Originally published 2013-07-11.
Garlic, honey, apples, sunlight and turmeric are often promoted as “food medicines” that can prevent or even treat serious disease. The honest answer is more modest. Each has real, interesting biology behind it, and some have a few well-supported uses, such as honey for minor burns and children’s coughs, or sunlight for vitamin D. But none of them has been shown to cure infections, cancer or other serious illnesses in people, and several can cause harm if used carelessly. They are worth eating and enjoying; they are not a replacement for medical care.
This guide looks at each one in turn: what the claims are, what the research actually shows, and how to use them sensibly.
Why “food as medicine” claims are so appealing
The idea behind the quote above is that natural foods cannot be patented, so no one pays for the large clinical trials needed to prove they work. There is some truth in that: big trials are expensive, and drug companies fund most of them. But publicly funded bodies such as the US National Institutes of Health do test herbs, foods and supplements, and many of those trials have been run. When the results are disappointing, that is evidence too.
Much of the excitement around these foods comes from laboratory and animal studies. A compound that kills bacteria in a dish or shrinks tumours in mice is a promising lead, not proof that eating the food will do the same in a person. Doses, absorption and the complexity of the human body often change the picture. Counting how many papers mention a food and a disease, as some websites do, says little about whether it works.
Garlic: strong in the lab, modest on the plate
The claim: garlic is a broad-spectrum infection fighter, able to kill even drug-resistant bacteria.
What the research shows: garlic contains sulphur compounds, especially allicin, which forms when a clove is crushed. In laboratory tests, garlic extracts inhibit a long list of microbes. One 2011 study in the Pakistan Journal of Pharmaceutical Sciences reported that garlic extract was active against multi-drug-resistant tuberculosis strains in the lab. Other lab work has tested it against organisms such as Helicobacter pylori, MRSA, Candida and herpes viruses.
In people, the results are far weaker. Reviews have found insufficient evidence that garlic prevents or treats colds. Clinical trials suggest garlic supplements may lower blood pressure slightly, by around 4 mmHg on average, without clear evidence of fewer heart attacks or strokes. Overall, reviewers have concluded that there is not enough clinical evidence to show garlic has specific health benefits beyond being a healthy part of a varied diet.
Use it sensibly: cook with as much as you like. Be careful with high-dose supplements if you take blood thinners such as warfarin or certain other medicines, because garlic can increase bleeding risk and interact with drugs. Never put raw garlic on the skin; it can cause chemical burns. Drug-resistant tuberculosis and other serious infections need medical treatment.
Honey: a real remedy for burns and coughs
The claim: honey heals infections, ulcers, burns, dental plaque and more.
What the research shows: honey is one of the better-supported items on this list. Its sugar concentration, acidity, hydrogen peroxide and, in manuka honey, a compound called methylglyoxal all slow bacterial growth. Reviews suggest honey dressings help partial-thickness burns heal several days faster than some conventional dressings, and medical-grade honey products are approved for minor wounds and burns in several countries. A small 2010 study in Contemporary Clinical Dentistry found manuka honey reduced plaque about as well as a chlorhexidine mouthwash.
For coughs, the World Health Organization lists honey as a home remedy, and systematic reviews have found it eases children’s coughs better than no treatment or placebo. The UK medicines regulator suggests honey and lemon for young children instead of over-the-counter cough medicines.
Other claims, from conjunctivitis to candida, rest mainly on lab or small studies.
Use it sensibly: never give honey to a baby under 12 months, because of the risk of infant botulism. Supermarket honey is not sterile, so do not put it on wounds; medical-grade honey is a different product. Honey is still sugar, so a spoonful in place of other sweeteners is fine, but it does not make large amounts healthy.
Apples: good food, not a cancer cure
The claim: “an apple a day” lowers the risk of colorectal and other cancers, and helps with everything from allergies to hair loss.
What the research shows: apples are rich in fibre, especially pectin, and in plant compounds called polyphenols, such as quercetin. Large observational studies have linked diets high in fruit, vegetables and fibre with a lower risk of bowel cancer, and some have linked apple eating specifically to modestly lower risk. Observational studies cannot prove cause, though: people who eat more fruit tend to differ in many other ways, including exercise, smoking and income.
Claims about apples or apple cider vinegar treating hair loss, radiation sickness, liver cancer or insulin resistance come largely from lab, animal or very small studies, and should not guide treatment decisions.
Use it sensibly: eat whole apples with the skin, where much of the fibre and polyphenol content sits. Apple juice loses most of the fibre. Undiluted vinegar can damage tooth enamel and the throat.
Sunlight: essential, with limits
The claim: sunlight is a kind of “food” for the body, and exposure protects against many cancers and diseases.
What the research shows: sunlight is the main natural source of vitamin D. Ultraviolet B rays convert a substance in the skin into vitamin D3, which the body needs for bones and muscles. Short regular exposure, often suggested as around 5 to 30 minutes on face, arms and legs a couple of times a week depending on skin tone, season and latitude, is enough for many people in summer. UVB does not pass through window glass. Bright daylight, especially in the morning, also helps set the body clock and is used to treat seasonal affective disorder.
The cancer claim needs care. Some ecological studies, including work by researcher William Grant published in Anticancer Research, found that countries with more UVB had lower rates of several internal cancers. Studies that compare whole populations like this cannot separate sunlight from diet, wealth and other factors, and later vitamin D supplement trials have not shown a clear reduction in cancer rates. What is certain is that ultraviolet radiation is a known human carcinogen and the main cause of skin cancer, including melanoma.
The idea that skin turns sunlight into usable metabolic energy, like a solar panel, is not supported by evidence. Melanin protects skin by absorbing UV; humans do not photosynthesise.
Use it sensibly: get some daylight every day, avoid burning, and use shade, clothing and sunscreen when the UV index is high. If you rarely go outside or have darker skin in a northern climate, ask a doctor whether a vitamin D test or supplement makes sense.
Turmeric: the most hyped of the five
The claim: turmeric, revered in Ayurvedic tradition, has hundreds of disease applications, with large numbers of studies on oxidative stress, inflammation, DNA damage and cancers of the breast and colon.
What the research shows: turmeric’s main active compound, curcumin, has been studied in thousands of papers, mostly in cells and animals. In people, the picture is thin. The US National Center for Complementary and Integrative Health (NCCIH) says “we don’t know enough to definitively conclude” whether turmeric or curcumin helps any health condition. There are early positive results for knee osteoarthritis pain, possible benefits in fatty liver disease, and some evidence that curcumin mouthwash or tablets help mouth sores caused by cancer treatment. All of these need better trials.
One reason for the gap is chemistry. Curcumin is poorly absorbed and quickly broken down, and it is a notorious source of misleading lab results because it interferes with many test methods. Promising lab findings rarely survive when tested in people.
Use it sensibly: turmeric in curries and golden milk is safe. Oral supplements are likely safe at recommended doses for two or three months, but liver damage has been reported, especially with “high-absorption” curcumin products. Stop and see a doctor if you notice tiredness, dark urine or yellowing of the skin or eyes. Turmeric supplements may be unsafe in pregnancy and can interact with medicines.
A GreenMedInfo video presenting the case for turmeric and curcumin.
The bottom line
All five of these are worth having in your life: garlic and turmeric in your cooking, apples in your fruit bowl, honey in moderation, and daily time outdoors. That pattern of eating and living is linked to better health overall. What they cannot do is replace antibiotics, cancer treatment or other proven care. If you want to use any of them, especially as supplements, alongside a medical condition or medication, talk to a doctor or pharmacist first.
Sources: NCCIH: Turmeric (April 2025); Wikipedia: Garlic; Wikipedia: Honey; Wikipedia: Health effects of sunlight exposure; Pak J Pharm Sci 2011, garlic and MDR-TB (PMID 21190924); Contemp Clin Dent 2010, manuka honey mouthwash (PMID 22114423); original article by Sayer Ji at GreenMedInfo.
COMMENTS