies in the same vein, for animals an humans.

The standard (Western) treatment for high blood sugar is metformin, which is a life extension drug in rodents, and probably in people. How does ginseng compare to metformin? The good news is that ginseng acts in a way complementary to metformin, so their benefits add, or possibly synergize. Metformin decreases the chemical production of sugar in the liver. Ginseng pulls sugar out of the blood and burns it. Both increase insulin sensitivy.

In addition to suppressing hepatic glucose production, metformin increases insulin sensitivity, enhances peripheral glucose uptake (by inducing the phosphorylation of GLUT4 enhancer factor), decreases insulin-induced suppression of fatty acid oxidation, and decreases absorption of glucose from the gastrointestinal tract. [Wikipedia]

One mechanism of ginseng’s anti-diabetic action involves the mitochondrial metabolism. Mitochondria are the part of the cell that turn sugar (fuel) into the form of energy the cell can use (ATP). Several studies have confirmed that ginseng improves the mitochondria’s efficiency in creating ATP [for example].

In a Korean study published in English [2007], metformin and a metabolite of ginseng were compared directly in their effect on mouse sugar/insulin metabolism. Benefits were found to be best for metformin and the ginseng metabolite taken together.

Another Korean study [2008] used mice that were genetically modified to give them diabetes. Those treated with 100mg/kg of ginseng for 10 weeks had reductions in fasting glucose that were about ⅓ as great as those treated with 300mg/kg of metformin.

Both ginseng and metformin contribute modestly to weight loss. Serious side-effects from metformin are rare, but ginseng is considered even safer.

These two reviews [2003, 2011] point out that the data is thin and sample size small compared to standard pharmaceutical studies. Yes, larger studies with better controls are warranted for ginseng, both in rodents and in people. But who will fund studies of a 4,000-year-old herb that grows widely in the wild and cannot be patented? All too frequently, capitalism and medical care proves to be a dysfunctional combination. Most modern pharmaceutical products had their origins in traditional herbal medicine, and it is a crime against humanity that patent law and profit motives are holding back the scientific exploration of therapeutical potential of thousands of traditional herbs.

The Bottom Line

The insulin metabolism is a natural modifier of the rate of aging, worth a few years of added life. It is the easiest and best-studied means that we have to affect our own longevity. Low calorie diets, intermittent fasting, low-carb diets, and exercise all work through the insulin metabolism to increase life expectancy. Metformin and ginseng are supplemental ways we can address our own aging through the insulin pathway. (Traditional Chinese medicine says that ginseng should not be taken daily for more than a few weeks without a break.)

As we age, we are all losing insulin sensitivity. Everything we do to keep insulin sensitivity up is helpful, but we know that this pathway can saturate, so we don’t expect additive benefits from supplements and dietary changes. In this context, the suggestion that metformin and ginseng may synergize is very promising.

Both metformin and ginseng are likely to be more effective for people who are overweight or have high blood sugar. For people who exercise a great deal and are already trim, the benefits may be small–unless you’re interested in having more energy, better mental focus, fewer colds and enhanced libido.

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This article originally appeared on Josh’s blog Aging Matters here.