I read a post on Instagram over the weekend that promoted the consumption dark chocolate for its cardiovascular benefits and whilst there is certainly an association, it very much missed the ‘research vs reality’ message. Let me explain…

You’ll often hear that dark chocolate is full of antioxidants and therefore is “good for your heart” – this idea didn’t come from nowhere. But when we look closely at the research, and compare it with what’s actually available from the shop, the story becomes much more nuanced.

Why did dark chocolate become so interesting?

Interest in cocoa began after observational research data suggested a pattern of lower blood pressure and reduced cardiovascular risk in populations consuming high levels of unprocessed cocoa.

Subsequent clinical trials demonstrated that cocoa flavanols could improve flow-mediated dilation (FMD) — a marker of endothelial function — and modestly reduce blood pressure (Grassi et al., 2005; Hooper et al., 2012).

Give this information to the media, and of course you get a widespread claim that dark chocolate is “heart healthy.”

But the benefits were attributed to cocoa flavanols, not chocolate itself.

 

What are cocoa flavanols?

Polyphenols are bioactive plant compounds. Cocoa is particularly rich in a subgroup called flavan-3-ols, which include (–)-epicatechin, (+)-catechin, and Procyanidins

Of these, (–)-epicatechin appears to drive many of the beneficial vascular effects - enhanced nitric oxide bioavailability, improved endothelial function, and reduced atrial stiffness.

These effects are dose-dependent. The European Food Safety Authority (EFSA) concluded that 200mg cocoa flavanols per day helps maintain normal endothelium-dependent vasodilation (EFSA, 2012).

Polyphenol content of cocoa vs commercially available dark chocolate

Raw cocoa beans are rich in flavanols. However, chocolate production involves a series of processes that can reduce flavanol content by 60-90% (Andres-Lacueva et al., 2008).

The processes are:

• Fermentation

• Roasting

• Conching

• Alkalisation (“Dutching”)

It is important to note that the cocoa percentage on the chocolate label does not reliably predict flavanol content. It is very rare to see the flavanol content labelled (you might only see this on an independent, artisan brand). This means that recommending an ‘85% cocoa’ dark chocolate is kind of pointless because two 85% cocoa bars can differ significantly in flavanol levels (Miller et al., 2008).

Independent analyses suggest commercially available dark chocolate contains approximately 100–500mg flavanols per 100g, often toward the lower end.

To reach ‘clinical dose’ of 200 mg flavanols, you may need 40–70g daily.

That equates to roughly 250–400kcal, 15–25g total fat, of which 9–15g comes from saturated fat.

If dark chocolate contained 200mg flavanols per portion, the manufacturers would make a claim!

I’m not saying there hasn’t been any research using dark chocolate…

… but, many of the most cited trials did not use standard shop-bought chocolate.

Instead, researchers use standardised cocoa flavanol drinks, or specially processed high-flavanol chocolate using cocoa extract.

Grassi et al. (2005) used controlled flavanol doses with matched low-flavanol controls. Larger trials such as COSMOS used standardised cocoa flavanol capsules (~500 mg/day) (Sesso et al., 2022).

Saturated fat content of dark chocolate and associated cardiovascular risk

Dark chocolate is approximately 45–50% fat – this fat comes from cocoa butter which has a high saturated fat content (approximately 60%). High saturated fat intake is linked to high LDL (bad) cholesterol, which then increases risk of CVD (cardiovascular disease).

A daily 50g serving of dark chocolate may provide up to 75% of the UK recommended daily limit to saturated fat intake.

Therefore, short-term improvements from flavanols to endothelial function do not necessarily translate into long-term reductions in cardiovascular events. Evidence from large trials remains mixed (Sesso et al., 2022).

Good news! There are other dietary sources of flavanols.

If you are activity trying to increase your flavanol intake, there are lower-calorie, lower/no saturated fat options to choose from including berries, apples, red grapes, extra virgin olive oil, and non-alkalised cocoa powder. A standard cup of tea can provide 150-250mg flavanols per cup – all the benefits, none of the drawbacks. As with anything, it’s the total dietary pattern which is important – choose a polyphenol-rich Mediterranean-style diet, which likely confers greater cardiovascular benefit than adding chocolate alone.

Dark chocolate can absolutely be enjoyed as part of a balanced diet.

I eat dark chocolate pretty much every day… because I like the way it melts into my porridge!

But eating commercially available dark chocolate for its health benefits is unlikely to be the most efficient or evidence-aligned strategy.

The benefits observed in research come from standardised cocoa flavanol doses, not from typical supermarket bars consumed ad libitum.

Eat dark chocolate because you enjoy it.

Not because you believe it’s a cardiovascular intervention.

Reference:

Andres-Lacueva, C. et al. (2008) ‘Flavanol and flavonol contents of cocoa powder products: Influence of the manufacturing process’, Journal of Agricultural and Food Chemistry, 56, 3111–3117.

EFSA (2012) ‘Scientific opinion on the substantiation of a health claim related to cocoa flavanols and maintenance of normal endothelium-dependent vasodilation’, EFSA Journal, 10(7), 2809.

Grassi, D. et al. (2005) ‘Cocoa reduces blood pressure and improves insulin sensitivity in hypertensive subjects’, Hypertension, 46, 398–405.

Hollenberg, N.K. et al. (2007) ‘Preserved endothelial function in Kuna Indians consuming flavanol-rich cocoa’, Journal of Hypertension, 25, 231–236.

Hooper, L. et al. (2012) ‘Effects of chocolate, cocoa, and flavan-3-ols on cardiovascular risk factors’, American Journal of Clinical Nutrition, pp. 740–751.

Hunter, J.E. et al. (2010) ‘Stearic acid and cardiovascular disease risk’, American Journal of Clinical Nutrition, 91, 46–63.

Miller, K.B. et al. (2008) ‘Impact of alkalization on flavanol content of commercial cocoa powders’, Journal of Agricultural and Food Chemistry, 56, 8527–8533.

Sesso, H.D. et al. (2022) ‘Cocoa flavanol supplementation and cardiovascular disease events’, American Journal of Clinical Nutrition, 115, 149–159.