Dangers of some food supplements- Interactions with foods and medicines- CYP3A4 enzyme

Photo by Polina Tankilevitch from Pexels

Many people believe when they see the word natural, its okay to take as much as they want since its ‘found’ in nature. However ‘natural’ products can be very dangerous.

One interaction most people are aware of is with grapefruit, this is seen as a warning on many prescription packets. Grapefruit juice affects how drugs are changed (metabolised) in the body for eventual elimination and can alter the amount of drug in your blood. This can lead to enhanced side effects or lower drug effectiveness. Drugs or toxins are usually broken down (metabolised) so that they can be eliminated from the body, and they pass through the liver. Grapefruit or grapefruit juice can alter enzymes in the body and affect how drugs are changed in the body before they are eliminated. In the case of grapefruit it decreases the activity of the cytochrome P450 3A4 (CYP3A4) enzymes that are responsible for breaking down many drugs and toxins.

Grapefruit contains compounds known as furanocoumarins that block the CYP3A4 enzymes. When grapefruit juice is consumed, the enzyme’s ability to break down the drug for elimination is decreased. Blood levels of the drug may rise, resulting in a risk for new or worsened side effects. Blood levels of the drug may rise, resulting in a risk for new or worsened side effects. One whole fruit or 200 milliliters of grapefruit juice (a bit less than one cup) can block the CYP3A4 enzymes and lead to toxic blood levels of a drug. (1)

Taking medications at a different time from when grapefruit juice is consumed may not prevent the interaction. The effects of grapefruit juice on certain medications can last for over 24 hours. So, even if you take a medicine that is given only once per day, grapefruit and grapefruit juice should still be avoided for the entire treatment period.

Most worryingly Susan sees on some sites that its okay to take certain supplements two hours after any prescription medication or four hours after a medication that says do not take with grapefruit juice, since the supplement uses the same CYP3A4 pathway. There is no evidence to support this, there are a variety of factors that affect how a drug is metabolised (2). Some interactions can inhibit or change the rate its metabolised, while it may not have much effect on you if your hayfever medication is affected, it could have more serious consequences if its your Contraception, Epilepsy or Blood Pressure medication is affected.

Photo by Nataliya Vaitkevich from Pexels

Other CYP enzymes are also affected, in particular the following foods often found in supplements can have an interaction:-

  • Gingko
  • Grape Seed Extract
  • Liquorice
  • Milk Thistle
  • Echinacea
  • Garlic
  • Ginger
  • Ginseng
  • Piperine
  • Pomegranate
  • Quercetin
  • St John’s Wort
  • Berberine
  • CBD oil
  • Chamomile
  • Cranberry
  • Curcumin

The CYP enzyme system is responsible for the metabolism of 90% of prescribed drugs and herbs can induce or inhibit the CYP enzymes. Medication, toxins and hormones are all processed through the liver and some have more than one pass (3), this varies from drug to drug which is why there is no general rule of when it’s safe to take a product that interacts. In particular as you age your liver metabolism slows down so the risk increases (4), quite often more side effects are seen and then more drugs are prescribed to counteract the side effects.

Susan carries out a drug interaction assessment with every client having a full review to ensure that any current self medicated supplements are safe , and any prescribed supplements are suitable.

  1. accessed 24th July 2021

2. 24th July 2021

3. accessed 24th July 2021

4. accessed 24th July 2021

Scientific Evidence

Food labelling and health claims

Health claims and other claims on foods we buy in the supermarket such as ‘free from additives’ , ‘preservatives’ etc are valuable tools for both the consumer and the manufacturer . The consumer sees them as a quick way of deciding if a food is what they require without reading the ingredient list and as a sale tool for the manufacturer. What goes on a food label however is highly regulated, but can still be misleading to the consumer.

Vitamin C, may be classed as an ingredient, such as when its added as a nutrient to a drink. A popular children’s drink has this added and the only additives declared on the label is sweeteners. However when it’s added to apple juice as an Antioxidant (Ascorbic Acid E300), for its technological function – The ascorbic acid allows certain oxidation reactions to happen in the juice which develop its flavour, but it prevents the browning of the tannins which make it look unsightly and lead to sedimentation – It’s then classed as an additive and the fruit juice can not be labelled additive free.

Health conscious consumers like to purchase food products that are ‘additive free’, and producers will use this label as a selling point. A high profile case1 concerned the addition of ‘ fermented vegetable broth’ being added to sausages and other cured meats as a way of preserving the meat and the colour, this meat was then labelled additive free. The fermented vegetable broth was high in nitrates, which is normally added to commercially produced cured meats, it was judged to be added solely for the purpose as an additive (as a technological function) and therefore illegal to label the food as additive free.

Label’s such as ‘natural’ there is no legal definition of natural on food labels, and while research shows that consumers believe that food labeled “natural,” according to the does not contain artificial ingredients or preservatives and the ingredients are only minimally processed. However foods labelled ‘natural’ may contain antibiotics, growth hormones, and other similar chemicals, and they do not have to be ‘healthy’.

There is more to a product that what the label may tell us.



Supplement Labelling

In the UK, food supplements are required to be regulated as foods and are subject to the provisions of general food law.

There are over 2 million people in the UK with some form of food allergy.

Under the Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA)The Federal Drug Administration (FDA) in the USA requires allergen labelling limited to eight food groups – Milk, Eggs, Fish, Crustacean shellfish, Tree nuts, Peanuts, Wheat and Soybeans

This act differs from the EU Food information for Consumers Regulation which requires fourteen food groups to be listed – celery, cereals containing gluten, crustaceans, eggs, fish, lupin, milk, molluscs, mustard, tree nuts, peanuts, sesame seeds, soybeans, sulphur dioxide and sulphites (if they are at a concentration of more than ten parts per million).

The danger arises with many individuals now purchasing supplements via e-bay or Amazon. In simple terms Celery and products thereof, Mustard and products thereof, Sesame seeds and products thereof, required to be listed in the EU/UK are NOT required to be listed on supplements from the USA. 

Practitioners must supply or recommend only products legally appropriate for sale in the UK. One of necessities for a product to be legally sold in the UK is that it complies with EU requirements for labelling. Susan uses Natural Dispensary to supply all her clients, to ensure that all products comply with regulations.


Food Intolerance tests

Because IgG blood tests have not been proven to identify food sensitivities or allergies, there is a lack of evidence to support making changes based on their findings. The restrictions suggested by IgG test results may lead you to unnecessarily avoid healthy foods. Or, they may prompt individuals with food allergies to include foods that could be harmful to them.

Professional organizations that specialize in the treatment of food allergies, do not recommend IgG testing due to the lack of evidence for this use.

Susan uses the elimination and challenge method to look at any possible food intolerances.


Zinc Deficiency and Covid-19

Lower levels of plasma Zinc on hospital admission, effected the outcome when admitted with Covid- 19. But before you reach for the Zinc supplements, this is one mineral where less is more. Zinc absorption is higher at lower dosages. Zinc also has many nutrient interactions, Iron, calcium and phosphorus all decreases its absorption levels. Zinc is in many protein rich foods and absorption rates are higher from animal sources than plant sources, those on plant based diets will need to consume a higher amount of zinc to ensure required amount is absorbed. Phytates, which are commonly found in plant foods, reduce zinc absorption, and some researchers have suggested that this increases the zinc needs of vegetarians by up to 50%. Foods high in Zinc include 1/2 a cup of baked beans will provide 26% of daily requirement, Chicken Thigh – 22%, 25g pumpkin seeds – 20%, 1/2 cup chickpeas – 12%. If you wish to look into supplements please contact Susan who can provide some recommendations.


Which Sugar is best?

Refined sugar is so processed that it has absolutely no nutritional value – no fibre, nutrients, healthy fats or enzymes. In fact, it acts as an “anti-nutrient,” robbing your body of precious minerals like calcium, magnesium and potassium. And as little as 36g of sugar for adults and 18g for children begins to suppress our immune system.⁣

But we have taste buds targeted for ‘sweet’, so we’re obviously designed to want this flavour. Luckily, there are some healthier, natural sweeteners we can use instead.⁣

This may seem obvious, but as more and more dubious products come out claiming to be “natural” sweeteners, I think I should explain more. Natural sweeteners are minimally processed (depending on the quality you purchase) don’t require the use of added chemicals, enzymes or expensive machinery, and still contain minerals and phytonutrients that occur naturally. For instance;⁣

Rice Bran Syrup — NOT NATURAL⁣
Sugar Alcohols (like xylitol or erythritol) — NOT NATURAL⁣
Stevia Leaf Powder — NATURAL⁣
Maple Syrup — NATURAL⁣
Raw Honey — NATURAL⁣
Rapadura Sugar — NATURAL⁣
Organic Dates — NATURAL⁣

These natural sweeteners nourish the body instead of deplete it.⁣

contains antimicrobial properties, enzymes, antioxidants, vitamins B1, B2, B3, B5, B6, calcium, iron, magnesium, phosphate, potassium. It also soothes sore throats, coughs, and respiratory conditions.⁣

are naturally loaded with potassium, copper, iron, manganese, Vitamin B6 and magnesium. You can also ferment them to make them even lower in sugar, full of probiotics and easier to digest (recipe/ instructions are on my website).⁣

doesn’t affect blood sugar levels, doesn’t feed Candida or pathogens in the gut, or set you up for sugar/ carbohydrate cravings. When purchasing stevia, find one that is pure, as so many contain fillers like maltodextrin, flavours, lactose, glycerin and alcohol.⁣

is an excellent source of manganese, zinc and other antioxidants. Be sure you purchase pure, organic maple syrup as many commercial brands use formaldehyde in processing.⁣

What’s your favourite natural sweetener?

sugar tax, weight loss

Sugar is sugar

In 2018 the UK introduced a sugar tax, with the government stating  ‘The ‘Sugar Tax’ will help to reduce sugar in soft drinks and tackle childhood obesity’  While many companies have reduced their formulas to now be exempt from this tax,  some products are shown as ‘price includes £x sugar tax’, so you would assume that those products in the same store that don’t have this labelling on are better for you.

One such example are popular fast food outlet.  One of their frozen drinks has the sugar tax added, it contains Sugar, glucose syrup, dextrose, fructose and lactose. all sugars, some added some found in the raw ingredients.   This drink equates to 37% of an adults daily intake of sugar.   Another drink they sell does not attract the sugar tax since its a frozen fruit smoothie, the sugar is all derived from fruit and lactose in the milk, and whilst this drink has less fat and one of your ‘five -a-day’ and therefore calories it contains 44% of an adults daily sugar intake. (11 tspoons of sugar)

At the end of the day sugar is sugar, its better for you when taken as a whole fruit since you also consume the fibre. Excess consumption of both glucose and fructose, will lead to weight gain and associated medical conditions.  Sucrose, often referred to as “table sugar”, is composed of one glucose molecule and one fructose molecule joined by chemical bonds. This means equal amounts of glucose and fructose are released into the bloodstream when sucrose is digested.  In Australia most drinks are sweetened by sucrose from cane sugar, while soft drinks are sweetened with sucrose-rich sugar beet (Europe) or high-fructose corn syrup (US). High-fructose corn syrup is also made up of glucose and fructose, but contains a higher fructose-to-glucose ratio than sucrose.

Do they have different health impacts?

Yes, over consumption of fructose has been shown to cause non-alcoholic fatty liver disease, and whilst fruit and vegetables in their natural form contain fructose, the fibre they contain when eaten as a whole fruit or vegetable its very difficult to over consume.

High glucose consumption rapidly elevates blood glucose and insulin. This may affect brain function, including mood and fatigue.

So choosing  a fruit smoothie may not be the best healthy option in terms of sugar.




For many of Susan’s clients they show symptoms of magnesium deficiency, unfortunately because serum magnesium does not reflect intracellular magnesium, the latter making up more than 99% of total body magnesium, most cases of magnesium deficiency are undiagnosed. In developed countries it has been found that just over 24% of youth have insufficient magnesium in their diets. The RDA for magnesium is between 300mg – 420mg per day.  It is estimated that less than 50% of Americans hit the recommended daily amount.  Magnesium deficiency has been found in 84% of postmenopausal women with osteoporosis.
Since 1940 there has been a tremendous decline in the micronutrient density of foods. In the UK for example, there has been loss of magnesium in beef (−4 to −8%), bacon (−18%), chicken (−4%), cheddar cheese (−38%), parmesan cheese (−70%), whole milk (−21%) and vegetables (−24%).The loss of magnesium during food refining/processing is significant: white flour (−82%), polished rice (−83%), starch (−97%) and white sugar (−99%).
Increased calcium and phosphorus (cola in particular is a large source of some individuals phosphorus intake)  intake also increases magnesium requirements and may worsen or precipitate magnesium deficiency.
A common misconception is that consuming phytate-rich foods can lead to nutrient deficiencies particularly magnesium depletion via binding by phytic acid. However, urinary magnesium excretion will drop to compensate for a reduction in bioavailable magnesium. And most high-phytate foods are also good sources of magnesium (grains and beans are good examples). Thus, it is unlikely that consuming foods high in phytate will lead to magnesium depletion. However, a vitamin B6-deficient diet can lead to a negative magnesium balance via increased magnesium excretion.
The reasons for magnesium deficiency are varied, some are dietary and since most vitamins and minerals work in synergy with each other they all must be balanced,

supplementing with calcium can lead to magnesium deficiency due to competitive inhibition for absorption and over supplementing with vitamin D may lead to magnesium deficiency via excessive calcium absorption. Use of diuretics and other medications can also lead to magnesium deficiency.

Kidney failure, alcohol consumption and absorption issues  (Magnesium is absorbed in the small intestine and colon)  also effect magnesium levels. Thus, individuals with intestinal or colon damage such as Crohn’s disease, irritable bowel syndrome, coeliac disease, gastroenteritis, idiopathic steatorrhoea, ulcerative colitis, resection of the small intestine, ileostomy patients or patients with ulcerative colitis may have magnesium deficiency.

So what are the best  dietary sources:-
Black beans
Dark Chocolate
Kidney beans
Peanut butter
Unrefriend Whole grains
Dietary sources are always the optimal way of obtaining your nutrients.
Social Prescriptions

Social Prescriptions and engaging in nature- the benefits to mental health


There are more and more programs that are prescribing nature-based therapy rather than medication.  These programs have shown that they improve well being and could lead to lower NHS costs.

One such program is River Remedies: Improving well -being through nature, this is a scheme run in the South Gloucestershire and Bristol areas on the River Frome.  The individuals in the original scheme their well being scores went from ‘poor’ to being in line with national averages.

Engaging in nature is beneficial for all. Several studies have revealed that exposure to nature has positive associations with well-being.  However Natural England’s last survey of engagement with the natural environment, only 42% of the population had visited the outdoors in the last seven days, and around 50% of these visits were to urban parks.

A report in The Lancet- Planetary Health, found a significant reduction in major depressive disorder in those living in closer proximity to green spaces.

A common factor attributed to the benefits in time in nature is those individuals partake in a greater level of physical activity. However ‘green exercise’ amplifies the benefits of physical activity indoors, being outdoors will also help top up your ‘vitamin D’ levels.

Vegan, Vegetarian

Increase your fibre intake by having a vegetarian meal.

Vegetarian and vegan meals, tend to have higher fibre levels, with both the vegetables and the protein source being good sources of  fibre, and the focus of the meal.

Today Susan made a version similar to Riverford’s Cauliflower Mujaddara,  packed full of vegetables, protein and healthy oils.  The four main ingredients in this dish were onions, cauliflower, kale and lentils.


The dish contained a large portion of onions, with a generous 1.5 onions per portion.  Raw onions are nutritionally better due to the sulphur compounds which can be destroyed by heat, however you can still get many of the benefits from cooked as well. Cooked onions tend to taste milder and are often gentler on stomachs.

Onions have been used in folk medicine for the relief of coughs, colds and catarrh, especially asthma (Susan’s great aunt swore by her remedy of Oh Be Joyful which was honey, lemon, onion and whisky! to cure most colds).  One medium onion can provide 20% of RDA of Vitamin C, 4% calcium and 4% of Iron and 12% of your daily fibre requirements.  Most onions are safe to eat, however green onions  (spring onions) contain a high dose of vitamin K, therefore those on Warfarin need to take care.

Curly Kale

Kale, over the years has been classed as a super food, just one cup will provide you with 3g of protein, 2.5g of fibre, vitamins A.C and K, folate, Alpha-linolenic acid, an omega-3 fatty acid, Lutein and zeaxanthin, nutrients that give kale its deep dark green colouring and may protect against macular degeneration and cataracts.  It also includes minerals such as potassium, calcium and zinc.

Kale being a dark green leafy vegetable, is better cooked than raw due to its indigestible fibre.  Kale is a goitrogenic vegetable and when eaten raw, this vegetable can inhibit the uptake of iodine by the thyroid gland. If it’s eaten in excess, these chemicals can inhibit the incorporation of iodine into thyroid hormone. Also since its a good source of vitamin K those on blood thinner medication need to take this into account.

The body relies on iodine (and tyrosine) to make thyroid hormones, so continually eating these raw greens can cause a thyroid hormone imbalance. Raw kale also contains oxalic acid, which binds with minerals such as calcium and magnesium in the body causing them to crystalize. These crystals can damage tissues, cause inflammation in the body and kidney stones. So, a daily dose of raw kale and other goitrogenic vegetables may not be such a great idea.

Roasted Cauliflower

Cauliflower is currently a popular  food with cauliflower rice, being a common ingredient for those on diets, it can be boiled, steamed or roasted.

A cup of boiled cauliflower is just 30 calories, provides 4% of daily protein, 92% of vitamin C, 22% of vitamin K, 14% folate, 12% of fibre, 6% potassium and 8% manganese.


Green Lentils

Brown, green, yellow, red or black — lentils are low in calories, rich in iron and folate and an excellent source of protein.  1/2 a cup of lentils provides 12g of protein and 32% of your daily fibre requirements.   Women need 2,320mg of Potassium per day (possible more if on a diuretic), a 1/2 cup portion provides, 12% of your requirement and 15% of your iron requirement. For vegetarians and vegans, getting enough iron  may be particularly challenging. Regularly including lentils in your diet can help boost your iron intake.

If you are not used to eating lentils it is advisable to slowly increase the amount in your diet to give your digestion system time to adjust to the increased fibre in your diet.

The whole meal provided a very nutritious balanced meal, at 600 calories per portion, it provided 55% of daily fibre requirement, 280% of vitamin C, 34% of protein, 17% of calcium and 30% of iron.

Try one or two vegetarian or vegan meals per week, to see if you can increase your vegetable and fibre intake.