As part of our Make Health Your Project response to Coronavirus, this series of articles describes how to improve your immune health through your gut. This update: an overview of foods and nutrients you should definitely try to include in your diet.
Why This Isn’t a “Diet”
If you’ve followed “a diet” — for example for weight loss or bodybuilding — you’ll perhaps be familiar with targeting food intake at a “macro” level. You may have focused on solely on calories or broad categories like “carbs”, fat or protein — or the levels of all three in your diet. This gives the impression that all carbs, proteins and fats are fundamentally the same. They definitely are not.
Take carbohydrates, as an example. You might think that all carbohydrates are eventually metabolised down to basic sugars — monosaccharides. But, actually — no. Plus, there are three common monosaccharides in our diet: glucose, fructose and galactose. And, despite sharing the same chemical formula, even these simplest of molecules are each processed differently by your body. Once they’re chained together into polysaccharides like starches… well, that changes everything again. The fact is, some carbs and even sugars are more helpful and others more problematic in your diet. Targeting levels of “carbs” without diving into the detail, isn’t that helpful if your goal is good health.
That’s why a health-focused diet — and one especially focused on gut and immune health — has to be more specific. And, because the goal is improved health — not losing weight or building muscle — there are no targets for calories, carbohydrate, fat or protein. You can set your own levels for these, depending upon your overriding need. Whether, you want to bulk up or lose weight, you can still meet your objective. Our objective is to help you do that in a immune-healthy way by using good foods not bad ones.
So, rather than a diet, think of this as a matrix of helpful food choices. Try to include a broad range of foods from across the matrix. Of course, there are villans too. They’ll be the focus of a separate post.
The ABC…DE of Supporting Immune Health
The health of your immune system and gut depends upon eating foods that combined deliver complete nutrition. All the essential vitamins, minerals and other dietary compounds can and should be delivered through your diet. In this matrix, these dietary needs have been divided across rows, to create easy to understand food choices. All you need to do is eat something from each row every day. Eating more than one thing is better, of course, and we recommend variety in your choices. Read on for the science behind this simple plan.
|Steamed spinach, broccoli or kale
|Salad including baby spinach, red peppers, romaine lettuce, sunflower seeds
|Salmon or poultry
|Lentils, seeds & nuts – eg Brazil, sunflower, sesame and cashew
|Brown rice, wholegrain wheat products (eg bread, pasta or cereal), potatoes or sweet potatoes
|Oats, peas, beans and other legumes, carrots, apples
|Garlic, any of onion family (allium), oats, wheat bran (eg Allbran), apples
Row A – Vitamins
Row A is predominantly for vitamins A, C and E. Some food choices here also deliver copper and B9. Include spinach, broccoli or kale with your favourite vegetables accompanying a cooked meal. Wilted spinach is a very versatile side dish; add it to anything from curry to poached eggs. Where a cold option is preferred, try to include red peppers, baby leaf spinach, Romaine lettuce and some sunflower seeds in your salad.
Row B – Minerals
Row B delivers selenium, iron and some B vitamins, plus copper for the vegetarian/ vegan nuts and seeds option. Choose salmon or poultry as your primary protein several times a week. Top up with nuts and seeds on other days.
Row C – Insoluble Fibre
The easiest way to increase your insoluble fibre intake is to swap white rice for brown, white bread for wholemeal and regular pasta for wholemeal. You can still enjoy your favourite Basmati rice with your curry on the weekends, but generally you should try to eat wholegrain versions of staple carbohydrates.
Row D – Soluble Fibre
They say an apple a day keeps the doctor away and, actually, doing so could be one of the easiest, more beneficial steps in improving health. Also try adding a dessertspoon of unrefined whole oats to your breakfast cereal or having garden peas more frequently with your main meal.
Row E – Prebiotics
Focusing on cultivating good microbes is easy and more reliable and cheaper than supplementing with probiotics. Simply include members of the tasty Allium family in your dishes: garlic and onion in cooked meals; spring onions in salads.
The Science of Gut & Immune Health
A lot of science is distilled into this seemingly simple ABCDE matrix. For those who want to know the why of what’s included, what follows is a summary of the science behind it. A huge amount of desk research regarding the current scientific opinion underpins the brief explanations shared here. In future posts, topics like prebiotics and the vitamin and mineral choices will be discussed in far greater detail.
When it comes to eating well, there are 4 broad types of good stuff that you should aim to include in your gut- and immune-healthy diet.
Good sources: the edible allium family (garlic, onions, leeks, spring onion, shallots), asparagus, jerusalem artichoke, barley, whole (unrefined) oats, apples, bananas (greener are better), flaxseeds, wheat bran, seaweed.
We call the beneficial microorganisms in our gut — especially bacteria — probiotics. Prebiotics are what we call the foods that nourish them. So, prebiotics are like fertiliser for the health-assisting microbes. Indeed, what makes prebiotics special is they that feed only beneficial bacteria like Lactobacilli. It’s not the whole food stuff that’s prebiotic. It’s actually several different types of carbohydrate within some foods, that we cannot digest, but good microbes ferment for energy. Prebiotic foods contain varying amounts of these carbohydrates.
To many of us, the term probiotic will be more familiar than prebiotic. We see probiotic claims on products and in advertisements extolling the benefits of consumer probiotics. But, actually, the less glamorous prebiotics are arguably more important, because there’s more scientific evidence they are effective.
If you only do one thing to boost your prebiotic food intake, then eat an apple at day. Apples have been found to be a super-prebiotic!
Regular dietary fibre is the stuff that keeps things moving smoothly, all the way through our digestive system. There are two main types: soluble and insoluble.
Soluble dietary fibre
Good sources: oats, peas, beans, avocado, apples, citrus fruits, carrots and barley.
This type of fibre dissolves in water producing a gel like substance. It has a regulating/ moderating effect on digestion. It helps to slow things down — like the emptying of the stomach (meaning you feel fuller longer) and the absorption of glucose into the blood.
New science shows soluble fibre has a regulating effect on your immune system as well. It “changes immune cells from being pro-inflammatory warrior cells to anti-inflammatory peacekeeper cells”, according to a University of Illinois study. That’s because it stimulates production of a specific anti-inflammatory protein in your gut. This speeds healing and recovery from infection.
Insoluble Dietary Fibre
Good sources: wholegrain wheat, brown rice and couscous; celery, cucumbers, courgettes, aubergine and avocado; root vegetables like carrots and potatoes; nuts and seeds.
Good old-fashioned roughage — as it used to be known — performs a more basic role in our body: it provides bulk to our stools (pooh), and keeps things moving, helping to prevent constipation. It speeds the expulsion of toxic waste material through the colon and reduces the risk of bowel cancer.
It’s worth noting that the UK Government recommends we get 30g / day of dietary fibre. Currently, UK adults average only 18g each/ day!
Vitamins & Minerals
The ultimate diet would provide everything the body needs to support every function in the ideal amounts. This list would include 13 essential vitamins, plus 16 essential minerals that you cannot produce yourself or in adequate quantities. These are in addition to the other dietary components mentioned elsewhere here. Narrowing the focus onto those most critical to the gut and especially immune health, leaves 8 key vitamins and minerals.
Good sources: legumes like chickpeas, lentils and beans, red meat, crab, mussels and prawns, hemp and sesame seeds, cashews and almonds, milk and cheese, dark chocolate
Zinc plays a central role in the immune system with impacts ranging across immunologic mechanisms: from antibody production and the development of acquired immunity to the barrier of your skin. Zinc helps prevent your immune response from spiralling out of control, avoiding damaging and even deadly excessive inflammation
Brazil nuts, Yellowfin tuna, salmon, sardines, ham and other pork, poultry, cottage cheese, eggs, brown rice, sunflower seeds
Like Zinc, selenium is a mineral fundamental to maintaining good health. Selenium’s primary contribution is to signalling within cells and the protection of cells against oxidative damage. Adequate selenium availability is absolutely essential to the functioning of the immune system and its ability to respond to infections.
Good sources: dark leafy greens, liver, red meat and poultry, beans, cashew nuts and sesame seeds, dark chocolate, lentils, beans and legumes.
Iron is critical for immune cell proliferation and activation. Some gut microbes are known to ‘steal away’ iron from the host to hinder phagocyte activity. Phagocytes are cells that envelop and kill harmful bacteria, and dead or dying cells; they need iron to be effective killers.
Good sources: Organ meats — such as liver, oysters(!), spirulina, shiitake mushrooms, cashews, almonds and sesame seeds, kale, Swiss chard, spinach and other leafy greens.
Copper is iron’s buddy; you need copper for the gut to absorb iron. Copper is also core to producing cell’s main source of energy: adenosine triphosphate (ATP). Copper deficiency can dramatically reduce neutrophils production. The most abundant white blood cell, neutrophils are your first defence against bacterial infections. Copper itself is antimicrobial and accumulates at sites of inflammation.
Good sources: sweet potato, carrots, broccoli, kale, spinach, sweet red pepper, beef liver
Vitamin A is necessary to structures and functions defending the body. It protects the cellular lining (epithelium) of the lungs and of your digestive system. It ensures adequate protective mucus secretion, entrapping bacteria, irritants, particles, etc. Gut affecting white blood cells cannot be generated without it.
The B-Vitamins B6, Folate/Folic Acid (B9) and Vitamin B12
- B6 sources: poultry, beef, pork, salmon, potatoes, peanuts, soya beans, bread, eggs
- B9 sources: spinach, Romaine lettuce, kale, liver and offal meats, chickpeas, lentils, kidney beans
- B12 sources: clams and mussels, beef, Greek yogurt, plain yogurt, milk, salmon
Vitamin B9/ folate, or its synthetic alternative folic acid, is necessary to cell survival and proliferation through cell division. Evidence suggests that vitamin B9 and fellow B vitamin B12 play are critical to the health of your immune system. Deficiency of vitamin B6 has been linked with immunological decline observed in the elderly.
Good sources: broccoli, cauliflower, kale, potatoes, sweet red, yellow & green peppers, carrots, citrus fruits, pineapple, mango, guava.
Vitamin C is an imperative micronutrient for humans, supporting key cellular functions. Specific to immunity, it assists epithelial lining (eg lung and gut lining) barrier to disease-causing organisms. It accumulates in microbe-killing phagocytic cells and can enhance their mobility, ingestive ability and microbial killing efficacy. At sites of infection, Vitamin C aids the clear up by large white blood cells called macrophages, helping contain tissue damage.
Good sources: spinach and broccoli, nuts including almonds and peanuts, sunflower seeds, sunflower oil, avocado, red sweet pepper, Atlantic salmon and rainbow trout
Vitamin E is a potent antioxidant that can improve immune functions. A high vitamin E diet has the potential to markedly improve age-related decline in cellular immunity. It can induce higher immature T-cell differentiation: where T helper cells become regulatory T-cells, which prevents unchecked immune response. T-cells are critical to the adaptive immune system, where the body adapts specifically to foreign invaders.
Fermented foods are a source of probiotics: friendly bacteria and yeasts that provide health benefits. Some common foods like yogurt are fermented by the very bacteria (bifidobacteria) we know play a role in training, modulating or assisting our immune response. They linger in unpasteurised versions of the food they helped produce. However, with limited scientific research, the question remains in many cases whether these helpful microbes survive the journey through the upper gastrointestinal tract to the colon. Some probiotics are proven to reach the gut alive — like those in Activia and Yakult — others may be helpful, but aren’t necessarily proven.
You should choose a yogurt containing live Bifidobacteria (Activia) or Lactobacillus paracasei Shirota (Yakult). These strains are proven to survive the journey through the upper gastrointestinal tract. The strains that actually ferment yogurt are generally thought to be destroyed by the acid of the stomach and pancreatic enzymes.
Also be sure to check the ingredients label for added sugars or artificial additives. Some artificial sweeteners — like sucralose and Acesulfame K — exert a bacteriostatic effect reducing bacteria reproduction, so you’ll want to avoid these.
Kefir is a probiotic milk drink: cultures of predominantly Lactobacillus (lactic acid), Lactococcus and Streptococcus bacteria, plus multiple genera of yeast are added to cow’s or goat’s milk. It is superior to yogurt, because of the diversity of microbes present. Also, a study by the BBC showed a greater impact on gut fauna composition than other probiotics.
Good news if you’re a cheese lover; some contain active probiotic cultures. Check the label of your favourite cheddar, Gouda, mozzarella or cottage cheese. It’s essential the cheese hasn’t been pasteurised.
Miso is a popular Japanese soybean seasoning in the form of a paste that’s fermented by fungi. Typically it is added to water to make a soup. The water must not be too hot, if you want the probiotic ingredient to survive
Famously German, sauerkraut is shredded cabbage fermented by lactic acid bacteria. Once made it can be stored for months. It has a salty, sour taste and the Germans love it with their sausages. You must either make it yourself or choose the unpasteurised option to ensure live cultures are present.
Some of these probiotics are perhaps a little exotic for some tastes. And, actually, probiotics might not be the most effective solution. Eating more prebiotics — bacteria fertiliser — to grow what you have may serve you better. One exception: if you’ve recently been on antibiotics or other bacteriostatic drugs, then probiotics certainly cannot harm repopulation.
Next Update – What Not To Eat
We’ll be covering the food and ingredients that won’t help your gut and immune health in the next update. Follow is on Instagram, Twitter, Facebook or LinkedIn for notifications.