Disease Proof

Berries help keep blood pressure down

Over 5,000 different flavonoid antioxidants have been identified, many of these in commonly consumed plant foods – there are many different types of flavonoids:

  • Flavanols are the most common, and are abundant in onions, kale, leeks, broccoli, apples, blueberries, red wine, and tea.
  • Less common are the flavones, which are found in celery and parsley.
  • Citrus fruits have high levels of flavanones.
  • Flavan-3-ols, which include catechins, are found in grapes, tea, and cocoa.
  • Soybeans contain isoflavones.
  • Anthocyanins (derivatives of anthocyanidins) are potent antioxidants and pigments that color red, blue, and purple foods like berries, grapes, currants, blood oranges, eggplant, red cabbage, red onions, and some beans and grains.1

In addition to their antioxidant capacity, flavonoids may help the ability of the muscle layer of blood vessels to relax (vasodilation). Endothelial cells, which make up the inner layer of blood vessels, produce nitric oxide in order to regulate blood pressure. There is evidence that flavonoids increase the activity of the enzyme (eNOS; endothelial nitric oxide synthase) in endothelial cells necessary for nitric oxide production.2 In agreement with the idea that flavonoids have beneficial effects on blood pressure, a meta-analysis of 15 studies concluded that regular cocoa consumption can reduce blood pressure in hypertensive and pre-hypertensive individuals.3

Strawberry. Flickr: Martino!A new study focuses on the anthocyanins in berries and their effects on blood pressure. Men and women from the Health Professionals Follow-Up Study and Nurses’ Health study, respectively were followed for 14 years, and their flavonoid intake was calculated based on the foods they reported eating. Reduced risk for hypertension was found for high intake of anthocyanins (an 8% decrease in risk), as well as apigenin (a flavone) and catechin (a flavan-3-ol). The foods that contributed the bulk of the anthocyanin in the diets of the subjects were blueberries and strawberries.

When the researchers analyzed blueberry consumption specifically they found that compared with those who ate no blueberries, those who ate one serving per week decreased their risk of hypertension by 10%. 4,5

If there was a 10% decrease in hypertension risk for one serving of blueberries per week, imagine how protective it would be to eat one serving of berries every day! Also flavonoids act in several other ways to protect against heart disease, for example by reducing inflammation, LDL oxidation, and platelet aggregation. 1,6 As a result of these effects, several prospective studies have found associations between high flavonoid intake and considerable reductions (up to 45%) in the risk of coronary heart disease.7-10 Flavonoids also have documented anti-cancer properties.11,12

Berries truly are superfoods – they are low in sugar, and high in fiber and phytochemicals, with the highest nutrient to calorie ratio of all fruits. Eating berries daily will not only promote vasodilation, but also provide the body with protection against free radicals, inflammation, and cancer.

 

References:

1. Erdman JW, Jr., Balentine D, Arab L, et al: Flavonoids and heart health: proceedings of the ILSI North America Flavonoids Workshop, May 31-June 1, 2005, Washington, DC. The Journal of nutrition 2007, 137:718S-737S.
2. Galleano M, Pechanova O, Fraga CG: Hypertension, nitric oxide, oxidants, and dietary plant polyphenols. Current pharmaceutical biotechnology 2010, 11:837-848.
3. Ried K, Sullivan T, Fakler P, et al: Does chocolate reduce blood pressure? A meta-analysis. BMC medicine 2010, 8:39.
4. Cassidy A, O'Reilly EJ, Kay C, et al: Habitual intake of flavonoid subclasses and incident hypertension in adults. The American journal of clinical nutrition 2011, 93:338-347.
5. Bioactive Compounds in Berries Can Reduce High Blood Pressure. In ScienceDaily; 2011.
6. Chong MF, Macdonald R, Lovegrove JA: Fruit polyphenols and CVD risk: a review of human intervention studies. The British journal of nutrition 2010, 104 Suppl 3:S28-39.
7. Huxley RR, Neil HA: The relation between dietary flavonol intake and coronary heart disease mortality: a meta-analysis of prospective cohort studies. Eur J Clin Nutr 2003, 57:904-908.
8. Knekt P, Kumpulainen J, Jarvinen R, et al: Flavonoid intake and risk of chronic diseases. The American journal of clinical nutrition 2002, 76:560-568.
9. Mursu J, Voutilainen S, Nurmi T, et al: Flavonoid intake and the risk of ischaemic stroke and CVD mortality in middle-aged Finnish men: the Kuopio Ischaemic Heart Disease Risk Factor Study. The British journal of nutrition 2008, 100:890-895.
10. Mink PJ, Scrafford CG, Barraj LM, et al: Flavonoid intake and cardiovascular disease mortality: a prospective study in postmenopausal women. The American journal of clinical nutrition 2007, 85:895-909.
11. Androutsopoulos VP, Papakyriakou A, Vourloumis D, et al: Dietary flavonoids in cancer therapy and prevention: substrates and inhibitors of cytochrome P450 CYP1 enzymes. Pharmacol Ther 2010, 126:9-20.
12. Ramos S: Effects of dietary flavonoids on apoptotic pathways related to cancer chemoprevention. The Journal of nutritional biochemistry 2007, 18:427-442.

 

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Comments (11) Read through and enter the discussion with the form at the end
Wendy (Healthy Girl's Kitchen) - March 23, 2011 4:45 PM

Dr. Ferreri, Thanks for reminding me to eat a food that I absolutely love way more often--blueberries!

DJ Freddie Palumbo - March 23, 2011 11:37 PM

Great report. The blueberries this winter have been unusually sweet,full of flavor and abundant. Most from Chile. Must have been a bumper harvest.

Zach - March 24, 2011 7:54 AM

Amen! Now if only the FDA would stop approving the use of known carcinogens as pesticides on my beloved strawberries and blueberries it would be all good in the hood.

StephenMarkTurner - March 24, 2011 9:05 AM

Gotta pick up another 4 pound bag of frozen strawbs today. Ditto with the concerns regarding pesticides, but I still think eating regular ones is better than not eating them (but if I were a bit richer..).

Cheers, Steve

StephenMarkTurner - March 24, 2011 5:23 PM

Hi Deana

I have a question re: the more exotic oranges that are in the stores right now. The 'cara cara' oranges, though usually quite sweet, often have a definite grapefruit flavour.

I believe Joel has said to limit grapefruit, and I was wondering if this might be true for these oranges as well.

Cheers, Steve

MIke Rubino - March 24, 2011 6:13 PM

Good srticle, as one who suffers bouts of HBP this is good to know.

Deana Ferreri, Ph.D. - March 25, 2011 3:53 PM

Steve,
I'm familiar with the Cara Cara oranges - my favorite kind of orange actually!

Grapefruit contains furanocoumarins, which inhibit an enzyme called cytochrome P450 3A - this enzyme is involved in breaking down drugs (people taking certain medications are advised not to eat grapefruit) and also estrogen. One study did associate grapefruit consumption (about 2 per week) with an increase in breast cancer risk, but also 2 more studies conducted since then found no association. So keep in mind that the risk is likely minimal anyway, and certainly it's simple to eat only one grapefruit per week.

That being said, furanocoumarins have not been found in sweet oranges, only in a type of sour orange called the Seville orange, and the pummelo, both of which are thought to be relatives of the grapefruit. The Cara Cara orange, on the other hand, is thought to be a cross between two different types of oranges.

Bottom line, no reason to limit oranges.

StephenMarkTurner - March 25, 2011 4:21 PM

Thanks a lot, Deana, for the prompt response.

My interest (glad to say) was essentially curiosity. Are the fura-whatzitz associated with the bitter flavour of grapefruit?

My shallow understanding is that cara caras are coloured with lycopene (tomato oranges?), and that blood oranges are coloured with anthocyanins (blueberry oranges?).

Cheers, Steve

PS I never tire reading about this stuff, in fact I am VERY seriously considering the NEI cert.

StephenMarkTurner - March 26, 2011 7:32 PM

One other thing Deana, thanks for the extra references you sent to me personally, but I must confess I am not fluent in 'study-ese'.

I have a solid educational background (elec. engineering degree about a hundred years ago) and I am not bothered by variables per se, of course, but I am not at all sure about all the n= and p= stuff that permeates study speak (I think n might be the sample size :-).

Perhaps you could suggest a 'study speak 101' resource for myself, if I am not imposing too much (perhaps in a separate post as I'd bet other readers would be interested as well).

Thanks so much,
Steve

Deana Ferreri, Ph.D. - March 28, 2011 3:41 PM

Steve,
Unfortunately no, I don't have a go-to reference. The best advice I can give you is to simply look up the jargon words.
The P value is a statistical value that determines whether the result is significant. Usually a P value of less than 0.05 denotes significance

StephenMarkTurner - March 28, 2011 4:17 PM

Thanks Deana

You often hear the phrase "19 times out of 20...". Sounds similar.

I'll dig out my applied probability book.

Steve

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