Grapes often get a bad rap as being too sweet or sugary, but they are a nutrient-dense fruit and pack a host of health benefits. Eating grapes can help support brain and heart health. Further, the vitamins and minerals in grapes may provide an immunity boost and more.
There are so many health benefits from eating grapes that they are now classified as a "functional food." Grapes are a rich source of bioactive molecules, which contribute to the health benefits. Grape consumption is linked to reduced incidence of cardiovascular disease and its major risk factors, including high blood pressure. When a food is referred to as being a "functional food," it means it can be considered a form of medical nutrition therapy. As such, grapes may be part of a "food as medicine" prescription to help those with high blood pressure.
Studies have shown that consuming grapes results in a reduction of inflammatory markers around the liver and kidneys. Some of the bioactive phytochemicals of grapes include phenolic compounds such as hydroxycinnamic acids, anthocyanins, proanthocyanidins and stilbenes.
"Grapes contain a key nutrient called resveratrol that might offer a lot of health benefits including protecting against eye problems, cardiovascular disease, cancer, improving microbiome diversity (in the gut), and other health conditions," said Dr. Vijaya Surampudi, an associate professor of medicine at UCLA Health, Los Angeles.
A clinical study published in the scientific journal Nutrients found that consuming grapes significantly increased the diversity of bacteria in the gut, which is considered essential to good health overall. Additionally, consuming grapes significantly decreased cholesterol levels, as well as bile acids, which play an integral role in cholesterol metabolism.
The findings suggest a promising new role for grapes in gut health and reinforce the benefits of grapes on heart health. In this study, healthy subjects consumed the equivalent of one and a half cups of grapes per day for four weeks. After four weeks of grape consumption, there was an increase in microbial diversity as measured by the Shannon Index, a commonly used tool for measuring diversity of species.
Among the beneficial bacteria that increased was Akkermansia, a bacteria of keen interest for its beneficial effect on glucose and lipid metabolism, as well as on the integrity of the intestinal lining. Additionally, a decrease in blood cholesterols was observed including total cholesterol by 6.1% and LDL cholesterol by 5.9%. Bile acids, which are linked to cholesterol metabolism, were decreased by 40.9%.
Dr. Surampudi, who helps run the UCLA Medical Weight Management Clinic, said red and green grapes have similar nutritional benefits, but do have some differences.
"Darker grapes may have more antioxidants than green grapes. Red grapes contain anthocyanin, quercetin, and catechin, which have anti-inflammatory properties and may help prevent cancer, diabetes and cardiovascular disease. Green grapes contain flavanols and polyphenols," said Dr. Surampudi.
You can eat grapes daily, but she cautioned that for some people it can worsen acid reflux or increase blood glucoses depending on the person and their medical history. So, a half cup to 1 cup of grapes daily is what she recommends for adults 50 and older.
She noted that grape juice might increase how quickly the liver breaks down some medications.
"Grape extract might slow blood clotting. Taking grape extract or high amounts in grape juice along with medications that also slow blood clotting might increase the risk of bruising and bleeding," said Dr. Surampudi.
Eating whole fruits in moderation clearly is better. However, the most important thing is considering your dietary pattern.
"One fruit or vegetable cannot provide all its benefits in the setting of an unhealthy dietary pattern. It has to work together with your overall diet. Whole foods like vegetables and fruits are always more beneficial to your health partnered with a healthy dietary pattern," said Dr. Vijaya Surampudi, who also is the co-creator of the newly developed Adult Nutrition Support Services Program at UCLA.
Grape consumption may benefit eye health in older adults
In a recent randomized, controlled human study, consuming grapes for 16 weeks improved key markers of eye health in older adults. The study, published in the scientific journal Food & Function, looked at the impact of regular consumption of grapes on macular pigment accumulation and other biomarkers of eye health. This was the first human study on this subject, and the results reinforce earlier studies where consuming grapes was found to protect retinal structure and function.
As a person ages, the risk of eye disease and vision problems increases significantly. Key risk factors for eye disease include oxidative stress and high levels of ocular advanced glycation end products (AGEs). AGEs may contribute to many eye diseases by damaging the vascular components of the retina, impairing cellular function, and causing oxidation. Dietary antioxidants can decrease oxidative stress and inhibit the formation of AGEs, with possible beneficial effects on the retina, such as an improvement in Macular Pigment Optical Density (MPOD).
In this study, 34 older adults consumed either grapes (equivalent to 1 and a half cups of grapes per day) or a placebo for 16 weeks. The grape eaters showed a significant increase in MPOD, plasma antioxidant capacity, and total phenolic content compared to those on placebo. Those who didn't consume grapes saw a significant increase in harmful AGEs, as measured in the skin.
There is a variety of foods that benefit eye health and only recently have studies been done looking at red and green grapes. "Grapes are a good source of vitamins, minerals and fiber. However, eating grapes daily cannot undo a dietary pattern that includes a lot of ultra processed foods," said Dr. Surampudi.
