Book of the Week: Will Salad Cure Covid?

ReadingRoom

Food researcher George Henderson inspects two vegetable-based cookbooks

What even are vegetables?

Vegetables, in scientific terms, trap the energy of the sun, which is delivered in quanta called photons, in webs of antioxidants and other colourful phytochemicals which funnel the energy to an enzyme complex that uses them to generate the standard unit of biochemical energy, ATP, and the reducing agent NADPH, which are then used to synthesise sugars, fatty acids, and amino acids, mainly from gases sourced from the air, plus water. These become storable energy sources which the plant can use in various ways, including attracting animals to eat its sweet fruit and spread its seeds, in which the more concentrated energy of fatty acids is the usual energy store for growth, although grains prefer starch.

Animals that eat these plants can then exploit the energy from the sun without needing to catch photons in webs. We can also eat the animals that ate the plants, and this is really where the human story begins, because, in the words of the 1942 US Navy survival manual for the Pacific, “all birds are edible” and very few animals are poisonous, whereas eating vegetables you don’t know is about as safe as picking mushrooms at random. Animals are wily, animals are dangerous in a different way from plants, and so humans became smart, strong and brave, but also very cowardly at the same time, and hence prone to cruelty and anxiety in ways that today play out on the internet instead of the savannah. Animals, being animals, like us, also collect everything an animal like us needs to survive from whatever food plants they are adapted to, plus, sometimes, their own gut bacteria, which makes them extremely handy nutritionally.

Who eats vegetables? All of the Earth’s peoples with access to starchy roots and tubers include these in their diets, and if you watch TV series like Bear Grylls’ The Island, Alone, Man Hunt, or Tribe you’ll find that both modern survivors and latter-day hunter-gatherers and herders value them almost as much as they value the protein and fat from animals. Fruit will be eaten occasionally. What no one does in such situations is eat salad, or much in the way of leafy greens. Eating non-starchy vegetables seems to have arisen as a way of surviving on nutritionally inferior cereal-based diets, perhaps because dried grains and legumes, which keep for a long time, supply no vitamin C (and very little magnesium or potassium). Hence the Scots, once dependent on oats, grew kale.

*

New Zealand is in trouble. Supply chain disruptions have greatly inflated the cost of Roundup and the other gunk that farmers need and this is expected to make veges very dear indeed in the near future.

To the rescue rides Kath Irvine, with her new book The Edible Backyard: A practical guide to growing organic fruits and vegetables all year round, which explains how to grow vegetables at home, and to do so organically (using the permaculture method) unaffected by the price of Roundup or anything else of that ilk. A lifetime’s lore of gardening experience is in here.

And if you don’t know how to use vegetables, or you do but you love new ideas, Margo and Rosa Flanagan’s best-seller Salad: 70 delicious recipes for every occasion will give you a lot of options for using a wide variety of plants, both raw and, where necessary, slow-cooked, together in delicious combinations, taking special care for those of us who are intolerant of gluten or FODMAPs, and including dishes for vegetarians and meat-lovers alike. There may well be, I expect, many other salad books in the shops, but Salad has the strong selling point for me that its authors’ interest in food arose from dealing with their health problems. These included poor mental health due to iron and B12 deficiencies, so although their book uses the now-obligatory “raw food”, “vegetarian” and “plant-based” wording and includes vegan desserts and salads (even I eat vegan desserts and salads) their interpretation of those terms is preferable to the irresponsible interpretations behind their use by malnutrition zealots or the processed food industry.

But enough of the lore of plants and gardens. What everyone really wants to know is, will salad cure Covid? And, will I get a better, longer-lasting vaccine response if I’ve been eating my greens?

The answer is – at least to the second question – probably. Supplementing antioxidants like the ones found in plants usually produces higher antibody levels after a vaccination, and there is very strong evidence that taking probiotic bacteria and the prebiotic fibres they feed on greatly enhances the response rate to the flu vaccine in free-living elderly people, in whom it’s pretty poor otherwise. Probiotics and prebiotics can be found together in fermented veges like sauerkraut and kimchi (as well as yoghurt) but raw salads may be useful sources of bacteria as well as fibre. Should you also take a probiotic supplement? Probably – that’s what most of the vaccine studies were testing, and probiotics also independently reduce the overall risk of upper respiratory tract infections.

Plants can be valuable sources of selenium, as are fatty meats, organ meats, and seafood. A recent scientific paper restates something that’s been said many times since May 2020: “Interestingly, a link between Se status and the outcome of Covid-19 patients has also been identified [113,114,115,116,117]. Overall, the available data so far strongly suggest that Se is essential for prevention of SARS-CoV-2 infection and may negatively impact on Covid-19 outcome particularly in populations where Se intake is low.”

Not all plants are good sources of selenium, and because our soil is low in this trace element it is all too easy to find many New Zealanders who are selenium-deficient in our recent medical literature on the subject; one finds Otago and Palmerston North mentioned. I’m a big fan of using Sir Austin Bradford Hill’s criteria to filter through the clamour of “X is associated with Y” that yammers in my medical inbox all day every day and bloviates across the media in an intermittently annoying fashion. Large associations, consistently found, and relatively specific for the outcome of interest, with plausible mechanisms to explain them, a dose-response, analogies with similar conditions, some sense of before-and-after, and, if at all possible, experimental proof, that’s what you look for to indicate a likely cause-and-effect relationship, and this level of confirmation does exist for selenium status influencing the risk of everything to do with Covid-19. (Applying the Bradford Hill criteria to the association between the Pfizer vaccine and Covid-19 outcomes in NZ to date has been a reassuring test of both the vaccine and the criteria).

The single best selenium source in the NZ diet is the Brazil nut, which I bet even Kath Irvine couldn’t get to grow here, with two a day being enough to raise your levels by a useful amount. If, God and Pfizer forbid, I catch Covid I’ll be taking a higher dose – you might not want to do this forever but it seems to be perfectly safe within the short time-frame of a respiratory infection. Plants of the allium family – garlic, onions, leeks and shallots as well as a thing called the ramp I have yet to experience, are good at concentrating selenium if it’s present in the soil. And they have those prebiotic fibres. Selenium, in the context of Aotearoa New Zealand, gets a definitely from me.

Another nutrient that passes the Bradford Hill test for Covid-19 is vitamin D. Unfortunately, plants don’t make any vitamin D, so people get it at lower levels from fatty fish, eggs, and full-fat dairy in winter, then build up their stores again while being out in the sun over summer. Doctors are still arguing about how and whether and in what forms vitamin D should be used for Covid-19 in hospital settings, but there’s no doubt that people who have had higher levels of vitamin D before they got infected have had far better outcomes than vitamin D-deficient people. But note that your vitamin D level can also reflect two other factors – the magnesium and vitamin C in your diet, which fruit and fresh vegetables mainly supply. Vitamin D? It depends on your relationship with the sun and fresh food.

If we hit one limitation of a plant-only diet with vitamin D, we hit other limits when we think of zinc, iron, and vitamin A, which are the most common nutrient deficiencies globally, and also essential for healthy immune function.

But that’s not the only way that meat avoidance can impact on the pandemic. Because we have in NZ an epidemic of poor mental health, especially depression, anxiety and self-harm, there’s some concern that these harms might increase under lockdown, and it appears that meat-eaters are at lower risk of these problems. The association is significant and consistent even before factoring in the quality and type of meat or what happens when the nutrients in other animal foods are also being skipped. Some plant foods used to replace meat may also be implicated – the isoflavones found in soy protein cause anxiety behaviours in young animals at similar amounts to those found today in many human diets. No other food that I know of does this.

So eat plants and animals; at least this should be the default, and if you do avoid meat and other animal foods it’s very important to have the resources and maturity to know about and supplement what you might be missing.

There are other nutritional factors with a great importance in Covid-19. Diabetes (of both types) as well as obesity are risk factors, due to the stimulating effect of excess blood glucose, high insulin, and larger fat stores on disease progress. Dietary approaches have been confirmed in the UK and USA as having the potential to put type 2 diabetes into remission in a large proportion of cases, with “Fast 800” type fasting and low carb or keto diets having the best results. Our health services should have been providing this information already – type 2 diabetes is the epidemic that is going to cost us most in the long term – but the last time we heard from the MOH on this subject they were still warning against trying anything extreme enough to be effective, other than the most extreme of all, surgery.

Realistically, the establishment of a permaculture garden within the cities where most of us live takes free time and money, even if there will be savings to look forward to. Eating the foods and taking the supplements that could help reduce risk implies some relative, if minor, privilege. But if every person who gets a vaccine is doing their bit for the greater good, so is every person who adds to that protection another means of reducing their risk of hospitalisation. Public health authorities have their hands full managing just one thing, and on past form it’s no small miracle that they’ve been able to manage that as well as they have. Show your gratitude by giving them a helping hand.

The Edible Backyard:  A practical guide to growing organic fruits and vegetables all year round by Kath Irvine (Penguin Random House, $50) and Salad: 70 delicious recipes for every occasion by Margo and Rosa Flanagan (Allen and Unwin, $45) are available in bookstores nationwide; meat is available in butchers, supermarkets, dairies, delicatassens, markets and farms.