4.3 Food Groups

Topic Progress:

In the previous section we have looked at the three main macronutrient groups in the diet and explored some of the functional and dysfunctional actions they may contribute towards health and disease depending on amount consumed and also the health and balance of the individual’s cells, organs and systems. We will now discuss the main food groups that contain differing proportions of macronutrients, as well as micronutrients, before we move on to considering combinations of foods from a functional nutrition perspective.


Meat is primarily used as a protein source with 100g cooked red meat delivering around 38g protein including the eight conditionally essential amino acids. Meat is a rich source of creatine (synthesised from arginine and glycine), which supports skeletal muscle function, and carnitine, an amino acid derivative functionally important in aerobic synthesis of ATP by mitochondria. Carnitine can be synthesised by the body, requiring Vitamin C, B6 and iron as enzyme co-factors, but is also available through meat eaten in the diet. We will discuss the pros and dietary shortfalls of vegetarian and vegan diets in Part 2 of this nutrihub advanced course.

Animal meats are also rich sources of micronutrients, such as minerals including zinc, iron and a variety of vitamins, which we will discuss further in Part 2.

Milk & Dairy Products

Milk and foods made from milk are high in saturated fat, as well as some protein and the milk sugar lactose. Many people find digesting lactose, and other dairy proteins such as caesin and A2, leads to digestive symptoms such as bloating and abdominal pain. For these individuals, avoidance of dairy products is recommended. There are now many readily available dairy milk alternatives like oat or almond milk that can be used in place of dairy. Soy milk is also a popular alternative but we suggest that it is not too heavily relied upon as an alternative, in part due to the allergenic potential in some people, processing and also origin of the soy product (i.e. GM).

There are also other reasons why milk, especially pasteurised milk, cheese and other related products, whether from cow or any other animal, should be reduced to support health.

The process of pasteurisation of dairy products:

  • Destroys desirable enzymes but leaves one undesirable enzyme – xanthine oxidase – still active, which has been linked to arterial disease and heart attacks.
  • Removes almost all bacteria including those that may have a beneficial effect in the GI tract.
  • Renders milk even harder to digest than it naturally is.
  • Destroys a good proportion of vitamins.
  • Destroys beneficial antibodies.

Famous experiments by Dr Pottenger has shown that feeding cats a diet rich in pasteurised milk, as opposed to raw milk, leads to physical degeneracy, and often death in the cat subject population. Whilst we in no way condone the use of animals in experiments, the results published by Dr Pottenger over the years has shown in great detail the pivotal effects that different diets can exert over health.

Other reasons diets rich in milk may cause health problems include:

  • Milk in quantity may neutralises stomach acid, contributing to poor and incomplete digestion of protein foods.
  • Milk may contribute to excessive mucus production in the intestines disrupting bacterial populations and optimal digestion.
  • Casein, the major protein in milk, is very hard to digest.
  • There may be hormones present in cow’s milk that have a negative health impact.
  • Allergies and intolerances to different milk proteins are increasing in the population – symptoms may include catarrh, sinus and hay fever problems.
  • Lactose intolerance – from the inability to digest lactose or milk sugar, leads to digestive disturbances in a great many people.

Whilst this is often viewed as controversial, there is certainly an overreliance on some food products in the diet, including dairy and wheat. It’s not always the original product that is the issue (raw milk contains many beneficial nutrients that may support health) but it’s the processing that can alter these mainstay food groups in our diet, as in the case of trans fats.

So what about reducing or even avoiding milk? As adults, we can still get high levels of the necessary dietary calcium from sources other than dairy including seeds and green leafy vegetables; it just means being a little more creative with the diet. In terms of managing dietary changes reduction of dairy products (for those that do not have a known intolerance or allergy) rather than blanket avoidance may well bring health benefits. It’s about being aware of the foods that we eat and ensuring variety and balance.

Fruit & Vegetables

The Government’s national ‘5 a day[1]’ health campaign is well known throughout the population but how many of us actually hit the recommended 5 daily portions of fruit and vegetables ? What’s more, a recent study by Imperial College London suggests that it’s actually more like 10 pieces of fruit and vegetable a day that are required to live long and healthy lives![2]

One study[3] compared people who ate no fruit and vegetables versus those who ate 200g (1 small banana is approximately 80g, ½ bag spinach leaves is 100g etc.) found those that ate 200g fruit and vegetables had reduced risk of:

  • Cardiovascular disease by 13% while 800g cut the risk by 28%
  • Cancer by 4%, while 800g cut the risk by 13%
  • Premature death by 15%, while 800g cut the risk by 31%

Please read the following short article:

Vegetarians have lower cancer risk

Other population studies confirm that increasing plant based whole foods in the diet also improve health via a variety of parameters, including a recent study that showed vegan diets conferred a significant 15% reduction in risk of incidence from total cancer.[4] Whilst for many people the complete avoidance of all animal based products, including eggs, dairy and even honey, to follow a vegan way of life is too great a change of lifestyle. However, there are still significant benefits to eating more vegetables and reducing animal product intake, such as enjoying 1-2 days meat-free diet per week.

It’s not just the amount but also the type of plant matter we eat that makes a difference to our health. Studies show that the Hadza tribe that have a hunter-gatherer way of life and exist on far higher levels of fibre plant fibre, as well as meat, than occur in the UK diet have a far wider a varied mix of gut bacteria phyla compared to urban Europeans.[5] We have already discussed the importance of fibre to feed beneficial gut bacteria and encourage the production of colonic SCFAs so eating more soluble and insoluble fibre from plant material can only be a good thing for health!

Functional nutrition encourages people to eat a rainbow of different coloured fruits and vegetables each and every day because of the vast array of different phytonutrients including antioxidant compounds contained within different coloured plants. So why is this so important? Please read nutrihub’s sponsor blog by Nutrigold “Different Antioxidants Work at Different Speeds”.

There are of course many challenges in compiling data sets around eating profiles and then translating this into meaning full approaches to health management via population studies but what we now know about the importance of fibre, gut microbiota and phytonutrients demonstrates the functional importance of vegetables, as well as fruit to the daily diet. You will learn in more detail about the health benefits of different phytonutrient groups and their sources in Part 2.

However, as we’ve discussed, simply increasing fibre through plant material (which includes beans, pulses and legumes as well as vegetables) may, for some people with dysfunctional digestive processes, negatively impact health contributing to IBS type symptoms. Consuming too much fibre may also lead to increased transit time and reduction of nutrient absorption in the gut. We will go into more detail about IBS and types of diets that manipulate plant intake to manage symptoms in Part 2.

For now, it’s worth remembering that consuming at least 4 portions of unprocessed vegetables and moderate consumption of fruit (up to 2 pieces per day) is one functional nutrition approach to ensure intake of high levels of beneficial nutrients but avoiding high levels of fruit sugar intake (i.e. fructose). Processed, shop bought fruit juices are not included in this message and are to be avoided due to the lack of fibre and high sugar levels.

Plants also contain a number of so called anti-nutrients, including saponins, lectins, phytates and oxalates. Anti-nutrients are produced by plants to protect the crop from natural pests and are so-called because they are of no nutritional use to us and can even block nutrition benefits from other foods. For example, phytic acid, found in high levels in grains such as wheat, chelates (binds) to dietary minerals such as calcium, magnesium, iron and copper so they are not available for absorption through the gut; Oxalates present in particularly high levels in rhubarb, tea, spinach and parsley also binds to calcium preventing its GI absorption; Glucosinolates prevent the absorption of iodine, potentially affecting thyroid function, and are so considered goitrogens. They are found in high levels in vegetables such as broccoli, Brussel sprouts, cabbage and cauliflower.

So if we’re suggesting increasing plant matter in the diet then we can’t avoid these anti-nutrients – confusing! But once again, we can take a functional approach not only to application of foods but also to their preparation to ensure the foods that we eat are in a form that our body can utilise. Functional nutrition encourages eating more whole foods via cooking processes such as steaming vegetables, as well as fermentation processes (e.g. miso and sauerkraut) to deactivate these anti-nutrients. We will cover this in Part 2.

Wheat & Rye

There’s no doubt the gluten and gluten-free (GF) diets are still top of many nutritional practitioners and health reporters agendas. But is excluding this protein from our diet really a benefit health? After all, GF diets exclude a food group of grains that contribute other important vitamins, minerals and functional nutrients, such as fibre, to our diet.

Let’s firstly explore what gluten is and how it may impact our health. Gluten, as we’ve discussed, is a set of proteins found in wheat, as well as rye, barley and triticale hybrid rye/wheat grains developed in the 1950s to produce a robust, high yielding grain crop. Gluten is comprised of storage proteins, including prolamin and glutelin fractions – called different names depending on the grain origin, e.g. wheat prolamins and glutelins are called gliadins and glutenin respectively – and are used commercially for their viscoelastic properties giving dough its elastic qualities and helping it to rise. After all, gluten is the Latin word for glue! Oats do not contain gluten proteins but may be processed in factories along with gluten containing grains so unless otherwise stated as “gluten-free” on packaging they may be assumed to contain low levels of gluten proteins.

Today, many millions of people suffer from digestive imbalances ranging from non-specific bloating, reflux and constipation, to named GI disease including IBS and inflammatory based conditions such as Crohn’s and coeliac disease, which is well known to have it’s origins in gluten allergies. Mounting research now suggests that gluten may play a role in a wide range of different GI conditions that also carry systemic inflammatory symptoms.

Please read the following comprehensive articles on the rise of gluten sensitivities, intolerances and allergies, including non-coeliac gluten sensitivity (NCGS), and the impact this is having on the nation’s health:

There are also several excellent books (optional reading for this course) written on this subject if you are interested in finding out more information including “Wheat Belly” by Dr William Davies.

Even if a therapeutic diet does not remove gluten completely (i.e. still permits some oats, rye and grains other than wheat), the elimination of processed breads and other processed wheat-based products can have a significant impact on many areas of health. Part of this reason is not just down to gluten but the associated reduction in salt, sugar and food chemicals, such as preservatives and additives that are found in so many processed wheat products.

The practical problems about excluding wheat, wheat-based products and gluten in general are often considerable, due to wheat having such a ubiquitous position in Western diets. It is not just bread, cakes, scones, pastry, pasta and puddings but also soya sauce, gravies, custard and sausages to name a few. But is gluten always the culprit behind GI symptoms?

Please read the following blog looking at self-diagnosis of gluten intolerance and why it may be carbohydrates (fructose) that is the trigger to digestive problems rather than proteins like gluten:

Self-Diagnosis of Gluten Sensitivity: Potentially Disturbing Trends

So where does this leave functional nutrition approach? There’s no doubt that gluten in its modern form and prevalent in so many processed foods with no real functional nutrient content to speak of (e.g. processed bread) is consumed in far too great a quantity for people’s health. Gluten can trigger a wide range of symptoms, both gastrointestinal and systemic in nature, so should be considered when addressing health through therapeutic diets. However, gluten alone may not be the sole trigger, or even the cause. Careful analysis at the beginning of a programme may avoid either health problems or limiting a therapeutic diet that a patient finds difficult to comply with.

Other Grains

As we discussed, whole grains can provide a useful array of functional nutrients including phytonutrients, minerals and B vitamins, as well as fibre and energy in the form of starch. Oats, rice, corn (maize) and buckwheat are generally accepted as gluten free (see previous section about oats; buckwheat is not a wheat grain but actually part of the rhubarb family) so can be recommended as part of a functional nutrition programme, unless specific allergies have been detected. This is especially true for corn.

However, whilst supplying essential nutrients, grains are also known to influence insulin and glucose control through their effects on absorption, liver enzyme activities related to gluconeogenesis, glycogen synthesis, adipocyte physiology and centrally mediated appetite. It’s a much more complicated story than just getting glucose from starch! The impact of many grain-based foods on blood sugars (glycaemic index) and insulin sensitivity, linked to metabolic syndrome, Type 2 diabetes and other inflammatory diseases including cardiovascular disease, is in part to do with the form of the grain – whole grains contain fibre and other nutrients in the outer husks that remain during food processing and help to slow down the glycaemic response thus benefitting our blood sugar and insulin levels. We explore the impact of grains on health when we look a blood sugar and glycaemic index in Part 2. For now, remind yourself of the impact of blood sugar on health by reading the course notes in module 3.

Seeds & Nuts

Seeds and nuts are generally thought of as positive health foods and are widely offered in health food shops and supermarkets. They are great sources of EFAs (omegas 3, 6 and 9), and also offer useful contributions of minerals and vitamins as well as fibre and fats.

Different nuts and seeds offer special functional nutrition properties. For example, 4-5 Brazil nuts per day can provide your daily intake of selenium. Sesame seeds are especially high in the amino acid methionine, which is generally restricted in vegetarian and vegan diets so 1tbsp sesame seeds can be used to boost methionine in any diet where protein is of vegetable origin.

However, nuts and seeds, as well as grains and beans, also contain the so-called anti-nutrients. Phytic acid is particularly prevalent in nuts and seeds. Soaking these food groups in filtered water is one way to reduce the effect of phytic acid, and other anti-nutrients, so that the beneficial nutrients these food groups contain can be absorbed through the GI tract. Soaking seeds, and also grains, for several hours and even to the point they start to sprout helps increase beneficial nutrients levels and reduce anti-nutrient activity thus enhancing nutrient content of the grain, nutrient absorption and also benefits their general digestibility.

General soaking times can be found in the Table 4.2 below:

Nut / Seed/ Bean/ Grain Dry Amount Soak Time (hours) Sprout Time (days) Yield (cup)
Alfalfa Seed 3 Tbsp 12 3-5 4
Almonds 3 Cups 8-12 1-3 4
Amaranth 1 Cup 3-5 2-3 3
Buckwheat 1 Cup 6 1-2 2
Cashews 3 Cups 2-3   4
Flax Seeds 1 Cup 6   2
Chick Pea 1 Cup 12-48 2-4 4
Lentil 3/4 Cup 8 2-3 4
Millet 1 Cup 5 12 Hours 3
Mung Beans 1/3 Cup 8 4-5 4
Oats 1 Cup 8 1-2 1
Pea 1 Cup 8 2-3 3
Pinto Bean 1 Cup 12 3-4 3-4
Pumpkin seeds 1 Cup 6 1-2 2
Quinoa 1 Cup 3-4 2-3 3
Rye 1 Cup 6-8 2-3 3
Sesame seeds 1 Cup 4-6 1-2 1
Spelt 1 Cup 6 1-2 3
Sunflower seeds 1 Cup 6-8 1 2
Walnuts 3 Cups 4   4
Wheat 1 Cup 8-10 2-3 3
Wild Rice 1 Cup 12 2-3 3

Table 4.2 Soaking Time of Nuts, Seeds, Grains, Beans and Pulses. Quantities are based on measuring cups. Soak seeds, nuts and grains in filtered water.

Fats & Oils

As we discussed in previous sections of this module, there are different types of dietary fats and these must be controlled to exert therapeutic, functional effects rather than negative health benefits.

Many therapeutic diets benefit from addition of cold pressed seed oil such as flaxseed oil, pumpkin seed or hemp seed oil – between 1tsp – 2dsp daily depending on dietary requirements. This provides good intake of the EFAs. Some other oils are richer in omega 9 fatty acids (mainly oleic acid) than in either of the omega 3 or 6. These include olive, hazelnut, sweet almond and avocado oils.

It’s recommended to use organically produced and (or at least) cold pressed oils to avoid contamination and damage to the delicate polyunsaturated fats during processing. These omega rich oils are also unsuitable for cooking, especially at frying or grilling temperatures (when the oil starts to smoke), due to the heat damage destroying the omega oils and resulting in production of chemically altered fats that may negatively affect health. This is why functional nutrition programmes strongly recommend avoiding any form of high-temperature cooking with oils that are liquid at room temperature; saturated fats withstand heat much better due to their carbon structure. This means organic virgin coconut oil, rich in medium chain saturated fats, is a good oil to cook with.

Margarines have long been regarded as adverse in therapeutic diets due to the process of partial hydrogenation to which most of them have been subjected creating trans fatty acids. These types of spreads may also contain interesterified fats that have been shown to affect blood cholesterol levels. Nutrition research now suggests that oil-based spreads are best eliminated from the diet to avoid ingestion of harmful fats, even if the labels purport to be healthy such as “lowering cholesterol”.

Please read the BDA information on Trans Fats

Since there is usually a need to have some form of spreading fat in the diet, up to 1tsp daily of butter is sometimes suggested in functional nutrition programmes. Butter does contain high levels of saturated fats but also contains SCFAs that may be of benefit, in moderation, to digestive health. Coconut oil can also be used in place of a dairy spread option like butter.


Eggs are a rich source of complete protein, as well as Vitamins A, B12 and D, choline and other important functional nutrients like the EFA DHA. Egg allergies are not uncommon so may be excluded from certain individual diets but these little nutrient powerhouses can play a very important nutritional role in many therapeutic programmes.

Please read the following article about eggs and health:

The Heart Health, Disease Preventing Health Benefits of Eggs


Fish is an excellent source of lean protein, whilst certain species also contain beneficial levels of EFAs; namely oily fish like mackerel and salmon, which contain high levels of Omega 3 EFAs. However, functional nutrition also takes into consideration the toxic heavy metal concentration in deep water fish such as tuna and swordfish. It’s therefore often recommended to include oily and white fish for dietary protein that are sourced from sustainable clean seas rather than farmed fish. Deep-water fish like tuna are either avoided, such as when pregnant, or reduced to 1-2 times per month to limit exposure to potential heavy metals.

If you’re interested in the area of heavy metal toxicity and health then please read the following blog:

Is Mercury Toxicity an Epidemic?

Fresh & Dried Peas, Chickpeas, Lentils, Beans

Pulses, beans and legumes, which include chickpeas and lentils, are rich in (incomplete) protein so are an excellent way to replace, augment and/or fine-tune the non-animal protein content of the diets. They also provide significant amounts of minerals and some vitamins, especially folate. About 40g per day of pulses (depending upon type) can be enough to boost dietary protein, but actual recommendations can vary around that figure. These food groups do not affect insulin levels in the manner of some grains so can be a useful addition for dietary carbohydrate without the associated changes in glycaemic index – we will discuss this in Part 2.

However, pulses, legumes and beans do have high levels of anti-nutrients in the form of plant glycosides called saponins and lectins. These compounds have some health benefits in moderation but may also be pro-inflammatory and exacerbate gut sensitivities, such as with some cases of IBS. This is an example of when manipulation of a therapeutic diet is required so reliance on pulses and beans for protein and other nutrients will be less (maybe even zero at the beginning of the programme) compared to other therapeutic diets. We will discuss this further in Part 2 when we compare the FODMAPs diet for IBS.

Legumes and pulses also contain the sugar raffinose, which may increase flatulence in some people, as it favours the growth of beneficial, but methane producing bacteria. Use of a plant digestive enzyme formulation containing alpha galactosidase will help to break down the raffinose and prevent this problem – ideal if you want to increase legumes, beans and pulses in your diet! You will learn more about digestive enzymes supplements in Part 2.

Note that runner or French beans, sugar snap peas or mangetouts are not considered within the heading of ‘beans’ because they are podded beans or peas so are not especially high in protein and hence they belong more to the vegetable food class.


There is no question about the toxic effects of inappropriate consumption of alcohol and its impact on health. Here are some facts:

  1. Ethanol acts as a central nervous system depressant producing, at progressively higher dosages, impaired sensory and motor function, slowed cognition, stupefaction and eventually unconsciousness. The mechanism of ethanol action in the central nervous system is by binding to a cell surface receptor, the GABA-A receptor, increasing the effects of the inhibitory neurotransmitter GABA.
  2. Prolonged heavy consumption of alcohol can cause significant permanent damage to the brain, liver and other organs.
  3. Ethanol within the human body is converted into acetaldehyde by alcohol dehydrogenase and then into acetic acid by acetaldehyde dehydrogenase within the liver. The product of the Phase 1 pathway breakdown, acetaldehyde, is more toxic than ethanol.
  4. Acetaldehyde is linked to most of the clinical effects of alcohol. Acetaldehyde inhibits energy production by the mitochondria, as evidenced by its inhibition of oxidative phosphorylation (i.e. cellular production of ATP). The data suggest that acetaldehyde effect on cellular energy production may be implicated in some of the toxic effects caused by consuming alcohol.

These considerations seem to make it obvious that alcohol and acetaldehyde are toxins within the sense of those we have discussed in the course so far. It makes no sense to regularly consume alcohol in any form, especially when nutrients such as antioxidants can be found in other foods such as blue-skinned fruits, and not just red wine. There are of course, many connotations to this socially acceptable toxic drink, which can be difficult to change habits around consumption but from a functional nutrition perspective the toxic effects of this group of drinks outweighs any purported nutritional or functional benefits.

Tea & Coffee

Tea and coffee contain certain functional nutrients, like the amino acid L-theanine found in tea, which is associated with reducing anxiety and aiding sleep quality. Please read the following blog:

Coffee and Health – What’s the Buzz?

However, both types of drink contain caffeine, which is a diurectic so when drunk in excess can lead to loss of minerals through the urine. Caffeine (also found in certain soft drinks and dark chocolate) also stimulates adrenal function, affects sleep patterns and increases blood glucose levels through reduction of insulin uptake.

Caffeine is actually classed as a drug because of its physical dependence – that’s the ability to induce physical symptoms on withdrawal. In the case of caffeine, this is often experienced as withdrawal headaches occurring within hours and lasting 2-5 days after the last intake of caffeine. Withdrawal symptoms are an indication of the addictive and profound change caffeine can cause within the brain and body. Alleviating a caffeine-withdrawal headache for the short period these are experienced can be achieved by eating a small snack between the main meals, such as a piece of fruit and handful of nuts. This raises the blood sugar levels (something that is done by caffeine) and prevents reactive hypoglycaemic symptoms.

Generally, one serving of coffee ranges from 40mg, for a single shot (30ml) of arabica variety espresso, to about 100mg for a cup (120ml) of drip coffee.[6] In general, dark-roast coffee has less caffeine than lighter roasts because the roasting process reduces the bean’s caffeine content. Arabica coffee normally contains less caffeine than the robusta variety. Although tea contains more caffeine than coffee (by dry weight), a typical serving contains much less, as tea is normally brewed much weaker. Black tea typically contains around 30mg (for a 240ml cup) and green tea slightly less at 25mg for a 240ml cup. A maximum of 2 cups of tea or fresh coffee daily, before 2pm, may be recommended to enjoy the health benefits and avoid the negative health consequences of over-consumpotion of caffeine. There are naturally caffeine-free tea and coffee alteratives likes chicory root coffee and redbush (rooibos) tea. This avoids the decaffeinated forms of tea or coffee that use chemical solvents in the extraction process, which may end up in your cuppa!

Here are the optional references for this section:

  1. https://en.wikipedia.org/wiki/5_A_Day
  2. https://www.imperial.ac.uk/news/177778/eating-more-fruits-vegetables-prevent-millions/
  3. Aune  et al (2017) Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality—a systematic review and dose-response meta-analysis of prospective studies. Int J Epidemiol 46,:1029–1056 Full paper
  4. Dinu M, Abbate R, Gensini GF, Casini A, Sofi F. Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies. Crit Rev Food Sci Nutr. 2017 Nov 22;57(17):3640-3649 Full paper
  5. Schnorr (2013) Gut microbiome of the Hadza hunter-gatherers. Nature Comms 5: 3654 Full paper