Grapes contain flavonoids. Flavonoids are interesting substances also found in fruits, nuts, vegetables, seeds and red wine. They are of interest to us because they act as antioxidants.
Researchers conducted a study of three women and 12 men who had known coronary heart disease. The average age of the group was 62 years. For 14 days participants were asked to drink approximately two-thirds of a quart – or 21 ounces – of Welch’s 100% Concord Grape Juice. A study was then undertaken of the diameter of an artery in the arm, and of the ability of low-density lipoprotein cholesterol (LDL) to be oxidized. LDL is often referred to as ‘bad cholesterol’. It is thought that the oxidation of the LDL is an important and necessary step for the LDL to enter blood vessel walls, causing arteriosclerosis
Results indicated that after the grape juice diet, the LDL was more resistant to oxidation, and that blood vessels possessed a greater ability to dilate. Both these reactions are likely to reduce the risk of heart attacks and coronary heart disease.
Comments on The Grape Juice Diet
The aforementioned research is a good, basic introductory study. However, that is all it is at this stage. It is uncertain whether correlating findings in the arm, with blood vessels in the heart, is in fact meritorious.
The study’s authors do emphasize that any benefits from the red wine is not alcohol related, but in fact from the flavonoids in the grapes used in red wine production. Flavonoids are a complex group of chemicals. While they do have different functions, these functions often overlap. Their complicated names are not generally household words:
- Tannic acid
- Querecetin – a very active antioxidant
- Catechin – a powerful inhibitor of LDL oxidation
It should also be considered that perhaps any positive effects revealed by this study might, in fact, be attributed to substances found in grapes other than flavonoids.
It appears that alcohol, particularly red wines, is beneficial in reducing the risk of heart attack. This reduction has been primarily attributed to:
- Diminished clotting tendencies – clotting can be the trigger for a heart attack
- Raised blood levels of protective lipoprotein cholesterol (HDL) or good cholesterol
It is noted, that in this study, the grape juice did not increase HDL levels.
Whilst it has not been definitively proven, the disruption of the LDL oxidation seems to be a key factor in reducing the likelihood of arteriosclerosis development.
It is still unsure whether flavonoids really do reduce the risks of heart attack and coronary heart disease – but, to a moderate extent, they may. Further carefully controlled and documented studies need to undertaken to determine if grape juice is as effective as red wine. That would certainly be beneficial to those who don’t drink wine, and would avoid other risks, such as alcoholism, for those who do.
However, many questions remain, including:
- Would a combination of drinking grape juice and a couple of glasses of wine increase potential benefits?
- What is the recommended daily intake of grape juice?
- Can grape juice really reduce the risk of a heart attack? The answer to this question would be very different to merely demonstrating that grape juice may assist in the dilation of blood vessels or reduction of LDL oxidation
- Are the benefits of grape juice directly linked to the flavonoids in the grapes?
- What place does grape juice or other flavonoids have in your diet?
The answer to the last question is that vegetables and fruit should make up a major portion of your diet. Vegetables and fruit are associated with the reduction of certain cancers, and the reduction in risk of heart attack and, to a lesser extent, strokes. However, whilst vegetables and fruits do contain flavonoids they also contain numerous other potentially health boosting substances. It is uncertain whether the benefits reaped from consuming vegetables and fruits are attributable to their flavonoids content.
Resveretrol is another constituent of grapes. It too may have beneficial properties against heart disease and cancer. However, more definitive studies would need to be undertaken before any recommendations could be made.