Is coffee a healthy weight-loss drink?

Black coffee has zero calories, releases a shot of adrenaline to give you morning pep and is a sociable drink. Good coffee is a functional food.  

The good appears to outweigh the bad  if you buy the right type of coffee.

]To obtain a healthy functional coffee It is best to select a high-quality bean (hand-picked over mechanical-picked) roasted at low to medium temperatures to a light-medium colour degree. Brewing water temperature should not exceed 90◦C–95◦C and drink it filtered. Medium-roast coffees contain relatively high amounts of antioxidant compounds, more Niacin (B3), low acrylamide and no PAHs. Avoid asking for ‘extra hot’ – coffee brews at high temperatures reduce chlorogenic content. Whole beans (packed airtight) stay fresh for longer. Avoid dark roasts. Choose arabica beans for lower caffeine content. It is best drank before noon in the day and never in excess (1 to 2 per day). It is best avoided if you are stressed or suffer from anxiety or depression.

The Effects of Caffeine in the Body

Positives Negatives
Caffeine causes adrenaline release increasing alertness, concentration and an energy feeling.In people with ongoing high stress, caffeine is an added burden on the adrenal glands.
Coffee increases the production of stomach acid, setting off the digestive enzyme cascade,   increasing gallbladder contraction and gut motility which can help with sluggish bowels (constipation) potentially reducing long-term colon cancer risk and gallstone risk. Coffee is best taken on a full stomach.Coffee increases the production of stomach acid, setting off the digestive enzyme cascade and is not suitable for those prone to diarrhoea. (IBS, IBD)High caffeine usage on empty stomachs over time may contribute to peptic ulcers, erosive esophagitis, and gastroesophageal reflux disease along with lifestyle factors in susceptible people.
BRAIN – neurotransmitters
Caffeine affects brain chemicals (antagonising dopamine thereby altering serotonin and acetylcholine effect). Acetylcholine is protective against memory deficits (Alzheimers) and depression. Acetylcholine increases sweating (note if this happens) Healthy levels of caffeine (100mg-200mg) may have motor benefit in Parkinson’s disease (slowing dopamine reabsorption)In susceptible people, caffeine appears to upset the brain chemistry and causes anxiety, sleeplessness and trembling, during its half-life, which is 2–6 hours after coffee intake. Clearance time is longer in pregnancy, with  oral contraceptives and in liver disease.
Adrenaline increases heart rate and dilates blood vessels which is helpful when you start exercising.In doses  3 – 9 mg per kilo/bodyweight, Caffeine (adrenaline) releases fats and sugars into the blood stream, thereby sparing glycogen stores (carb + water). This can increase endurance for athletes.If sedentary, caffeine (adrenaline) releases fats and sugars into the blood, speeds up the heart and dilates blood vessels when you don’t need them.   Long-term, acute coffee intake can have negative effects on glucose tolerance, glucose disposal, and insulin sensitivity in lean, obese and type 2 diabetic humans.
It releases calcium from storage sites in muscles cells, thereby increasing muscle contraction (potentially helpful for exercise) but leading to a loss of calcium if sedentary and not replacing with the enough calcium food sourcesPoor metabolisers may experience difficulty clearing methylxanthines and these may contribute to breast cysts or painful breasts. Caffeine is best avoided at hormonal peaks (ovulation & pre-flow)

The Bean

There are 2 commercially successful beans – Arabica and Robusta.

Robusta is more robust to pests (higher in anti-oxidants) but therefore more easily oxidised through roasting yielding an aggressive flavour. Robusta is higher in caffeine (2.4%-2.5%) than Arabica (1.1%-1.3%). Robusta is about half the cost of Arabica. However Arabica is thought to provide a superior quality and aroma.

Coffee’s primary health benefit comes from it Chlorogenic Acids(CA), an anti-oxidant which protect us from free radicals. Scientific studies using just caffeine, do not reflect the effect of the whole coffee bean on human health.

It contains Vitamin B3 (Niacin) which during roasting produces trigonelline, thought to regenerate dendrites and axons potentially improving memory.

Also it contains minerals potassium (40%) phorphorus, sodium, magnesium, calcium and sulphur along with trace minerals including zinc, strontium, silicon, manganese, iron, copper, barium, boron and aluminium.The main constituent of coffee is carbohydrates, mainly in the form of complex sugars which are a source of good food for gut bacteria

However coffee contains caffeine, a drug therefore moderation is required  It also contains Diterpenes –  linked to  elevated cholesterol but they can be avoided by filtering coffee. Avoid Scandinavian boiled coffee, Cafetière (plunger pot), Greek and Turkish coffee.

High roast temperatures (220° +), produce potentially carcinogenic compounds from beans– Acrylamide, Polycyclic Aromatic Hydrocarbons (PAH’s). Choose slow roasts.

Some people are sensitive to caffeine and it affects their nervous system, ‘rattling’ them by releasing too much adrenaline or triggering histamine.

In sensitive people, the biogenic amines in coffee can trigger a headache or migraine or aggravate hormonal problems.

200-300mg caffeine per day is ok for healthy people   

Why is coffee not suitable for everybody

Some people are slow metabolisers i.e. they may have defective or deficient liver enzymes (cytochrome P450 family) or neurotransmitter enzymes (MAO or COMT). They are slower in clearing drugs, food metabolites, alcohol or hormones from their body.  Coffee takes 2-6 hours to clear in healthy people, hence it is best enjoyed morning time to allow clearance.

Caffeine Content

Coffee beans contain varying caffeine levels 1.1% – 1.3% (arabica bean) to 2.4% – 2.5% (robusta bean)  per 100g of coffee. Usually 8g–20g coffee/100 ml water is used globally.  Instant coffees will contain a higher % blend of the  higher caffeine bean, robusta, as it is higher in soluble solids which increases the yields.

Caffeine Sources Qty caffeine mg   Shop Coffee** Caffeine mg*
Coffee (instant)**** 5g – 8g 55 – 200mg BUTLERS 17g  187-221mg
Coffee (cafetiere/filter)  3.5g 40 – 80mg  INSOMNIA 14g 


Espresso 7g  77 -175mg STARBUCKS ? **






*Starbucks do not state the grams of coffee used per serving but publish their caffeine content per size drink suggesting lower levels of coffee are used than Butlers or Insomnia but prices are the same or higher

Why does coffee have a bad reputation?

Coffee contains CAFFEINE  (1,3,7-trimethylxanthine), a drug, not a nutrient. In small amounts (1% – 2.5% of 100g coffee) it acts on the central nervous system stimulating the release of adrenaline. It acts on receptors in the brain affecting the balance of 3 brain chemicals:

  1. acetylcholine (muscle movement, heart, sweating)
  2. serotonin (mood, sleep, appetite, dreaming, gut motility, sex drive, temperature)
  3. dopamine (energy, pleasure and enthusiasm).

This can be positive for some people and negative for others depending on their existing chemical balance, lifestyle and how much coffee they drink.

In people with diagnosed depression, caffeine occupies essential receptors in the brain, exacerbating their chemical imbalance.

 What is in coffee?                                                             

 per 100g coffee BEFORE ROASTING – GREEN AFTER ROASTING – light–medium-dark
Water 8g – 12g  
Carbohydrates 45g – 64g (polysaccharides, sucrose, lignin, pectin) 31g-40g
Protein 12g-19g (peptides, free amino acids 7.5g – 10g
Fat 7g – 15g (coffee oil & diterpenes) 11.2g-18g
Minerals 3g – 4.5g n/a
Chlorogenic acids 4g – 11g 1.9g – 3.8g
Aliphatic acids 1g 1.6g
Quinic Acid 0.4g 0.8g – 1g
Trigonelline/ Niacin (B3) 0.6g – 2g 0.016g – 0.025g
Caffeine (protein) 0.9g (Arabica) – 2.5g (Robusta) 1.1g – 2.5

Table 1. Approximate Constituents of 100g of green coffee and roasted green coffee

Useful information source used for constituents of coffee and background data

Coffee: Emerging Health Effects and Disease Prevention, First Edition. 2012 John Wiley & Sons, Inc. Blackwell Publishing Ltd.

Institute of food Technologists media library

A blend of both beans can be used by coffee shops making accurate caffeine calculations impossible hence the wide ranges you see in the table above.

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