Fruit & vegetables - news reports
About these topic collections
I’ve been reporting on memory research for over ten years and these topic pages are simply collections of all the news items I have made on a particular topic. They do not pretend to be in any way exhaustive! I cover far too many areas within memory to come anywhere approaching that. What I aim to do is provide breadth, rather than depth. Outside my own area of cognitive psychology, it is difficult to know how much weight to give to any study (I urge you to read my blog post on what constitutes scientific evidence). That (among other reasons) is why my approach in my news reporting is based predominantly on replication and consistency. It's about the aggregate. So here is the aggregate of those reports I have at one point considered of sufficient interest to discuss. If you know of any research you would like to add to the collection, feel free to write about it in a comment (please provide a reference).
A study in which 23 healthy volunteers ate half a kilo of strawberries every day for a month has found that their levels of bad cholesterol and triglycerides reduced significantly.
"Sprouted" garlic — old garlic bulbs with bright green shoots emerging from the cloves — have been found to have even more heart-healthy antioxidant activity than fresh garlic.
Data from AREDS2, involving 4,203 older adults with age-related macular degeneration, has found that daily dietary supplements of either omega-3 polyunsaturated fatty acids (also found in fish) or lutein and zeaxanthin (nutrients found in green leafy vegetables) were not associated with reduced risk for cardiovascular disease (CVD).
A review of 19 studies involving over 162,000 people has found that adherence to the Mediterranean diet was associated with a 21% reduced risk of diabetes, with a greater effect (27%) for those at high risk for cardiovascular disease. The association was found in both European and non-European groups.
The research was presented at the American College of Cardiology's 63rd Annual Scientific Session.
A very large Italian study provides more evidence that the Mediterranean diet reduces inflammation, with their finding that those with a greater adherence to such a diet had significantly lower levels of platelets and white blood cells. These are both inflammatory markers: high platelet counts are associated with both vascular disease and non-vascular conditions such as cancer, and a high white blood cell count is a predictor of ischemic vascular disease.
A small trial involving seven older adults with insomnia has found that when they consumed 8 ounces of tart cherry juice twice daily for two weeks, they were able to sleep more than an hour longer each night (averaging 84 minutes) compared to when they took the placebo, and their sleep tended to be more efficient.
Montmorency tart cherries are a natural source of melatonin, a hormone that helps regulate the sleep-wake cycle. The juice also helped to increase the availability of tryptophan, an essential amino acid and a precursor to serotonin that helps with sleep.
Preliminary studies have demonstrated that grape skin extract exerts a novel inhibitory activity on hyperglycemia and could be developed to aid in diabetes management.
A finding that free radicals promote longevity in the roundworm challenges the theory that free radicals (oxidants) are damaging and cause aging.
Like us, guinea pigs can’t make vitamin C, but must obtain it from their diet. This makes them a good model for examining the effects of vitamin C deficiency.
In a recent study looking specifically at the effects of prenatal vitamin C deficiency, 80 pregnant guinea pigs were fed a diet that was either high or low in vitamin C. Subsequently, 157 of the newborn pups were randomly allocated to either a low or high vitamin C diet (after weaning), creating four conditions: high/high (controls); high/low (postnatal depletion); low/high (postnatal repletion); low/low (pre/postnatal deficiency). Only males experienced the high/low condition (postnatal depletion).
Only the postnatal depletion group showed any effect on body weight; no group showed an effect on brain weight.
Nevertheless, although the brain as a whole grew normally, those who had experienced a prenatal vitamin C deficiency showed a significantly smaller hippocampus (about 10-15% smaller). This reduction was not reversed by later repletion.
This reduction appeared to be related to a significant reduction in the migration of new neurons into the dentate gyrus. There was no difference in the creation or survival of new neurons in the hippocampus.
This finding suggests that marginal deficiency in vitamin C during pregnancy (a not uncommon occurrence) may have long-term effects on offspring.
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Full text is available at http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048488
Over the years, I have reported on several studies that have found evidence that colorful berries — blueberries in particular (but I think that’s more of an artifact, due to the relative cheapness of these berries in North America) — benefit older brains. Indeed, I myself consume these every day (in my lunch smoothie) for this very reason (of course, the fact that they taste so good doesn’t hurt!).
But to date these studies have involved rodents or only very small numbers of humans. Now a new study analyzes data from the very large and long-running Nurses' Health Study, which has questioned 121,700 female, registered nurses about their health and lifestyle since 1976. Since 1980, participants were also asked about their frequency of food consumption. Between 1995 and 2001, memory was measured in 16,010 participants over the age of 70 years (average age 74), at 2-year intervals.
The study found that those women who had 2 or more servings of strawberries and blueberries every week had a slower rate of cognitive decline. The effects were equivalent to some 1.5-2.5 years of normal cognitive aging.
While the researchers cannot completely rule out the possibility that higher berry consumption is associated with slower cognitive decline because of its association with some other factor that affects brain aging, they did take into account a large number of potentially confounding factors, including: education, smoking history and status, antidepressant use, BMI, blood pressure, cholesterol, diabetes, physical activity, total calorie intake, fish consumption, alcohol use, overall diet scores, and various indirect measures of socioeconomic status.
Moreover, the findings are both consistent with both animal and cell studies, and with what we know about how the brain ages. The ‘magic’ ingredient of these berries is thought to lie in their flavonoids (particularly anthocyanidins), which have powerful antioxidant and anti-inflammatory properties. It’s thought that berries help the brain stay healthy both because they contain high levels of antioxidants, which protect cells from damage by harmful free radicals, and because they change the way neurons in the brain communicate, protecting against inflammation and oxidative stress.
As a rule of thumb, the deeper the color of the berry (or other fruit or vegetable), the more flavonoids it has. You can see a list of anthocyanin-rich foods here (acai isn’t in the list, but it also has a very high rating).
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Full text available at http://www.napavalley.edu/people/esullivan/Documents/General%20Psycholog...
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A study involving 676 children (7-9) in rural Nepal has found that those whose mothers received iron, folic acid and vitamin A supplementation during their pregnancies and for three months after the birth performed better on some measures of intellectual and motor functioning compared to offspring of mothers who received vitamin A alone. However, there was no significant benefit for those whose mothers received iron, folic acid and zinc (plus vitamin A), or multiple micronutrients.
A negative effect of adding zinc is consistent with other research indicating that zinc inhibits iron absorption. Interestingly, new “ground-breaking” research demonstrates further the complexity of iron’s effects on the body. The researcher argues that many neurodegenerative diseases (such as Alzheimer’s) are partly caused by poorly bound iron, and it is vital to consume nutrients which bind iron and prevent the production of the toxins it will otherwise produce.
Such nutrients include brightly-colored fruits (especially purple) and vegetables, and green tea.
It’s also argued that Vitamin C is only beneficial if iron is safely bound, and if it’s not, excess Vitamin C might be harmful.
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Following on from previous studies showing that drinking beet juice can lower blood pressure, a study involving 14 older adults (average age 75) has found that after two days of eating a high-nitrate breakfast, which included 16 ounces of beet juice, blood flow to the white matter of the frontal lobes (especially between the dorsolateral prefrontal cortex and anterior cingulate cortex) had increased. This area is critical for executive functioning.
Poor blood flow in the brain is thought to be a factor in age-related cognitive decline and dementia.
High concentrations of nitrates are found in beets, as well as in celery, cabbage and other leafy green vegetables like spinach and some lettuce. When you eat high-nitrate foods, good bacteria in the mouth turn nitrate into nitrite. Research has found that nitrites can help open up the blood vessels in the body, increasing blood flow and oxygen specifically to places that are lacking oxygen.
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Inflammation in the brain appears to be a key contributor to age-related memory problems, and it may be that this has to do with the dysregulation of microglia that, previous research has shown, occurs with age. As these specialized support cells in the brain do normally when there’s an infection, with age microglia start to produce excessive cytokines, some of which result in the typical behaviors that accompany illness (sleepiness, appetite loss, cognitive deficits and depression).
Now new cell and mouse studies suggests that the flavenoid luteolin, known to have anti-inflammatory properties, apparently has these benefits because it acts directly on the microglial cells to reduce their production of inflammatory cytokines. It was found that although microglia exposed to a bacterial toxin produced inflammatory cytokines that killed neurons, if the microglia were first exposed to luteolin, the neurons lived. Exposing the neuron to luteolin had no effect.
Old mice fed a luteolin-supplemented diet for four weeks did better on a working memory test than old mice on an ordinary diet, and restored levels of inflammatory cytokines in their brains to that of younger mice.
Luteolin is found in many plants, including carrots, peppers, celery, olive oil, peppermint, rosemary and chamomile.
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A number of studies have found evidence that fruits and vegetables help fight age-related cognitive decline, and this has been thought to be due to their antioxidant and anti-inflammatory effects. A new study shows there may be an additional reason why polyphenols benefit the aging brain. One reason why the brain works less effectively as it gets older is that the cells (microglia) that remove and recycle biochemical debris not only fail to do their housekeeping work, but they actually begin to damage healthy cells. Polyphenols restore normal housekeeping, by inhibiting the action of a protein that shuts down the housekeeping (autophagy) process.
While many fruits and vegetables are good sources of polyphenols, berries and walnuts, and fruit and vegetables with deep red, orange, or blue colors, are particularly good.
Poulose, S. & Joseph, J. 2010. Paper presented at the 240th National Meeting of the American Chemical Society.
A number of rodent studies have shown that blueberries can improve aging memory; now for the first time, a human study provides evidence. In the small study, nine older adults (mean age 76) with mild cognitive impairment (MCI) drank the equivalent of 2-2 l/2 cups of a commercially available blueberry juice every day. After three months they showed significantly improved paired associate learning and word list recall. The findings will of course have to be confirmed by larger trials, but they are consistent with other research.
A companion study involving 12 older adults (75-80) with MCI found that those who drank a pure variety of Concord grape juice for 12 weeks also saw their performance progressively improve on tests in which they had to learn lists and remember items placed in a certain order.
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A pilot study involving 21 institutionalized individuals with moderate-to-severe Alzheimer’s found that, although drinking two 4-oz glasses of apple juice daily for a month produced no change in the Dementia Rating Scale or in the Activities of Daily Living measure, there was a significant (27%) improvement in behavioral and psychotic symptoms. The largest changes occurred in anxiety, agitation, and delusion.
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Full text is available free for a limited time at http://aja.sagepub.com/cgi/reprint/25/4/367.
Older news items (pre-2010) brought over from the old website
Drinking Concord grape juice may improve memory in older adults
A small pilot study, involving only 12 older adults with early memory decline, has found that those who drank Concord grape juice daily for a 12-week period showed significant improvement in list learning compared to those taking a placebo, and trends suggested improved short-term retention and spatial memory.
The results were presented at the 38th annual scientific meeting of the American Aging Society in Boulder, Colo., May 30-June 2, 2008.
How blueberries help the aging brain
An animal study has found that supplementing the regular diet of older animal with blueberries over a 12-week period, produced improvements in spatial working memory tasks emerged within three weeks. This improvement was associated with the activation of the protein CREB and increases in the level of BDNF in the hippocampus. Blueberries are a major source of flavonoids, in particular anthocyanins and flavanols.
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Blackcurrants may protect against Alzheimer's
A cultured cell study has found that compounds in blackcurrants strongly protect neuronal cells against the types of stress caused by dopamine and amyloid-b, a peptide associated with Alzheimer's disease. Blackcurrants and boysenberries also contain anthocyanins and polyphenolics. Those that are darker (like British blackcurrants) have more anthocyanins and are likely to be more potent. Compounds from these berries are already known to act as antioxidants, but a role in neuroprotection has not been demonstrated previously.
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Antioxidant-rich diets reduce brain damage from stroke in rats
A new rat study suggests antioxidant-rich fruits and vegetables may limit brain damage from stroke and other neurological disorders. The study built upon previous research showing that diets enriched with blueberries, spinach or spirulina reversed normal age-related declines in memory and learning in old rats, and found that the same diet significantly reduced brain cell loss and improved recovery of movement in rats who had an ischemic stroke induced. The size of the stroke in the rats fed blueberry or spinach supplements was half that seen in the brains of untreated rats. Rats fed spirulina-enriched diets had stroke lesions 75% smaller than their untreated counterparts.
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Diet, exercise, stimulating environment helps old dogs learn
A new study of beagles provides more evidence that diet and mental stimulation are important in reducing or preventing age-related cognitive decline. The study, involving 48 older beagles (aged 7 to 11), compared four combinations of behavioral enrichment (regular exercise and lots of mental stimulation) and supplementation of diet with antioxidants had on a beagle's ability to learn: regular diet and regular experience; regular diet and enriched experience; regular experience and an enriched diet; and enriched diet and an enriched experience. The study followed the beagles over two years. Those in the groups with either an enriched diet or enriched environment did better than those without either, but those who had both the enriched diet and an enriched environment did noticeably better than all the rest.
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More support for the benefits of blueberries
Several recent studies have provided evidence for the benefits of blueberries in preventing age-related cognitive decline. Consistent with this, and with the linking of cholesterol levels and age-related cognitive decline, is a new study suggesting a compound in blueberries may lower cholesterol as effectively as a commercial drug, with the potential for fewer side effects. The compound pterostilbene is an antioxidant that is similar to resveratrol, an antioxidant identified in grapes and red wine that is also believed to lower cholesterol. Pterostilbene has also been implicated in helping fight cancer, as well as having anti-diabetic properties.
The findings were presented on August 23 at the 228th national meeting of the American Chemical Society.
Grape juice may help memory in older adults
A study of older rats has found that Concord grape juice significantly improved their short-term memory in a water maze test as well as their neuro-motor skills in some coordination, balance and strength tests. The results are similar to those found with blueberries. Concord grape juice has the highest total antioxidants of any fruits, vegetables or juices tested (I assume the point of using “Concord” grape juice is the concentration of grape juice, not that this effect is specific to Concord grapes – although the fact that it is a “purple” grape juice is probably significant).
The preliminary report was presented at the 1st International Conference on Polyphenols and Health recently held in Vichy, France.
More support for value of antioxidants in protecting against age-related cognitive decline
Several studies have come out supporting the value of a diet rich in antioxidants to help stave off cognitive impairment in old age. A recent study has found that old dogs on an antioxidant-rich diet performed as well as young animals on a variety of cognitive tests. Young dogs did not benefit from the diet. Two years ago, researchers reported that a blueberry-enriched antioxidant diet may prevent age-related deterioration of object recognition memory in aged rats. A new report, from a study of the same rats, reveals that the diet also prevented an age-related increase in a protein (NF-kappaB) that responds to oxidative stress, a probable cause of brain aging. This adds to growing evidence that a buildup of oxidative damage is an important factor in brain aging. Another rat study has found that blueberries can help lessen some of the damage caused by a brain injury.
The research was presented at the 2003 annual meeting of the Society for Neuroscience.
Apples fight memory loss
The study involved adult and old mice (some engineered to develop Alzheimer's-like symptoms) being fed either a standard diet, a nutrient-deficient diet, or a nutrient-deficient diet supplemented with apple juice concentrate. The mice on the apple juice-supplemented diet showed an increased production of acetylcholine in their brains and performed significantly better on maze tests. The amount of consumption was comparable to humans drinking approximately two 8 oz. glasses of apple juice or eating 2-3 apples a day. The findings also suggest that the apple-supplemented diet was most helpful in the framework of an overall healthy diet. Acetylcholine levels declined in both adult and old mice on the nutrient-deficient diet.
Chan, A., Graves, V. & Shea, T.B. 2006. Apple juice concentrate maintains acetylcholine levels following dietary compromise. Journal of Alzheimer's Disease, 9(3), 287-291.
Apple consumption protects against age-related cognitive decline
Previous research has found apple juice concentrate alleviated cognitive decline in genetically engineered mice compromised by a deficient diet. A study in normal, aging mice has now found that regular consumption of apple juice (in the context of a balanced diet) protected against the oxidative damage to brain cells that occurs in normal aging. Further, stronger mental acuity resulted when the mice consumed the human equivalent of 2-3 cups of apple juice or 2-4 apples a day. Apples are high in antioxidants.
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Compound in apples may help fight Alzheimer's disease
Researchers are recommending that apples may be a particularly beneficial food to protect against Alzheimer’s. A study that exposed groups of isolated rat brain cells to varying concentrations of either quercetin or vitamin C supports the theory that quercetin protects against cellular damage. A particularly good source of quercetin is apples — mainly in the skin. In general, red apples tend to have more of the antioxidant than green or yellow ones. Other foods containing high levels of quercetin include onions, which have some of the highest levels of quercetin among vegetables, as well as berries, particularly blueberries and cranberries.
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Plant flavonoid reduces inflammatory response in the brain
Cell and mouse studies have found that luteolin, a plant flavonoid available in abundance in celery and green peppers, has a dramatic effect on a key component of the inflammatory response in the brain. The findings have implications for research on aging and diseases such as Alzheimer’s and multiple sclerosis.
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Vegetables, not fruit, help fight memory problems in old age
A study of 3,718 Chicago residents aged 65 and older found that people who ate at least 2.8 servings of vegetables a day had a 40% slower rate of cognitive decline compared to people who consumed less than one serving of vegetables a day — equivalent to about five years of younger age. Green leafy vegetables had the strongest association to slowing the rate of cognitive decline. The benefit was greater the older the person. However, unexpectedly, fruit consumption was not associated with cognitive change.
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A natural chemical found in strawberries boosts memory in healthy mice
The search for a safe, orally active drug that activates memory-associated pathways and enhances memory has uncovered fisetin, a naturally occurring flavonoid commonly found in strawberries and other fruits and vegetables. Fisetin was one of several flavonoids (substances with anti-oxidant activities found in many plants) found to induce differentiation or maturation of neural cells. The signaling pathway activated by fisetin in neural differentiation also turned out to play a role in memory formation, specifically in the process called "long-term potentiation". When tested on mice, fisetin was found — after a single dose — to improve recall of familiar objects. Besides strawberries, fisetin is found in tomatoes, onions, oranges, apples, peaches, grapes, kiwifruit and persimmons (but not gingko biloba, although it is rich in other flavonoids). However, you would need to eat about 10 pounds of strawberries a day to achieve a beneficial effect.
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Juices may reduce Alzheimer's disease risk
In a large epidemiological study, that followed 1836 Seattle residents for up to 10 years, it was found that those who drank three or more servings of fruit and vegetable juices per week had a 76% lower risk of developing Alzheimer’s disease than those who drank juice less than once a week. The benefit seemed greatest for those who carried the so-called “Alzheimer’s gene”. Previously, researchers suspected that antioxidant vitamins (vitamins C, E and -carotene) might help protect against Alzheimer's disease, but this has not been supported in recent clinical studies. Another class of antioxidant chemicals, polyphenols, are now suspected. Polyphenols generally exist primarily in the skins of fruits and vegetables and are particularly abundant in teas, juices and wines.
Dai, Q. et al. 2006. Fruit and Vegetable Juices and Alzheimer's Disease: The Kame Project. The American Journal of Medicine, 119 (9), 751-759.
Antioxidant-rich diets improve age-related cognitive decline in rats
Two new animal studies add to the growing body of evidence that certain fruits and vegetables may slow down or reverse age-related cognitive decline. In the first study, older rats fed a diet rich in spinach for six weeks learned a simple association faster than those fed regular rat food. The second study compared three different foods - one group of older rats ate a diet supplemented by spirulina (high in antioxidants), another was fed a daily ration of apple (moderate in antioxidant activity),and the third was given a cucumber-enriched diet (low in antioxidants). Those fed either spirulina-or apple-enriched diets for two weeks demonstrated improved neuron function, and a suppression of inflammatory substances in the brain. Indeed, spirulina reversed the impairment in adrenergic neural function normally associated with aging. There was no improvement in rats fed a diet supplemented with cucumber. The best fruits and vegetables for antioxidant activity are generally the most colorful.
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