It might have been the house where the occupants had burned the front door in order to stay warm. Or the homes where no one had any idea how to cook even an egg, so meals came straight from packets or the local chip shop. Or perhaps it was finding a girl of about nine, with her parents standing helplessly in a corner, trying to calm an aunt with mental health problems and threatening to kill herself. Lindsey Davies isn't sure which of her experiences as a community paediatrician made her go into public health.

Today is the first day of Davies's three-year term as president of the UK Faculty of Public Health. It represents the 3,500 professionals working specifically in public health across the NHS, local government, academia and NGOs. Davies recalls how it increasingly struck her during her early career that there were things that could and should be done to improve the health of people who needed more than a one-to-one doctor consultation.

"For some vulnerable people, simple doctoring is not enough, absolutely," she says. "Because for a child, adult or family, your environment – such as poor housing – and the services that are available to you can have a huge impact on your health and wellbeing."

The list of things she saw that motivated her to go into public health include: "poverty, low expectations, neglect definitely – children underfed or overfed, abuse, the impact of alcoholic parents, smoking…" The contrast between children from Nottingham's poorer estates and those in its leafy suburbs also reinforced her growing belief that tackling these bigger issues, not just the resulting ill-health, was what she wanted to do. So she began developing sexual health services, smoking cessation clinics, healthy eating initiatives, and schemes to immunise children in the east Midlands, and later became a regional director of public health.

Another anecdote illustrates the key difficulty inherent in public health – the constant need to change individuals' behaviour for sound medical reasons but not make them feel demonised or patronised. One day a six-year-old boy was brought into her clinic in a pushchair. She asked his mother why he wasn't walking. "He can't breathe," came the reply. When asked why, the mother, a chain smoker, didn't know. It turned out the boy was seriously asthmatic, his condition not helped by living in a house where tobacco fumes were a permanent presence.

Bigger picture

"I referred him to hospital and got his treatment started. But you know that he's going to go back to a house full of smoke, which is the bigger picture," says Davies, who acknowledges that the real need was to change his environment – which meant asking his parents to stop smoking indoors. "I did have that conversation with them," she says.

She knows that it would not have been easy – hearing a doctor suggest changes to your smoking, drinking or eating habits is rarely comfortable. "In public health one is constantly walking a tightrope between the nanny state concept of do-gooding …and just saying 'everybody can do everything they want'," explains an animated Davies. "I hate the phrase nanny state, because it's used as a pejorative. It gives the impression that these things are being done to a population rather than for – and with – a population. It's about making it easier for people to do the things they need to do to lead a healthy life."

One of Davies's priorities is hygiene. She wants far more people to use a tissue and wash their hands after coughing or sneezing, in order to stem the spread of germs that cause coughs, colds, flu and stomach upsets, and believes that public toilets should be much more numerous – in shops, parks and high streets, not least to encourage people to be more physically active. She was national director for pandemic influenza preparedness at the Department of Health (DH) during last year's swine flu outbreak, and would love us all to routinely use the small bottle of hand gel many of us began carrying then, to protect ourselves and others.

Today is also the faculty's annual conference in London, where the star speaker will be the new health secretary, Andrew Lansley. In theory, he and the audience should get along well. After all, it was the Conservatives who for months before the election stressed the importance they attached to public health (rather improbably for a party that is usually opposed to intervention).

"I was really encouraged to see they were expressing a commitment to public health; that they wanted to invest in prevention as a way of improving health and [ultimately] saving money," Davies recalls. "They seemed to understand that there are wider determinants that need to be addressed, in addition to health services, in order to improve the health of the population."

Optimistic

Two months after the election, and part of a coalition, have they delivered? "I'm waiting with interest to hear about their public health plans. I remain optimistic," Davies replies. She is unconcerned by the Tories' failure to honour their attention-getting pledge to rename the DH as the Department of Public Health. "There are pros and cons," she says. What she does want from the coalition is a "practical commitment to public health and a clear vision for it". She met public health minister Anne Milton last week for the first time, and understands that government plans in this area will be unveiled in the autumn.

Lansley's speech today will be his first substantive remarks on public health since taking office. But there have already been clues about the coalition's attitudes that have sent judders of apprehension through the public health community. For example, the government has made it clear that it will ignore the advice from its own National Institute for Health and Clinical Excellence (Nice) to introduce a minimum price for every unit of alcohol sold, a move backed by most of the medical community but opposed by most of the drinks industry. Davies says she hopes time and argument will persuade ministers otherwise.

Similarly, the DH rubbished Nice's recent, radical suggestions on improving the quality of food we eat to make it much healthier – as a way of saving about 40,000 lives a year from strokes and heart attacks. Davies describes the proposals as "brilliant, very straightforward measures that would make a big difference to public health". She wants statutory reform of food if negotiation with the industry does not produce the cuts in fat, salt and sugar that the nation's health requires.

Another dividing line is school food. The government's decision to scrap Labour's planned extension of free school meals to 500,000 more pupils from poor backgrounds was done, it claimed, as a money-saving necessity. "That's disappointing," says Davies. "I would like to see free school meals for everybody under 16. They really do make a difference, get people into good eating early and mitigate the effects of poverty, which is crucial."

Lansley made a major gaffe during a speech a week ago, when he criticised Jamie Oliver's campaign to transform school dinners as an example of the foolishness of "lecturing" people to change their ways. Widespread ridicule ensued. Today he will once again be walking what Davies calls the public health tightrope. So far she is showing greater sureness of foot as she tries to talk an apparently non-interventionist government round to her way of thinking.

Curriculum vitae

Age 57.

Status Partner, and two sons from previous marriage.

Lives Nottinghamshire.

Education Horsham high school for girls; Nottingham University, B Med Sci; Royal College of Physicians, FFPHM & FRCP.

Career 7 July 2010: starts as president, UK Faculty of Public Health; 2009-10: interim regional director of public health, NHS London; 2008-09: director of health, Olympics and Paralympics Programme; 2006-10: national director, pandemic influenza preparedness, Department of Health; 2002-06: regional director of public health, East Midlands; 1994-2002: regional director of public health, Trent region, DH; 1993-95: head of public health division, NHS Executive, DH; 1989-93: director of public health, Nottingham health authority; 1985-89: director of public health, Southern Derbyshire HA; 1983-85: senior registrar in public health medicine, Trent regional HA; 1980-83: senior clinical medical officer, Nottingham HA; 1976-80: clinical medical officer, Nottingham HA; 1975-76: junior house surgeon, Mansfield general hospital.

Public life 2004 CBE.

Interests Gardening, architecture and rugby.