What’s the ideal fruit to vegetables ratio? The new Harvard study explained

A recent study from Harvard researchers involving nearly 2 million adults revealed what might be an ideal ratio of fruit to vegetables to consume each day. So, what might that ideal ratio be? Aiming for a ratio of 2:3 vegetables to fruit may confer the highest longevity benefit and the optimal balance to reduce the risk of many chronic health conditions.

To find out where we are with the recommended 5-a-day (or should it be 10-a-day?) and understand the potential implications of this study, in particular fruit sugars and starchy vegetables, we caught up with our own Chief Science Educator at The Health Sciences Academy and UCL Doctoral Researcher, Alex Ruani.

Get ready to learn from these eye-opening insights!

Are we currently still below the 5-a-day intake? 

Pre-pandemic, the low fruit, and vegetable consumption disappointedly remained unchanged for decades, with the Public Health England national survey results published in 2019 revealing that most people still didn’t eat their 5-a-day.

But then the COVID-19 pandemic came about and we witnessed an unprecedented swing in fruit and vegetable intake, with the world’s largest dietary study during lockdowns involving a whopping 1.1 million UK and US participants telling us what we’ve been waiting to hear for a long time: over a third (32.5%) increased their daily fruit and vegetable intake from 3.5 to 5.6 portions per day.

That said, we also observed a huge individual variability in this study, because 22.7% of participants actually decreased their intake from 5.6 to 3.8 portions per day. The good news is that we still saw an upward shift in fruit and vegetable consumption overall, meaning that the pandemic could have given many of us the impetus to eat healthier and include more plant foods in our diet.

What are some of the pitfalls of the 5-a-day campaign?

Launched nearly two decades ago, the ‘5-a-day’ campaign has been meant to make it as easy as possible for people to reach their 5 portions of fruit and vegetables per day. But then why, after 2 decades, fruit and vegetable consumption has remained so low? Which aspects of the campaign don’t work, and what can we do to change that?

At this moment, we have more questions than answers, but one thing we know for sure is the influence of the food industry as a whole and the 5-a-day claim on all kinds of processed food packaging that we still see – from Peppa Pig pasta shapes to sugar-loaded and heavily refined bear fruit shapes, fruit wriggles, fruit yoyos, and fruity nut bars. All promising to deliver one of your 5-a-day, even for little children – but no real, direct research to back it up.

It’s just tragic that the campaign resulted in the food industry making sugar-loaded processed fruit products more marketable.

Then 5-a-day… or more like 10?

The 5-a-day number wasn’t originally meant to be a target, but more like a minimum! Eat ‘at least’ 5-a-day.

The original recommendation originates from the Word Health Organization for a minimum of 400 grams of fruit and vegetables – that is, a least five 80-gram portions meant to lower the risk of serious health problems, such as heart disease, stroke, type 2 diabetes, and obesity.

So, the correct public health message was meant to be: Eat your 5-a-day… minimum!

In Australia, the government’s advice is 2 PLUS 5-a-day, encouraging people to eat two 150-gram helpings of fruit and five 75-gram portions of vegetables.

What’s more, other important and well-designed research by University College London argues that 7 to 10-a-day confer the most benefits. This 7- to 10-a-day research is robust and we shouldn’t discard it. There could be enhanced benefits from eating 7 to 10-a-day portions of whole plant foods, without all the refined sugary products the food industry is plugging as one of your 5-a-day. The ultimate behavioural goal is eating more portions of fruit and vegetables without needing to count.

So, 5-a-day or 10-a-day? We don’t necessarily need to change the 5-a-day public message itself because it’s already ingrained in our minds. But we definitely need to exclude quite a few foods and drinks from it and revisit the rules for 5-a-day labelling claims from a regulatory perspective, especially on processed foods and juices marketed to parents for their little ones.

In the Harvard study, peas and corn weren’t associated with reduced mortality risk. What’s wrong with peas and corn?

Starchy vegetables like potatoes don’t count towards our 5-a-day in the UK, but are we now putting peas and corn into question?

You’ll be happy to hear that there’s nothing wrong with peas and corn – especially when they are fresh or frozen, and not canned.

This interpretation by the Harvard researchers has more to do with ‘canned’ peas and corn, because during the process of canning they lose a significant portion of their vitamins and antioxidants, even more so if they’ve been pre-cooked.

The study abstract is a tad misleading in relation to peas and corn. But when we dive into the explanation of the researchers inside the paper, we gain some clarity and a reference to the canning process.

Put simply, peas and corn are less correlated to a longevity benefit in the study not because they are starchy, but because most people eat them canned!

Although they do have some starch content, both peas and sweetcorn have a low glycaemic index value – meaning that they have a slower, smaller effect on blood sugar, helping keep blood glucose levels even.

We could go on for days talking about the health benefits of these two plant foods. So, if you consume them regularly from fresh or frozen, it’s worth keeping them in your diet because they have a low glycaemic load and are very nutritious. For example, both peas and sweetcorn are packed with folate, which is vital for DNA repair and cell longevity, and with soluble fibre which has prebiotic potential, helping with the growth of helpful gut bacteria. Besides that, peas are one of the top iron-rich foods, an essential mineral for immune support, and also a good source of protein, containing most of the essential amino acids (except for methionine).

(In the study, where it reads ‘corn’, the authors are talking about sweetcorn.)

Are there any vegetables omitted in the study that we should eat more of?

Foods with small serving sizes such as red chili sauce, garlic, and mushrooms were not included in the study analysis. And this is a limitation of the study, because if we combine all these small-serving vegetables consumed in a day, they may compound to an 80-gram portion altogether.

Besides that, these smaller-serving vegetables may pack more health benefits per gram than many others!

Allium vegetables like garlic, onion, scallion, shallot, leek, and chives are known to support important detoxification processes in the body. This is because they have sulphur-containing amino acids needed for one of our main detoxification pathways, called sulphonation, which works to detoxify heavy metals like mercury, painkillers like paracetamol, and bacterial endotoxins (toxic by-products of bacteria living in the body).

Chilli peppers and bell peppers have a high concentration of carotenoids, including capsanthin – a bioactive compound known to attenuate obesity-induced inflammation and to raise ‘good’ blood cholesterol levels. Also, the alkaloid responsible for the spicy flavour in hot peppers is called capsaicin. This pungent compound has been reported to increase energy expenditure (through its epigenetic action on the UCP3 gene) and to induce fat oxidation – two desirable mechanisms in weight loss. Capsaicin has also been associated with a reduced risk of various cancer types, including glioma, colorectal, breast, lung, and liver cancers.

Mushrooms are the richest source of ergothioneine, a potent antioxidant with anti-inflammatory, DNA-protective, and free-radical scavenging actions. Consuming 100 grams of white button mushrooms daily for 16 weeks has been shown to double ergothioneine concentration in blood, helping to mitigate the risks of metabolic syndrome and obesity. Luckily, ergothioneine levels do not decrease when mushrooms are cooked.

With the recent backlash against sugar, should we fear eating fruit?

In the minds of many, fruit is sugar. So, are the Harvard researchers telling us to each sugar?

Not at all! The main benefit of consuming whole fruits isn’t from the fruit sugars (fructose). Besides fibre, fruits are packed with numerous beneficial antioxidants and phytochemical compounds that are beneficial to health and longevity.

And this research confirms that fresh or frozen vegetables have the strongest protective effect, followed by whole fruits.

Some people may worry that fruits have sugar and should therefore be avoided, but human biochemistry is not that simplistic.

Although most fruits have a higher glycaemic load than green, allium, and cruciferous vegetables, certain fruits are very low in the glycaemic index. This means that, when eaten whole, they don’t cause a sudden increase in blood sugar and instead provide a slow, steady healthy release.

Low-glycaemic fruits include berries, grapefruit, pears, green apples, plums, peaches, green kiwis, grapes, coconut (flesh), passion fruit, pomegranate, figs, tomatoes, avocado, and olives (Yup, the last 3 are officially classed as fruits!).

On the other hand, tropical fruits tend to have a higher glycaemic value, and these include pineapple, banana, papaya, mango, Sharon fruit (persimmon), watermelon, and melon.

But all in all, fruits are packed with beneficial polyphenols and other phytochemical compounds that have potent protective effects against disease risk. Besides, the fibre in them slows down digestion, making them filling and keeping us fuller for longer.

And remember that soluble fibre has prebiotic potential too, meaning that it feeds good gut bacteria to foment microbiome diversity and gut health!

Do bananas count as one of our 5-a-day?

For now, a small banana still counts toward your 5-a-day. Bananas are one of the top sources of soluble fibre with prebiotic potential. Ripe bananas have a higher glycaemic load compared to unripe bananas, so they can be digested more quickly and the sugar in them absorbed faster, which is why it’s a popular staple among endurance athletes.

But if you’re looking at managing your blood glucose levels and keeping these more stable, then opting for low-glycaemic fruits may work better.

Isn’t it better to eat a piece of fruit than fruit juice or smoothies?

Although less-than-desirable items like fruit juice, canned fruit, and dried fruit are said to count towards your 5 day, in reality, they probably shouldn’t. And consumers remain disoriented from the ambiguity of ‘5-a-day’ labels. All that sugar, yet one of 5-a-day?

Sadly, fruit juices, canned fruit, and dried fruit packaging remain plastered with the ‘1 of 5-a-day’ claim, and this can be utterly confusing for consumers, because it may lead to believe that if we have 5 portions of that same less-than-wonderful product, then we’re sorted. But the truth is that we’re not – far from it.

Previous research involving 65,226 men and women also indicated that fruit juice as a 5-a-day confers no benefit, while canned fruit appears to increase the risk of death! This could be because it’s stored in sugary syrup or fruit juice.

Fruit juice, including freshly-squeezed orange juice, is high glycaemic, leading to a faster spike in blood sugar, shortly after followed by a dip in blood sugar which may leave us hungrier and craving for extra food. On top of that, a 2015 study found that a high-fructose, fibre-free drink activates reward regions in the brain that make you more likely to seek out food and eat more.

So, what should we include inside the sugar limit?

The current sugar limit only refers to free sugars. What are free sugars?

Free sugars are sugars that have been added to your food, or those sugars which are naturally present in honey, syrup, or in unsweetened fruit juices.

Whole fruits don’t count as ‘free sugars’. But fruit juices do, even that freshly-squeezed orange juice.

Fresh juices and smoothies DO count towards your daily limit of free sugars.

The UK’s Scientific Advisory Committee on Nutrition recommends that free sugars should be no more than 5% of your daily calories.

For the average adult, that’s no more than about 25 grams of free sugars a day. Yet a small 180ml serving of commercial smoothie has about 20 grams of sugar – nearly maxing out your daily limit just from a small smoothie drink.

Also, when we blend fruits, we are making them more easily digestible and may get more calories from it. On the other hand, whole fruits take longer to eat and there’s more chewing effort involved. And we know from research that complex textures and more chewing effort increase feelings of fullness – which is less of a case when we wolf down a fruit drink or smoothie.

Should we stop drinking smoothies?

Not if you blend them at home and know what goes in to make them low-glycaemic!

One unbeatable, low-glycaemic smoothie home recipe that keeps the suggested 2:3 ratio is a handful of frozen berries, a small apple, at least 300 grams of raw carrots, plus sugar-free, fat-free coconut milk and a dash of cinnamon both for flavour and blood sugar control.

One more thing:

Let’s remember that even when following this 2:3 ratio of fruits to vegetables, ‘5-a-day’ is not a target but a minimum!

Your next steps…

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