Diabetes mellitus, a chronic metabolic disease, characterized by elevated levels of blood glucose and insufficiency in production and action of insulin is the seventh leading cause of death worldwide.

There are several known risk factors including genetic predisposition, obesity, sedentary lifestyle, chronic poor gut health and high sugar intake (read more).

On top of this, an increasing body of evidence is demonstrating important advantages of dietary phytochemicals for preventing type two diabetes (T2D) and mitigating the adverse consequences of T2D amoung those who already have disease, including cardiovascular disease, dementia, peripheral neuropathy, ocular damage and cancer [Song, Wedlick].

How phytochemicals help:

It is well established that diabetes mellitus is associated with increased formation of free radicals and decrease in antioxidant enzyme potential leaving to greater, damaging oxidative stress. Many laboratory studies have shown that phytochemicals, which can enhance antioxidant enzyme efficiency and free radical scavenging activities, can reduce markers of oxidative stress and also improve the insulin sensitivity [Bacanli]. Clinically, a combined analysis of the massive Nurses’ Health Study (NHS) and the Nurses’ Health II prospective study has confirmed that people with higher intake of phytochemicals, measured by urinary excretion of flavanones, flavonols, phenolic acid caffeic acid had a lower incidence of T2DM compared to others with the same demographics and risk factors [Sun, Song].

The anti-diabetic effects of phytochemical rich foods are multifactorial. One aspect relates to the effects of the pulp and fibre often which help gut mobility and health [Thompson, Turco, Johnson]. Phytochemical rich foods slow the glycaemic index of carbohydrates, help control body weight and improve insulin sensitivity.  In addition, laboratory studies have reported that glucose transport in gut cells was directly inhibited by flavonoid glycosides and non- glycosylated phytochemicals such as EGCG [Kim]. Other in vitro and animal studies have reported that phytochemicals may exert their anti-diabetic effects through mechanisms including inhibition of the production of α-amylase and α-glucosidase, reduction of hepatic glucose output, stimulation of insulin secretion and enhancement of insulin-dependent glucose uptake, and activation [Johnson]. Several phytoactive compounds such as flavonoids, lignans, prophenylphenols, are also found to combat the complications of diabetes such as reducing the risks of metabolic syndrome, vascular damage all of which are indirectly linked to a higher risk of multiple degenerative disorders including cancer [Thomas, Bi, Kim, Kato].

Phytochemicals with known anti-diabetic properties

Phytochemicals occur nationally in a wide variety of healthy plants, particularly those with vivid colours, strong taste and aroma. Many plants, especially herbs have been linked with anti-diabetic properties including cinnamon, mulberry, ginger but the following stand out in terms of robust laboratory and clinical studies:


Curcuma longa, L. is rich in curcuminoids bisdemethoxycurcumin, curcumin and demethoxycurcumin which these have been found to exhibit α-glucosidase and α -amylase inhibitory activity [Lekshmi,  Kalaycıoğlu].  Clinically,  Curcuma longa showed prominent antihyperglycemic action in T2DM patients by reducing fasting blood glucose, HbA1C, HOMA-IR (insulin resistance) without showing any side effects [Sukandar]. In addition curcuminoids have been reported to improve in diabetes-associated endothelial dysfunction, body mass index levels, increasing adiponectin level and hyperlipidemia [Pivari]


Matricaria chamomilla L. is rich in the phytochemicals apigenin, quercetin, esculetin, umbelliferone and luteolin [Kato] . Concentrated extracts of chamomile leaf have been shown to, dose-dependently, lessened post meal blood glucose levels and protect pancreatic β-cells from oxidation in laboratory studies [McKay]. In one study, it significantly diminished the fasting blood glucose levels by over 60% [Najla]. In another, RCT involving patients, patients with T2DM given chamomile had significantly improved HbA1C and serum insulin levels compared to placebo [Cemek]. Another RCT confirmed that chamomile significantly improved glycemic control by lessening fasting blood glucose and post meal blood glucose and improved lipid profile [Darvishpadok].

Citrus fruits

Flavonoids are the main bioactive compounds in citrus fruits, with known gut health, anti-viral and antidiabetic effects. They are rich in a number flavonoids, such as hesperetin, naringenin, quercetin, tangeretin, and xanthohumol, all of which have been individually linked have antidiabetic potential. These flavonoids regulated biomarkers of glycemic control, lipid profiles, renal function, hepatic enzymes, and antioxidant enzymes, and modulated signalling pathways related to glucose uptake and insulin sensitivity that are involved in the pathogenesis of diabetes and its related complications [Gandhi].


Punica granatum Linn is rich in tannins, anthocyanins, punicalagin, ellagic, gallic, oleanolic, ursolic, and uallic acids, which have been identified as having anti-diabetic actions. One key mechanism by which pomegranate fractions affect the type 2 diabetic condition is by reducing oxidative stress and lipid peroxidation. This reduction may occur by increasing certain antioxidant enzyme activities which then reduces excess levels reactive oxygen species, inducing metal chelation activity, reducing resistin formation, and inhibiting or activating certain transcriptional factors, such as nuclear factor κB and peroxisome proliferator-activated receptor γ. Fasting blood glucose levels were decreased significantly by seed and peel extract [Banihani].


Resveratrol found is number of plants most notably red grapes and polygonum rhizomes from which it is often concentrated for nutritional supplements. Resveratrol is a polyphenolic compound with strong prebiotic protective effects which supports energy production pathways. Recent studies strongly suggest that the consumption of resveratrol offers protection against diabetes by enhancement of insulin sensitivity. The protective effects of resveratrol on cardiovascular and other complications of diabetes is via its effect on pleiotropic multiple signalling pathways, including inhibition of oxidative stress and inflammation, and  regulation of lipid metabolism [Su].

Phytochemicals Diabetes

How to boost phytochemical intake

As well as adopting lifestyle strategies to reduce the risk of diabetes (more exercise, looking after your gut health,  maintain a normal body weight, eat less sugar) the evidence briefly reviewed on the page strongly suggest increasing the intake of phytochemical rich foods.

Asian and Mediterranean diets are typically abundant in phytochemical-rich fruits, mushrooms, vegetables, salads, herbs, spices, teas, nuts, berries, seeds and legumes. Typical western diets, on the other hand, are dreadfully deficient in phytochemicals, meaning we need to eat a lot more of them with every meal of the day. Great emphasis is often placed on exotic foods from distant sources, yet polyphenol-rich foods are all around us and readily available in most local supermarkets.  Here is some practical advice what to to do and what not to do to boost phytochemical intake on a daily basis:

Juices and smoothies – Many of the fruit juices available on the market today aren’t actually ‘real’ fruit juices. They consist of water mixed with concentrate and extra sugar. Even real fruit juice has a high concentration of fructose as so many fruits are used to make them. There is also little chewing resistance to slow down consumption, making it very easy to drink a large amount of sugar in a short period of time. Juicing, which entails the whole fruit being put in the blender, is more effective at maintaining the pulp and fibre, yet still often involves a high fructose content. To overcome this, smoothie aficionados add avocado, vegetables such as kale or spices such as ginger, lowering the sugar content while improving the polyphenol intake.

Soups – Most polyphenols survive a degree of cooking, making soups an ideal way to guarantee an effective intake. Tomato soup significantly increases lycopene intake, making it perfect for those not keen on raw tomatoes. A vegetable broth flavoured with extra spices and herbs and consumed before a meal tends to fill the stomach, helping with weight loss regimens, while broccoli, onion and pea soup, with a sprinkle of turmeric and a generous twist of fresh ground pepper, constitutes the perfect superfood mix. To get the most out of soups, eat them with a fresh salad containing raw onions, lettuce or radish, all of which contain the enzyme myrosinase which is required to convert the sulforaphane in cooked cruciferous vegetables into the bioactive antioxidant enzyme glutathione. Also add pepper liberally, as the peperine it contains helps the bioavailability of polyphenols in both the vegetables and other spices.

Shots – Some more forward-thinking food outlets are offering healthy shots (around 50ml) of polyphenol-rich ingredients. The fact that they are not heated means they preserve their nutrient and polyphenol content. Common shot blends include ginger with apple, and turmeric and chilli with orange juice. These provide a quick boost but are usually not cheap. It is possible to make your own shot by grating fresh ginger into a small apple juice and adding a twist of lemon. If you have the time, it is also possible to make ginger shots with a high-powered blender, a technique which gets much more out of the root. Roughly chop ginger and add a few tablespoons of water or lemon juice to the blender. Blend until the ginger is broken down and then, if you don’t like the bits, pour the blend through a fine mesh. For a green shot, try combining a 2cm length piece of fresh-scrubbed clean ginger with 1/2 small green apple, 1 cup of packed spinach leaves and half an avocado, before adding the juice from 1 large lemon and a small pinch of cayenne pepper.

Blending grains and seeds – Although individual foods can be very healthy, mixing them together is a fantastic way to provide your body with a great variety of essential nutrients. Most health food shops now sell mixed grain and seeds, either ground in bags or in the form of health bars, cereals or drinks. They tend to be expensive and still have to be processed in some way. You can, however, make your own superfood grain mix very easily with the help of a blender.

Benefits of some whole food supplements

A good quality nutritional supplement can be a practical way to increase specific healthy phytochemical intake from the start of every day. There are very few whole food supplements which have been evaluated in robust national randomised trials with the exception of YourphytoPhyto-V and  Pomi-T. Yourphyto was chosen for the national nutritional intervention study for prostate cancer. The pomi-t study evaluated the impact of a whole food nutritional supplement containing green tea, pomegranate, turmeric, and broccoli in a previous prostate cancer trial and a trial involving menopausal women. In 2022, the phyto-v study evaluated a blend of pomegranate, citrus bioflavonoids, turmeric, chamomile and resveratrol and found a significant benefit for long covid, fatigue and overall well being. After it’s publication there was extensive media attention and public interest in this product.

In terms of diabetes, Phyto-v would be the recommended choice at it contains all 5 of the phytochemical rich anti-diabetic foods highlighted above. Reassuringly, as it was evaluated in a national ethically approved study, the quality assurance is well above what is normally expected form food supplement and it was proven save for short and long term intake.



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