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Nutrition

The Power of Plants

Selection of veg

We all know that veg, pulses, nuts and other plants are good for us and we should be eating more. Many of us have taken a few steps further and are now buying plant based versions of dairy products, meats and fish, thinking we are doing right by our bodies and the environment, only to inspect the ingredients list to find we are consuming a highly processed congealed mess of strange sounding ingredients and chemicals. So how do we strike the right balance?

Let’s set the scene, we know that the burden of morbidity and mortality from diet related diseases is increasing and that global food production is draining planet resources and jeopardizing future food security. We also know that shifting global dietary patterns to high quality plant based diets could alleviate these health and environmental burdens and that healthy plant based diets are associated with lower risk of obesity, type 2 diabetes, cardiovascular disease and some cancers.

Data collected from epidemiological studies such as the Nurse Health Study and EPIC have shown that:

Eating 200g/day more fruit and veg

  • 16% reduction in stroke
  • 8% reduction in CVD
  • 3% reduction in cancer

Eating at least 70g/day:

  • 22% reduction in all cause mortality
  • 23% reduction in CVD mortality
  • 20% reduction in cancer mortality

Eating nuts is associated with reduced risk of:

  • Ischaemic health disease
  • Type 2 diabetes
  • Cardiovascular disease
  • All cause mortality

Eating legumes is associated with:

  • Reduced risk of ischaemic health disease
  • Improved lipid profile

Drinking tea and coffee (3-5 cups/day) is associated with reduced risk of:

  • Neurological diseases
  • Liver disease
  • Type 2 diabetes
  • Cardiovascular disease
  • Some cancers

It has been theorised that our genetic physiology is suited to diets high in fruit, vegetables and other plants, at least 70%, over double that our current intake that averages around 25%. An example is our response to fat and its effect on cholesterol. We need fat in the diet so our bodies can make cholesterol for lipoprotein transport, bile acid production and hormone synthesis. Because fat intakes from a highly plant based diet was low, adaptations were made so that we could absorb as much fat as possible and counteract that effects of substances such as stanols which remove cholesterol from the body. Therefore, problems start to occur when the fat content, particularly saturated fat, increases and our bodies make excessive amounts of cholesterol which has a redundant role. Rather than being used for the processes mentioned above, it travels through the blood stream, clogging up arteries, forming plaques and increasing the risk of heart disease.

Theories are one, thing but what about evidence? There has been endless amounts of research and published evidence on the effect of substances contained in plants on human health. Over 50,000 have been identified, but this may just be the tip of the iceberg, there could be many more we don’t yet know about. Many of these substances are secondary metabolites. These are made by plants in response to different stresses placed on the plants from various biotic and abiotic factors such as bacterial infection or extreme weather condition, to help them adapt to their environment and survive. By contrast, human cells make much fewer secondary metabolites in response to stresses and as a result we are more vulnerable to disease. We do benefit, however, when we eat the plants and consume the secondary metabolites. These includes substances such as vitamins, fibre, polyphenols, carotenoids, biogenic amines and bioactive peptides.

A few examples of why they are beneficial include:

  • Biogenic amines have antioxidant properties, interact with gut bacteria and help the bioavailability of other nutrients.
  • Carotenoids are lipophilic antioxidants including lycopene, beta carotene, lutein and zeaxanthin that can boost eye health and protect against heart disease and cancer.
  • Polyphenols include anthocyanins, flavanols, isoflavanoids, resveratrol, catechins, chlorogenic acid. They have antioxidant and anti-inflammatory effects, that can lower blood sugar levels, improve insulin sensitivity and protect against many chronic diseases.
  • Bioactive peptides are protein fragments that have many properties – antioxidant, anti-inflammatory, antimicrobial, immunomodulatory, anticancer, antihypertensive
  • Fibre including viscous fibre and resistant starch are fermented by the gut bacteria producing short chain fatty acids which improve satiety, low the pH of the colon and therefore helping to preventing cancer, as well as the ability to boost immunity

It is beyond the scope of this blog to detail all the mechanisms, but if we take the example of cancer, some of the above substances are able to help prevent cancer in the following ways:

  • They can modulate enzymes that detoxify carcinogens within the cell or produce proteins that transport carcinogens out of cells
  • They can induce or promote apoptosis (cell suicide) and the cell death of tumours
  • They can inhibit the growth of tumours.
  • They can reduce inflammation by inhibiting enzymes, cancer-related inflammation is considered as a key characteristic of cancer, with a well-established link between chronic inflammation and tumour development.

So there is strong evidence for specific types of plants in preventing disease, yet many of our plant based foods have been heavily criticized for being ultra processed and recent research published in the BMJ linked the high consumption of ultra processed foods to 32 health problems including obesity, diabetes, poor sleep and depression. It’s very likely that the problem with these foods is what is not in them as much as what is in them. Of course, high intakes of refined sugars, salt and saturated fats are a bad thing, but the loss of plant substances through refining and processing is just as harmful.

If we take the simple example of wholewheat, refining it to make white flour means huge amounts of vitamins such as vitamin E and minerals such as magnesium are lost, not to mention all the secondary metabolites. Just adding vitamin and minerals back in after refining as happens with white flour – it is mandatory to fortify white flour with thiamine, niacin, calcium and iron in the UK – is not good enough. It is important to maintain the food matrix. The food matrix can be viewed as a physical domain that contains and/or interacts with specific constituents of a food (e.g. a nutrient) that provides functionalities and behaviours which are different from those exhibited by the components in isolation or a free state. 

The bottom line

  • Eating more whole plants is good for our health and the environment.
  • Eating more plants may better suit our genetic make up.
  • There are over 50,000 identified plant substances that may benefit our heath, and many more that we don’t know about.
  • Although many have been researched in isolation, they work synergistically.
  • Many plant based foods are highly processed.
  • It is more likely that UPFs are bad for us because of what they don’t contain rather than what they do.
  • Plant based foods need to improve to pass on the benefits and protect the health of the consumer.

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