Mediterranean Diet and Cancer

The numbers are frightening. In 2017 it was estimated that 1 in 2 people will be diagnosed with cancer by their 85th birthday [1-3]. That means either Batman or Robin, Bert or Ernie, Bonnie or Clyde, you or me. Perhaps even more concerning is that as many as 30-35% of cancer-related deaths are linked to diet [4]. And that’s not even counting those linked to physical inactivity and stress!

It’s estimated that 3-4 million cases of cancer worldwide might be avoided by adopting a healthier lifestyle5.We know that diets rich in whole grains, vegetables, fruits and legumes; and lower in red and processed meat are protective against cancer [5,6]. It doesn’t take a rocket scientist, or even a dietitian, to see why the Mediterranean diet (MedDiet) would have health benefits. It’s loaded with these plant-based gems, quality fats and limits processed foods. There’s some promising research that a mediterranean style diet can assist with cancer prevention by reducing risk of weight gain and obesity [5] but also through some other protective mechanisms.

The Med-Diet and cancer

Scientific reviews have demonstrated that the MedDiet is protective against overall cancer incidence and mortality [7]. One particular clinical trial has shown a 61% decrease in overall cancer incidence [8]. We could stop there and all pop home for a med style lunch….but it gets better. As well as the convincing evidence that Med-style eating can reduce the incidence of cancer overall, data also suggests that the MedDiet is associated with lower risk of specific cancer types [9,10]. Strongest adherence to MedDiet has shown reductions in risk of colorectal, breast, gastric, liver, head and neck, gallbladder, and biliary tract cancer [9,10].

Figure 1 below highlights the strength of evidence for each of the reported health outcomes, including overall cancer incidence and mortality as well as the positive association with specific cancer and disease types.

Figure 1: Summary of the strength of evidence for the evaluated health outcomes. Numbers indicate the number of meta-analyses with convincing, highly suggestive, suggestive, weak or no evidence for each outcome [10].

The MedDiet: is it all or nothing?

While it is far more meaningful to consider the overall dietary patterns of the MedDiet, there are some key players that help keep these health promoting associations strong (refer to Figure 2). The EPIC study of 28 572 participants from Greece in 1994-1999 found that substantially reducing red meat intake and substantially increasing legume intake or substantially increasing intake of vegetables and substituting olive oil in place of butter was associated with a 12% reduction in overall cancer incidence [11]. Talk about smart swaps.

The MedDiet emphasizes intake of fish or poultry at least twice per week. Inclusion of moderate amounts of fish, including oily fish, will improve intake of omega-3 polyunsaturated fatty acids, which, in contrast to omega-6 fatty acids, have shown tumour inhibitory effects [9]. Our friend extra virgin olive oil (EVOO) may also play a role in reducing cancer risk. Studies have suggested that the protective effects of EVOO may be linked to the oleic acid content, as well as presence of bioactive compounds including squalene, biophenols, phytosterols and vitamin E [9]. These compounds, in conjunction with other elements of the MedDiet, have been found to down-regulate inflammatory pathways and reduce oxidative stress and hormones associated with cancer development. The high oleic acid content of EVOO makes it less susceptible to damage from oxidation than polyunsaturated fatty acids [12-15]. The phenols in EVOO are also thought to be effective scavengers of reactive oxygen species that can lead to cell damage and disease risk. These pathways may help to reduce cancer-related mutations and overall cancer risk [7,12,16].

Figure 2: Pooled risk ratios of individual Mediterranean diet components and overall cancer risk [7].

What nutrition research has been telling us loud and clear is that we don’t eat foods or nutrients in isolation and it is the combination of health-promoting foods that work in synergy to maximise these benefits. Cruise to your maximum daily calories by sculling some EVOO and you sure won’t be reaping the same rewards as going full Med.

We also shouldn’t overlook the lifestyle associated with the MedDiet. The social, economic and environmental themes of the MedDiet – sourcing seasonal food locally, focus on plant-based diets, preparing and eating food with loves ones – may also play an important role in the health promoting benefits.

Head to the Med

It’s shown health benefits far beyond reducing cancer incidence, but we think even that’s enough reason to eat a little more Greek!

Your map to the Med in a nutshell (pun intended) :

Eat a diet rich in vegetables and fruits (and don’t ditch the skin!). Go for 2 fruit and 5 veg per day (a good guide is to fill half your plate with non-starchy veggies at each meal) and eat a rainbow. The micronutrients, antioxidants, phytochemicals and prebiotics will all help to reduce your risk of becoming one of those nasty stats!
If fruit and veg are your rainbow, legumes, nuts, seeds and whole grains are all in the pot of gold. Put some lentils, chickpeas, pinto or cannellini beans front and centre on your meat-free Monday!

Add a small handful of nuts and seeds to your daily routine and always choose wholegrain breads and cereals. The closer they are to their natural state the better (tip: look for shorter ingredients lists). Broaden your grain horizons – try quinoa, barley, freekeh, buckwheat and thank us later when you’re feeling fuller and energised for longer. Anyone who wants to talk glycaemic response, insulin-resistance, insulin-like growth factor-1, or just be an anti-carb- hater in general, please call me!

Choose lean proteins, limit red meat to less than 500g per week and don’t forget your omega-3 rich fish (salmon, sardines, trout, herring, flathead, tuna).
Chill your grill. Avoid overcooking or charing meats. This process can produce heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs) that can increase cancer risk.
Traditional Med diets (the ones with all the research showing health benefits) are low in salt and deli meats. Don’t let Italian flags on all the salami packets fool you! Swap out nitrates, nitrites and other preservatives found in processed foods and deli meats for herbs and spices. Nitrates and nitrites can increase cancer risk. Herbs and spices such as curcumin (turmeric), ginger, cloves, garlic and tea can reduce your risk. Simple.
Aim for a high monounsaturated to saturated fat ratio by using predominantly EVOO, avocados, nuts and seeds. Go easy on saturated fat from butter and reduce trans fats by limiting take away and commercially baked goods.
Include alcohol in moderation, predominantly flavonoid-rich red wine, and mostly at meals. But if you don’t drink, don’t feel obliged to start.
And last but definitely not least, LOVE YOUR FOOD! Source seasonal produce locally wherever possible, prepare meals with love and savour them with loved ones.

Source: Lauren Atkins – OnCore Nutrition www.oncorenutrition.com

Accredited Practising Dietitian