New studies reveal broccoli lowers your risk of heart attack, stroke and cancer

by Jennifer Bowden / 08 December, 2018
Illustration/Getty Images

Illustration/Getty Images

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As more of us swallow pills to cover dietary lapses, new research suggests our money is better spent on hero vegetables, nutritionist Jennifer Bowden reports.

Good news about the health benefits of broccoli, cabbage and cauliflower just keeps on coming.

But, as for the supplements we’re increasingly swallowing in the hope they will make up for our dietary lapses, new research suggests they may be doing more harm than good.

If you’re taking multivitamin, vitamin C and D, beta-carotene, calcium and selenium supplements for heart health or to increase your life expectancy, you’re wasting your time and money. In fact, if taken in combination with statins, antioxidant mixtures and niacin, you’re in danger of shortening your life.

This analysis comes from a systematic review of randomised control trials (the gold standard for proving causation), published in the Journal of the American College of Cardiology in June. It concluded that evidence of the beneficial effects of dietary supplements across all dietary backgrounds wasn’t demonstrated and that current research on supplement use reinforced advice to eat a healthy diet with plenty of plant foods in which many of these vitamins and minerals are found.

The same message can be applied to cancer prevention. The World Cancer Research Fund’s 2018 report, “Diet, Nutrition, Physical Activity and Cancer: a Global Perspective”, reinforces advice to ignore supplements to prevent cancer and to meet nutritional needs through diet alone. The report is the third comprehensive analysis since 1997 of worldwide research on cancer prevention. It notes there is strong evidence that certain supplements can be harmful to health – for instance, high-dose beta-carotene supplements can increase the risk of lung cancer in some people.

An earlier review, by British medical research charity Cochrane, found that vitamin E and vitamin A supplements may also be extremely harmful.

The Journal of Cardiology-published review did find, however, that folic acid may have preventive benefits for cardiovascular disease, and teamed with B-vitamins, may help prevent strokes. But the backing for folic acid came with the rider that high folic-acid intake might increase the risk of prostate cancer.

Photo/Getty Images

Photo/Getty Images

Eat more greens

Meanwhile, the evidence for a diet full of fruit and vegetables keeps stacking up. Two major studies in 2018 have highlighted the health benefits of cruciferous vegetables. In April, Australian researchers found that women aged 70 and older who ate plenty of vegetables, particularly cruciferous vegetables, had less carotid artery wall thickness. Women who ate three or more servings of vegetables each day had .05mm less carotid artery-wall thickness than those consuming fewer than two servings. Carotid arteries carry blood to the head and a reduction of just .1mm in carotid-wall thickness is associated with a 10-18% decrease in the risk of strokes and heart attacks.

Each additional 10g of cruciferous vegetables eaten a day lowers average carotid artery-wall thickness by 0.8%.

In another study, unveiled in July, drawing from data in the US Nurses’ Health Study, American researchers investigating potential links between fruit and vegetable consumption and breast-cancer reduction revealed an 11% lower risk of breast cancer among women eating more than 5.5 servings of fruit and vegetables a day, compared with those eating 2.5 or fewer servings.

Cruciferous vegetables were found to be particularly beneficial in reducing the risk of breast cancer, along with yellow and orange vegetables – more on those later. Previous studies had hinted at a link between breast cancer reduction and fruit and vegetable intake, but this larger study allowed the researchers to obtain statistically significant smaller findings, particularly for individual vegetables.

We’ve known for some time now that fruit and vegetables are good for your heart. However, only recently have the benefits of the various subgroups of fruit and vegetables been revealed.

Clean bill of health: the US Nurses’ Health Study contributed to the link between fruit and vegetable consumption and breast-cancer reduction. Photo/Getty Images

Clean bill of health: the US Nurses’ Health Study contributed to the link between fruit and vegetable consumption and breast-cancer reduction. Photo/Getty Images

Growing reliance on supplements

Despite this, many New Zealanders continue to fall short of the recommended daily intake. Popping multivitamin supplements has become something of a nutritional insurance policy. The most recent National Nutrition Survey, conducted in 2008/09, found only 66% of the population aged 15 years and over ate the recommended three or more servings of vegetables a day, while the recommended two or more servings of fruit was eaten by just 60.4%.

The same survey found around half of us occasionally used a dietary supplement and around 31% were regular (daily or more than once a week) supplement users. Women (35.5%) were more likely to regularly supplement their diet than men (25.5%).

A more recent study suggests the trend towards supplement reliance is increasing. The 2015 survey by Southern Cross Healthcare Group found 35% of New Zealanders routinely used supplements, with multivitamins, vitamin C and fish oil the most popular. Again, usage was higher among women (42%) than men (27%). Regular supplement users spent on average $21 a month on the products.

A smaller survey of 265 adults visiting their GP in the Bay of Plenty, published in 2010, found 74% were taking at least one dietary supplement, the most common being a multivitamin.

Ironically, evidence suggests those most likely to take dietary supplements are older adults, better educated, with less social disadvantage – in other words, the population demographic who already have a better diet and are least likely to need a micronutrient top-up.

But is it money well spent? Whether they eat well or not, mounting evidence suggests that multivitamin supplement takers are no better off than the rest of us when it comes to reducing their risk of cardiovascular disease, cancer or ill health generally.

The simple fact remains – dietary supplements aren’t the silver bullet we’re looking for when it comes to our health and preventing chronic diseases.

The Global Burden of Disease study, published in 2016, estimated that about one in five premature deaths globally, between 1990 to 2016, was due to “suboptimal diets”. Low-quality western diets are a prime contributor – processed foods, made with refined grains and high in sugar, sodium and fat, with little in the way of wholefoods such as fruits, vegetables and wholegrains.

Trusty brassicas

So, which foods can help to ward off chronic diseases? Broccoli is high on the list. Ranked seventh among vegetables for household expenditure in 2016, there’s much more to it than fluffy florets.

A cruciferous vegetable, broccoli is a member of the brassica family, along with cauliflower, cabbage, brussels sprouts, broccoflower and Asian cabbages. Native to the eastern Mediterranean and Asia Minor, it was cultivated in Italy and introduced to England and America in the 1700s. It became a commercially grown crop in New Zealand only in the 1970s.

Broccoli is packed with helpful nutrients – one serving (80g) provides our entire daily vitamin C needs (45mg), along with some vitamin A, folate, vitamins B6 and E, dietary fibre and a range of helpful dietary phytonutrients. These nutrients help the body convert carbohydrates and fat into energy and fight infections; they reduce damage to bones and skin as well as the risk of heart disease and some cancers; they support healthy development of babies in early pregnancy, weight control and the management of diseases such as diabetes.

Another popular cruciferous vegetable is cabbage. One of the oldest-known vegetables, cabbage is a cost-effective and nutritious option for families. Steamed, roasted, stir-fried or sliced into a coleslaw, cabbage is easily used throughout the seasons. Although historically thought of as food for the poor, cabbage is not to be scoffed at nutritionally. It offers vitamins A and C, folate, fibre and important phytonutrients, such as the purple-pigmented anthocyanins found in purple cabbage.

Scientific studies, including cell culture and animal studies, along with human clinical trials, suggest anthocyanins have antioxidant and antimicrobial effects, may improve visual and neurological health and protect against various non-communicable diseases. They are found in purple cabbage and other red, blue and purple fruits and vegetables such as berries, currants, grapes and leafy vegetables.

Cauliflower, another Mediterranean native, offers more in the way of vitamin C than cabbage. One boiled and drained floret of cauliflower contains around 29mg of vitamin C, over two-thirds of our daily requirements, along with a range of other important nutrients.

Photo/Getty Images

Photo/Getty Images


Yellow and orange vegetables are typically high in antioxidants, particularly carotenoids, which give them their colour. The yellow and orange vegetables linked to a lower risk of breast cancer in the US study include carrots, corn, winter squash, and sweet potatoes.

There are many different types of carotenoids, and traditionally the focus has fallen only on those that the human body can convert into all-important vitamin A. However, much research has now demonstrated the health benefits of carotenoids such as lycopene, found in tomatoes, and lutein in broccoli.

Both lycopene and lutein are powerful antioxidants that protect our body from free radicals. In excess, free radicals can damage cells and contribute to the progress of chronic diseases. Lutein, for example, works to protect our eyes from damaging free radicals, while lycopene has repeatedly been linked to improved cardiovascular health.

So, if lutein is beneficial for our eyes, should we take a lutein supplement to protect our eyes? In a word: no.

Benefits of synergy

We don’t eat lycopene in isolation. More to the point, we tend not to eat even tomatoes in isolation. We eat many foods together to create a health-promoting diet, and that food is a complex mixture of vitamins, minerals and phytochemicals – all of which work together synergistically to protect our health.

Vitamins and minerals don’t provide the benefits of fibre or the phytonutrients in the foods. And it turns out, the components in one food can synergistically combine with components in other foods to improve our health. For example, sofrito is a Spanish dish typically containing garlic, onion and tomatoes sautéed in olive oil. And yes, tomatoes in isolation are a rich source of lycopene, a powerful antioxidant. But this classic dish boosts our antioxidant uptake because lycopene is more easily absorbed from cooked tomatoes and the olive oil also enhances lycopene absorption from our gut. When researchers tested this combined dish, they found more than 40 types of polyphenols, compounds that may protect against a range of chronic diseases.

Avocado’s secret

Adding avocado to your lunchtime salad is another example of synergy in action. The healthy monounsaturated fats in avocado make it a heart-healthy option, with a number of clinical trials finding that avocado consumption may improve blood cholesterol and lower cardiovascular risk. In a salad, those healthy fats also boost our absorption of fat-soluble vitamins and antioxidants in the other salad ingredients, such as tomato, carrots and leafy greens.

Research has also found that avocado added to tomato salsa enhanced absorption of lycopene 4.4 times better, and beta-carotene (found in carrots and leafy greens, among other things) 2.6 times better. Adding 150g of avocado to a salad enhanced lutein, alpha-carotene and beta-carotene absorption by 7.2, 15.3, and 5.1 times respectively.

Photo/Getty Images

Photo/Getty Images

The Mediterranean diet

What these demonstrable effects tell us is that very complex interactions are occurring as we combine food ingredients and dishes to meet our energy needs for the day and protect our long-term health. There is no supplement on the planet that can hope to replicate these effects. The closest we have come to understanding the effects is looking at the diets of long-living population groups – such as the Mediterranean diet of traditional Crete.

It all comes back to those often quoted but less often followed guidelines: eat more whole foods such as fruits, vegetables, wholegrains, nuts, seeds and legumes, along with lean meat, fish, low-fat dairy and plant-based oils such as olive oil.

A largely plant-based, wholefood diet has been shown time and again to reduce our risk of chronic illnesses such as cancer and cardiovascular disease. The fact that we don’t yet fully understand which components in those foods are responsible for improving our health, or how they interact with each other, in no way detracts from the powerful impact that wholefoods can have on our health and well-being.

Wasted on women?

Prolonged multivitamin use appears to benefit men – but not women.

Multivitamin use has no effect on the risk of hypertension in women, according to a 2016 study involving 28,157 women published in the Journal of Hypertension.

Similarly, a 2017 study of 86,142 women aged 34 to 59, published in the European Journal of Neurology, found that multivitamin use had no impact on the risk of strokes.

These findings contrast slightly with a 2016 study focused on multivitamin use amongst men. Researchers followed 18,500 male physicians for 12.2 years and observed that those who had used a multivitamin for 20 years or more at entry to the study had a lower risk of heart attacks and strokes.

Stalk and all?

Eating broccoli is a great idea – it can be boiled, steamed, stir-fried, roasted or eaten raw.

What isn’t a great idea, though, is tossing out the broccoli stalk in the rubbish. Love Food, Hate Waste NZ has some helpful ideas for using up broccoli stalks. These include chopping up broccoli florets and stalks and blitzing them in a food processor, then adding eggs, flour, cheese and other ingredients to make fritters.

If you don’t have a food processor, you can grate up the broccoli stalk to add, with the cooked florets, to onion, egg, flour, cheese and seasonings to make broccoli balls.

Broccoli stalks can also be added to salads – simply peel the stalk, finely slice it into 5mm thick slices, blanch the slices in boiling water for a few minutes, refresh in cold water and then combine with the other ingredients.

If you’re not overly fond of the texture of the broccoli stalk, you can always use a food processor to blitz up the cooked stalk to make a pasta sauce, or raw stalk to make a broccoli-based pesto. Broccoli stalks can also be cooked with the florets as the foundation for a nutrient-packed soup in cooler months.

This article was first published in the November 24, 2018 issue of the New Zealand Listener.


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