We will probably be arguing about what and how we should eat for years to come. The over-riding factors seem to be a combination of uncertainty over what we think we know, and people’s desire to make money (and maybe help people). As an example, the “diet” book industry is worth millions of pounds, driven by confused people who are desperate to lose weight and (hopefully) be healthier. This confusion is amplified by the conflicting information churned out via social media. On top of that, people are inclined to promote and defend whatever dietary strategy got them their results. Though we may never have all the answers, what we are told often completely lacks (or flies in the face of) scientific evidence.
When I have written about food previously, which I do frequently (I love food), I have generally said things along the line of:
- Eat less processed food and sugar.
- Eat more protein and the right types of fat.
- Eat more vegetables.
A couple of times people have commented on my posts that this is “just common sense”, and it really should be. However, when you spend a large amount of time reading and researching diet and health, in both the media and scientific literature, you notice two things:
- Common sense isn’t that common.
- People like rules…
Rules: Rules are a big reason why “diets” work, be it vegetarianism, paleo, the mediterranean diet, or diets based on your blood group or metabolic type. If you identify and believe in the set of dietary rules you have chosen to follow, you are more likely to succeed. All those diets listed above (and many more) will work if done correctly, but also fit roughly into the three points I outline above.
Problems often arise when people swap one set of rules for another, based on what diet is currently popular. This probably won’t help them find a sustainable diet that promotes long-term improved health.
The final piece of this confusing puzzle comes from people who say that it doesn’t matter what you eat, as long as you don’t eat too much, and are active. If you’re healthy, this is probably also true.
All these mixed messages stop us from ascertaining how we should be eating for our personal health. No single diet will work for everybody, as we all have different goals, diseases and genetics. In fact, every person who has ever asked me for dietary advice has received a different answer based on all of those factors. I could also never promise the perfect result straight away.
Anybody who says that they can is just lying.
Despite all this, some common important themes do emerge from the noise. These are discussed below, in the context of some popular diets. Then, if you like that kind of thing, I’ll give you some rules at the end.
Vegetarianism (in its various guises) is almost certainly the most long-standing diet based around restricting the intake of a certain food group. Though it was an important way to avoid certain food-borne diseases historically, vegetarianism is still a (relatively) modern invention. Nonetheless, the omnivorous Western populations could learn a lot from it. I certainly think that intelligent vegetarianism beats what most people tend to eat. The environmental (pesticide, land use etc) arguments behind vegetarianism don’t always pan out, but that is beyond the scope of this article.
The key questions to ask in the current context are:
- Are vegetarians healthier?
- Do vegetarians miss out on any specific nutrients?
Vegetarians aren’t healthier: Actually, that’s not quite true. Compared to the average Western population, vegetarians do live longer, and have a lower risk of obesity, diabetes, heart disease, and some cancers. However, there isn’t much evidence to suggest that this is purely because they abstain from meat or certain other animal products. In general, vegetarians are more health conscious. They exercise more, drink less and smoke less than omnivores. This is known as the “healthy user bias”.
Although studies often try to adjust their data for the beneficial effects of other positive lifestyle factors, many people would argue that this is probably impossible. In an attempt to control for this, two large long-term studies (one in England and one in Germany) compared vegetarians to “health-conscious” non-vegetarians by studying those that read health magazines and shop at health food stores. The study design was by no means perfect, but it found no significant difference between vegetarians and health-conscious omnivores. The real reductions in mortality and cardiovascular disease were seen in those who ate more fruits and vegetables, smoked less and exercised more. Not surprising.
There are some nutrients that you just can’t get from vegetables: Vegetarians (especially vegans) are at an increased risk of a number of vitamin deficiencies. This is particularly true for vitamin B12, K2, A and D, as well as iron and zinc, and omega-3 fats.
Unfortunately, the versions of certain nutrients (such as vitamins B12 and A, and the omega-3 fats) found in plants are very difficult for the body to access and use. For example, vegan children have previously been found to have cognitive deficits because of B12 deficiencies, which can take years to correct after re-introducing animal products to the diet!
Vegetarian diets also tend to leave people more likely to be anaemic (due to low iron), and have lower zinc levels (important for normal hormone regulation). Plant foods contain a lot of phytates (compounds that naturally bind to metals like iron and zinc and stop them being absorbed). Therefore, people that eat a lot of vegetables need to compensate by taking in more of these minerals. This is difficult on a largely plant-based diet, but easily fixed with a more omnivorous approach.
Finally, fat-soluble vitamins (such as A, D, E and K2) are hard to find in plant-based foods. Vitamin K2 (not quite the same as vitamin K1, found in leafy greens) is fairly new to the nutrient party, but has been shown to be vital for normal calcium metabolism (such as telling the body to put the calcium in your bones rather than in the arteries of your heart). There is a lot of K2 in fermented foods, and dairy fat, which is probably one reason why high-fat dairy may protect against heart disease.
The discussion surrounding animal products in a healthy diet is unlikely to be resolved in the near future. However, a huge intake of animal products is not essential. Some occasional oily fish or cod liver oil (omega-3 (DHA), A, D, E), high-quality (especially unpasteurised and grass-fed) cheese, cream or butter (K2, calcium), liver (iron, zinc, K2, B12) and eggs (B12, A, D) would be a great start.
What can we learn from vegetarians?
- Eat more vegetables and fruit. One raw salad a day might even reduce your risk of heart disease by 26%!
- Exercise more.
- Smoke less.
- Drink less.
- Eat some animal products (including high fat dairy) to maintain good vitamin, mineral and fat intake.
- If not, consider at least supplementing with Zinc, Krill oil (omega-3, vitamins A,D) and vitamins K2 and B12.
Finally, we could probably all do with taking a greater interest in the environmental and animal welfare impacts of how and what we eat.
One of the most widely-publicised diets at the moment is the “Paleo Diet”. I’m a big fan of the paleo diet. My last article about food (here) is based on a loose version of “paleo” guidelines. Paleo is short for “Palaeolithic” and therefore typically promotes the exclusion of foods that were not eaten by our ancestors. This tends to mean no grains or dairy, and no legumes.
However, unlike a number of paleo proponents, I don’t think it matters too much what we ate 10,000 years ago, though it is a good starting point. The most important thing is that the diets of our ancestors varied hugely. There has even been recent evidence to show that we were eating grains over 100,000 years ago. What makes sense to me about the paleo diet is the focus on maximising health by removing processed food, and eating mainly nutrient-dense, varied, whole foods.
Those at the forefront of the paleo movement are also adjusting their recommendations based on the best evidence we have, much of which is discussed here. For instance, there is good evidence to support the healthfulness of certain wholegrains, legumes and dairy products in those that tolerate them.
However, the paleo diet is often portrayed as and interpreted as an excuse to eat nothing but bacon and eggs, and forsake anything that looks like a carbohydrate. This should not generally be the case (though low carbohydrate diets certainly have their place).
Some key attributes and pitfalls of a paleo diet relate to:
- Thinking about how your food affects you.
- The health benefits of eating more fat.
- Why you can’t just eat meat all the time.
Listen to the science, and your body: Paleo proponents are really good at thinking about how their food affects them, and changing what they eat if necessary. This doesn’t mean being obsessed with everything that goes into your mouth, but we could all think about this a bit more. The corollary of this is that is that we should also be listening to what the scientific studies actually tell us, and view dogma with scepticism.
For instance, grains (especially wheat) are typically off the paleo menu. However, there isn’t much evidence to suggest that these are detrimental to health outside of the 10% or so of us that have gluten/wheat sensitivity, and perhaps those with autoimmune disease (particularly thyroid disease) and some neurological problems.
The theory behind why grains and legumes (beans, lentils etc - also a paleo no no) might be bad for us is sound, and very interesting, but hasn’t played out in large scale population studies. In fact, regularly eating legumes has only ever been shown to be beneficial, including reducing cardiovascular disease and colon cancer. Despite this, grains and legumes (grains in particular) are still not that nutrient-dense, especially compared to offal, (shell)fish and vegetables. Many people (myself included) also feel bloated or sleepy after eating a meal centred-around bread or pasta.
I’d recommend that people who are already struggling with weight or chronic disease issues consider removing wheat as a dietary staple. Due to the inconclusive nature of the scientific evidence available, I think there’s something going on that we don’t fully understand yet. And the least that will happen is a drastically reduced cake intake. Is it scientific? No. But why would you have sandwiches for lunch if you’re going to be useless all afternoon?
The key should be to follow all the data we have, and balance that against how the food you eat makes us feel and perform. This will take some time, and experimentation.
Fat isn’t bad for you: Paleo people love fat, and with good reason. Low-fat dietary guidelines have resolutely failed to halt the ongoing march of diabetes and obesity. Eating saturated fat is important for proper hormone function and metabolism. Recently, a large meta-analysis (study of many studies) showed that saturated fat intake was not associated with increased risk of cardiovascular disease. Increasing saturated fat intake can raise cholesterol, but often in a beneficial manner. Additionally, measures like “bad” LDL-cholesterol are increasingly seen to be unreliable indicators of heart health, especially in elderly, overweight and diabetic patients. In fact, especially in women, higher cholesterol levels even appear to reduce the overall risk of death and dementia. More on this soon.
Following this recent U-turn on fat, hundreds of articles have been written, which tell us that “butter is back”. Personally, I think this is very encouraging. However, this is not a carte blanche to start eating pastries again. Your fat still needs to come from whole foods (avocado, meat, fish, eggs, dairy, nuts and seeds).
Combining processed fat and sugar is still the best way to get fat quick.
Man cannot live from bacon alone: Sadly, it’s true. One big misconception both inside and outside the paleo community is that eating meat all day will fast-forward you to optimal health. Even conservative estimates say that typical ancestral diets got at least 50% of their calories from plants. For the “average” male, that would (should) involve the equivalent of at least 4Kg of broccoli per day!
Though we could argue all day about study design, there have also been numerous reports over recent decades implicating meat (particularly red meat) in cardiovascular disease, and certain types of cancer. This data is often manipulated to make the effect of meat seem more significant that it is, and there certainly are a number of confounding factors. For instance, in Western populations, more bacon equals more sitting, more smoking and more cake. However, there is rarely smoke without fire, and there are two main potential reasons for this:
- Carcinogenic heterocyclic amines (HCAs) are produced when protein is cooked at high temperatures. This is not specific to meat, but people don’t tend to barbeque lentils.
- One specific amino acid (methionine), which is high in animal muscle but low in plant protein (legumes), is connected with increased disease risk across a number of animal models.
In fact, all the benefits of calorie restriction or intermittent fasting (which tend to increase lifespan) are lost if methionine intake is kept high. This could be a reason why some studies suggest replacing animal protein with plant protein is protective. Additionally, cultures that traditionally have high animal protein intake (and not suffer because of it) eat a lot of organs, skin and connective tissue (think chicken feet). These have much less methionine and more of the amino acid glycine, which minimises some of the effects of high methionine intake. Organ meats are also the best source of the whole range of B-vitamins, which are harder to find elsewhere.
What can we learn from paleo?
- Eat more vegetables.
- Saturated fat isn’t bad for you.
- Eat more bits of the animal, especially if your meat intake is high.
- Also include plant-based proteins, such as beans and lentils.
Finally (and importantly), production of HCAs is drastically reduced by marinating meat in red wine, olive oil, acid (vinegar or citrus) and herbs and spices, and cooking at lower temperatures (stewing rather than grilling/frying). And, if you don't fancy chicken feet, stocks made from bones are a good source of glycine.
You could repeat the above process for all the diets we have floating around.
Evidence is fairly solid for the Mediterranean diet, the low Glycaemic Index diet and certain “balanced” diets (such as the DASH diet) helping people lose weight and reduce their insulin resistance and risk of cardiovascular disease. However, most of this occurs when versions of a diet focus on:
- Removing processed foods.
- Increasing whole plant foods to make a substantial proportion of calories.
- Substituting some carbohydrates to ensure adequate protein and fat, particularly sources of omega-3s (as in the Mediterranean diet).
Another example of this is the “blood type” diet, which bases dietary recommendations on your blood group. Though the amount of grains, dairy and meat differ across the different blood type recommendations, they are all based on whole foods, with a high intake of fruits and vegetables recommended for all groups.
In a recent Canadian study, those with diets most resembling any one of the “blood-type” diets all had improvements in various modern disease factors, regardless of their blood type! Eating whole foods and more vegetables made people healthier! Shocking.
A recent analysis also suggests that the reason that many of the above dietary approaches work is because they encourage an increased protein intake, which can make you feel more full, increase metabolism, and maintain muscle mass during weight loss and aging. These are times when muscle health and strength are key to reducing risk of frailty and metabolic disease.
Other than that, exactly how much fat or carbohydrate you should eat is far from an exact science. Tailoring carbohydrate intake to activity levels is important. However, being hugely exact probably doesn’t matter too much as long as your nutrients come from real food sources.
In summary, despite the current approach to diet and health, some common truths do seem to appear. However, they aren’t sexy. They aren’t novel. And they don’t sell books.
Importantly, things will never be the same for everybody, and greater dietary manipulation can be important for some.
However, this is what we really can say about diet and optimal health:
- Don’t eat too little or too much.
- Don’t eat lots of the same thing.
- Eat lots of vegetables. Really. Lots.
- Eat enough protein, including from plant sources.
- Don’t eat processed foods.
- Do more exercise. You just can’t avoid it.
We know from numerous large-scale studies that we don’t move as much as we used to. It is no coincidence that the obesity-revolution gained pace alongside the digital-revolution, where everything is automated and people can go for days without needing to walk, run or lift anything. Our lack of movement might even be more important than what we eat!
Anybody that says anything else is just trying to sell you a story.
This is a short summary on what I think dietary research currently tells us, but obviously doesn’t include the numerous possible iterations that could or may work for you. However, if you truly stick to the above principles, I believe they will get most people most of the way. In near future I will write about how I personally would eat in the context of certain common diseases and specific goals. In the mean-time, if this article doesn’t answer any particular questions you have, please feel free to ask them in the comments, and I will answer as best I can.
As with previous articles with a long list of references, relevant scientific papers are listed in this document: