It looks like a carrot, it tastes like a carrot, but is it as good for us as it once was?
The nutritional values of some popular vegetables, from asparagus to spinach, have dropped significantly since 1950. A 2004 US study found important nutrients in some garden crops are up to 38% lower than there were at the middle of the 20th Century. On average, across the 43 vegetables analyzed, calcium content declined 16%, iron by 15% and phosphorus by 9%. The vitamins riboflavin and ascorbic acid both dropped significantly, while there were slight declines in protein levels. Similar decreases have been observed in the nutrients present in wheat. There are a few reasons for this decline.
Prompted by food shortages after World War Two, scientists developed new high-yield varieties of crops and breeds of livestock, alongside synthetic fertilizers, pesticides and herbicides, to boost food production. Coupled with improvements in irrigation and the advent of affordable tractors, crop productivity increased dramatically. The average global cereal yield rose 175% between 1961 and 2014, with wheat, for example, rising from an average yield of 1.1 tonnes per hectare to 3.4 tonnes per hectare in around the same timeframe.
While yields went up, nutrient levels in some crops declined, bringing intensive farming techniques under scrutiny. The increased use of artificial pesticides, fertilizers and other chemicals disrupts the fine balance of soil life, the health of crop plants, and affects the quality of the food we eat.
A 170-year study into wheat grown using different farming techniques in the UK suggests there is more going on.
"The Broadbalk experiment is one of the oldest continuous agronomic experiments in the world. Started in 1843, it has been comparing the effect of inorganic [artificial] fertilizers and organic manures on winter wheat. It has specifically examined the levels of iron and zinc in wheat grown under different farming methods," explains Steve McGrath, a professor in soil and plant science at Rothamsted Research in the UK.
"First, our findings show that it isn't a lack of micronutrients in the soil that is driving the lower nutrients in the crop. Those that are bioavailable, that is, in a form that the plant can absorb, don't change with intensive farming methods."
This shows that the soil itself is not the only cause of nutrient loss. Something else must be happening.
In the 1950s, an American scientist named Norman Borlaug working in Mexico created "semi-dwarf" varieties of disease resistant-wheat. By reducing the stalk height by 20%, the plants were far less likely to fall over – an issue known as "lodging" – which reduced their productivity and made diseases more likely to take hold, as well as making mechanical harvesting far less effective.
"An additional benefit of the discovery of those dwarfing genes was that rather than putting the energy into growing a longer stalk, the plant put it into the spike [the ear, where the wheat grains grow]," McGrath continues. "The smaller plant pumps carbohydrates into the grain instead, increasing the amount of grain per plant."
It did this by favoring an enlarged wheat grain endosperm, which the seed uses to feed the growing plant embryo like an egg yolk feeds a growing chick. This is packed with carbohydrate in the form of starch – the main component of flour.
Producing bigger and more plentiful grains was a welcome improvement at a time when populations in developing countries were rapidly expanding and famine was a threat. However, an unforeseen side effect was that while wheat produced more grain per plant, nutrient levels did not increase in the same way.
"What we end up with is a scenario where, while the nutrients remain at the same level in a single wheat kernel, the starch is up two or three-fold. This means that once the wheat is processed into flour you get a dilution effect. The ratio of carbohydrates to nutrients is down," says McGrath.
And while carbohydrates are crucial for human health – they provide the energy that keeps us moving and functioning day to day – we also need our diet to provide protein, minerals, and vitamins which are critical for growth and biochemical processes in the body. Selenium, for example, is needed in processes that make DNA, zinc helps the body's immune system to work properly, while magnesium maintains nerve, muscle, and heart function, and helps bones remain strong.
While the Green Revolution helped to tackle world hunger, today we find ourselves with a global food system that in some cases has been designed to deliver calories and cosmetic perfection but not necessarily nutrition. This is contributing to a phenomenon called hidden hunger, where people feel sated but may not be healthy, as their food is calorie-rich but nutrient-poor. It might initially sound counterintuitive but obese individuals can be nutrient-deficient. So, can the nutritional quality of our food be restored?
While some scientists feel the fall in nutrient levels in our food over the decades is too small to be significant compared to the increase in food availability provided by improved yields, the health of our soils is still thought to have an important relationship to the nutritional quality of our food. A trial in the US has been examining vegetables grown under different farming techniques to better understand exactly what this link is.
"The vegetable systems trial started in 2016 and is a side-by-side comparison of crops grown in soils managed with intensive practices and regenerative organic tillage practices," says soil scientist Gladis Zinati of the Rodale Institute in Pennsylvania.
The goal of the study, which is designed to run indefinitely, is to link farming practices and soil health to crop nutrient density (or the amount of nutrients a food contains relative to the amount of calories) and human health.
Zinati's research suggests that the more fungi and microbes that are active in the soil, the better equipped it is to get nutrients into plants and our diet. In other words, soil teeming with fungi and bacteria is better able to break down nutrients into a form that can be more easily gobbled up by the crops.
The initial findings are due to be peer-reviewed with a view to publishing in the coming year.
Soil is made of four elements in varying proportions: minerals in the form of rock particles, organic matter (plant, fungal, and animal materials including microbes and microscopic worms, either dead or alive), air, and water. But the important thing is how these elements interact.
A teaspoon of soil contains more microbes than there are people on the planet – we're talking billions, and as many as 10,000 individual species. Intertwined with all that mind-boggling life is a network of fungal filaments called mycorrhiza, a symbiotic relationship with plants and microbes that act as extensions to their roots. There is a constant dance of nutrient pass-the-parcel from soil to plant, powered by complex biochemical pathways, fungal superhighways, and exotically named root exudates, which is basically root snot that stimulates or represses a wide array of biological activity in the soil.
The influence of mycorrhizae is such that it has been commercially harnessed to improve crop productivity. GroundworkBioAg in Israel has produced a soil inoculant based on particularly vigorous strains of mycorrhizal fungi, sourced from the Israeli desert.
These specialized soil fungi effectively extend the plant root system with mycelium – a web of long microscopic filaments called hyphae. They work in a symbiotic relationship with the plant, releasing nutrients from deep in the soil, in a form that the plant can absorb.
When this commercially produced powder is used to coat roots or seeds, the resulting impact on crop yield has some farmers embracing these remarkable fungi over artificial agrochemicals.
US farmer Cory Atley farms 8,000 acres (32 sq km) of maize and soybeans in Ohio and has been trial-testing the use of the inoculants. As well as seeing a boost in crop growth through the release of nutrients from the soil, he has found he is spending less on chemical inputs.
"What we are really trying to focus on is soil health, so once you get your soil health aspect of it down, it will translate into plant health. We're still using synthetic fertilizer but we're using less and less, about 25% less. What we're trying to do is break apart more of what is already in our soil, instead of constantly adding more to the soil."
When you reach for that bottle of vitamin C or fish oil pills, you might wonder how well they’ll work and if they’re safe. The first thing to ask yourself is whether you need them in the first place.
More than half of all Americans take one or more dietary supplements daily or on occasion. Supplements are available without a prescription and usually come in pill, powder or liquid form. Common supplements include vitamins, minerals and herbal products, also known as botanicals.
People take these supplements to make sure they get enough essential nutrients and to maintain or improve their health. But not everyone needs to take supplements.
“It’s possible to get all of the nutrients you need by eating a variety of healthy foods, so you don’t have to take one,” says Carol Haggans, a registered dietitian and consultant to NIH. “But supplements can be useful for filling in gaps in your diet.”
Some supplements may have side effects, especially if taken before surgery or with other medicines. Supplements can also cause problems if you have certain health conditions. And the effects of many supplements haven’t been tested in children, pregnant women and other groups. So talk with your health care provider if you’re thinking about taking dietary supplements.
“You should discuss with your doctor what supplements you’re taking so your care can be integrated and managed,” advises Dr. Craig Hopp, an expert in botanicals research at NIH.
Dietary supplements are regulated by the U.S. Food and Drug Administration (FDA) as foods, not as drugs. The label may claim certain health benefits. But unlike medicines, supplements can’t claim to cure, treat or prevent a disease.
“There’s little evidence that any supplement can reverse the course of any chronic disease,” says Hopp. “Don’t take supplements with that expectation.”
Evidence does suggest that some supplements can enhance health in different ways. The most popular nutrient supplements are multivitamins, calcium and vitamins B, C and D. Calcium supports bone health, and vitamin D helps the body absorb calcium. Vitamins C and E are antioxidants—molecules that prevent cell damage and help to maintain health.
Women need iron during pregnancy, and breastfed infants need vitamin D. Folic acid—400 micrograms daily, whether from supplements or fortified food—is important for all women of childbearing age.
Vitamin B12 keeps nerve and blood cells healthy. “Vitamin B12 mostly comes from meat, fish and dairy foods, so vegans may consider taking a supplement to be sure to get enough of it,” Haggans says.
Research suggests that fish oil can promote heart health. Of the supplements not derived from vitamins and minerals, Hopp says, “fish oil probably has the most scientific evidence to support its use.”
The health effects of some other common supplements need more study. These include glucosamine (for joint pain) and herbal supplements such as echinacea (immune health) and flaxseed oil (digestion).
Many supplements have mild effects with few risks. But use caution. Vitamin K, for example, will reduce the ability of blood thinners to work. Ginkgo can increase blood thinning. The herb St. John’s wort is sometimes used to ease depression, anxiety or nerve pain, but it can also speed the breakdown of many drugs—such as antidepressants and birth control pills—and make them less effective.
Just because a supplement is promoted as “natural” doesn’t necessarily mean it’s safe. The herbs comfrey and kava, for example, can seriously damage the liver.
“It’s important to know the chemical makeup, how it’s prepared, and how it works in the body—especially for herbs, but also for nutrients,” says Haggans. “Talk to a health care provider for advice on whether you need a supplement in the first place, the dose and possible interactions with medicine you’re already taking.”
For vitamins and minerals, check the % Daily Value (DV) for each nutrient to make sure you’re not getting too much. “It’s important to consider the DV and upper limit,” says Haggans. Too much of certain supplements can be harmful.
Scientists still have much to learn even about common vitamins. One recent study found unexpected evidence about vitamin E. Earlier research suggested that men who took vitamin E supplements might have a lower risk of developing prostate cancer. “But much to our surprise, a large NIH-funded clinical trial of more than 29,000 men found that taking supplements of vitamin E actually raised—not reduced—their risk of this disease,” says Dr. Paul M. Coates, director of NIH’s Office of Dietary Supplements. That’s why it’s important to conduct clinical studies of supplements to confirm their effects.
Because supplements are regulated as foods, not as drugs, the FDA doesn’t evaluate the quality of supplements or assess their effects on the body. If a product is found to be unsafe after it reaches the market, the FDA can restrict or ban its use.
Manufacturers are also responsible for the product’s purity, and they must accurately list ingredients and their amounts. But there’s no regulatory agency that makes sure that labels match what’s in the bottles. You risk getting less, or sometimes more, of the listed ingredients. All of the ingredients may not even be listed.
A few independent organizations conduct quality tests of supplements and offer seals of approval. This doesn’t guarantee the product works or is safe; it just assures the product was properly made and contains the listed ingredients.
“Products sold nationally in the stores and online where you usually shop should be fine,” Coates says. “According to the FDA, supplement products most likely to be contaminated with pharmaceutical ingredients are herbal remedies promoted for weight loss and for sexual or athletic performance enhancement.”
To make it easy to find reliable information, NIH has fact sheets on dietary supplements at ods.od.nih.gov/factsheets/list-all/. NIH also recently launched an online Dietary Supplement Label Database at www.dsld.nlm.nih.gov. This free database lets you look up the ingredients of thousands of dietary supplements. It includes information from the label on dosage, health claims and cautions.
For more personalized, on-the-go information about dietary supplements, check out NIH’s free updated app for your smartphone or tablet: My Dietary Supplements (MyDS).
The MyDS app provides the latest supplement information and lets you keep track of the vitamins, minerals, herbs and other products you take. You can even keep track of supplements taken by your parents, spouse or children.
“Deciding whether to take dietary supplements and which ones to take is a serious matter,” says Coates. “Learn about their potential benefits and any risks they may pose first. Speak to your health care providers about products of interest and decide together what might be best for you to take, if anything, for your overall health.”