OVERVIEW
· Touted as healthy, what’s good about vegetarian-style diets?
· Although they are a whole lot better than bog-standard Western fare, diets that rely solely on plant-based foods can fall short of the mark.
· Understand the nutritional shortfalls commonly seen in people following plant-based diets that could undermine heart health, bone health, brain health, hormonal health and the immune system.
· Learn how to fill in the gaps in plant-based diets, and why carefully chosen animal-based foods can help give you the best of both worlds.
Compared to the average meat-chomping Westerner, vegetarians appear to be a pretty healthy bunch. The idea that vegetarians are all pale, anaemic and sickly is a load of bunkum, and a lot of the research conducted into the health of vegetarians indicates that they fare well. So that got us thinking: can we thrive on plant foods alone?
A glimpse at the evidence on the health of vegetarians certainly tells an impressive story. Overall, vegetarians have lower rates of heart disease, lower levels of ‘bad’ LDL cholesterol, less high blood pressure, less diabetes and less obesity1. If that isn’t enough to get you excited about lentils, they seem to have lower rates of cancer too, and can even look forwards to greater life expectancy1. Authorities such as the prestigious American Dietetic Association are vociferous in their support of vegetarian diets, stating that they are ‘healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases’2. It seems that there are many virtues associated with the vegetarian life.
A ‘SAD’ diet
Are we really so surprised that vegetarians have such good health stats compared to those eating an average Western diet? Or should we rephrase that to those eating a rubbish diet? Indeed, the Standard American Diet, or SAD for short, leaves a lot to be desired (and we can easily include the UK here too). In a year, the average American reportedly wades through 13kg of French fries, 10kg of pizza, 10kg of ice cream, 240 litres of soda, and 10kg of artificial sweeteners3. In the year 2000, it was estimated that the average American consumed 32 teaspoons of added sugars per day4.
This is in stark contrast to the foods that are more likely to crop up in the diet of health-conscious vegetarians, namely fruit and veggies, cereals, pulses and nuts. Our modern diet is woefully lacking the plethora of beneficial phytochemicals found in plant foods. If vegetarians are eating more of these foods, we should hardly be surprised to find they experience better health. We challenge you to read the next paragraph and argue against eating more veggie stuff.
You’ve heard it all before, so we won’t go on about fruit and veg too much, but suffice to say, eating plenty of the stuff reduces the risk of heart disease, high blood pressure and stroke, lowers cancer risk and reduces diabetes, and just for good measure, helps to promote healthy bones5,6. Next up, nuts. Full of ‘good’ unsaturated fats, antioxidants, fibre, vitamin and minerals, they are a recipe for a heart-friendly food if ever there was one. The risk of coronary heart disease is 37% lower in people consuming nuts more than four times per week compared to those eating them rarely or never7. Eating wholegrain cereals (such as wholegrain bread, rice and pasta, oats, and so on) appears to protect against heart disease, obesity, diabetes and cancer8,9. As for legumes (beans, peas and lentils, etc.), their substantial soluble fibre content lowers LDL cholesterol and triglycerides, and in addition to their cardio-protective credentials, they may also protect against diabetes and obesity10,11.
Who would turn their nose up at such a who’s who of health benefits? It doesn’t really matter two hoots whether you eat meat or not; either way, you should be ditching the junk and including more of these foods. Enough said.
The Standard American Diet is typified by overconsumption of refined grains, sugars, trans-fats, fast foods, and high-energy-dense snacks. A truly ‘SAD’ way of eating that is fuelling the epidemic of chronic degenerative disease.
Vegetarians do not consume any meat, poultry, game, fish or shellfish, or by-products of slaughter, but can choose to eat dairy products and eggs. Vegans additionally avoid eating dairy products and eggs, and any other products derived from animals.
We would do well to bear one important fact in mind. Most of the studies into the health of vegetarians are epidemiological. Generally, that means taking a bunch of vegetarians and a bunch of non-vegetarians, and following their health over time to see what happens. Most of the time, the vegetarians come out on top, getting less disease. But these are only associations, they don’t prove that it’s the avoidance of meat that makes the difference. It’s a pretty reasonable assumption that vegetarians might generally be a more health-conscious lot, with a range of healthy behaviours that make them different from their non-vegetarian counterparts. For example, vegetarians are likely to be slimmer, to smoke less, and to have a higher socio-economic status compared with the wider population12,13, and there could be any number of other subtle differences in behaviours and attitudes that aren’t so easy to measure.
The point is: it would be a leap of faith to say with any certainty that the health benefits seen are down to not eating meat. There’s a clever study, which recruited almost 11,000 British men and women, that illustrates this. The participants were either customers of health food shops, or people with an interest in health foods or vegetarianism. It’s fair to say that they were all likely to be health-conscious individuals, but only 43% were vegetarians. The study found no significant differences in all-cause mortality, or mortality from heart disease or cancer, between the vegetarians and the non-vegetarians (in fact, the study actually found increased mortality from breast cancer among the vegetarians)14.
Not so heart healthy?
So, what would happen if we switched to a diet that was made up of just plant foods? After all, the research tells us that these foods are the business when it comes to keeping us healthy, so why not just ditch the animal foods once and for all? Well, despite all their nutritional plus points, the bare fact is that plant foods struggle to provide some of the important nutrients that are simply much more readily available from animal sources.
With all that fibre, all those fruit, veggies and wholegrain cereals, and the lack of saturated fat, you’d think that a plant-based diet was the absolute daddy of all diets to prevent heart disease… well, not quite. Vegetarians, and especially vegans, can easily find themselves lacking vitamin B1215,16. This might quickly undo the cardio-protective qualities of the veggie diet by raising levels of homocysteine, a toxic by-product in the bloodstream that is strongly implicated in heart disease, as well as a range of other diseases. Non-meat eaters have been shown to have higher homocysteine levels than meat eaters16,17, showing us that this is one area where plant-based diets fall down. We can only get vitamin B12 from animal foods (including dairy products and eggs), so eat nothing but plant foods and sooner or later you’ll end up deficient. If you wish to eat a strictly plant-based diet, the only way around this particular conundrum is to regularly consume foods fortified with vitamin B12 (e.g. fortified soy or rice beverages, fortified breakfast cereals, fortified meat analogs, or B12 fortified nutritional yeast), or take it in the form of a supplement18.
We’re not quite done here yet. Plant-based diets are sorely lacking in another piece of the cardio-protective jigsaw – the long-chain omega-3 fats EPA and DHA. These are the types of omega-3 fats found almost exclusively in oily fish. They simply don’t occur in plant foods, yet they’re highly beneficial for cardiovascular health (not to mention brain health, and helping to control inflammation in the body). It is possible to get omega-3 from plant foods in the form of alpha-linolenic acid, found in foods like flaxseeds/flaxseed oil, walnuts/walnut oil and rapeseed (canola) oil. However, this is a poor man’s version of omega-3 and lacks the clear health benefits associated with the more potent EPA and DHA. Now, in theory, the body can convert the plant form of omega-3, alpha-linolenic acid, into the more desirable EPA and DHA. The problem is that it’s just not very efficient at it. The conversion of alpha-linolenic acid to EPA is about 8–20%, while to DHA is 0.5–9%19. The lowest conversion rates are seen in men, and women achieve the meagre but relatively higher end of the range. So, don’t be conned by so-called nutritionists and supplement companies claiming that their plants and oils, such as flax, provide great sources of omega-3s.
The truth is that eating a purely plant-based diet leads to significantly lower levels of EPA and DHA. A study of British men found that, compared to meat eaters, EPA was 28% lower in vegetarians and 53% lower in vegans, whereas DHA was 31% lower in vegetarians and 59% lower in vegans20. Not only that, but the ratio of fats in typical plant-based diets tends to be heavily skewed towards omega-6, contributing to a decline in tissue levels of omega-321. As you’ll see in Chapter 16, an excess of omega-6 relative to omega-3 is not good news for our cardiovascular system, our brain, or for keeping inflammation in check.
It is now possible to buy supplements of DHA derived from algae. These are a suitable source of long-chain omega-3 fats for vegans and vegetarians.
A bone to pick
The two biggies when it comes to bone health are calcium and vitamin D. Vegetarians who consume milk and dairy products will do just fine when it comes to getting calcium. But the calcium intake from a purely plant-based diet, without any dairy products, can be pretty marginal22. When it comes to vitamin D, as you now know, deficiency is rife, but this is especially so if you shun animal-based foods. Admittedly, meaningful dietary sources of vitamin D are few and far between, but include oily fish, and, to a lesser extent, eggs and milk, so it’s little surprise that plant-based diets fall well short of the mark23,24.
This should all be ringing a few alarm bells for bone health, and as might be expected, following an exclusively plant-based diet is associated with lower bone mineral density24,25. In the Oxford cohort of the EPIC study, fracture risk was compared in 19,249 meat eaters, 4,901 fish eaters, 9,420 vegetarians and 1,126 vegans. While there was no difference among meat eaters, fish eaters and vegetarians, the vegans showed a 30% increased fracture occurrence, which appeared to be a consequence of their low intake of calcium26. While it is possible to get calcium from a plant-based diet, getting enough is hard work, and such studies underline the fact that plant-based diets struggle to make the grade when it comes to bone health.
Plant sources of calcium include low-oxalate green vegetables (e.g. kale, broccoli, Chinese cabbage, collards), calcium-fortified beverages (soya milk, rice milk, fruit juices), tofu set with calcium, sesame seeds and almonds.
Missing without a trace
Most dietary minerals are only needed in small, trace amounts, yet they have a big role to play in keeping us healthy. Some, such as copper and manganese, are abundantly available in a plant-based diet27, whereas others can be in short supply. On one hand, minerals like iron and zinc are less ‘bioavailable’ from plant foods, which means the body just can’t absorb and use them as efficiently. This causes concern that levels of these key minerals could be pretty marginal in a plant-based diet. On the other hand, plant-based diets can also lack other trace minerals, like selenium28,29, especially in a country like the UK, where the selenium status of the population is already low.
Vitamin C greatly assists with the absorption of iron from plant foods30. This can be achieved by consuming vitamin C-rich fruit/fruit juices and vegetables with meals.
Soaking and sprouting/germinating beans, grains and seeds can reduce the inhibitory effects of phytic acid, improving iron and zinc bioavailability2.
Another good example is iodine. Very high rates of iodine deficiency (80% for vegans and 25% for vegetarians) have been found in people eating plant-based diets31. While universal salt iodization is an effective strategy for eradicating iodine deficiency32, the UK is rock bottom of the international league table when it comes to availability of iodized salt33. Consequently, practically no one in the UK is using it, which means we’re totally dependent on getting it from our diet. This comes from eating fish and seafood, and also milk. You can see where we’re going with this – eat a diet of only plant foods without iodized salt, and you’re likely to run into trouble. Why does all this matter? Iodine is vital for making thyroid hormones, which are absolutely critical in governing our metabolism. Failure to get enough iodine will compromise this, which as you’ll see in Chapter 15, may have particularly severe repercussions in pregnancy.
Plant-based diets often include foods that contain substances known as goitrogens, such as soya, cruciferous vegetables, flaxseeds, millet and sweet potatoes. Goitrogens – which are inactivated by cooking – can interfere with thyroid function, especially when iodine intake is insufficient. So vegetarians are especially at risk, and getting enough iodine is crucial.
Seaweed is very rich in iodine; however, it can contain extremely high and potentially excessive levels34. Just as too little iodine is harmful to the thyroid gland, so is too much.
THE PARTING SHOT
If we put all the ethical and moral issues to one side and focus purely on the health aspects, we don’t think there’s a strong argument for eating a purely plant-based diet. The fact that a plant-based diet lacks so many really important nutrients suggests to us that it was never intended as the optimal diet for a human being. Sure, there are literally loads of benefits to be had from eating a diet rich in plant foods, especially given the funky array of phytochemicals they contain. Anyone eating the ‘SAD’ way would do well to urgently heed that message. But we reckon a plant-based diet gets even better if you supplement it with some carefully chosen animal-based foods. That’s not to say that you can’t achieve these benefits with a purely plant-based diet, but if that’s your inclination, then you’ve got to give the whole thing a lot of thought and ensure that you attain all those missing bits by careful dietary choices and appropriate supplementation.
SUMMARY AND RECOMMENDATIONS
· Vegetarians generally experience good health, with less chronic disease and greater life expectancy. However, putting this down to the exclusion of meat is a premature conclusion.
· The benefits of a vegetarian diet have a lot to do with the consumption of a wide range of plant foods, which have well-documented health-promoting qualities and are sorely lacking from the standard Western diet.
· This means we should all be striving to eat a diet that contains plenty of plant-based foods, such as fruit and vegetables, wholegrain cereals, legumes and nuts.
· However, purely plant-based diets run a big risk of nutritional deficiencies, which could be counterproductive to the health of our hearts, brains, immune system, hormones and bones.
· Well-chosen animal-based foods, especially fish and low-fat dairy products, plug the gap perfectly.
· If you’re committed to avoiding animal-derived foods, then having a carefully planned diet, plus appropriate use of nutritional supplements and fortified foods to provide vitamin B12, vitamin D, calcium, iron, zinc, iodine, selenium and omega-3 fats, will protect you against deficiency.