Grape seed extract, or GSE, is now a hugely popular dietary supplement that's said to harness the power of grape seeds in either capsule, tablet or liquid form. It's been claimed to encourage weight loss, promote younger-looking skin, improve heart health and even kill cancer cells. But what does the science have to say about these supposedly power-packed pills?
One of the most exciting things about GSE is that it's showing promise as a safe and effective anticancer agent. While chemotherapy, the conventional cancer therapy, is known to kill good cells along with the bad, GSE is apparently more selective.
In a study by University of Colorado researchers, GSE was found to kill head and neck cancer cells in the lab while leaving healthy cells unharmed. The extract, which was tested in both cell cultures and in mice, was shown to damage cancer cell DNA as well as stop the pathways that allow its repair. This means that the cancer cells weren't able to grow and ended up dying instead.
Despite this dramatic effect, the healthy cells were left intact and the researchers saw absolutely no toxic effects to the mice themselves (Carcinogenesis, 2012 Feb 22; Epub ahead of print).
Similar findings were reported by scientists in Chongqing, People's Republic of China. Their test-tube study on leukaemia cells showed that GSE forced the cancer cells to commit suicide (known officially as 'apoptosis') while, again, the normal cells were left unharmed (Clin Cancer Res, 2009; 15: 140-9).
Clinical trials (in people) are now needed to see whether the same thing happens in patients taking GSE.
There's also evidence to suggest that taking GSE might help to keep your heart healthy. In a study by University of California at Davis researchers, GSE supplements significantly lowered blood pressure in a group of people with the metabolic syndrome-a combination of disorders that increase your risk of having heart disease and diabetes. Some of the participants had normal blood pressure, but most had 'prehypertension', when blood pressure falls somewhere between what is considered normal and high blood pressure.
The researchers found that both low-dose (150 mg/day) and high-dose (300 mg/day) GSE significantly reduced blood pressure compared with a placebo (dummy pills) after four weeks of treatment. What's more, these changes were seen across the board, not just in those with prehypertension. The researchers were also happy to see that there was no dangerous drop in blood pressure in the 'normal' participants (Metabolism, 2009; 58: 1743-6).
Another study showed that GSE might be able to reduce the risk of heart disease in people with type 2 diabetes-a group known to be more prone to high blood pressure, heart attacks and stroke.
Those given a daily dose of 600 mg of GSE saw several physical changes, including improved blood glucose levels, which the researchers say may bring about long-term benefits for the heart (Diabet Med, 2009; 26: 526-31).
Other evidence points to GSE's cholesterol-lowering potential. In people with high cholesterol, 100 mg of GSE twice daily significantly cut levels of LDL ('bad') cholesterol when taken in combination with chromium (200 mcg twice daily)(J Med, 2000; 31: 227-46).
GSE is a common ingredient in anti-ageing creams as it's rich in antioxidants-those free-radical fighters thought to slow the ageing process and protect the skin. According to scientists from the Food Research Center in Guelph, Canada, "extensive research" in the lab suggests that GSE can "bond with collagen, promoting youthful skin, cell health, elasticity, and flexibility" (J Med Food, 2003; 6: 291-9). However, there don't appear to be any clinical trials showing such anti-ageing benefits in people.
One Danish study, however, has looked at the effect of a supplement called Imedeen Prime Renewal on skin ageing in postmenopausal women. The supplement contained GSE along with fish protein, polysaccharides, vitamins C and E, zinc, and extracts of white tea, tomato, soy and chamomile. After six months, the researchers claimed that women taking Prime Renewal had better skin condition, structure and firmness compared with those taking a dummy pill (Eur J Clin Nutr, 2006; 60: 1201-6).
Another skin-focused study has indicated that GSE might be useful if you suffer from 'cholasma', also known as 'melasma', where the pigmentation of the facial skin appears brown and blotchy. A small trial in Japan showed that cholasma improved after six months of GSE supplementation (Phytother Res, 2004; 18: 895-9).
A small trial by a team from Maastricht University in The Netherlands found that GSE might be a helpful slimming aid. They decided to test the extract in people after previous research in rats had suggested that it had satiating effects, cutting the amount of food the animals ate. Also, test-tube studies had shown GSE to stimulate the breakdown of fat.
In this study in people, 50 normal-weight and overweight men and women took 300 mg of GSE before breakfast, lunch and dinner for three days. After a 'washout' period of three weeks, the participants then repeated the test while taking a placebo pill before every meal.
Although the team saw no differences in the amount of food eaten (energy intake) under the two conditions overall, in those who had higher-than-average energy requirements (because they indulged in more exercise, for example), their energy intakes were reduced by 4 per cent after GSE compared with the dummy pills. In fact, roughly half the group had higher-than-average energy requirements.
Although we don't know whether this positive effect would be maintained over the long run, the researchers believed that if the energy intakes of the participants remained 4-per-cent lower for a year, it could result in either weight loss or prevention of weight gain of nearly 4 kg/year (Eur J Clin Nutr, 2004; 58: 667-73).
Factfile: What's so great about grape seed?
The seeds of the grape, as well as the skin, contain numerous active components known to have health-boosting effects, including flavonoids, polyphenols, anthocyanins, proanthocyanidins, procyanidins and resveratrol. These are all potent antioxidants, particularly proanthocyanidins, which have 20 times more antioxidant power than vitamin E and 50 times more than vitamin C (J Med Food, 2003; 6: 291-9). Antioxidants are substances that can protect your cells against the effects of damaging free radicals (molecules created when oxygen interacts with certain other molecules), thought to play a role in a broad range of diseases and conditions.
Grape seed extract (GSE) also displays anti-inflammatory and antimicrobial activities, and may well have heart-, liver- and brain-protective effects (Phytother Res, 2009; 23: 1197-204).
At the same time, GSE appears to be safe, although it has the potential to interfere with certain medications such as blood thinners (for example, warfarin).
Factfile: Other potential benefits
Evidence, at least in animals, suggests that GSE may be useful for the following conditions.
- Alzheimer's. GSE may be able to block the formation of the abnormal protein plaques that disrupt normal brain function in Alzheimer's disease (J Alzheimers Dis, 2011; 26: 657-66).
- Huntington's disease. GSE, when fed to mice, slowed the progressive loss of motor (movement-related) skills caused by this neurodegenerative disease. These mice also lived longer compared with the animals fed inactive pills for comparison (Transl Neurosci, 2010; 1: 95-100).
- Hair loss. Proanthocyanidins from grape seeds promoted the growth of hair follicle cells taken from mice and tested in the lab (Acta Derm Venereol, 1998; 78: 428-32).
- Arthritis. Mice with rheumatoid arthritis showed improvement after being injected with GSE. The extract appeared to reduce joint inflammation as well as bone and cartilage erosion (Immunol Lett, 2009; 124: 102-10).
WDDTY VOL. 23 NO. 1, APRIL 2012